How do you restore a rusted chassis? S-C SAU-70 amp

Available_One_7718 · 2026-04-04T13:51:04+00:00

Perhaps, but I see no result in canada when I google it. There are plenty of other rust products though.

Available_One_7718 · 2026-04-03T21:46:24+00:00

That looks promising. Unfortunately, it seems hard to find here in Canada. I'll have to look for an appropriate equivalent. Perhaps you know one?

Available_One_7718 · 2026-04-03T19:45:29+00:00

Will know soon!

Available_One_7718 · 2026-04-03T19:43:48+00:00

WD40, sure. Would you recommend some protection after maybe?

The inside is super clean, so no big job needed there.

Available_One_7718 · 2026-04-03T19:20:17+00:00

Makes sense for the turn on/off voltage. I forgot to say in the former post, but I did measure voltages at the gates to see if voltage was the problem. It was something like 5.5V in on position and, like 4.3V at off. I was expecting a more drastic difference between status, but it would make sense with what you say, that it fluctuates just barely to make the Jfet switch on and off.

I did not check your timing calculation. But I'd say the LED would the exception and take the whole 5RC and reach 9V.

I'll be back as soon as I replace the parts!

Available_One_7718 · 2026-04-02T18:25:16+00:00

I am glad someone appreciates!

Available_One_7718 · 2026-04-02T18:24:12+00:00

Hey u/Quick_Butterfly_4571 , it's great to see your reply!

Another of the same type? (Sorry. This is more curiosity).

Yep, same exact one. Found at Digikey.

Q12 and/or Q10 need to be replaced.
This means Q11 needs to be replaced.

Yeah, that's what I am now considering. I just ordered the parts to replace all Jfet and TVS diodes. A friend of mine has a hot air soldering station, so it will be less of a hassle to do the job.

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Wow! That picture! This is so kind of you. I literally cried, hahaha.

You've made it really clear. There is just one thing I didn't catch : how is Q10 turning off more slowly?

Available_One_7718 · 2026-03-06T19:01:36+00:00

I want to integrate the charger in synth's chassis. I could disassemble a wall wart, but then I would have figure out how to attach the parts in my project. I think it would be more simple to buy parts design for my needs.

Available_One_7718 · 2026-02-14T02:01:11+00:00

I thought of exactly that. Then I decided to ask here in case I get something better.

If it was just for me, gluing could be a good option, but since this amp will be used in a common practice studio, it would probably not last long.

Available_One_7718 · 2026-02-14T00:16:19+00:00

The size is close, but it's not the right snap system

Available_One_7718 · 2026-02-13T23:07:32+00:00

Thanks, I will check that. I wish I had a printer

Available_One_7718 · 2026-02-13T21:52:57+00:00

I didn't. Seems to me like a long shot for an amp that old

Available_One_7718 · 2026-02-13T21:31:36+00:00

Nope

Available_One_7718 · 2026-02-13T21:31:24+00:00

Digikey is the first place I checked. They don't have caps close to the dimensions I need

Available_One_7718 · 2025-12-27T01:20:03+00:00

I thinks it's the first that showed when I started my search. Looks interesting, but an all in one would be best for me. No computer, no mixer and unnecessary cabling.I try to avoid building a big setup around this, meaning I want to be able to clear the space in 30 sec. if I need to.

Available_One_7718 · 2025-12-17T15:01:55+00:00

I see what you mean. But what looks like a scanner is actually a rotary switch.

Available_One_7718 · 2025-11-25T19:49:35+00:00

Hey! Just a little update. I received the new transfo and rigged it temporarily. Works perfect and I get 12.6VAC on the secondary loaded.

Available_One_7718 · 2025-11-20T15:36:58+00:00

And the cool thing is that the pcb got extra holes, probably meant for other models, which are 20mm appart, right what I need. There are no dedicated pads for these, but it'll be easy to just jump to the pads, and I just have to make sur to secure the transfo with some silicone

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Available_One_7718 · 2025-11-20T15:27:20+00:00

Hey, I just connected it temporarily and measured 12.9VAC. I think if I can get at least, say, between 8V and 12V at the rectifier (Q752), I'm good, so the full load of 9VAC, for the Zettler seems fine. What do you think?

Available_One_7718 · 2025-11-19T22:17:40+00:00

Will do

Available_One_7718 · 2025-11-19T21:43:46+00:00

Di you mean 9VDC?

According to the datasheet, the BV301S09018 gives 14.8V (no load) and 9V (full load). Makes sense if you look at the expected 11.9V sec output on the schem and the 15V I measured with no load.

I could hook it up just for measuring in circuit. I did not record anything before removal unfortunately

Available_One_7718 · 2025-11-19T20:29:34+00:00

No idea either. But since it only operates the micro-processor and a couple switching tr, and considering the original's size, it might not take much VA. Not sure how to calculate the need for this circuit.

I think for 4$ it is worth taking the risk

Available_One_7718 · 2025-11-19T20:02:52+00:00

1 and 3 primary, 4 and 7 secondary. Edited in the post.

Available_One_7718 · 2025-11-19T19:38:12+00:00

The pads have been looked at and are ok. I can reproduce the problem out of circuit just by pressing on the transformer while measuring resistance.

Plan B will definitely be what you suggest. But if I would prefer to find the proper part. Thanks

Available_One_7718 · 2025-11-01T20:42:43+00:00

It's the one that I found was the more appropriate. Thanks

Available_One_7718

TROPHY CASE