[Amps] Strange behavior (at least to me

[Jim Thomson]

Date: Fri, 29 May 2015 01:52:11 +0000
From: Steve Bookout <steve at nr4m.com>
To: Jim Hargrave <w5ifp at gvtc.com>, amps at 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 at 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