dodgy amp power supply

obaka-san · 9th January 2008, 08:50 AM

I've recently purchased a second hand power amp. After setting it all up i found it would powerup but produced no sound, so being the type of guy I am I opened it up.

When I opened it I found that the fuses on the DC rails had blown so i replaced 'em. The new fuses promptly blew the next time I turned it on. Testing revealed that there was >100A(as high as my multimeter would go) between the fuse contacts, slightly more than to 10A indicated for the fuses

.

I suspect the culprit to be a capacitor between the AC inputs to the bridge rectifier, which seems rather peculiar. I tested the rectifier and it appears to be working fine. The AC from the transformer is fine, I can only find an issue after it's converted to DC.

I'll try to get a picture up as soon as I can, if you guys think it'll help. thanks for any help

acid_k2 · 9th January 2008, 09:12 AM

There is a short circuit
check wires
check power transistors/mosfets in audio amplifier section

9th January 2008, 08:50 AM	#1
obaka-san diyAudio Member Join Date: Jan 2008	dodgy amp power supply I've recently purchased a second hand power amp. After setting it all up i found it would powerup but produced no sound, so being the type of guy I am I opened it up. When I opened it I found that the fuses on the DC rails had blown so i replaced 'em. The new fuses promptly blew the next time I turned it on. Testing revealed that there was >100A(as high as my multimeter would go) between the fuse contacts, slightly more than to 10A indicated for the fuses. I suspect the culprit to be a capacitor between the AC inputs to the bridge rectifier, which seems rather peculiar. I tested the rectifier and it appears to be working fine. The AC from the transformer is fine, I can only find an issue after it's converted to DC. I'll try to get a picture up as soon as I can, if you guys think it'll help. thanks for any help

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9th January 2008, 09:12 AM	#2
acid_k2 diyAudio Member Join Date: Oct 2006	There is a short circuit check wires check power transistors/mosfets in audio amplifier section

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