Albarry M-408 repair and mods

[pulsestudio]

Hi Duncan, thanks for the info but I have already seen these circuits on the Italian site, the M-408 is a completely different ball game, and quite different to the M-1008 unfortunately, but I appreciate your help and time. I have been working on the duff M-408 for the best part of the day and I believe that I have now found the problem, there are 2x 0.22 ohm 4 Watt Welwyn resistors gone open circuit, one is fried, both output transistors TIP146 and TIP147 are reading around 1 ohm between collector and emmiter junction and the 2SC546 that senses the temperature of the output devices was totally cooked, all this adds up to a very sad amp, I have most of the parts so a rebuild will be underway when I get the Welwyn resistors from Farnell, I think I will eventually remove the protection circuit as a good colleague of mine has suggested that it does not really need it provided I don't try to run it into a couple of ohm load, so the day draws near for the final push to hear these birds sing again.
Thanks again Duncan for your offer of help, truly appreciated

Paul

[Dandy]

Hi Paul,

Only the "power" LED in the middle should be lit. The "protection" LED will only be lit when something has gone wrong e.g. shorted output.

Dave

[DSJR]

When you have the amps dismantled Paul, any chance of some pics to go with the others here, so we can all see the differences in their layout?

[pulsestudio]

When you have the amps dismantled Paul, any chance of some pics to go with the others here, so we can all see the differences in their layout?

Hi Dave ( Dandy ), thanks so much mate, that has confirmed my thoughts 100%, many thanks.

Hi David so you want to see my poor old Albarry innards?? these are the M-408 mono blocks as you know David, I fully intend to reverse engineer the complete circuit for all to see at some stage, and finally get some form of technical history for these old retro classics, but first I must get the broken one un-broken, I have all the parts to afford the repair now so maybe tonight if I feel in the mood to do the swap out.
I will post some pics of the innards of the M-408 mono block and DMP1 pre-amp in a bit, need to upload them to photobucket
paul

[pulsestudio]

Albarry M-408 Series II mono bocks internals:







Albarry DMP1 will be posted later

Paul

[pulsestudio]

Albarry DMP1 Pre-amp innards:

Original look of the pre-amp and power regulator boards:





Now remove these horrible things: and replace with Panasonic FC for the large 4700uF and Panasonic NHG's for all the others.



And leave it looking like this:





That's it, I will post the circuit when it has been done, and that will be a few weeks away yet.
Paul

[pulsestudio]

You may remeber that I have been searching for a pair of the Albarry M-408 mono blocks for some time, well I eventually got a pair albeit one was smoked, so a repair was needed to get them singing as a pair again, so I set about the repair and a total upgrade for these old 80's classics, and this is whhat they look like now that both amps have undergone surgery.





Doncha love em !! well OK maybe not, but for me they represent an era in the 80's that was all a little too, well brilliant in the world of hi-fi.
It has been an uphill struggle to get them this far, I have re-capped the 2x M-408 mono Blocks and the DMP1 pre-amp, the smoked mono block had both output transistors and the thermal compensation transistor cooked, repaired, re-capped, rewired and generally cleaned that one up and set up the bias and then the other one smoked, they had been in a damp storage unit for some time before I recieved them, so after a few weeks of slogging over a hot Weller they are both now up and singing. I am not going to offer my verdict yet as it is early doors, and I have to re-arrange my lounge set-up a bit, so a full review in a couple of weeks, hopefully!! that is if they survive long enough
Paul

[Spectral Morn]

Nice job.

I remember Albarry as the shop I worked in as a Saturday boy used to do them...but stopped for some reason. I can't remember what they sounded like at all...I can't even remember if I ever heard them....but I saw them. I love the look of them...simple understated and classy. Love the red acrylic.

Very nice photos too.


Regards D S D L

[pulsestudio]

Yes you may have guessed !! the M-408 that was originally dead, has now phizzed, crackled, burning smell and smoked again, this all happeded the other night I simply powered up the pre-amp followed by the M-408 mono blocks and bang I am totally gutted after spending a month getting everything rebuilt and re-capped simply for this to happen on power up.

I have removed the offending 408 amp board and again the 2x output devices are an almost dead short across the collecter/emitter junction as too is the thermal auto bias transistor, I am now debating whether to replace the Albarry designed/built amp boards with a pair of Avondale NCC200 amp boards in both of the M-408 mono blocks. I have built many NCC200 amps and they are superb, and they don't smoke being a very stable deriative of the original RCA design as used in many Naim amps, I really would have liked to get the Albarry amps running just to have something that was typical of the 80's era but with the almost unpredictable reliability factor of these amps in question, is it worth it ??

I would love to hear from anyone out there that has a pair of Albarry M408's in good running order that may be prepared to offer me some help with the bias setting as I feel that this may not have been set correctly by me, I did set it to 5mV across the 0.22 ohm emitter resistor which would yeild a bias current of around 20mA, does anyone know if this is correct?? could you possibly check it on your M-408's and advise me what they are reading, or even loan me a single M-408 to carry out some tests on, just so that I have the correct voltage/current set-up on my amps, anyone to my rescue please, I am more than prepared to pay for any time and expences incurred as a result of any info provided, so please can anyone help here?
many thanks
Paul

[DSJR]

What on Earth happened to the chap who designed (?) and built them? I hope he's still around, but possibly someone may be able to contact him. I did check with HiFi Dave but he couldn't help (and is away for a short while now).

Good luck Paul......