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In Reply to: RE: update 2 posted by vinnie2 on June 01, 2017 at 10:30:20
I decided to switch some 813's around and I also put several twists in the wires going up to the plate connector. That seemed to help quite a bit (not sure which one) as the hum level is way down again now. The filaments are still not even, but that is probably due to the fact it was difficult to get an accurate measurement of the AC voltage coming off the small switchers. I will just have to live with it for now and hope it isn't high enough to do any real damage.
The other problem is I have is that I have no way to test 813's except by plugging them into the amp. None of my testers are set up for transmission tubes. I guess I will just plug my extras in one at a time in a side that I know is working right and see what happens.
I think I am just going to run it for awhile now and see if anything else turns up before going on to measure the power output and the operating points. They should be close because I did not change any thing from when it was bread boarded.
Comparing your photos in you first post and the photos after you messed with the amp, it appears that the two on the left side are now dimmer than in the first post. Check that the caps for the AC switchers on the dimmer side are still connected. If they are not, you would be getting lower voltage and some hum.
It probably is not the answer but it is a possibility.
The surprising part is that both tubes seem to be the same brightness on each side, which leads me to believe it might be the mains feed, but I will have to check all possibilities. Thanks for the tip.
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