[R-390] R: Antenna trimmer

[fdigio1 at gmail.com]

Thank you Larry for the kind answer.

I’ll go and check the messages.

 

This morning I have made the modification at R523 as described by David Wise.

I installed a new Allen Bradley 100 Ohm potentiometer and, at the moment, a 8.2 Ohm resistor for R537.

When some resistor I ordered will arrive, I’ll change its value to 6.8 Ohm.

This upgrade is awesome! No problem to calibrate the Carrier Level Meter. What a smooth adjustment!!!

I put 100µV into the antenna input and adjusted R523 for 100dB on the meter,

as written on “The Almost Ultimate R390A Upgrade Schematics” of Perry Sandeen (thank you Perry for you

invaluable help). I checked the meter with 10, 20, 30….80, 90 µV and the meter indicates

10, 20, 30….80, 90 dB!!! Fantastic!!!!

Thank you guys!

 

Francesco Di Giovanni -  IN3XZP

 

 

Da: Larry H <larry41gm at gmail.com> 
Inviato: venerdì 12 aprile 2019 11:10
A: fdigio1 <fdigio1 at gmail.com>
Cc: R-390 Forum <R-390 at mailman.qth.net>
Oggetto: Re: [R-390] Antenna trimmer

 

Hi  Francesco,  Glad you are making progress on your A.

 

When the Ant Trim knob is straight up, the cap should be at it's 1/2 way point.  There was a discussion about the pin on Wed, Jun 20, 2018, 4:20 AM.  Take a look.

 

Regards, Larry

 

 

 

On Wed, Apr 10, 2019 at 11:02 PM fdigio1 <fdigio1 at gmail.com <mailto:fdigio1 at gmail.com> > wrote:

Hi guys, the restoration of my R-390A goes on. All the missing screws, lock and flat washer are on their position. All of wrong type are been replaced with the correct one, even the missing green screws. Every RF deck gear is cleaned and lubed. I have some issues with the antenna trimmer. 1) the red dot is vanished. Which is the right alignment? Full, minimum, half capacitance? 2)I suspect it is contaminated by oil or grease. I tried to remove its cover from the bottom, but the 3 wires are too short to let me expose the dual section variable capacitor and their solders to the rotary switch are difficult to reach.I could remove the worm gear on top, but I am unsure in which direction to push the pin. Any idea? Best regards, Francesco - IN3XZP Inviato da smartphone Samsung Galaxy.
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