[ICOM] Icom PW1 SWR Metering Failure

[Mike Mellinger WA0SXV]

Long, long story.

Theoretically the resistor is underrated if you run the amp straight-through
and use the tuner in your exciter and the SWR is more than 2:1.  When the
ARRL did the lab tests on the PW-1 I talked them into testing those kinds of
conditions.  They did their best but the part did not fail.  So I concluded
that the problem was probably defective manufacturing and it just took a
while to cause a failure through the minimal surface that remained connected
on the broken resistor.  The resistor manufacturer's spec sheet does say
that you can run it at higher ratings if you empirically determine that it
doesn't fail.  I didn't consider that great design but once I replaced the
resistor I've not had any failures with two amps and maybe 15,000 RTTY
contest QSO's since.

Symptom was exactly yours -- everything worked except the SWR indication.
The first amp was in warranty so I sent it back.  But when I discovered the
fix I did the second amp myself.  I think that Icom gave me the resistor but
again we had many discussions about the design and maybe it was a case of
the squeaky wheel...

Mike


-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of Bruce J. Howes
Sent: Monday, May 30, 2005 12:11
To: 'ICOM Reflector'
Subject: RE: [ICOM] Icom PW1 SWR Metering Failure

I wonder what the repercussions would be if I subed in a 4.7K 1/4 watt
resistor for testing purposes and until I receive a replacement from Icom.

When this failed in your amp Mike did all other functions also work?
Mine seems to function normally in every way, but does not display SWR.
Seems to tune fine and have plenty of power output.

So has Icom upgraded the part to a more robust version?
Did you carry out the work yourself?
Looks like the splitter board is simple to get to.

Thanks!

-Bruce W1UJR