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My home built deluxe kit is having problems and I can't isolate the cause. This amp has worked perfectly for over a year and a half and is essentially a stock build without many tweaks (I did put a larger value resistor [470 ohm] in by the filter caps and had the amp running at about 12.5 watts. i thought that would actually make it less prone to burning anything out and a the same time closer to the intended voltages). The amp has always checked out just fine (within normal parameters for this build) when I've tested the voltages on the tubes, caps, etc. and has never had any major problems in its short life. It performed exactly as one would expect this amp to and I've even built another. So I was a bit surprised when the fuse blew the other day when I turned it on. I replaced the fuse and tried again only to have it blow again. Mind you, the amp will turn on and the jewel lamp will light and such but it's when I flip the STANDBY switch after letting things warm up that the fuse blows.
I started by replacing every tube - no change. I suspected the rectifier tube and tried a solid state Weber copper cap rectifier that I've used in the amp before. When I flipped the standby switch the fuse did not blow right away but instead took about 15 seconds. during those 15 seconds the rectifier started smoking and before I could hit the kill switch on the surge protector the fuse blew. it took quite awhile for the rectifier to cool down enough for me to take out. I took the copper cap off and both of the 10 watt resistors inside had cracked in half and were scorched to ashes inside.
Long story short I've tested what I can with the amp on but in standby mode and voltages check out except for pins 2 and 8 on the rectifier. they should be about 5v right? Well I'm getting 340v dc readings at both with the tube plugged in and 0v dc with no tube.
Any ideas at what might be the problem here? Could a short somewhere cause this? or do you think the PT has kicked the bucket? none of the parts are older than the build itself except for the NOS tubes I'm using. The amp literally was working one day and wasn't the next. didn't even move it from the spot it was in. I checked the outlet just to be sure and it's fine (about 122v ac). any help would be greatly appreciated!
I started by replacing every tube - no change. I suspected the rectifier tube and tried a solid state Weber copper cap rectifier that I've used in the amp before. When I flipped the standby switch the fuse did not blow right away but instead took about 15 seconds. during those 15 seconds the rectifier started smoking and before I could hit the kill switch on the surge protector the fuse blew. it took quite awhile for the rectifier to cool down enough for me to take out. I took the copper cap off and both of the 10 watt resistors inside had cracked in half and were scorched to ashes inside.
Long story short I've tested what I can with the amp on but in standby mode and voltages check out except for pins 2 and 8 on the rectifier. they should be about 5v right? Well I'm getting 340v dc readings at both with the tube plugged in and 0v dc with no tube.
Any ideas at what might be the problem here? Could a short somewhere cause this? or do you think the PT has kicked the bucket? none of the parts are older than the build itself except for the NOS tubes I'm using. The amp literally was working one day and wasn't the next. didn't even move it from the spot it was in. I checked the outlet just to be sure and it's fine (about 122v ac). any help would be greatly appreciated!
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