Power supply for main amp blows fuses after replacing filter caps.

[petehall347]

Re: Power supply for main amp blows fuses after replacing filter caps.

What was wrong with the original capacitors that you needed to replace them?

good question

[lotas]

Re: Power supply for main amp blows fuses after replacing filter caps.

I want to add, when you test transistors on the board, it is better to remove these capacitors so that their large capacitance does not interfere with the measurement.

[acedogblast]

Re: Power supply for main amp blows fuses after replacing filter caps.

What was wrong with the original capacitors that you needed to replace them?

I had random popping sounds on all speaker channels. I have a post about it in this forum a week ago. When I re-flowed the original capacitors I saw some corrosion on one of the solder connections. I feared that the original caps had a leak so I replaced them.

[acedogblast]

Re: Power supply for main amp blows fuses after replacing filter caps.

Quick question. Can I use thermal pads instead of thermal paste/compound with the mica insulator? I can get these sooner than the new mica insulators.

[acedogblast]

Re: Power supply for main amp blows fuses after replacing filter caps.

This transistor may have been damaged, so you will need to inspect it to make sure there is no burnt carbon track on the back of the transistor and no rough metal if it did indeed arc. This is if the transistor itself did not short internally

While the tabs on the transistor measure out OK the plastic around the hole on the back has been damaged and can cause a short with the screw attached so I am going to replace it (again as that position is where the original transistor was shorted collector to editor. Just my luck). All other transistors test out OK. I should be getting the thermal pads tomorrow so I will post an update then. Again thanks for all of your help everyone.

[acedogblast]

Re: Power supply for main amp blows fuses after replacing filter caps.

Thermal pads are installed and the AV receiver powers up but a problem that I think I solved is back. Whenever a loud sound is being played on the center channel the receiver goes into ASO protection mode. I think something is still wrong with the center channel on the main power amp.

The transistor that I have replaced twice now is properly a symptom of something else going on. I am going to create a new thread discussing this issue as the original issue for this tread is solved which is caused by not isolating the heat-sink from the power transistors.

[petehall347]

Re: Power supply for main amp blows fuses after replacing filter caps.

not looked at protection but i guess it monitors dc offset and possibly overcurrent .it may be working as intended and the source might be the problem

[Devil_rider]

Re: Power supply for main amp blows fuses after replacing filter caps.

Or a bad filter in speaker.....