[R-390] COSMOS PTO EP ADJUSTMENT

[Pete Williiams]

G'day Russ. You will have to take off the outer  and inner covers. The
threaded slug in the EP coil is easily screwed back in again if you were
unlucky  enough to screw it right  through.

No other disassembly is  required.

To make the  EP  adjustment approximately correct on the  bench, I suggest
you make up/acquire  apower supply to give you the 150  and 250 V plus 6.3
for heater . Make the appropriate  connections. Just put the inner cover on
pro tem and do the 10 turn trick checking both points.

When you find you have  sufficient adjustment range by doing the  1 turn
removal  or a series capacitor on the EP coil, a more deliberate /accurate
setting  can be got  when it's all back together.

I am fortunate  that I have a dual adjustable  2 voltage  supply and have
made up a test cable with a  spare plug to do EP  and  linearization.

Let the PTO warm up  at room temp for  an hour or  so..DON"T use the oven -
you'll go ballistic  trying to keep the  freq from moving  around ( lots of
HZ )

Best of luck

Pete  VK3IZ

 

 

  _____  

From: wa3frp at aol.com [mailto:wa3frp at aol.com] 
Sent: Tuesday, 20 April 2010 11:54 PM
To: jupete at internode.on.net
Cc: r-390 at mailman.qth.net
Subject: RE: COSMOS PTO EP ADJUSTMENT

 


Pete, 

 

One question for you (and anyone else on the list who may wish to comment)
as I want to go in, fix the problem and get back out quickly. I can't afford
to have a lot of downtime as this R-390A is my primary receiver.  And,
knowing how things work, something that I haven't worked is sure to show up
if I am off-the-air.

 

You said "...once the endpoint adjustment slug is fully in and out of
thread, you've got to have the PTO  apart and put back in..."

 

Are there any hints or things that I should know in working to get the
endpoint adjustment slug screw back in the threads.  Or, is this fairly
straightforward once I've removed the coil from the PTO?  I have tried
turning the screw counterclockwise with a hope that the threads would simply
re-engage - without success.

 

Thanks and 73 Russ WA3FRP