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Re: [Amps] Strange behavior (at least to me - APPARENT SUCCESS! -

To: Jim Thomson <>
Subject: Re: [Amps] Strange behavior (at least to me - APPARENT SUCCESS! -
From: Steve NR4M <>
Date: Tue, 02 Jun 2015 14:44:35 -0400
List-post: <">>
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<>
To: Jim Hargrave<>,
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.


73 de Steve, NR4M

On 5/28/2015 14:50 , Jim Hargrave wrote:
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 -

###   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 
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 
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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