Posted by
KK1W on
Feb 10, 2020; 8:45pm
URL: http://elecraft.85.s1.nabble.com/QRO-KPA500-Failure-tp7658244p7658356.html
UPDATE:
Jack/W6FB contacted me directly shortly after posting. I sent him my fault
log to analyze and a detailed description of my equipment setup. Best guess
is a cable or antenna failure causing high SWR sometime in the recent past
that stressed the finals. They gave up the ghost when I was running 17m FT8.
I'm leaning toward a bad patch cable I found between the KPA500 and KAT500 a
few months previous to the failure. A cheap cable that became very costly!
His guess was right on, when I was pulling the power transformer out of the
amp to make it easier to ship I found the ceramic part of a VRF2933 MOSFET
rattling around in the cabinet. The problem is now obvious :(
The amp left today to Elecraft for repair. I'll let the group know the
results once it gets there.
Thanks everyone for your constructive comments and to Jack for reaching out
and helping me find the problem.
'73...
Jim
KK1W wrote
> Was running about 150W on 18 MHz this afternoon. My KPA 500 made a loud
> pop. No more output. Any pointers of where to start looking?
>
> *Details:*
> KPA500 (use with KAT500 and Icom 7610)
> Antenna on this band is a SteppIR
> Amp has been running FB
> KPA Utility 1.13.7.16
> 240V supply
> A single loud pop was heard.
> Mode remained in OPER
> No fault light displayed, nor can I find one in the Fault Table
>
> *After the failure:*
>
> *In STBY:*
> Radio and antennas work fine. SWR shown to exciter is low, as expected.
> Exciter power is displayed on KPA500 power meter.
> HV = 78.2
> Works correctly on all bands
>
> *In OPER:*
> HV = 78.2 key up
> On key down (input of 15W) the asterisk briefly displays, then display
> changes to 18.1, back to HV display on key up.
> Zero output, SWR shown to exciter is very high (over 3 to 1)
> No power shown on output meter.
> Fails *on all bands* with high SWR to the exciter.
> No fault indication.
>
> *Other data:*
> Here's the last three entries from the fault table:
> 00000000 00 PWR ON -- 0007 Power was turned on
> 00000039 09 REFL HI 80 00F0 Excessive reflected power (high SWR)
> 00000000 00 PWR ON -- Power was turned on
> .............
>
> Apparently only faults get logged, subsequent power cycles have not
> changed
> the table.
>
> I power cycled the amp, including removing the mains power. - no change.
> I reloaded the last configuration - no change.
> I removed the cover and looked for any visible damage or bad odors.
> Nothing
> stands out.
>
> Amp is about 4 years old and was a kit model. Before I start to
> disassemble
> if anyone can offer a likely culprit I'm all ears.
>
> Thanks,
>
> Jim/KK1W
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