are these capacitors installed correctly

moss99 · 10th March 2009, 08:04 PM

Hi all i am trying to repair this old yamaha amp i have put these 2 black new capacitors in now i seem to have this fuse blowing on the board just above them (see photo) is there any way to tell if i have installed them with the polaritys wrong i was sure they went back the same though..

moss99 · 10th March 2009, 08:10 PM

This circled in red was getting very hot..

taj · 10th March 2009, 10:32 PM

The stripe on the capacitor is negative. That will usually be marked on the circuit board somewhere as well. Other than that, it's pretty hard to tell from a photo.

If the caps are in backwards, I'd expect them to release their smoke (rapidly).

That white thing looks like an auxiliary power bridge rectifier, which would probably normally get a little warm, but if it's dangerously hot, then there's probably some circuit problem.

..Todd

moss99 · 11th March 2009, 08:28 AM

Hi yes it did get very hot i de soldered 2 of the output transistors(C789) last night and 2 of 4 are dead ,, possibly shorted on the heatsink as the little plastic bush/washer things all broke up when i screwed them back in for the first time ,,

jacco vermeulen · 11th March 2009, 08:53 AM

Quote:

Originally posted by moss99
This circled in red

Look more like they should read MPC708 or MPC733, 0.22Ohm.
Dual metal plate emitter resistors by Fukushima Futaba (with three legs each).

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10th March 2009, 10:32 PM	#3
taj diyAudio Member Join Date: Feb 2005	The stripe on the capacitor is negative. That will usually be marked on the circuit board somewhere as well. Other than that, it's pretty hard to tell from a photo. If the caps are in backwards, I'd expect them to release their smoke (rapidly). That white thing looks like an auxiliary power bridge rectifier, which would probably normally get a little warm, but if it's dangerously hot, then there's probably some circuit problem. ..Todd

11th March 2009, 08:28 AM	#4
moss99 diyAudio Member Join Date: Feb 2009	Hi yes it did get very hot i de soldered 2 of the output transistors(C789) last night and 2 of 4 are dead ,, possibly shorted on the heatsink as the little plastic bush/washer things all broke up when i screwed them back in for the first time ,,

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