Here's another measuremens I took.
IC01 7815 ~ input 26.3V output 14.9v
IC02 7915 ~ Input 27.6v output 14.9v
IC01 7815 ~ input 26.3V output 14.9v
IC02 7915 ~ Input 27.6v output 14.9v
What you circled appears to be remaining glue for those power wires that someone has tried to remove, but didn't get all of it. Should be ok.
As far as the capacitors - I would replace both, since you know one was destroyed, whatever did it probably affected the other one too.
They aren't that expensive, but might be worth an extra $1 to get 105-degree ones (up to you, as 85-degree is the minimum)
Main thing is trying to clean up as much of that electrolytic as you can before re-mounting the new ones. That stuff will cause all kinds of "issues" if you don't get it off of and out of the board. It tends to cause shorts between tracks and corrode tracks.
I would start with alcohol (90% or higher) and a hard bristle toothbrush. If that doesn't get it off, try a de-greasing soap, but use sparingly because you don't want to leave soap on the board either.
Be sure the board, and all components are completely dry before attempting to turn it on again. I would use a hair-dryer, or heat gun (carefully) or let it sit overnight.
Can't stress enough - you don't want any liquid on the board when you are running power through it. Fastest way to have fireworks and smoke.
As far as the capacitors - I would replace both, since you know one was destroyed, whatever did it probably affected the other one too.
They aren't that expensive, but might be worth an extra $1 to get 105-degree ones (up to you, as 85-degree is the minimum)
Main thing is trying to clean up as much of that electrolytic as you can before re-mounting the new ones. That stuff will cause all kinds of "issues" if you don't get it off of and out of the board. It tends to cause shorts between tracks and corrode tracks.
I would start with alcohol (90% or higher) and a hard bristle toothbrush. If that doesn't get it off, try a de-greasing soap, but use sparingly because you don't want to leave soap on the board either.
Be sure the board, and all components are completely dry before attempting to turn it on again. I would use a hair-dryer, or heat gun (carefully) or let it sit overnight.
Can't stress enough - you don't want any liquid on the board when you are running power through it. Fastest way to have fireworks and smoke.
These are good results.
Proves the cap, has thrown off the protection circuit and the relay stepped in to save the amp. Hopefully that is all it was and you clean up and replace those you should be up and running.
The +/- 15VDC low current regulated supplies are working fine. He has HIGH CURRENT supply problems, only about 3VDC or so. I have him checking the voltages on the bridge rectifier. The high current AC voltages to the board look OK.
I do not see a problem with any of the capacitors, it's all glue.
Craig
I do not see a problem with any of the capacitors, it's all glue.
Craig
I finally pulled these pics up on a proper monitor - agree with Craig, the low-voltage appears fine.
Do as Craig mentions, which is test the rectifier (big square with silver heat sink on top). Top opposite pins (diagonal from each other) will be AC from transformer and the other two are DC that goes to the capacitors.
With power off, check for resistance and/or continuity/Diode check. If you are very careful, you can check for AC and DC with the power on, but be very careful.
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Hi Craig, Bullittstang,
The AMP started working. When I measured IC01, 7815, I used the probe to touch the grn middle pin the first time, I saw spark and a click sound from the AMP. I touched it the second time and and it didn't do that and I was able to get a good measurement.
Since then, I was able to get correct readings from both red/black/yellow connectors on the AMP board coming from power supply, which is around 60vdc.
I just had a chance to plug in a speaker just now and it's been playing loud music for the last five minutes.
Any idea why?
The AMP started working. When I measured IC01, 7815, I used the probe to touch the grn middle pin the first time, I saw spark and a click sound from the AMP. I touched it the second time and and it didn't do that and I was able to get a good measurement.
Since then, I was able to get correct readings from both red/black/yellow connectors on the AMP board coming from power supply, which is around 60vdc.
I just had a chance to plug in a speaker just now and it's been playing loud music for the last five minutes.
Any idea why?
Honestly - it sounds like that IC01, 7815, may have a bad solder joint. You touched it and it made good contact and sparked, which sent it into protection.
Then you turned it off and retested, now with good contact and the amp came out of protection.
Only way to know for sure is to pull that Power Supply board out and turn it over and take pictures if you want a second opinion.
Those IC01 and IC02 are KNOWN to run VERY HOT - which is why most problems are because of them. They become un-soldered from the PCB due to the heat, or just blow up adn either short out, or run low voltage when any current is drawn.
Glad to hear it's up and running - up to you if you want to find out why, or just use it until it acts up again and then troubleshoot.
Then you turned it off and retested, now with good contact and the amp came out of protection.
Only way to know for sure is to pull that Power Supply board out and turn it over and take pictures if you want a second opinion.
Those IC01 and IC02 are KNOWN to run VERY HOT - which is why most problems are because of them. They become un-soldered from the PCB due to the heat, or just blow up adn either short out, or run low voltage when any current is drawn.
Glad to hear it's up and running - up to you if you want to find out why, or just use it until it acts up again and then troubleshoot.
It's not a protection problem, it's that RL01 on the power supply board was not energizing as he had no voltage from the high current supply.
Craig
Craig
You are correct - should not refer to that as protection. Glad you stepped in and corrected my error.
I don't see anything wrong with the soldering - but my experience tells me it's the +/-15 regulator (IC01/IC02), because I have repaired 4 of these amps and all four had a bad -15 voltage regulator as the problem.
I would replace both 7815 and 7915 and buy some finned heatsinks (see pics in this thread) and you should get many years of service from the amp without a problem. First amp I fixed is going on 5 years since repair and has daily use in the HT without an issue.
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