[Johnson] Reality Check please!

[David C. Hallam]

Dick,

I have spend a lot of hours and hours and hours working on Invaders.  I
currently have 4: 2 -2000's and 2 - 200's.  Aligning one can be an exercise
in frustration.

A couple of things.

"Coupling a sensitive detector" to pin 1 of V8 means to use a well
calibrated receiver with a short length of wire for an antenna.  Put the
wire near but not touching pin 1.

The VFO tunes backwards on 80M  4.050 MHz on the dial is 4.950 MHz on the
VFO.  3.550 MHz on the dial is 5.450 MHz on the VFO.

Connecting the frequency counter directly to pin 1 of V8 is not a good idea
unless it has a very high impedance input.  I use a spectrum analyzer
because I have one on the bench.  However, the well calibrated receiver is
better than connecting a frequency counter directly to the pin.

What done is done, but for future consideration I do not recommend a general
replacement of capacitors in the VFO unless you have been able to secure NPO
and N750 temperature coefficient ceramic capacitors as used by Johnson.

I will be glad to help if you have any more questions.

73

David
KC2JD/4

> -----Original Message-----
> From: johnson-bounces at mailman.qth.net
> [mailto:johnson-bounces at mailman.qth.net]On Behalf Of Dick
> Sent: Wednesday, November 14, 2007 2:25 PM
> To: johnson at mailman.qth.net
> Subject: [Johnson] Reality Check please!
>
>
> I don't think I'm in Kansas anymore.  While I've never claimed to be an
> expert technician or troubleshooter I have a modicum of experience in
> electronics (45 years as a ham)  but have a problem that has me
> bewildered.  Here's the situation:
>
> Rig is an Invader 2000.  I am trying to align the VFO.  According to the
> manual I am supposed to couple a  "detector" capable of covernng  3550
> to 4050 kc (khz) to pin 1 of V8 (the second mixer).  After tuning the
> transmitter to 4050kc I should be able to adjust L8 to "zero beat".
> Well, I can only get it down to about 4600kc before it starts
> to go up again.  Additionally, tuning the transmitter down towards
> 3550kc,  the frequency actually goes up!  In stead of using a "detector"
> (they actually mean receiver I think) I am using a calibrated frequency
> meter hooked to pin1 of V8.  That shouldn't make any difference, right?
> I have replaced all the caps in the VFO (a real pain) and all the
> resistors for V4 (the VFO tube) all to no avail.  All grounds have been
> resoldered/re-riveted.  All coax in the VFO has been replaced along with
> the VFO tube itself (6AU6).
>
> What am I missing or not seeing?  I'd really like to get this old gal
> back on the air but I am about to really start using this thing as a
> "boat anchor" unless I can find a solution.  All you experts out
> there.....PLEASE HELP!!!! Thanks in advance.
>
> 73's
> Dick
> WA6UBJ
>
> Johnson mailing list
> Home: http://mailman.qth.net/mailman/listinfo/johnson
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:Johnson at mailman.qth.net
>
>
>
>