37-10 plate voltages 100 vdc high - Printable Version
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RE: 37-10 plate voltages 100 vdc high - codefox1 - 09-17-2015
Well, great suggestions so far, but DC voltages on a small set 100+ volts positive means either bad measuring equipment or real bad prior alterations. A schematic posted would be really helpful and a few snapshots would also help. So far, not enough to go on IMHO.
RE: 37-10 plate voltages 100 vdc high - ttmiller - 09-18-2015
this radio works but not properly. i have recapped it and changed resistors #80, # 83, # 86 and replaced cap #31 with 18 mfd.
I have checked most resistors and changed out those that were broken, burned or out of tolerance.
Ok i am starting over. ECG DM-38A Digital multimeter measured to chassis.
osc control tube 6N7G CALLS FOR 260 VDC ON P1 & P2. Actual is 184.5 and 3.3 on K.
6F6G OUTPUT CALLS FOR 250 0N P & 235 on S and 260 on S & 250 on P.
Actuals are 295 & 290 / and / 274 & 264.
6A8G calls for 250 & 85 & (150 0sc plate), actuals are 285.5 & 78,5 and (osc p 135.4)
6K7G (if) calls for P=260, S = 85, & neg 2.5 / actuals are P=295.6, S 79.4, & neg 2.7.
6K7G (rf) calls for 250 & 85 and actuals are 284.5 & 79.5 and neg 2.7
6Q7G calls for 170 and actual is 116.6 on P.
signal is weak unless i hook up 80' of antena and signal is distorted if i was working on a guitar amp i would say it sounds like the pre amp is over driving the output or the neg bias on the outputs is too low making the output fuzzy.
terry
RE: 37-10 plate voltages 100 vdc high - ttmiller - 09-18-2015
FYI I posted pictures to my dropbox account
CHECK AN EARLIER REPLY FOR THE DROPBOX INFO
RE: 37-10 plate voltages 100 vdc high - Arran - 09-18-2015
Have you checked the tubes in a tube tester yet? High B+ voltages can be caused by weak tubes, particularly the power output tube.
Regards
Arran
RE: 37-10 plate voltages 100 vdc high - BrendaAnnD - 09-18-2015
Those voltages are not really out of line. You must consider that the original voltages were taken on most likely a 5000 ohm/V meter. This will drag down the voltages quite a lot compared to a modern DMM with 1 Megohm/V.
I suggest that your poor reception problem may well be one or more of the antenna coils having an open secondary winding.