In Reply to: enough current to bias 2 x kt150 tubes You don't need current posted by Chip647 on January 12, 2017 at 16:50:03:
Ok, so the .5A 6.3vac filament trans should be perfectly fine for the job?
I still don't understand why it worked in my shop for over an hour with solid cathode current on the output tubes of 75ma and the bias voltage was rock steady as well at -52vdc measured at the last dropping resistor. I took out the "test tubes" which were a mismatched duo of a GE 6550A and a Russian kt88. Plugged in the kt90s and after about a 5 minutes the current started to steadily climb while bias voltage steadily lowered. I turned it off, put in the old testing tubes and this time they could not hold bias worth a darn.
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Follow Ups
- RE: enough current to bias 2 x kt150 tubes - DAK 17:08:46 01/12/17 (26)
- RE: enough current to bias 2 x kt150 tubes - 6AS7_6SN7 23:10:22 01/12/17 (1)
- RE: enough current to bias 2 x kt150 tubes - DAK 09:56:50 01/13/17 (0)
- Unstable amp - FenderLover 17:43:26 01/12/17 (23)
- RE: Hi FL. can you contact me offline? - DAK 19:23:34 01/13/17 (0)
- RE: Unstable amp - DAK 19:37:39 01/12/17 (21)
- RE: Unstable amp - PakProtector 04:38:44 01/14/17 (20)
- Powered it up WITHOUT the driver tubes...still misbehaving - DAK 13:09:40 01/14/17 (18)
- RE: Powered it up WITHOUT the driver tubes...still misbehaving - PakProtector 03:34:18 01/15/17 (6)
- RE:What would i be looking for in the meter readings? nt - DAK 23:27:00 01/15/17 (5)
- RE:What would i be looking for in the meter readings? nt - PakProtector 03:48:33 01/16/17 (4)
- RE:What would i be looking for in the meter readings? nt - DAK 08:08:19 01/16/17 (3)
- RE:What would i be looking for in the meter readings? nt - PakProtector 08:38:46 01/16/17 (2)
- I was not being facetious or disrespectful. - DAK 11:44:11 01/16/17 (1)
- RE: I was not being facetious or disrespectful. - PakProtector 16:41:14 01/16/17 (0)
- RE: Powered it up WITHOUT the driver tubes...still misbehaving - Tre' 16:20:34 01/14/17 (10)
- Residual AC in the bias supply is .002v - DAK 15:22:48 01/15/17 (9)
- RE: Residual AC in the bias supply is .002v - Tre' 16:07:07 01/15/17 (5)
- Where would i put the ferrite beads? - DAK 22:52:30 01/15/17 (4)
- RE: Where would i put the ferrite beads? - Tre' 08:27:00 01/16/17 (3)
- RE: Where would i put the ferrite beads? - DAK 11:50:08 01/16/17 (2)
- RE: Where would i put the ferrite beads? - Tre' 19:14:58 01/16/17 (1)
- It helped a little. - DAK 20:47:41 01/16/17 (0)
- RE: Residual AC in the bias supply is .002v - Michael Samra 16:06:40 01/15/17 (2)
- Both coupling caps are new Mundorf Silver/gold and oil - DAK 23:08:58 01/15/17 (1)
- RE: Both coupling caps are new Mundorf Silver/gold and oil - Michael Samra 12:06:23 01/16/17 (0)
- RE:You mean run the amp w/out the driver tube? - DAK 08:47:42 01/14/17 (0)