Please help, I've wrecked my Beresford

Hello everyone, my first post and all. Great forum, so many interesting things here.

I'm new to the audio mod stuff and I tried to mod21 (http://www.beresford.me/Downloads/Mod21.pdf) my Beresford and it didn't like it, so now I've got two of them. I'm terrified to try anything with the 2nd one at least until maybe I can figure out what went wrong with my first attempt.

What happened is right after I performed the solder bridge part I hooked it back up and tried it out. It started playing initially, then after about 20 seconds the left channel started crackling, then quit. I'm pretty sure I didn't burn anything up with the iron and I checked the connections with a ohm meter and they seem to be sound. But I don't really know where to start troubleshooting this.

If you guys have any ideas for me to try your suggestions would be greatly appreciated.

Can you take an in-focus close up shot of the inside and post it?

Did you get the 'lytic caps the correct way round?

Quote:

---

Originally Posted by jgarner71

Hello everyone, my first post and all. Great forum, so many interesting things here.

I'm new to the audio mod stuff and I tried to mod21 (http://www.beresford.me/Downloads/Mod21.pdf) my Beresford and it didn't like it, so now I've got two of them. I'm terrified to try anything with the 2nd one at least until maybe I can figure out what went wrong with my first attempt.

What happened is right after I performed the solder bridge part I hooked it back up and tried it out. It started playing initially, then after about 20 seconds the left channel started crackling, then quit. I'm pretty sure I didn't burn anything up with the iron and I checked the connections with a ohm meter and they seem to be sound. But I don't really know where to start troubleshooting this.

If you guys have any ideas for me to try your suggestions would be greatly appreciated.

---

Post a couple of close up pics and we'll first see if we can see anything obvious .

I don't have one of these dacs but should be able to spot anything that looks suspicious

What I'd do is check the signal lines on a scope from the dacs output pins and further up stream

If you changed the capacitors as in the mod21 pdf be sure they are in the correct way around

The op-amp may have blown on one side, this can be caused by shorts or over heating of the pins

The dac chip may have blown its left side (unlikely)

There maybe a tiny intermittent solder short

If you give up and feel like binning it , sell it me;)

Boy oh boy am I glad I got Stan to do mine.....
I learnt my lesson trying to mod a Trends amp with the Audiomagus kit-I had to send it off to get almost completly rebuilt.
Good luck

Quote:

---

Originally Posted by NRG

Can you take an in-focus close up shot of the inside and post it?

Did you get the 'lytic caps the correct way round?

---

Everyone thanks for the replys. Attached is a photo. I don't think I broke anything, but who knows. The small wire is a silver plated copper strand I used to bridge the gap. If I leave it on for a while I can start to hear it sputter through the left channel once in a while like it's trying to come back to life. The right channel sounds fine though.

The problem happened before I changed the caps, but now I have changed them to 47uF/16v and double checked to make sure they are positioned the same as in Stan's pdf.

When the sound goes down do you still get DC voltage to the coupling capacitor on the faulty side? does it measure the same as the side which is ok

Maybe you could remove the output coupling capacitors and run a wire from the coupling capacitors before the op-amp to the neg marked hole of the output capacitors if that makes sense? you then would be bypassing the active op-amp output stage

If it works this tells us the dac chip is ok and the fault is around the op-amp

Also carefully check the solder joints on the phono sockets etc, its possible there was a weak solder joint and after doing the mods it could have upset it

I presume theres no sound on the same channel headphone outputs or variable out?

Quote:

---

Originally Posted by jgarner71

The problem happened before I changed the caps, but now I have changed them to 47uF/16v and double checked to make sure they are positioned the same as in Stan's pdf.

---

Doing half the mod first is the likely cause. The 4558 might have done a Luke. The mod21 involves changing the output stage configuration and biasing method. You are going to need a scope to check if the audio signal on the output of the PCM1716 is OK, and if it is also OK in and out of the 4558. I reckon Leo would figure that out in less than 5 minutes;).
My advise: don't tamper with your other TC-7510, cut a deal with Leo, and take up the AoS member's offer on the TC-7520. And leave the latter well alone mod wise...

Stan

Leo, Stan Thanks for stopping by. I've been reading a lot from you guys and got really interested in this stuff.

I don't have an oscilloscope or anything like that, just a mulitimeter. I guess I can try measuring the DC voltages from side to side. Maybe I'll see something that's obvious even to me.

It's worth $5 for me to stop by Akihabara and pick up a couple of chips to try out. If it's the opamp I might be ok, but if it's the dac chip I think I'm doomed. I don't have the finesse to change that out. So for that reason I'm hoping it's just the opamp that's the issue here.

Oddly enough, when I got home from work I turned it on just to see and both channels were playing! But it was pretty distorted and after about 1 minute I could hear it starting to fade out so I just turned it off. Guess it's time for more probing...

Sounds like a faulty component to me, either op-amp or dac chip

Does the op-amp get warm/hot ? its going to be harder without a scope, you may have to resort to changing parts until you come across the fault.

If one channel is ok this tells me the regulation is probably ok.
When the music on the faulty channel goes off, do you hear any hum or buzzing on that channel?

Quote:

---

Originally Posted by leo

Sounds like a faulty component to me, either op-amp or dac chip

Does the op-amp get warm/hot ? its going to be harder without a scope, you may have to resort to changing parts until you come across the fault.

If one channel is ok this tells me the regulation is probably ok.
When the music on the faulty channel goes off, do you hear any hum or buzzing on that channel?

---

Leo, Leo, Leo! Just on a hope and a prayer I took a trip and picked up an LME48720 (the only thing the shop had that said might work), cut the old one out and popped it in and now I'm back in business! :) Lucky!

I've only been listening for 20 minutes, but I can't say that the 48720 sounds that much better than the original. Not too bad though and at least I know what the problem was now.

Thanks everyone for the help with troubleshooting. Stan, I recommended the 7520 to a friend that's using a fubar in his setup. I'll be getting more of your products in the future I'm sure!

Excellent stuff! Thats great news:)

Good to read you got it working! The LM4562 is worth looking at when you feel up to a bit more soldering. Works really well and is part of Stan's MoD21 part 2. Also you might want to junk the cermic bypass o/p caps, never found those to sound any good...

Quote:

---

Originally Posted by jgarner71

Just on a hope and a prayer I took a trip and picked up an LME48720 (the only thing the shop had that said might work), cut the old one out and popped it in and now I'm back in business! :) Lucky!

---

As I said, the 4558 might have done a Luke ( it went sky walking). Glad to know that was it, and that you are up and running again.

Stan

Looking closely at your pic, are you sure EC4 and EC5 are in the right way round? The stripe appears to be on the side facing the op-amp whereas on Stans photo it's on the opposite side. Assuming your caps stripe is marked as negative not positive.

He'd have to check, its hard to see the pcb marking in the pic

Are EC4/5 the ones at the bottom of the pic? I presume these are for the op-amps input? not having a dac to check I have to guess:)

Yes, bottom of pic. They are the input caps for the op-amp I believe.

See: http://www.beresford.me/Downloads/Mod21.pdf

The o/p seems to have them the wrong way 'round

Quote:

---

Originally Posted by NRG

See: http://www.beresford.me/Downloads/Mod21.pdf

The o/p seems to have them the wrong way 'round

---

Oh yes, can see it on there:lol:

Quote:

---

Originally Posted by ultraviolet

Looking closely at your pic, are you sure EC4 and EC5 are in the right way round? The stripe appears to be on the side facing the op-amp whereas on Stans photo it's on the opposite side. Assuming your caps stripe is marked as negative not positive.

---

Haha, I hadn't noticed that! :doh: But the pic I posted was before I did any changes to the caps, so that's the way they were when I got them.

Attached is a photo of my unmodded DAC. They are also the same way.

Should I turn these around to match the photo? :scratch:

I just checked around on the net and found that others are also the opposite of mine. Maybe someone that bought one in the past couple of weeks can compare to see if it's the same as mine? Thanks.

Quote:

---

Originally Posted by jgarner71

Haha, I hadn't noticed that! :doh: But the pic I posted was before I did any changes to the caps, so that's the way they were when I got them.

Attached is a photo of my unmodded DAC. They are also the same way.

Should I turn these around to match the photo? :scratch:

---

You have to turn them round as indicated in the MOD21 sheet. The sound difference is going to blow you away.
If I have to tell you why, I'll have to kill you afterwards just so you don't pass on my secret;).

Stan

Quote:

---

Originally Posted by Sensimilia

You have to turn them round as indicated in the MOD21 sheet. The sound difference is going to blow you away.
If I have to tell you why, I'll have to kill you afterwards just so you don't pass on my secret;).

Stan

---

...Because the caps came stuffed the wrong way 'round from the factory? ;)

There's 3.55v accross those caps (on my example) +5.5v opamp side and +1.95v on the other side so the caps need to be switched around as they are 'lytics.

Quote:

---

Originally Posted by Sensimilia

You have to turn them round as indicated in the MOD21 sheet. The sound difference is going to blow you away.
If I have to tell you why, I'll have to kill you afterwards just so you don't pass on my secret;).

Stan

---

Oh wow, ok. I'll switch them around. Good looking out to ultraviolet who spotted my mistake. :youtheman:

....Ah! I see the PCB Legend is incorrect....

Quote:

---

Originally Posted by jgarner71

Oh wow, ok. I'll switch them around. Good looking out to ultraviolet who spotted my mistake. :youtheman:

---

You didn't make a mistake, its not clear from the MOD21.pdf the need to rotate the caps and if you just followed the PCB legend then you will set the caps the wrong way 'round....just like I did. ;)

Single rail supply isn't it ;)

So as a guess there could be more people thats tried the mod21 and fitted the caps the wrong way around

I turned the caps around and like Stan said it has made a big, big difference. My dac is no longer "wrecked"! Thanks again everyone.
:gig:

Quote:

---

Originally Posted by leo

Single rail supply isn't it ;)

So as a guess there could be more people thats tried the mod21 and fitted the caps the wrong way around

---

My electrical engineer fitted the caps in the mod21 part one so positive is connected to positive and the negative to negative. it sounds good now but you've all confused me with the comments about switching the caps around .What does this mean?:scratch:

It means getting the polarity of the caps the correct way 'round.

The marking on the PCB for the positive cap connection of EC4/5 is incorrect so the cap needs to be fitted opposite to that of the PCB marking.

Quote:

---

Originally Posted by NRG

...Because the caps came stuffed the wrong way 'round from the factory? ;)

---

The mod involves changing the circuit configuration, and that also changes a number of DC voltage levels around the output stage. So those caps need to be reversed in order for them to remain properly biased.

Stan

Quote:

---

Originally Posted by NRG

It means getting the polarity of the caps the correct way 'round.

The marking on the PCB for the positive cap connection of EC4/5 is incorrect so the cap needs to be fitted opposite to that of the PCB marking.

---

Thats just great!! Stan said if we knew why they need to be opposite then he'd have to kill us! Well he can kill us without us knowing cause i now have the hassle of taking it back to the elec. engineer to reverse them and he already wants to kill me! Stan your little secret has caused me alot of grief!!
But in an effort to better myself I can see the funny side of it ......:lol:

So to get it right Finally for us electronic dumbos....

I now have to connect the the positive on both caps to the negative on the EC4/5 . is this correct now? And are the top caps okay are there any more surprises?:scratch:

Quote:

---

Originally Posted by Sensimilia

The mod involves changing the circuit configuration, and that also changes a number of DC voltage levels around the output stage. So those caps need to be reversed in order for them to remain properly biased.

Stan

---

All I've done is replace the opamp, output caps and EC4 and 5. R11 and 14 are still in place, theres nothing there I can see Stan that would change the DC offset... :scratch:

Incorrectly marked PCB's are nothing new - I am a telecoms engineer by trade, and one piece of equipment from Panasonic springs to mind.

On the training course for this piece of eqiupment it was pointed out that the jumpers on one of the cards was incorrect. Unfortunately the markings related to molex jumpers which had to be set correctly dependending on how the card was required to function. You had to set the card up to the opposite of the board markings.

The incorrect markings remained on the card for the entire time that the unit was in production.

Chris:)

Quote:

---

Originally Posted by Stratmangler

Incorrectly marked PCB's are nothing new

---

In this case, the PCB is not incorrectly marked. The MOD21 requires the caps to be swung round. If you look at the PCM1716 datasheet you'll see that the cap and the PCB markings are as per datasheet.

Quote:

---

Originally Posted by NRG

All I've done is replace the opamp, output caps and EC4 and 5. R11 and 14 are still in place, theres nothing there I can see Stan that would change the DC offset... :scratch:

---

:eyebrows:

Quote:

---

Originally Posted by kalozois100

I now have to connect the the positive on both caps to the negative on the EC4/5 . is this correct now? And are the top caps okay are there any more surprises?:scratch:

---

You got to take them out and rotate them by 180 degrees so that they appear to be incorrectly mounted. But if it sounds good already, why worry:)?

Quote:

---

Originally Posted by Sensimilia

You got to take them out and rotate them by 180 degrees so that they appear to be incorrectly mounted. But if it sounds good already, why worry:)?

---

Worry leads to an unpleasent state( and one cannot stay there indefinately), which leads to contemplation, which leads to action, which leads to an improvement( hopefully in practice) to the previous predicament. :)

Okay Stan the Main Man, i took the tc-7510 to the elec. engineer ( you ve heard so much about him i ll introduce him - he is Mario and he works in the army in communications. In the evenings his second job is fixing mobile phones. I was amazed watching him at work fixing mobile phone using a microscope to see and soldering at the same time!! Any way hes been a saint with all the mods hes done for me.) he said no problem to switch around the caps so off i went LIke a rat in a pied piper pantomine off to seek audio absolution.
After the electrical operation i got home and as Stan says i was blown away with the sound improvement. Most noticeable was the trebles being unbelievably genuine - the cymbals and snares being really clear and defined.
Also yet again a noticable improvement in stage presence and imaging.
The completed mod21 1 & 2 on the tc-7510 sounds very impressive now.........A warm thank you to Stan and all for the valuble help......:clap::clap::clap::clap::clap::clap:

Quote:

---

Originally Posted by Sensimilia

In this case, the PCB is not incorrectly marked. The MOD21 requires the caps to be swung round. If you look at the PCM1716 datasheet you'll see that the cap and the PCB markings are as per datasheet.

---

I hadn't gone through the rest of the thread properly - I see what you mean Stan.

Chris:doh:

I have moved from the "mod your Beresford 7510" thread to the "I've wrecked my Berersford" thread. :(

I'm really not good with lead free solder. Solder keeps getting stuck inside the hole after desoldering the component.

If you take a look at my board, I think i may have damaged the EC 8 and EC 9 holes.

Any help/advice is greatly appreciated!!!

This are my question.

1. Are there any connections from the top side of the board (surface mount side) to EC8 and EC9 ? I believe i see some tracks on the top side running to EC 8 and EC 9.

Also I've wrecked the copper tracks on the bottom of the board.

2. Can i just bend the leads and join them to CC1 and CC2 since I know that they're in parallel.

3. Can I take out CC1 and CC2 and place the EC 8 and EC 9 caps in their place since it's they're connected in parallel?

Busted EC8 and EC 9 holes

http://i44.tinypic.com/w9gy1w.jpg

Busted copper tracks

http://i42.tinypic.com/fo3s6c.jpg

Healthy Board (photo taken from freddiecas on another post)

http://i44.tinypic.com/2l87rif.jpg

It looks like you have torn the solder pad away whilst de-soldering the caps. If the caps at CC1 and CC2 are in parallel, then there should be no problem in joining them together with a bridge uderneath the board.

Quote:

---

Originally Posted by Puffin

It looks like you have torn the solder pad away whilst de-soldering the caps. If the caps at CC1 and CC2 are in parallel, then there should be no problem in joining them together with a bridge uderneath the board.

---

Hi Puffin,

Thanks so much for your quick reply!

So its OK that the holes on the top side of the board are busted?

Of course it has occurred to me that although continuity between EC8 and CC1 and the opposite 2 will be o.k you will have to make a bridge between the connections on EC8 and EC9 on top of the board where the holes are, as you say, busted!

You can do this by scraping some of the lacquer off the track you can see coming from the + and - holes and solder a thin solid wire to the copper track and solder it to the cap.

I would put a very small amount of super glue on the bridge and let it dry thoroughly, so that if you move the cap with the bridge attached, it will not (hopefully) rip the track up you have soldered to.

Quote:

---

Originally Posted by Puffin

Of course it has occurred to me that although continuity between EC8 and CC1 and the opposite 2 will be o.k you will have to make a bridge between the connections on EC8 and EC9 on top of the board where the holes are, as you say, busted!

You can do this by scraping some of the lacquer off the track you can see coming from the + and - holes and solder a thin solid wire to the copper track and solder it to the cap.

I would put a very small amount of super glue on the bridge and let it dry thoroughly, so that if you move the cap with the bridge attached, it will not (hopefully) rip the track up you have soldered to.

---

Thanks Puffin,
I'll have a go at it tomorrow. Need really nimble hands to solder a wire from a scratched off track to a capacitor leg in such a small space.

BTW, that's a very nice looking speaker you have on your avatar. After I've mastered soldering, I'm moving on to speaker construction. :lol: Look out for busted speakers in the near future!

The speakers were made with birch ply to the specs on the Fostex site (208 Sigma cabinet) a full range horn design. The drivers are Fostex 206E 8" full range. I have had them a couple of years now and will never get rid of them. By the way they weigh 65kg each.