Yamaha A-1 Repair and restore: beyond Deoxit

This is the list of the caps in the electrolytic board as the yamaha service manual calls it:

63v 470uF x5
50v 47uf x4
16v 10uF
50v 10uF
35v 10uF
16v 100uF

1 - the problem is that i idont know what to order. Nichion has so many different series, i dont know which one is good for this application.

2 - secondly there are two tiny caps right next to the output relay and a tiny silver box that looks like a tiny transformer, those look like they are in the signal path. they are very hard to reach. what should i do with them?

3- the two big caps are Nichion are 18000 uF 63 vw. does vw mean volts? what should i buy for that?
 
for the sepaker terminals there is no space behind them i dont know what kind of binding post will fit.
 
Wire wrap is a better connection than solder. Theres more crimped wire & wirewrapping connections in military electronics ie. avionics. Than soldered wiring.Superior connection.;)
 
avionic said:
Wire wrap is a better connection than solder. Theres more crimped wire & wirewrapping connections in military electronics ie. avionics. Than soldered wiring.Superior connection.;)
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But how do you “rewrap” them and get the same surface area of contact, and not have them fray? That would change my life :).
 
Dadbeh said:
what about the caps? ,y questions? what should i get for it?
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Higher temperature is always good. Higher voltage won’t hurt, unless it won’t fit. Don’t change uF values unless for a specific reason, and make sure you don’t miss any nonpolar caps. I generally stay with whatever brand was in there, and get the best “quality” available. You should look closely at all of them, and test them if possible if you are going to replace any.
 
BrianKBaur said:
But how do you “rewrap” them and get the same surface area of contact, and not have them fray? That would change my life :).
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With new gold wire wrap pins , wire and electric wire wrapping tools.If needed. Didn't require much on the aircraft because they were pretty much maintenance free.
On vintage audio. The key! is not to disturb the wire wrap connections or as little as necessary. Sometimes you it can't be helped. Like on Soundcraftsmen amplifiers. The wire is single strand , old and brittle.
 
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avionic said:
I'll unsolder the wire wrapped pins from the circuit board before undoing a wire wrap.
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I had thought about just leaving them wrapped that way, but my dad told me to just go for it and rewrap them. He forgot to tell me he has the tools, or more likely, wanted me to try without them first... He's a retired EE, and we bond over electronics and a beer weekly now. Sometimes his advice seems less than optimal, but he's never not fixed (or not helped me fix) anything. It is hard for me not to just give him my gear for a few days, but I don't learn as much that way.

The C-70 is the first thing I've ever attempted it on, I was worried about keeping the two boards connected by the wires during work and stressing the connections too much. The one that was loose on the transformer ground was one that was still wrapped, but the chassis bottom cover has a nice dent in that area, and that board is warped from heat

Sorry to hound you, but do you use wire with special "properties" for wrapping? It seems to me it would need the right "memory."

Thank you for your replies. My professional ts and repair experience is limited to semiconductor and food manufacturing machines, printing presses and forklifts. At the time being I cannot prioritize spending $300 or more to pay someone to do it. I want to avoid butchering my gear any more than it has already been, while at the same time learning new "machines."
 
well ****

i got my air compressor out of the basement just so i can dust it and then cleaned every single contact surface with contact cleaner and then i fired it up and after one Adele song loud huge pop out of one of the speakers and it dies.
 
Dadbeh said:
well ****

i got my air compressor out of the basement just so i can dust it and then cleaned every single contact surface with contact cleaner and then i fired it up and after one Adele song loud huge pop out of one of the speakers and it dies.
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Expand on " it dies ".
 
So loud pop and it went quiet. I unplugged it quickly. after a few minutes plugged back in and it is back to playing normally. I think at this point i should take the advice that i got from the other topic and be as systematic as i can. As ya'll suggested i guess i should check the bias and offset. i have the manual open in front of me but im not sure how to go about it. it says to no have speakers connected and instead a 70 watt resistor as load and then wait 3 to 5 minutes and then measure. i have my multimeter here and no clue how to start. should i really go find a 70 watt resistor on digikey or something?

so this is what it looks like after cleaning:

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1 - Ok first thing is the power supply voltage which the service manual says should be 35V +-1 and i read 35.2 on my trusty walmart multi meter. very nice.

2 - second item is the equalizer circuit DC offset voltage which should read 0 +- 200 mV measured on the preamp PCB for each channel but there is discrepancy that there are supposed to be 3 leads, the middle one ground, but there are two. there is nothing in the middle. there is a hole with no lead smack dab in the middle but the prbes from my multimeter dont fit in there so i used a pirce of wire to touch that hole as the ground and then measure the two ,leads. my reading is not stable and is in the ramge of 500 mV

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3 - third item is the drive circuit DC offset voltage which should read 0+- 10mV measured on the drive board, i measure TP1-TP2 = 70mV and TP2-TP3 = 110mV. the service manual says that i should measure TP4 and never mentions TP3 but all i see on the board is TP3.

4 - TP1-TP3 = 0
TP2 -TP4 = 0.5V but should read 7.4 += 2mV
 
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