Hello all,
WPX is over so Mike, K4GMH and I, dug back into the amp.
We discussed the various suggestions and decided that the one to try
first was shorting out the vacuum relay to parallel any bad contacts.
That seemed to take care of the problem, as we went between xmit and
receive 10 times with no strange behavior noted. Before, you MIGHT get
two cycles before it screwed up, so that looks like success to me.
Because Gerald submitted the correct fix, he 'wins' the bad relay, and
as a special bonus, he gets a 4cx800 that has an open filament. Congrats!
Seriously, thanks for all the suggestion.
73 de Steve, NR4M
On 5/29/2015 21:10, Jim Thomson wrote:
Date: Fri, 29 May 2015 01:52:11 +0000
From: Steve Bookout<steve@nr4m.com>
To: Jim Hargrave<w5ifp@gvtc.com>, amps@contesting.com
Subject: Re: [Amps] Strange behavior (at least to me)
Hello Jim,
This is something that should be easy enough to do and does make some sense.
Will wait till next week to deal with it as I will be very involved in
the WPX CW contest this weekend.
Thanks.
73 de Steve, NR4M
On 5/28/2015 14:50 , Jim Hargrave wrote:
Steve,
It sounds like a bad connection on the variable capacitor. It
could be external or inside the bottle.
Depending on the construction of the capacitor, you may or may not
be able to fix it. In some construction they use finger stock on the
variable shaft. I have had some success in positioning the shaft
facing up and spray a little Tri-flow lubricant on the shaft and
rotate it back and forth until it goes In a little.
73, Jim - w5ifp@gvtc.com
### Moot point. He is using a 375 pf vac cap. One side is fixed...and the
variable side is just the compressible bellows..which is driven by a lead screw.
The only thing that gets greased is the bearings on the variable end.
## If you want to do a real test on the vac cap, use a digital LCR meter, and
measure the pf across the cap, starting at the min C end. Then slowly crank
in more
and more turns..until u reach max C..... all the while keeping ur eyes glued to
the
lcr meter. I have never seen one go defective as u describe.
## if it is the cap... the 10-375 pf @ 7.5 / 10 / 15 kv glass caps are in
plentiful supply
on the surplus market. Ditto with the ceramic 12-500 pf vac caps.
## What are u using for a load cap ? U could swap the tube if a spare is
available.
U could also swap the existing tube into another, known good 8877 amp , like an
Ameritron AL-1500.
# Let us know what u find.
Jim VE7RF
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73 de Steve, NR4M
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