Sugden A88

[Jo90]

Hi, I bought this very rare 110v A88 for spares to repair a broken 240v one. Because of it's voltage, it had not , I think, been used much. The nextel was all gloopy and it looked terrible. I converted it to 240 volts, according to helpful instructions from Sugden. Unused for many years, it worked beautifully first-time (after passing the light-bulb test)! A tribute to Sugden build quality! The sound is sublime- clearly Sugden, but also very fast, a bit like Naim! It's a slightly odd design, I think, with 2 transformers (in series?), and puts out 80w into 8 ohms and 150w into 4 ohms. Patrick Miller at Sugden told me that they had been specially made for export to Nigeria, but the buyer was fraudulent, so they were sold in the UK and US markets for a brief period instead. Sonically it is just excellent! I am working from an A44 schematic, which is similar, but with only one transformer. I have 2 amps to make one out of, one working nicely (though with a slightly quiet left channel) and one very battered and intermittent. I am not brilliant at electronics, but really want to restore one to perfection. I have 4 questions, firstly does anyone have any recommendations about capacitor make to preserve the sonic signature? Secondly, does anyone know where one could get small bits re-coated with nextel (or should I just go with paint or powder coating?), thirdly, how do you re-label the dials on the front after re-surfacing the coating? I could just try to re-case it all, but that seems wrong really! I have included some pictures! Thanks for any help or comments
Jo

[AMV8]

Hi
I have a Sugden A44 which was damaged in moving house and I have not got around to repairing it. I am unsure about your quoted power outputs. I believe the A44 is around 25 watts with some 5 watts in class A.. The A44 is a Class AB design whereas most of the better known Sugden amps are single ended class A.
For capacitors it would help if you posted a schematic as some of the electrolytic capacitors on the pcb could either be replaced by or paralled by polypropylene capacitors. Otherwise I would replace all electrolytics on the pcb with Elna 105 degree electrolytics. The power supply electrolytics could be Kendeil or another good make such as Elna.
I am not familiar with the coatings you mention for the front panel.
Don

[Jo90]

Don,
Thanks so much for replying. Thanks also for the advice about the capacitors- I will definitely follow that. The A88 is also AB, and apparently is based on the A44. According to Sugden (I think that I spoke with either Mr Tony Miller or Patrick Miller on the phone), they were asked to modify the A44 to 80wpc rms for the special order to Nigeria. How this was done, is lost in time sadly! I tried Sugden for the schematic. They were brilliantly helpful, as always, but it seems that the original circuit diagram was kept as a copy made with ink that has faded to illegibility. I am trying (!) to reverse engineer the circuit from the diagram of the A44 and the actual amplifier, but it is hard going! I also don't have an A44 to compare the physical differences. A number of changes were made, including the addition of the second transformer. Apparently it was more powerful than the later models of A48. It certainly is a different thing to my previous A21a, but shares a similar sound. If the a44 schematic would help, I would be happy to post that? Thanks so much again,
best wishes,
Jo

[AMV8]

Hi

It would help if you could post the A44 schematic and indicate if you can where you believe changes where made. For example I would guess that there are more output devices per channel; probably twice as many. It would also help if you measure the working + and - voltages and how the two transformers are wired together. Possibly the amplifier uses one amplifier per channel whereas the A44 uses a common transformer to supply both channels.

I am not sure how familiar you are with revamping an amplifier. However if you are not familiar here is a quick summary of the main steps. Transistors and resistors should still be ok unless damaged by heat. Clean all contacts and switch wipers and check the integrity of all solder joints especially those in the power supply and in circuit with the output devices. Change all electrolytic caps as in my earlier post. When you start up again I would use a variac if you have one otherwise start with a 100watt light bulb in series with the amplifier to lower the voltage going into the amplifier. Check for any dc voltage on the output of either channel and if ok start up normally. Then sit back and start playing music.



Don

[Jo90]

Don, thanks very much again! My electronics CV is such that advice is always welcome! It reads a bit as follows: OA in electronics when such things existed (!), but working long hours as a medic now. One Marantz CD-80 re-capped, clocked and op-amps replaced based on what I have read on the net and electronics books (all Lego stuff really!)- but great result; One technics amp recapped and PSU capacitors replaced with bigger ones. This sounded great till I blew all the transistors in one channel setting the bias current (after replacing the potentiometers with sealed ones). This was due to a faulty £10 multimeter (lesson learnt!). It was a 'practise' amp, so not so awful, though it felt it at the time! My wife thought I was setting the house on fire.....
I will try to upload the schematic and what I think the main changes are with some photos at the weekend, if you can bear to glance at them. Best wishes,
Jo

[Michel]

Hello Jo and Don,

If still interested I do have the Sugden A88 service manual in electronic format and can send it if needed.
I also have a bunch of boxed A88 lying in my basement and if my memory is good one of them was in pretty good shape last time I looked. I also have a stock of brand new knobs and possibly other parts.

Cheers,

Michel

[Jo19]

Hi Michel,
I would love a copy of the service manual- I'm still trying to guess the correct bias current! I would be very interested in the knobs or any other parts that you have -would you be willing to sell them?
Many thanks,
best wishes,
Jo

[Michel]

Hello Jo,

Sorry for the delay, for some reason I was not notified of your reply...

Send me your email address and I will send you the file I have on the A88.
Some notes are in French so let me know if you need any help translating.

As for the parts let me know what you need, I am pretty sure I will be able to help you.

Cheers,

Michel

[Jo90]

Hi Michel, yes a schematic would be brilliant! The finished amp looks like this, with third party buttons. I guessed the DC offset from an A48 schematic (not ideal!).
The front was hard, but a Rotring stencil on matt primer followed by clear lacquer seemed to work! I missed out the A88 bit though! The new PSU caps are a bit oversized, but it is what I had left over from another project. I used elna for the pre, and some Nichicon for the power amp. It sounds really great, but a bit modern for the vintage! I'm working on a very old sugden preamp now, and I think that vishay sprague capacitors suit the original sound better. I'd be happy to buy genuine buttons, but the nextel coating tends to go all gloopy with time?
My teenagers are so keen on the amp they have temporarily stolen it for the bass, despite the slightly more modern sound! Shall I post my email address here for the schematic?

[Jo90]

I have just checked my old emails from Sugden and found that the current should be set @ 160 mA measured through the fuse and the mid point should be set @ 46V.They suggest checking at 20 mins after setting as they can drift. I posted this just in case someone else is renovating an A88!