linuxslate
Well-Known Member
A couple evenings ago my Harman Kardon a224 suddenly started buzzing/humming.
I pulled the bottom, and found that one of the caps that I installed when I first got the amp, was leaking.
Note also liquid on the tie wrap and the other end of the capacitor (right near the (-) mark).
The main can cap was replaced with a good, German 50 + 50 can capacitor, but this capacitor (original 40+40+ lowvoltage100+100) was discovered to be bad after I ordered the other capacitor.
In my haste to get the thing up and running (and to see if it had any other problems) I bought the shown capacitors at a local surplus place.
They were new (full leads), but of unknown age or previous storage/handling.
Note also value -- They are 80µF caps replacing each 40µF element. the low voltage caps that replace the 100µF sections can just be seen behind the HV caps. I was anxious to get this running, and these capacitors are far enough down the divider chain that I figured 80µF wouldn't hurt the rectifier tube.
I now replaced the shown leaking capacitor and the one next to it with new 47µF/450V parts from a local tube supplier. I have much more trust in what he sells than what I find on the floor (literally) at the surplus place. I've also never heard of Belmoor.
I also replaced that cardboard covered thing with a more modern 50µF 50V part. The replacement is surplus, too, but it's a real Sprague, and given the application of that capacitor, I'm sure it will be fine for quite a while.
I still have not changed the ceramic disc coupling caps or the shown 0.1/400 coupling caps. Just sitting here as I type this, I guess I should have replaced them. I have a bag of new 0.1/630V Chiclets.
I ran the amp for at least 2 hours last night, and it seems fine. It's dead silent in idle, and again sounds as good as it ever has.
I can't see that anything external would cause that cap to fail like that. I'm assuming it failed just be cause it was another old electrolytic. I guess I'm lucky that it didn't fail in a worse way. I could have been cleaning up a real mess. Note the corrosion it caused.
I pulled the bottom, and found that one of the caps that I installed when I first got the amp, was leaking.
Note also liquid on the tie wrap and the other end of the capacitor (right near the (-) mark).
The main can cap was replaced with a good, German 50 + 50 can capacitor, but this capacitor (original 40+40+ lowvoltage100+100) was discovered to be bad after I ordered the other capacitor.
In my haste to get the thing up and running (and to see if it had any other problems) I bought the shown capacitors at a local surplus place.
They were new (full leads), but of unknown age or previous storage/handling.
Note also value -- They are 80µF caps replacing each 40µF element. the low voltage caps that replace the 100µF sections can just be seen behind the HV caps. I was anxious to get this running, and these capacitors are far enough down the divider chain that I figured 80µF wouldn't hurt the rectifier tube.
I now replaced the shown leaking capacitor and the one next to it with new 47µF/450V parts from a local tube supplier. I have much more trust in what he sells than what I find on the floor (literally) at the surplus place. I've also never heard of Belmoor.
I also replaced that cardboard covered thing with a more modern 50µF 50V part. The replacement is surplus, too, but it's a real Sprague, and given the application of that capacitor, I'm sure it will be fine for quite a while.
I still have not changed the ceramic disc coupling caps or the shown 0.1/400 coupling caps. Just sitting here as I type this, I guess I should have replaced them. I have a bag of new 0.1/630V Chiclets.
I ran the amp for at least 2 hours last night, and it seems fine. It's dead silent in idle, and again sounds as good as it ever has.
I can't see that anything external would cause that cap to fail like that. I'm assuming it failed just be cause it was another old electrolytic. I guess I'm lucky that it didn't fail in a worse way. I could have been cleaning up a real mess. Note the corrosion it caused.
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