Vintage Synth Repair

Tips:

A digital camera is a good friend to a set of schematics. I like to go on macro and shoot what I am about to work on. If you need to stop and order parts and come back weeks later

you may learn that some connectors can go on either way (ARPS for example) or you might forget which side was the + on that cap and the board is not marked.

Generally if you are changing tants or polarized capacitors on a board, do it one value at a time, so you do not accidentally put one in reversed. In a complex rebuild that can cause a lot of head scratching hours later when you boot up.

If there are sockets, then why not change them as well. They can be a mechanical or cold solder weak point. Some techs hate them. But, after your done test every pin for continuity before you reseat the ICs. Look at the pics as well before reseating because every now and then a designer is inconsistent about IC orientation (truer for older circuits, why I don’t know).

I have at least once accidentally put a socket in reversed when distracted. Then I used the socket notch to put the chip back “correctly,” surprise it didn’t run. User error. ; Didn’t kill the IC though.

Be a turtle with a camera not a hare with a desoldering sucker.

desolder plungers are great.

Too much desolder heat will double your original damage.

Cheers Lorne in canada

From: vintagesynthrepair@yahoogroups.com [mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of Daniel Forró
Sent: Saturday, February 16, 2013 1:00 AM
To: vintagesynthrepair@yahoogroups.com
Subject: Re: [vintagesynthrepair] Recapping

As I'm in project of recapping my older devices, I'd like to ask all
of you more experienced gurus here your opinion:

1. I started with changing electrolytic capacitors in PSU. Do you
think it would be good to change all electrolytic capacitors in the
machine (on digital and analog boards)? I want to use the opportunity
of opening the machine and to avoid possible problems in near future...

2. Is it necessary to change also all bipolar, tantalum, ceramic,
polyester... capacitors? Do they also deteriorate in time?

3. Is there some age of the device from which would be good to change
capacitors? 15 - 20 - 25 - 30 and more years?

4. When changing old capacitors with nowadays non-existing values, of
course I must follow voltage or use higher value. Concerning capacity
value should I use the nearest higher value, too? Modern capacitors
are usually smaller than old ones, so size is not critical. I'm just
afraid if in certain kind of circuits higher value couldn't be some
problem...

5. Do you have eventually any other tips & tricks for maintenance of
older machines? Of course I do cleaning, reseating IC's in sockets,
cleaning and reseating all connectors, cleaning keyboards... I will
also change displays in about 10 of my machines for modern LED
backlighted types. I disassemble keyboards, clean them, lubricate if
necessary, change key bushings... If necessary, I change
microswitches... And I'd like to upgrade OS EPROM's in some of my
instruments.

6. I have also two old Hammond organ (CV model from 1945 and M3 from
1960). Do you think I should change capacitors (or even more
components) in preamplifier (CV), amplifier (M3), tonewheel generators
and vibrato lines? There are specialized firms offering sets of
capacitors or other components for old Hammond organ.

I will add that all my old machines work well, and I know there's an
old wisdom "don't touch it if it works", but... What's your opinion? I
want to change capacitors because I'm nervous that old machines can
have problems. But is it REALLY necessary to change it when machine
works well?

Thanks for any answer.

Daniel Forro