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-12V reading on -18V spot
Posted:
Tue Jul 24, 2012 9:32 amby nickarnal
I finished building two T15s. One of them completely checked out as far as the test voltages go. The other one checked out with the +18V and the phantom power but I got a -12V reading on the -18V spot. I checked the polarity of the diodes and capacitors but have not seen any errors. Any ideas on what this could be?
Thanks,
Nick
Posted:
Tue Jul 24, 2012 10:30 amby tpryan
Is the LM337 getting warmer than the LM317? If so, you have a load problem. If not, you probably installed the wrong resistor value at the regulator.
Posted:
Tue Jul 24, 2012 1:25 pmby nickarnal
neither got too hot but it seemed that the LM337 was a little warmer than the LM317
R30 measured 148 ohms with 1.24 V across it
R31 measured 1.84 kohms with 16.81 V across it
R33 measured 150 ohms with 1.25 V across it
R34 measured 1.85 kohms with 13.20 V across it
Posted:
Tue Jul 24, 2012 10:12 pmby nickarnal
So I checked it again and I got -16.47 V. How could it have changed?
Posted:
Wed Jul 25, 2012 7:26 amby tpryan
1) cold / bad solder joints
2) measurement error, as in dirty probes, etc.
3) intermittent short / open from wayward component leads, debris, etc.
4) faulty / damaged component, as in cracked resistor
Posted:
Wed Jul 25, 2012 8:51 amby nickarnal
I am now reading -17 V on it... wierd. It works fine and sounds just like the other T15