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bad transformer?

M

mrdixiepride

New Member
Last night, I was recaping my vintage Sony STR-6045, (and leave it to me to get the polarity of the main filter caps wrong):stupid:. I turned it on and noticed a hissing noise coming from the capacitors or the transformer. Right before I was about to turn it off, the power fuse blew. I replaced the fuse and fixed the polarity on the caps, turned it on, the fuse blew instantly. suspecting that there might be a problem in the power amplifier, I disconnected it from the filter caps, replaced the fuse, turned it on, and again, the fuse instantly blew. Is there a possibility I might have damaged the power transformer?:scratch2:
 
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The power cap(s) you had in backwards is/are toast - you need replacement(s).

It is quite likely you have a blown rectifier, and the transformer may well be OK. The hissing noise you heard was probably the capacitor boiling inside - it might even be shorted - but toast even if not.

Make sure the unit is powered off and unplugged from the wall before you start, safety first.

Use your multimeter on Ω range to find the short, understand that the transformer secondary winding will have quite a low resistance, you may need to disconnect or remove the bridge rectifier (or 4 x rectifier diodes) whichever is fitted, to test.
 
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I'd be looking at those capacitors. That reversal of polarity has almost certainly turned them into giant, short-circuiting paperweights.
 
Capacitors are gone now. Bridge rectifier is likely too. Replace both before you try to turn receiver on again.
 
mrdixiepride said:
I put the old caps back in (as they were still fine).
the rectifier diodes are 10D2. is 1n4004 suitable replacement
Click to expand...

10D2 is a 200v 1.5 amp part, 1N4004 is a 400v 1 amp part , so :no: - have you tested them?

1N5393 (exact) or 1N5402 (better).
 
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I just tested the rectifier diodes, and one of them is definitely toast.
I have some new diodes (and capacitors) on order, and shiuld be in sometime this week
 
I hate to be Captain Hindsight, but this would be a good time to bone up on a Dim Bulb Tester.

When I designed my new cap board I almost forgot to clearance some boltholes on the positive side of the board. I was much less nervous firing my amp up the first time out with the DBT.
 
Son-of-Vere said:
I hate to be Captain Hindsight, but this would be a good time to bone up on a Dim Bulb Tester.

When I designed my new cap board I almost forgot to clearance some boltholes on the positive side of the board. I was much less nervous firing my amp up the first time out with the DBT.
Click to expand...
I was thinking about doing something like that myself. what wattage bulb would I need to use?
 
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