19-04-2011, 11:11 AM
I think the darned thing is trying to drive me off my onion.
Last night I tried connecting a tranny to the speaker and that sounded rough as well. After reading Chris's advise I tried this again but with the speaker sitting on the bench and it sounded fine so it seemed like it was some dirt or something that was moving about.
I put it back together this morning as it still sounded fine and while I was at it changed C27 which was a Hunt's with a cracked case. I'd previously left it thinking that it was only something to do with the tuning indicator. The old one did prove to be slightly leaky.
When I tried it the speaker sounded OK but there was a hell of a general hum, which had been completely absent yesterday. Altering the volume makes no odds to it, though obviously the higher that is the less it's noticeable.
I've just put new smoothing/reservoir caps in and tried a different one in C43 but these modifications have made NO odds at all.
I've also taken some more careful readings around the EL84 with my AVO:
Black lead on chassis and red on pin 2 = 5V
Black lead on chassis and red on pin 3 = 12V
Black lead on pin 2 and red on pin 3 = 2V
Besides these I connected my megger to pin 3 and went 'round the others but that didn't seem to show anything, but I don't know if it would or not.
It's thoroughly maddening as it sounded fine until putting it back together yesterday. I'm inclined to think that there must be a bad contact somewhere but I'm damned if I can find it.
It just shows that the simple-seeming jobs never are.
Yet again, thanks for the help.
Joe
Last night I tried connecting a tranny to the speaker and that sounded rough as well. After reading Chris's advise I tried this again but with the speaker sitting on the bench and it sounded fine so it seemed like it was some dirt or something that was moving about.
I put it back together this morning as it still sounded fine and while I was at it changed C27 which was a Hunt's with a cracked case. I'd previously left it thinking that it was only something to do with the tuning indicator. The old one did prove to be slightly leaky.
When I tried it the speaker sounded OK but there was a hell of a general hum, which had been completely absent yesterday. Altering the volume makes no odds to it, though obviously the higher that is the less it's noticeable.
I've just put new smoothing/reservoir caps in and tried a different one in C43 but these modifications have made NO odds at all.
I've also taken some more careful readings around the EL84 with my AVO:
Black lead on chassis and red on pin 2 = 5V
Black lead on chassis and red on pin 3 = 12V
Black lead on pin 2 and red on pin 3 = 2V
Besides these I connected my megger to pin 3 and went 'round the others but that didn't seem to show anything, but I don't know if it would or not.
It's thoroughly maddening as it sounded fine until putting it back together yesterday. I'm inclined to think that there must be a bad contact somewhere but I'm damned if I can find it.
It just shows that the simple-seeming jobs never are.
Yet again, thanks for the help.
Joe
