Using non-matching caps in McIntosh 2125 repair? Or will it destroy amp/burn down house?


Hi all,

Please take 5 minutes to read and let me know if what I am going to attempt poses any physical danger (fire, broken McIntosh amp, etc.)


today is my last day off before I start an 8 week rotation of working 7 days a week from 4am-8pm (the joys of med school) so I am scrambling to replace the caps on my old McIntosh 2125 amp. I didn't consider it until I would hear an occasional crackle from time to time, and also BOTH meters have never worked (although the light up fine). 
I already cleaned all connections with DeOxit, replaced all 6 IC's on the meter PC board, as well as all of the electrolytic caps. Which offered no change. My plan today is to correct a few signal diodes on that same board which have their polarities reversed, according to the service manual at least, but they are reversed in a symmetric fashion so I don't even know if it matters since the culprits are in pairs, never solo or at a point of termination, so overall the phase output shouldnt be changed by their configuration (I'm guessing).

with that said, I'm working on to the Power Supply PC Board today while I still have the time. 
First major issue I discovered when looking closely between the big parallel axial caps were 2 signal diodes that looked obliterated. I have enough silicone signal diodes and zener diodes to do the whole board, as well as the caps, well almost all the caps. I DONT have exact replacements for the 2 big electrolytic caps (C307, C308) that are rated to "85c, 2200MFD-16v". They don't appear to be In bad shape, but I will have to take them off anyways to get to the busted diodes inbetween them. 

So option #1, remove them from the circuit board and test them with a digital multimeter (Klein Tools model MM2000) if that's possibly? I wouldn't know what readings would equate to "bad" though?

option #2: I have 2 Kimber Kaps .22+/-10% @ 600V. I'm assuming the .22 is micro (u) units, because it's not stated on the cap wrapper.....obviously this is pretty far off from the originals, but just so I'm prepared - when I remove/test the originals if I find they are bad will these Kimber Kaps suffice for a few months until I have time to install a proper replacement? Or would I run the risk of them blowing up/starting a fire/breaking my amp?

any input would be greatly apprefiated! I am damned and determined to get these meters working today...

thanks!)

hockey4496
Okay, I re-did everything. All new caps and diodes, even swapped out that D119 that was missing originally for a 6.2V Zener and removed that mystery diode on the back of the board as suggested.

After replacing everything except transistors and the C307/C308 caps I triple checked polarities plugged only the power supply board back in (leaving out the meter board)...turned on the power (preamp disconnected), and this time all the lights were brightly illuminated, no power guard warning, then 2 seconds later a plume of smoke....yep same thing. BOTH D302/303 cracked in half

either way I know I need to replace C307 and308 (recommendations??) but in addition to that, could the batch of rectifier diodes I’m using be bad? This is what I am using for d302/303: http://www.amazon.com/1N4004-Axial-Silicon-Rectifier-Diodes/dp/B008LTJOX6?ie=UTF8&psc=1&redi...


pleaseeeee help I just want my music back
Hello, sorry I've been away . . .
I was under the impression that you'd replaced the two 2200uF caps per gs5556's advice, but in skimming through again I'm not certain now.  BTW your choice of diodes is fine, provided they're not counterfeit or anything weird.

If you haven't replaced the two 2200uF caps yet, that's the first step.
I'm dying to know how this ends?  Kirkus, hockey4496, gs5556 you guys are awesome!  Next time I blow something up I'll make sure you're all on speed dial. 

N