Quad 405 No Left Channel

[dantheman91]

Hi Lads

I went to play some music on the Quad 33 & 405 this morning powered up fine then i heard a faint pop and then no left channel? I have tried my 33 with it and its still the same no left channel. i have tried a different speaker but its still the same so i know that the other on is fine The 405 was recapped in October could it be a output cable although i'm not to sure it still does the normal pop when turned on so that tells me something will check all cables just in case though it has not been used for a couple of weeks. What do you guys think i don't really want to be spending more on it its cost £90 for the recap what do you guys suggest?

Thanks
Dan

[Firebottle]

Check the fuses on the amp pcb first Dan

Alan

[dantheman91]

Check the fuses on the amp pcb first Dan

Alan


:scratch: Clueless When it comes to things like that.............

[The Barbarian]

unplug it, take the top off, you will see a power amp PCB mounted on it's side, each side of the amp, two glass fuses on each board, check em bustah. :eyebrows:

[Light Dependant Resistor]

sorry posted twice

[Light Dependant Resistor]

Hi Dan
Yes unplug first as Andre advises. The fuse rating on each of the rails for a 405 is 4 amp and their size is M205 the fuses are placed to protect both the Negative and Positive one fuse for each rail per channel ie DC 50v + and DC 50v - rails. You should be able to see the physical condition of the fuse which is going to either be intact in which case the fault is elsewhere possibly a wire has dropped being the only fault I can think of, or the fuse or fuses have blown.
Note Do Not reapply power unless the lid is on.

If its just one fuse make a note which fuse noting its location as one controls negative rail and the other positive and will be easier to fault find a answer for you. also the condition of the fuse is important to note, if its internal parts have gone everywhere rather than just a break then the fault is severe. Quad installed what appears as a salt type substance fuse in some amps so condition with these is not as easy to tell.

405's prior to about 1977 did not have what is called a crowbar circuit designed to blow the fuse if the speaker lead shorted, Quads rationale a good one was that its easier to replace 405 parts than your speakers, so after 1977 a crowbar circuit made up of a triac and diac was simple but its location on the speaker sockets makes it very difficult to service. Quad then moved the crowbar circuit on to the circuit board.

If this is all bewildering a service with Quad would be the best way of getting your amp fixed. If not there are many on the forum including myself who can guide you. The typical rebuild will be replacement of the output transistors, as most of the other circuitry tends not to fail with the exception of the crowbar that occasionally needs replacement. The ideal transistors are MJ15003 which are TO3 cased transistors.12622

[dantheman91]

Cheers guys i have booked it in for a look over again :scratch:. Frustrating to say the least as was perfectly fine when last used...

Thanks

[dantheman91]

Hi Guys

Will take a look inside to see if it is a fuse HOPEFULLY thats what keeps coming up as the answer if this is the case what fuse do i need to buy?

[DSJR]

Dan, Quad still have an excellent service department who will advise and do a good repair at modest cost. This amp is a pain to work on unless you're careful in removing the boards and crimped connectors - I'm clumsy here so left alone!

The Dada/Quad revision BlogSpot has loads and loads of articles regarding sorting out a 405 of any age to something that won't fall down when driving modern speaker loads. The MK2 boards are much better than mk1's on most loudspeakers I used with them (including 57's believe it or not. My sets were Issue 7 and Quad were on Issue 10 fairly recently as I believe they still make boards for it?????????) and of course Dada do some faithful modern boards too. Net Audio are also well known, but I'm not sure if they try to evolve Quad amps into something they're not (apologies if I'm being grossly unfair here).

If you have a mk1 405, you'll really need to do some thorough surgery to the existing boards a la Keith Snook - http://www.keith-snook.info/quad-405-mods.html

It's still a very nice compact amp when working so WELL WORTH getting sorted and updated where possible.

[The Barbarian]

Hi Guys

Will take a look inside to see if it is a fuse HOPEFULLY thats what keeps coming up as the answer if this is the case what fuse do i need to buy?

Chris told you 4A {FS1/2] on the Schematic}

[StanleyB]

There are some fuses on the 405 PCB. The originals were even gold plated. I sold my two reserve 405 boards last year and remember the fuses very well after a potential buyer asked if they were the gold or chrome plated ones.

[Lodgesound]

Hi there;

Where in the south are you?

We have a great deal of experience with these amps as we use them to drive our monitors.

Let me know if we can be of assistance...

[The Barbarian]

Dan:
I would personally get a pair of Net Audio '405' Mk.3 Amplifier boards fitted. I fitted the '303' Mk.3 boards to one of my old '303's they were superb..

If you are useless with anything like this i think they charge about £70 fitting.I know you had the PSU Re-capped but Net's dual mono PSU board is well worth the effort...

But in the meantime take up anyone's offer to get it sorted out for you..

[tubehunter]

Hi Dan,

I have a pair of genuine upgraded.Quad 405 boards built into an old case I used for testing purposes, that I could let you have and fit for a small fee.

In my main system I use two mono blocked Quad 405's modified with top quality F&T power supply caps.
Burr Brown OPA604 op amps with their own power supplies upgraded and improved.
The OPA604 have FET inputs which to me sound very valve like, and I have tried most others.
I have also fitted Velleman K4700 loudspeaker protection boards which prevents switch-on clicks and DC components on the output, I recommend fitting these.
I'm using a simple Stepped Ladder Attenuator for volume control.

Powering my serviced Kef105's they sound amazing.

Duncan

[dantheman91]

Correct Fuse?

http://www.amazon.co.uk/250v-Slow-Blow-Glass-electrosmart%C2%AE/dp/B0036A97KU

[The Barbarian]

That's em Danny boy the pipes the pipes are calling

[dantheman91]

That's em Danny boy the pipes the pipes are calling


Cheers dude have also bought a new 4 pin din to 4 pin din cable just encase as mine are surprisingly dodgy and bought the fuses will take a look on friday.....Hopefully will have it singing again in no time :)

[dantheman91]

Hi Guys

Looking inside now but the fuses have like a clear white film inside how can i tell if there gone do i just replace all 4 or get someone specialist to look at it? which board is for each channel i presume Left = Left Right = Right on the PCB boards?. PS and the casing is a bitch to get back on any tips it does not slide in the front fasia where they meet.:(. Losing the will here............

[The Barbarian]

Do you have a multimeter with continuity bleep?

[dantheman91]

Do you have a multimeter with continuity bleep?

No mate........i might be able to borrow one what do i need to do.? Check the fuses to see if there at fault to be honest it looks REALLY clean inside :) Advise would be greatly appreciated.

Thanks
Dan

[Firebottle]

Hi Dan, from your description it sounds like the fuses may have failed catastrophically, i.e. gone with a bang.
As mentioned before there are different types of fuse:
Glass bodied with no filler. You can see the wire when it is intact. If severely overloaded the wire tends to vapourise and coat the inside of the glass with what looks like a white/metallic film. I'm guessing that's what you have, any chance of a close up photo?

Glass bodied with sand/quartz filler. You can't tell whether these are intact or not by looking at them.

Ceramic body, usually a white or off white colour. Again you can't tell whether these are intact or not by looking at them.

When my 405 was a lot of years old the driver transistors failed in both channels, at different times, causing the fuses to vapourise. I changed the transistors for higher rated ones and it's been fine since, in use daily.

Hope this helps,
Alan

[The Barbarian]

This is why i always advise that vintage amps be fully Re-Built before use, if not you are always going to be faced with unreliability. Before i re-built my Ferrograph amp it was forever coming up with issues. Since they i have not heard a single murmur from it..

As Alan points out it does sound like a Transistor issue..

[The Barbarian]

No mate........i might be able to borrow one what do i need to do.? Check the fuses to see if there at fault to be honest it looks REALLY clean inside :) Advise would be greatly appreciated.

Thanks
Dan

As Alan points out the white coating on the inside of the Glass is a sign the fuse has blown. 9/10 the next fuses you fit will also blow.

Multimeters are something everyone should at least have in their tool box, the continuity bleep is dead handy for a whole hoast of different quick fault finding ie fuses, identify breaks in cables etc.. Switch the meter on bleep one lead on one end of a fuse, the other lead on the other end, it bleeps the fuse is not broken.

Please always make sure no power is on when doing electronics..Always always pull the plug out.. When working on power supply please also bear in mind that the Reserviour caps especially still will be holding charge even when off...

[dantheman91]

Its out of my league guys ive looked and not going any further :) thanks again for all the advise much appreciated guys :)

[PaulStewart]

Dan you just say you're in the south, if you are near west London, bring it over and I'll ahve a look

Cheers

[dantheman91]

Hi Paul

Thanks for the offer but i'm in Bournemouth so too far to get it to you. Its currently in for repair with my local repair engineer hopefully should be back with me early this week.

Thanks again for the assistance guys but its not my area of expertise and don't want to blow anything or myself up so best left to someone qualified for the job.

:)

[The Barbarian]

O Danny boy:
Get yourself on a basic electronics course, honestly it will save you £££ in the long run.

I took a Studio Engineering course & Electronics Engineering courses in my spare time years ago i got myself a BTEC level 1-3 in the latter.. The Studio Engineering course did not work out as good as it could have as it turned out to be mainly working with Digital Engineering something i have no interest in.

[dantheman91]

O Danny boy:
Get yourself on a basic electronics course, honestly it will save you £££ in the long run.

I took a Studio Engineering course & Electronics Engineering courses in my spare time years ago i got myself a BTEC level 1-3 in the latter.. The Studio Engineering course did not work out as good as it could have as it turned out to be mainly working with Digital Engineering something i have no interest in.


:) Cheers for the tip dude will look into it.......

:cool:

[dantheman91]

Hi Guys

This is the email from the repair guy. Question is is it worth doing.? :)

Hi

Ive had a look at the amp the channel which was down has got a few problems.
The 12v + and - supply resistors to the OP amp were both faulty. Changed them both and new ones and they both started to over heat. This is caused by a faulty Op amp. Swapped the op amp over from the other channel and the faulty channel was working ok but at about 80% of its output. after about 2 mins of running it blew the output transistors on that channel

Now these output transistors have been changed before on both sides i think as they should be all the same
But both sides have 2 different types ?? Been changed before ????

The working channel has some issues and was going the same way as the faulty channel , the supply resistors for the OP Amp are showing signs of over heating. This channel would be going the same was as the other. But will all the testing it has developed its own fault.

I had an amp ( not quad ) in last week with a similar issue and the easiest way to sort it is to change all semi conductors . I did that and its all working

So i think the best bet here is to order a list of parts and that will sort out both channels

Parts £48 and labour £40 Total £88

Trouble is i have spent a total of £90 for the Recap Plus the purchase price of £130 trouble is you can only spend so much on something before it starts to loose valve hmm what to do.....?

[istari_knight]

I haven't read 99% of the thread but from your last post I would look for a new "tech" Dan me old mucker !

Firstly, anyone that replaces burnt out resistors without first investigating WHY they burnt out is a moron. Secondly, when testing "dodgy" kit 2 minutes is a lifetime... Its painfully obvious when an output stage is going into thermal runaway - If he were even semi-professional he would have the use of a variac or at least a current limited bench supply for preliminary testing purposes... Expensive disasters are easily averted when you have the right kit ;)

Finally, in my opinion... "Carpet bombing" IE. replacing everything because you don't have the experience/knowledge/skill to find which component is at fault is no good at all. It costs the client more money & the "tech" learns nothing, so next time he has something with a similar fault he'll be none the wiser how to fix it !

The price quoted isn't bad but I would be keen to inspect the work, I have a feeling it might not be the finest we've ever seen :D

[dantheman91]

I haven't read 99% of the thread but from your last post I would look for a new "tech" Dan me old mucker !

Firstly, anyone that replaces burnt out resistors without first investigating WHY they burnt out is a moron. Secondly, when testing "dodgy" kit 2 minutes is a lifetime... Its painfully obvious when an output stage is going into thermal runaway - If he were even semi-professional he would have the use of a variac or at least a current limited bench supply for preliminary testing purposes... Expensive disasters are easily averted when you have the right kit ;)

Finally, in my opinion... "Carpet bombing" IE. replacing everything because you don't have the experience/knowledge/skill to find which component is at fault is no good at all. It costs the client more money & the "tech" learns nothing, so next time he has something with a similar fault he'll be none the wiser how to fix it !

The price quoted isn't bad but I would be keen to inspect the work, I have a feeling it might not be the finest we've ever seen :D

Hi James

To be honest its not even what i asked him to do i asked him to fix the left channel and not piss about with doing the other stuff. Basically in the popular sense of the word its even more fucked now. :scratch:

[istari_knight]

I would cut your losses Dan, you mentioned it was lovely & clean inside so don't let a cowboy bodge it up. I would get it back from him & save up for a service from someone competent be they Quad themselves or H.T.Baker Audio who specialize in Quad repairs.

[dantheman91]

Hi James

Its too late he has already touched it and by the look of it its not a pretty sight. I took it in to get the channel fixed it was working until he started to piss about and then something blew and something else followed steam: No i'm up shit creak BIG TIME. Now its back in a far worse state then it arrived in complete buggered he even stacked the power amp on top of the 33 pre to give it back to me in the box. :wanker:

LESSON LEARNT

[istari_knight]

Sorry to hear that Dan :(

FWIW faulty examples appear to sell for around £100 on the bay & you can pick up working examples for around £200... Could be worth looking into ? Or possibly its the end of an era and time to look at alternatives :)

[dantheman91]

Sorry to hear that Dan :(

FWIW faulty examples appear to sell for around £100 on the bay & you can pick up working examples for around £200... Could be worth looking into ? Or possibly its the end of an era and time to look at alternatives :)


Hi James

Only so much you can spend i have put about £200 in it and thought that would be the end but oh no..........i still have my old trusty 33 & 303 so that will be going to my dad for his Xmas pressie sad as i have had it since 2010 and it was my first buy of something vintage..

Just goes to show what reviews you read online are no always as they seem thats what i went against feel like a right TWAT.

[DSJR]

GOOD 405-2's tend to go for nigh-on £300 I thought?

PLEASE check with dada to see if they have any good working 405-2 boards (unlikely Net-Audio will have any as IMO there's not much point in upgrading if you have a series 2 already!). Quad themselves may well be able to supply you with new issue 10? boards as I think they still supply them. The boards are easy to remove as long as you can CAREFULLY prise the push-on connectors off and you use a long posidrive screwdriver through the holes in the back of the case specially provided for the purpose to remove the beard fixing screws.

T'would be a shame to scuttle this amp and surely, if the techie mullered a good working channel, then surely he should personally take the blame for the channel he blew, even if the bad one was all but destroyed already!

There ARE real experts out there on this circuit, which has been extensively studied in the last 40 years (hell, my old Crowns use something not too dissimilar if cruder perhaps) and I don't think expensive or unobtainable parts were ever used (quite the opposite where supply caps are concerned methinks), so either get a pair of new boards or hope that Quad can sort the ones you have!

[istari_knight]

GOOD 405-2's tend to go for nigh-on £300 I thought?

Most sell for between £180-£220 IME. Maybe £300+ for a VGC example or if purchasing from a dealer with warranty & overheads...

As for servicing, QUAD are very reasonable compared to the likes of Cyrus / Naim et al.

[Lodgesound]

Just replace the entire module - cost around £90 - 130.

Amplifier in good order is worth £300 so worth doing - I would imagine the cause of the initial fault was one of the output or driver transistors going short.

In their AM 8/16 variant used for driving BBC LS 5/8 monitor speakers we charge a great deal more than this as they are crucial to the correct operation of said monitors.

As has been said already blanket replacement is not always a good idea - faults should be traced and eliminated one by one.

[Firebottle]

Dan, if you can remove the two pcbs and post them to me I will fix them for you at component cost only.

Cheers,
Alan

[The Barbarian]

People seem to get it in their head that buying old vintage gear would give you an high build quality item at a cheap price but im afraid that is you want the reliability to match a total re-build is in order. My amplifier cost me a paultry £35.00, the total cost for complete strip & total re-build cost me well in the region of £700.00 & that's doing it all myself. mad you might ask but this is the amp i wanted, i wanted the reliability. im 99.99% sure this amp will now see me out.

Buying & rebuilding vintage gear can cost more than buying new equipment.

[dantheman91]

Dan, if you can remove the two pcbs and post them to me I will fix them for you at component cost only.

Cheers,
Alan


PM sent. :)

[istari_knight]

Nice one Alan :clap:

[dantheman91]

Nice one Alan :clap:

I think i may owe Alan a pint or 5 in the near future. :)

Respect where its due :cool:

AOS is my home.

[Firebottle]

This is what you need to remove from the chassis:

http://photos1.blogger.com/blogger/1644/1858/1600/Boards_01.jpg

Cheers, Alan

[Firebottle]

Here are the two boards, now fixed and upgraded to latest spec.
Interesting for me as I'd not seen the mk 1 boards before.

Details for James particularly, there wasn't really that much wrong, the reason the resistors feeding the op amp were overheating was short circuit zeners. For anyone who knows the circuit that is one of the first things to check :doh: One of the op amps was duff as well.

http://i601.photobucket.com/albums/tt97/Paramotorpilot/P1040025.jpg

:cool: Alan

[dantheman91]

Here are the two boards, now fixed and upgraded to latest spec.
Interesting for me as I'd not seen the mk 1 boards before.

Details for James particularly, there wasn't really that much wrong, the reason the resistors feeding the op amp were overheating was short circuit zeners. For anyone who knows the circuit that is one of the first things to check :doh: One of the op amps was duff as well.

http://i601.photobucket.com/albums/tt97/Paramotorpilot/P1040025.jpg

:cool: Alan


Hi

Alan knows what he is talking about and like i said in previous emails MANY MANY MANY MANY THANKS :) Just need to work out payment and things and then we can get them on their way home :)

Thanks
Dan

[istari_knight]

Top job Alan :respect:


there wasn't really that much wrong, the reason the resistors feeding the op amp were overheating was short circuit zeners. For anyone who knows the circuit that is one of the first things to check One of the op amps was duff as well.

So much for replacing every transistor like the "tech" wanted... It still wouldn't have worked :rofl: I wonder...He sounds like a dabbler in too deep but possibly knows exactly what he's doing... Charge for complete replacement but in reality only replace £2 worth of parts :hmm:

Anyway, congrats Dan :)

[Barry]

Here are the two boards, now fixed and upgraded to latest spec.
Interesting for me as I'd not seen the mk 1 boards before.

Details for James particularly, there wasn't really that much wrong, the reason the resistors feeding the op amp were overheating was short circuit zeners. For anyone who knows the circuit that is one of the first things to check :doh: One of the op amps was duff as well.

http://i601.photobucket.com/albums/tt97/Paramotorpilot/P1040025.jpg

:cool: Alan

Good work Alan. The resistors feeding the op amp run close to their power dissipation rating (especially with the 12V Zeners). I had one go o/c on one of my 405s, so I both resistors were replaced with ones having double the dissipation rating.

[cloth-ears]

Quad 405, best power amp ever made

[dantheman91]

Quad 405, best power amp ever made

+1

[PaulStewart]

Quad 405, best power amp ever made

Yep, apart from the ones that were better :sofa:

[istari_knight]

Yep, apart from the ones that were better :sofa:

Ouch !

[cloth-ears]

Yep, apart from the ones that were better :sofa:

I can see why valve owners don’t like them. It is hard to cope with an amplifier that doesn’t distort, fizz or ring. Quad 405 “The closest approach to the original sound”

[Firebottle]

Bob you're not using the right valve amps :eyebrows:

Personally I think the 306 beats the 405 by a small margin.

Cheers,
Alan

[cloth-ears]

[QUOTE=Firebottle;564108]Bob you're not using the right valve amps :eyebrows:

What, there’s a valve amp that distorts less than a 405. I could never understand why seemingly intelligent people believe in god, or valve equipment. The evidence is available yet still they believe.

[istari_knight]

I think overall I prefer the 303 but am yet to try a 405-2, hmm :bulb:

[The Barbarian]

I think overall I prefer the 303

O yes

:peace:

[DSJR]

In my experience and therefore opinion, the 606mk2, 707 and UK made 909's were Quad's best (I don't think the 520f is far behind though). Easy 4 Ohm driving and decent power output, these did make passive-speaker driving a rather easier experience, as the 405-2 was still hobbled in design by the pitiful heatsinks fitted. The op-amp was also moved away from the signal path in the 606 too I think, reducing noise and distortion even more.

I haven't heard the current 606 derivatives, but see no reason why these aren't good too, despite Stan-the man tweaking them...

[istari_knight]

520F is a good shout. Had one that came out of a local cinema which I should have held onto :rolleyes:

[The Barbarian]

The '240' are ok i had one in my Synthesizer rig years ago..

[Barry]

520F is a good shout. Had one that came out of a local cinema which I should have held onto :rolleyes:

Still use one in my second system.

[Barry]

In my experience and therefore opinion, the 606mk2, 707 and UK made 909's were Quad's best (I don't think the 520f is far behind though). Easy 4 Ohm driving and decent power output, these did make passive-speaker driving a rather easier experience, as the 405-2 was still hobbled in design by the pitiful heatsinks fitted. The op-amp was also moved away from the signal path in the 606 too I think, reducing noise and distortion even more.

I haven't heard the current 606 derivatives, but see no reason why these aren't good too, despite Stan-the man tweaking them...

For a 100 watt/channel amplifier, the heatsinks on the 405 and 405/2 are on the small side. However the ostensibly larger heat sinks on the 606 are there because the power output is 50% greater.

In the 606 the op-amp is in the feedback loop, with it's ouput connected to the base of the first long-tail transistor pair at the input. So in some ways, the op-amp can be said to be in the signal path.

A fully-fettled 405 or 405/2 remains an excellent and fine-sounding power amplifier. The 520, 606, 707 and 909 designs are/were simply developments of the 405 circuit; usually with the doubling or tripling of the ouput devices to increase the power output.

These days I wouldn't touch a 606 amp that had not been made in the UK. Since Quad were bought up by the Chang brothers, locally sourced (and inferior) capacitors are now being used in the construction of the later power amp designs; much to the detriment of the sound quality.

[PaulStewart]

I can see why valve owners don’t like them. It is hard to cope with an amplifier that doesn’t distort, fizz or ring. Quad 405 “The closest approach to the original sound”

I use valves on my main system 'cos I like the dynamics and detail, I have always found the 405s to be bland. But I use Yamaha P2075s, I have three of them at the moment and I own and use, Amcron, Arcam, NAD, Sony, JVC, Denon and a pair of Quad 50e monoblocks, all of which I think come "closer to the original sound" than the 405 or 405-2 because of their better dynamics.

Frm Quads own range I think the 303, and 306 are better products, tend to blow up less too :)

[The Barbarian]

I use valves on my main system 'cos I like the dynamics and detail, I have always found the 405s to be bland. But I use Yamaha P2075s, I have three of them at the moment and I own and use, Amcron, Arcam, NAD, Sony, JVC, Denon and a pair of Quad 50e monoblocks, all of which I think come "closer to the original sound" than the 405 or 405-2 because of their better dynamics.

Frm Quads own range I think the 303, and 306 are better products, tend to blow up less too :)

I still have a pair of 50E power amp, they are good, it took me ages to get a mint set of Plessey/Jones Input/Output connectors for em..Great amps they will drive virtually any load you throw at them..One of the most reliable & bomb proof amps on earth..

[PaulStewart]

Great amps they will drive virtually any load you throw at them..One of the most reliable & bomb proof amps on earth..

About 25 years ago I had a lovely pair of Audiostatics, sounded great but a bitch to drive and they blew up an Exposure X and a pair of bridged MF p-150-Xs. A mate at the BBC brought round a pair of 50Es, tried them out and bought the ones I still have 3 days after that. Tried them last week with the Spendor BC1s and they sounded great. :)

[The Barbarian]

Mine came out of some theatre in London apparently, their was not a single mark on them apart from a tiny chip in the paint on one of the heat sink fins..

The only issue i had when servicing them was a bad burn on the power board of each made by a power resistor, scorched but the tracks around he area & PCB are still ok. Ive replaced the resistors now & lifted them away from the PCB. Apparently rumour has it that Britsh Rail used to use the '50's so im guessing that a large amount of these amps may have possibly been skipped years ago.

[Barry]

British Rail did indeed use Quad 50s for their public address system. Mine are ex-BBC (surprisingly they are 50Es, rather than the customised 50Ds), so use a Cannon mains connector rather than the Bulgin type.

Quad gear is still used by the BBC and the 510 power amps are used for the sound reinforcement at the House of Commons. My local film club uses 510s for the cinema sound.

[dantheman91]

Hi Guys

Just an update the boards arrived home safe this morning have now fitted them checked and double checked and re fitted the and its now working again although the hum that was repaired previously has reappeared again :rolleyes:. Alan's work looks great and done a superb job and this is nothing to do with him and indeed MANY MANY THANKS. I have tried a new 5 pin din cable nope its still there although somewhat louder then was previous and Audioble through quiet passages of music. Any thoughts as gradually losing the will with this one think i'm gonna store it in my room till i decide what to do with it there's only so much money you can put into something. Any thoughts.

Thanks
Dan

[spendorman]

Have phono input sockets been added? If so, these might be the problem. I'm assuming the hum is through the speakers and not mechanical vibration of the transformer, which was a point on some 405's.


Hi Guys

Just an update the boards arrived home safe this morning have now fitted them checked and double checked and re fitted the and its now working again although the hum that was repaired previously has reappeared again :rolleyes:. Alan's work looks great and done a superb job and this is nothing to do with him and indeed MANY MANY THANKS. I have tried a new 5 pin din cable nope its still there although somewhat louder then was previous and Audioble through quiet passages of music. Any thoughts as gradually losing the will with this one think i'm gonna store it in my room till i decide what to do with it there's only so much money you can put into something. Any thoughts.

Thanks
Dan

[dantheman91]

Hi Alex,

No phono sockets just a standard din as its an early 405 MK1. Ive not tried it with just pre and power with nothing connected to it ie cd player or whatever. I don't really want to be mucking about with it as ive done to much of that already and don't want anything else to go on it. Thanks though :)

[The Barbarian]

Something that people seem to do with Quad sets sometimes over earth them.. What you using with the '405' a '33'?

Just check if it hums on both Turntable & Aux {CD} first

[istari_knight]

If its humming with no input connected then it sounds like an internal grounding issue for sure, unless... if its a 50Hz hum old reservoir capacitors could be possible culprits.

[dantheman91]

Something that people seem to do with Quad sets sometimes over earth them.. What you using with the '405' a '33'?

Just check if it hums on both Turntable & Aux {CD} first


Yep 33 & 405. Just need to cover all areas when i get round to hooking it up again.

[dantheman91]

If its humming with no input connected then it sounds like an internal grounding issue for sure, unless... if its a 50Hz hum old reservoir capacitors could be possible culprits.

Hi James,

Shall i take pictures of what i have done just to make sure ive not done anything wrong.

[The Barbarian]

Yep 33 & 405. Just need to cover all areas when i get round to hooking it up again.

You cant have the Power amp & the pre amp earthed to the mains with a earthed interconnect lead it will hum.

[The Barbarian]

Dan

3 Core Mains lead for the '33' Pre amp into the wall
2 Core Mains lead connects the '405' to switched main out on the back of the '33'

The '405' will then get it's earth from the 4 Pin interconnect lead that connects the '33' to the '405' The rig then uses the '33' volume control/power swith to switch it on..

[dantheman91]

Dan

3 Core Mains lead for the '33' Pre amp into the wall
2 Core Mains lead connects the '405' to switched main out on the back of the '33'

The '405' will then get it's earth from the 4 Pin interconnect lead that connects the '33' to the '405' The rig then uses the '33' volume control/power swith to switch it on..


Hi

Yep that's the way i do it..unless i'm missing something :scratch:. i will try MY 33 sometime just to check and see if its any better with that. They do have a normal "Buzz" some say but i think this is defiantly an earthing issue.

[istari_knight]

By all accounts C5 [100uF/6.3v] is the single most common cause of hum in 405's.

[The Barbarian]

But i thought Dan said 'hum that was repaired previously has reappeared again'

[istari_knight]

But how & by who ? I think he needs to test both the 33 & all the cabling by replacing the 405 with his 303 and seeing if the hum remains... At least then we can eliminate them as possible sources.

[The Barbarian]

But how & by who ? I think he needs to test both the 33 & all the cabling by replacing the 405 with his 303 and seeing if the hum remains... At least then we can eliminate them as possible sources.


Hi Guys

Just an update the boards arrived home safe this morning have now fitted them checked and double checked and re fitted the and its now working again although the hum that was repaired previously has reappeared again :rolleyes:.

There ^

Yeh i recon he ought to firstly try both Records & Aux {CD} source on the '33' connected to the '405' if they are both humming it aint a Turntable lead issue. Then swap out the '405' for the '303' if it's still there it has to be an interconnect or mains lead issue.

[spendorman]

Could be an earth loop, anyone suggestions? I know what I would try, but I won't recommend it.

[The Barbarian]

Has to be Alex..

[istari_knight]

if it's still there it has to be an interconnect or mains lead issue.

Its highly likely, if they're old & have been recently disturbed... I suffered with endless din cable problems until I got so fed up of it I threw them all away & assembled new.

[spendorman]

I've not checked previous posts, but a first step would be to run the power amp with speakers and nothing connected to the din input socket. Like this is hum still present?

[dantheman91]

Hi Lads

Thanks for all suggestions will look at it later on next week to try an eliminate most cables are new including 5 pin dins and 4 pin to 4 pin from sounds heavenly. I need to eliminate by first trying my 33 which has also been serviced as has the one i'm using at present just confusing because yes its had work to cure the hum issue which indeed worked for a time until the left channel went just close to giving up with this one it works then something else goes wrong which for quads if pretty unusual which is why it was probably cheap in the first place i spent £145 on the 33 FM3 and 405 with B&W DM2 speakers plus and extra £90 to have the previous work done + £20 to get the PCB boards done and there fine maybe i should just cut my loses really not sure this was an Xmas present for my father and its caused nothing but problems. Will look again next week just having a break from it for no as too much stuff going on in life.

Thanks for all reply's though helpful to use next week

Dan

[dantheman91]

Update.

With no input and output lead connected between the 405 and 33 it still hums i have also tried without any aux or phono connected and its still the same powered from its own main cable to wall to power the 405 separate. Maybe i'm being fussy and should just put with it? Tried my 33 and its still the same this is with powering both 33 & 405 with the main output and 4 pin din connected to the input and output. :doh: so it lies with the 405 somewhere.

Any further thoughts unless ive not done something right inside pics below. All was reconnected via the pictures it took previous to taking the boards out.

Thanks

[spendorman]

Sorry to be a a pain, but is the hum through the speakers?

[dantheman91]

Sorry to be a a pain, but is the hum through the speakers?


Hi Alex

Yep hum through speakers sorry should of said not sure if its mechanical........not using anything decent just a pair of teac ls-x8mk2 unless its picking up frequency from the solid metal cabs?

[spendorman]

A slight aside, from the pics it looks like the speaker protection board that is fitted to most 405's is not there. It is located on the back of the speaker terminals, and is a crowbar circuit. I bought my 405 new when they first came out, and that had the board. Apparently, some very early ones didn't.

[spendorman]

Disconnect the speakers and hear if the hum is still there.


Hi Alex

Yep hum through speakers sorry should of said not sure if its mechanical........not using anything decent just a pair of teac ls-x8mk2 unless its picking up frequency from the solid metal cabs?

[dantheman91]

Back to the drawing board sending it off to get it looked they have agreed to look at it for free he has 25+ years experience and deals with quads in his daily work also a good friend of my dads too. Although i'm sure i have done something wrong and advised on him checking it inside before trying it for reassurance and i'm confident that its nothing to do with Alan's work. Got to stick with it i have decided these old bastards are funny but once up and running again i shall be :)

[The Barbarian]

As i said before Dan get yourself on an Electronics course buddy, it will save you tons of time money & grief..

[istari_knight]

Good on ya Dan. Although its turned into a money pit at least nobody can call you a quitter ! :D

[The Barbarian]

You know that jinxed English Electric Type 4 Diesel locomotive that was involved in the early 1960's train robbery, well other than the robbery it was nothing but trouble with accidents before & after that.Well they scrapped it in the mid 80's..

[Macca]

You know that jinxed English Electric Type 4 Diesel locomotive that was involved in the early 1960's train robbery, well other than the robbery it was nothing but trouble with accidents before & after that.Well they scrapped it in the mid 80's..

...And some of the steel got recycled into the case of Dan's QUAD. I see where you are going with that. Dan you don't need an engineer you need an exorcist.

[The Barbarian]

:rfl:

[dantheman91]

Update chaps its back on form working again :) The first tech took 2 screws from the base of the transformer these earth the front and the back of the chassis together :)

Cowboys the world is full of them..........any local lads BEWARE of john Benton.......

[Firebottle]

Excellent Dan

[dantheman91]

Excellent Dan

Hi Alan

I would like to take this opportunity to THANK you again for your brilliant work and co operation indeed your a guy with talent and how knows how to work properly and takes pride in doing so. I hope you bought yourself a beer or 2 :respect::champagne:

Thanks Again
Dan

[rangioran]

Having read through all of this thread, having a problem that could almost share Dan's title, I hope that adding to the end of a successful conclusion isn't considered 'bad form'?

I have a 405-2 (that I'm about to upgrade with the Dada kit and two new sets of MJ15003 output transistors when they arrive) that's suddenly begun losing the left channel after approx seven minutes playing. Quite suddenly the left channel appears to quit but if I crank the balance hard over and (carefully) increase volume there's something there, albeit very muffled and crackly?

I figure that (hopefully) the upgrade (including main caps and op-amps) as well as the new output pairs will probably fix it, but has anyone got any theories?

Thanks

Eric

[DSJR]

Got to be dry joints I reckon. I have a lot of respect for Dada, who don't seem to rip you off (they need to make a living so only add a nominal amount to their (bulk) component costs I think. There are fuses on the board which may have aged and popped for no real reason (Arcam A60's did this all the time). It was recommended to me that OPA134's were as good as anyone would need for audio, although it's the 604 and family that seem to be used now. It has been suggested that the 604 and over have too wide a bandwidth and can cause instability in some situations, but I never tried it in the 405-2's I once had, both with then brand new replacement Issue 7 Quad boards (I read Quad are on issue 10 now and they're over double the price they were).

Good luck ;)

[rangioran]

Hi David,

You may well be right about it being a dry joint, although, the seven minute thing is a bit puzzling. Certainly not the fuses, first thing checked and re-seated. When it's working it's almost subliminal, just missing it at the moment.

[tubehunter]

Hi Eric

You say you crank the balance control!

I presume you have a preamp, possibly the quad 34 as this particular preamp has a cheap notoriously unreliable balance control.
Your symptoms point to this.
I have repaired a few of these and it's not a complicated job.
If you don't use the balance control you can just bypass it.

Duncan

[rangioran]

Hi Eric

You say you crank the balance control!

I presume you have a preamp, possibly the quad 34 as this particular preamp has a cheap notoriously unreliable balance control.
Your symptoms point to this.
I have repaired a few of these and it's not a complicated job.
If you don't use the balance control you can just bypass it.

Duncan

Hi Duncan,

Yes it is the 34 that I'm using. When the channel goes dead winding the balance hard over to the suspect channel results in a very low, distorted output. More inclined to think that the control itself is OK and the problem is in the 405, but not investigated any further as I'm waiting for the Dada kit to arrive before pulling it apart.
Hopefully the kit (less output transistors) will be here this week and I'll have a better idea then. Just checking to see if anyone here had come across anything similar.

[rangioran]

Ruled out 34 pre-amp yesterday and the problem is soooo repeatable - performs perfectly and then seven minutes after switch on the left channel disappears, every time!

[Desmo]

This sounds like a capacitor problem to me. The dada kit will probably resolve the problem when you fit it.

[rangioran]

This sounds like a capacitor problem to me. The dada kit will probably resolve the problem when you fit it.

Hi Graeme,

That's what I'm hoping, ordered the two kits (34 and 405) last week, was hoping they'd have been here by now.

[DSJR]

IMO the 405-2 can perform far better than the 34 allows it (Harbeth's AS shakes his head in total disbelief :)). While you're servicing the pair, have a look at gain from both and see if the 405-2 performs batter by reducing the gain a little (as the 303 can and does) and if the 34 wakes up a bit (as the 44 did) if the output is increased (early 44's had high output phono's on the board). probably a load of nonsense, but worth investigating.

P.S. We used copious cans of freezer-spray precisely for this kind of fault. A quick spray usually showed the culprit ;)

[Light Dependant Resistor]

IMO the 405-2 can perform far better than the 34 allows it (Harbeth's AS shakes his head in total disbelief :)). While you're servicing the pair, have a look at gain from both and see if the 405-2 performs batter by reducing the gain a little (as the 303 can and does) and if the 34 wakes up a bit (as the 44 did) if the output is increased (early 44's had high output phono's on the board). probably a load of nonsense, but worth investigating.

P.S. We used copious cans of freezer-spray precisely for this kind of fault. A quick spray usually showed the culprit ;)

I agree, the 405 is quite capable, the standard opamp implementation is poor though. it has a very cheap resistor zener diode
supply delivering 15v +/- and 12v+/- in very early 405's. Keith Snooks pages and implementing the op amp
as non inverting yields good result. The Net audio Mk3 implementation is inverting but great care with PSU and
I think one of the best 405 improvements you can make.

There are much better ways of doing attenuation than a 34 and LDR's are a
logical choice being contact less attenuation.

I also have a 34 with balance issues, so must rewire it to accept NSL32SR3 LDR's I am presently using a 33
as an LDR pre retaining the great look of the classic Quad era but sounding so, much better. :)

[PaulStewart]

There are much better ways of doing attenuation than a 34 and LDR's are a
logical choice being contact less attenuation.

Leaving aside the fact that LDRs compand and should, in my opinion never be used in a high fidelity application, I think that to "shill" your products on a thread about something else is very bad form.

[Marco]

Yeah, I wouldn't go as far as shilling, but your recommendation is probably a little out of place here, Chris. If you're going to 'sell' your products outside of the trade area, then they really need to be on threads where the OP's chosen discussion topic is directly related to LDRs.

Cheers! :cool:

Marco.

[Light Dependant Resistor]

Leaving aside the fact that LDRs compand and should, in my opinion never be used in a high fidelity application, I think that to "shill" your products on a thread about something else is very bad form.

There are many manufacturers of LDR products, I am not the only one, mentioning LDR's gives equality
that they are simply an audio device amongst many others, such as transistors, op amps fets, capacitors resistors.etc.

Paul I think this IS bad form attached to each of your posts. "Rebirth Of The Cool Visit our eBay store"

[Marco]

Chris, I've sent you a PM about this. Paul has done nothing wrong.

Marco.

[Light Dependant Resistor]

Leaving aside the fact that LDRs compand and should, in my opinion never be used in a high fidelity application, I think that to "shill" your products on a thread about something else is very bad form.

Companding is method to preserve dynamic range, not recognising its ability to do that is akin to preferring reproduction and
capture from ( in the case of digital ) lower bit recorders 14 bit as example. There are probably some very nice 14 bit recordings
but a quad 405 will no doubt sound better if provided source material that was captured as 20 bit or 24 bit capable.
You are then strangely critical of many recordings made with Dolby which is a compander.

[PaulStewart]

Chris,

This in ot the thread to discuss this but, the idea of "High fidelity" is to be faithful to the original, the clue is in the name. When REPRODUCING music the idea, as far as audiophiles are concerned surely, is an accurate representation of the product released by the musician/producer/Mastering engineer, not an arificially enhanced version there of. LDRs are non linear and do not belong in a reproduction chain, their use or the use of any other companding device in a PRODUCTION chain is a completely different kettle of fish, there the effect is a part of the intended sound. Pretty simple really, do try to keep up.

[Light Dependant Resistor]

Hi Paul
Companders are used to preserve dynamic range, not change the sound in any way, I thought you would have known that.
Just using compression or gates for effects Yes can be done but companding when I discuss that term is all about
preserving dynamic range, are we on the same page now ?

[PaulStewart]

Hi Paul
Companders are used to preserve dynamic range, not change the sound in any way, I thought you would have known that.
Just using compression or gates for effects Yes can be done but companding when I discuss that term is all about
preserving dynamic range, are we on the same page now ?

Yes I know Chris, ypu must be right, you're an "Expert". I guess my time studying for my BSc in physics and the doctorate were just plain wasted. I suppose that the years spent working for an international electronics company, an audio and video company by the way, was wasted too. Yes because you are right, I'll right off the many moons spent as a special audio effects designer and supervising tech (where BTW I used companders a lot). I guess my time as a record producer and recording engineer was all a waste 'cos I'm not an expert like you :laugh: On the same page, I don't think you know the language to read the book sonny jim :) Anyway I'm outta here

[rangioran]

IMO the 405-2 can perform far better than the 34 allows it (Harbeth's AS shakes his head in total disbelief :)). While you're servicing the pair, have a look at gain from both and see if the 405-2 performs batter by reducing the gain a little (as the 303 can and does) and if the 34 wakes up a bit (as the 44 did) if the output is increased (early 44's had high output phono's on the board). probably a load of nonsense, but worth investigating.

P.S. We used copious cans of freezer-spray precisely for this kind of fault. A quick spray usually showed the culprit ;)

Odd isn't it, using freezer spray to locate intermittent faults such as this was second nature back (way back!) when I was an engineer, thanks for the reminder :-)

[Firebottle]

Freezer spray is very good at getting the heat out of soldering iron burns.

Spray on the burn until you can't stand the freezing cold, possibly with a second application if the burn still hurts :mental:

[rangioran]

Freezer spray is very good at getting the heat out of soldering iron burns.

Spray on the burn until you can't stand the freezing cold, possibly with a second application if the burn still hurts :mental:

A good tip, I'll keep that in mind.

I saw your helpful comments earlier to Dan the Man re his 405 problems, hope that I can call upon your knowledge if I run into any problems getting the 405-2 updated?

[DSJR]

Old B&O centres with cramped circuit 'environments' could often only have intermittent faults traced using a freezer spray...

[rangioran]

Old B&O centres with cramped circuit 'environments' could often only have intermittent faults traced using a freezer spray...

Too true, I was working for a company name of Millwards in Wolverhampton and they were one of the first B&O dealerships in the UK. I remember we packed the Wolverhampton Civic Hall one evening just demonstrating B&O. Also had a Beomaster 1000 and Beogram 1000 in those early days - looked super alongside Sugdens and Rogers but really was a pig to work on.