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In Reply to: RE: Can any of you guys help diagnose this???? posted by tubular.well on March 17, 2013 at 08:41:25:
The bias adapter was purchased on Ebay,
http://www.ebay.com/itm/Tube-Amp-Bias-Tester-Meter-adapter-6V6-6L6-EL34-6550-KT88-7027-5881-PlateCurrent-/400432120554?pt=Vintage_Electronics_R2&hash=item5d3b9d42ea
and it sits in the socket, the power tube goes into it, and you read the bias in MA. Before this problem, I have used it, and it worked perfectly. I would set bias at around 37ma, and the amp sounded beautiful. I have two of them, both reading the same exact thing. These readings are with both 20K trim pots cranked 100% all the way to reduce the -DC to the lowest it will go, which is -35VDC. As you can see, the MA reading is 192MA with absolutely no red-plate. If the pots are cranked 100% in the other direction all the way, the tube is at 6 MA, and the voltage reads -66 VDC on pin 5. I've posted photos. Now you can see why I'm losing my mind. I've read a ton of other methods to read the bias, but at this point, it really doesn't matter, since I can torque these pots 100% in both directions. It makes sense that they would go that high. Is it NOT red-plating due to the high -VDC?? What can cause that to be so high?
http://www.dfinephoto.com/IMG_1407.jpg
http://www.dfinephoto.com/IMG_1408.jpg
http://www.dfinephoto.com/IMG_1409.jpg
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Follow Ups
- RE: Can any of you guys help diagnose this???? - Dfine 12:56:32 03/17/13 (14)
- RE: Can any of you guys help diagnose this???? - tubular.well 13:25:00 03/17/13 (13)
- RE: Can any of you guys help diagnose this???? - Dfine 18:00:40 03/17/13 (12)
- Idle Bias - Triode_Kingdom 19:54:57 03/17/13 (11)
- RE: Idle Bias - Dfine 04:46:47 03/18/13 (10)
- RE: Idle Bias - Triode_Kingdom 07:02:49 03/18/13 (9)
- RE: Idle Bias - Dfine 07:10:34 03/18/13 (8)
- Sorry to butt in, but.... - FenderLover 11:11:47 03/18/13 (7)
- RE: Sorry to butt in, but.... - Dfine 12:11:13 03/18/13 (6)
- Uh,... - FenderLover 12:23:41 03/18/13 (5)
- RE: Uh,... - Dfine 16:01:20 03/18/13 (3)
- data - FenderLover 16:54:59 03/18/13 (2)
- RE: Uh,... - Dfine 13:59:30 03/18/13 (0)