[Elecraft] OT - troubleshooting NIR-12

[nwtcc at earthlink.net]

Hello:

 

I know this has nothing to do with Elecraft gear, but having built the 3
radios, I knew this is the place to come for experienced troubleshooters. I
have an old JPS NIR-12 DSP unit, that, after applying power, decided to
quit. The power lamp will not now light. This unit does not have a fuse. So
I decided to get out the DVM and attempt to see what's going on. 

 

The DC power jack goes to a T-network consisting of two 0.1 uf caps with a
bead inductor before going to a DPDT switch. Beyond this is a 0.1 uf cap in
parallel to ground and then a series 1N4004 rectifier diode to a 1000 uf
electrolytic capacitor in parallel to ground. From there it branches to a
couple of  voltage regulators to get different voltages. When voltage is
applied, I get 13.7 volts on the cathode side of the diode, but zero on the
anode side (and beyond). I initially thought that this diode was at fault
and desoldered it and replaced it with another 1N4004. But, alas, this was
not the culprit. I desoldered the 1000uf electrolytic, but my capacitance
meter reads it correctly at 1000uf.

 

Can somebody help shed some light - voltage ? - here ?

 

Thanks - 

 

73, Jamie

WB4YDL