[Premium-Rx] Tuning problem with Racal R1772 / R1776 receiver

[richardreich at aol.com]

Hello Nico,
If I understand you correctly, the first fault could be something as simple a physically mis-aligned encoder unit which is bad enough to overcome the natural hysteresis in the unit. The frequency jumping in this case is caused by very slight physical movement (vibration) of the tuning knob as you turn the switch. To prove it, lock the tuning knob with some kids putty, then try to reproduce the problem. To repair - follow the encoder set-up instructions in the manual.
The tuning encoders can be a bit twitchy when changing MHz range, but not usually as bad as you describe.
The second fault is likely to be  a logic problem - could be anything on the up-down counter.
R
Sent from my BlackBerry® wireless device

-----Original Message-----
From: Nico Dongen <nico.vandongen at online.nl>
Sender: premium-rx-bounces at mailman.qth.net
Date: Fri, 10 Sep 2010 16:31:06 
To: <premium-rx at mailman.qth.net>
Subject: [Premium-Rx] Tuning problem with Racal R1772 / R1776 receiver

Hello all,

I recently purchased a Racal R1776 receiver what is the maritime version of the R1772 and it has a fault in the tuning. When I switch the Tuning Rate switch from fast to slow or vice versa the frequency jumps up or down. It is a random frequency change in the range from KHz to 100 KHz but mostly in the10Khz range. It happens most of the time but sometimes the effect disappears for a couple of minutes. Most of the time it will count up each time I switch the Tuning Rate till it reaches the end of the scale but I have seen it count down as well. 

I have another strange tuning effect
When I set the MHz switch for example to 3 MHz and with the tuning knob I tune down below 0 so it starts at 99999 again when it reaches 979.90  the 3MHz light goes off and the 2 and 4 MHz lights come on. The tuning then is locked until I switch the MHz switch to a different range. 

I don’t know if the two problems are related but I think it is a problem in the counter chain on the display board.

Any ideas on what could cause this kind of problems? 

Regards,  
Nico, Netherlands  

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