Yamaha A-1 Repair and restore: beyond Deoxit

Good call Nash..


Yeah, I have a thread where I was looking for the fusible resistors where I discovered the bad emitter resistors. But while
adjusting things I then shorted the output !! that when I got micro grabbers to do some of the testing in tight locations.

We learn more from our failures than successes.


Athanasios
 
i tried to unscrew the output trans out. it was plugged in but off. touched the screw with my screw driver and the biggest spark i have ever seen. it was powerful like a camera flash.
 
i feel like the scum of the earth. now im not gonna have the confidence to touch the 2010 as well. it is ruined and let me guess, those transistors are impossible to come by.
 
i just got done testing and actually all measured right

the right channel:
the 2sc1116 which is an NPN trans measured
B->E ~ 0.5 (meaning positiver on B and negative on E)
B->C ~ 0.5
everything else OL

the 2SC747 which is PNP
B->E OL
B->C OL
E->B ~ 0.5
c->b ~ 0.5

EVERYTHING ELSE also OL

left channel the same but a little lower ~ 4.8

actually i know what NPN and PNP mean. i have done one summer of Fourier transform spectroscopy on ultra wide band gap semi conductors research in my grad school. it is nice to understand what im doing but really i would have preferred to find something wrong so ican be sure of what needs to be done.


the mica insulators are mostly intact.

i have half a mind to put everything back on without new thermal paste since the old one looks so good and sticky and wet lol
 
i tried to unscrew the output trans out. it was plugged in but off. touched the screw with my screw driver and the biggest spark i have ever seen. it was powerful like a camera flash.
Did you check your drawers ? .. LOL
 
will do i also replaced the light bulbs with authentic (not LED) new ones
 
the emitter resistor is coming from mouser. should be here on Thursday.
 
HOURS AFTER BEING UNLPLUGGED, IT KEEPS CPNTACNTY SHOCKING ME. I Tried connecting a wire to the ground terminal and connecting it to the floor but still. wtf?
 
at this point id be shocked if every single component in this ****ng thing is not zapped. it sparked like 7 times and shocked me like 4 times and the heatsink made shorts in every single board in there.
 
I am sure that output transistors were working before you touch this unit . (bias problem at the beginnig)
2SA747 et 2SC1116 are not difficult to find , you just need to know where there is no fake Japanese transistors !
Help you with the fact that you don't know that we NEVER work on a charged amplifier is critical
Discharge your big electrolytic capacitors through a resistor NEVER discharge them making a short between contacts !
Check :
- your fuses
- your drivers
-your emiter and fuse resistors
- your output transistors
"rebuild " your amplifier before to switch the power on
I don't feel confortable with your acts
 
The fuses are all good.tonight when I i get off work ill first discharge the caps and then go through the list.I'll check the output transistors again as well. I guess I'll pick up some thermal compound

I guess i should worry about safety a bit more.
 
Lol I was looking at this video and it says the exact opposite



I guess this one it's better advice.

 
I am sure that output transistors were working before you touch this unit . (bias problem at the beginnig)
2SA747 et 2SC1116 are not difficult to find , you just need to know where there is no fake Japanese transistors !
Help you with the fact that you don't know that we NEVER work on a charged amplifier is critical
Discharge your big electrolytic capacitors through a resistor NEVER discharge them making a short between contacts !
Check :
- your fuses
- your drivers
-your emiter and fuse resistors
- your output transistors
"rebuild " your amplifier before to switch the power on
I don't feel confortable with your acts

I thought i was learning a lot, but i guess im just an idiot who makes people who are trying to help him uncomfortable :(
i did ask about discharging tho.
 
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