On Nov 4, 5:06*pm, "Larry Gagnon" wrote:
Hello. I have a homebrew linear 13.8V 20A power supply I have been using *
for some years to power an IC-735, a 2M rig and some accessories. The PS *
has these characteristics:

- well filtered (35000uF)22AMP, 21 volt DC output from diode bridge circuit
- LM-317 regulator circuit (as per LM-317 datasheets)
- MJ2955 NPN feeder transistor from regulator driving 4 - 2N3055 PNP power *
transistors in parallel
- large heat sinks (I don't think heat is a problem)
- good air circulation with fan

I have the regulator set to 13.7 VDC out. Lately however, I have had some *
problems with voltage drops: while drawing 20 amps the voltage drops to *
about 11.3 volts and I have had reports of a rough CW signal as a result.

I have tested the reg circuit and even replaced the LM-317 to no avail. I *
cannot see where the problem lies, unless perhaps the MJ2955 feeder *
transistor is not working as it should? (I don't yet have a replacement *
transistor to test that idea, hence this post).

Any ideas greatly appreciated.

Larry VE7EA

--
For direct email remove fake.

Sounds like my power supply. One of the emitter resistors on a pass
transistor opened. The transistor did not fail. I replaced the
resistors and decided to upgrade the 2n3055 to some NTE181s. Also
modified the power supply for remote sense to allow for IR losses in
the power cable.