[R-390] Intermittent Calibrator Signal !

[Roger Ruszkowski]

Rick,
You ask,

I’m having an issue with a R-390A I'm working on - TheBFO/ calibrator signal is random - sometimes it's there, other times it's not andsometime it's there and then just fades away. Any suggestions on the best place to start digging ??  
Thanks ! Rick Popovich
 

You have two different oscillators in operation here.
Which one is intermittent.

Tune up some CW with the BFO.
IF it stable or does the receiver drop the CW as the BFO fails. 
If CW is good then fix the calibrator oscillator.
If not then fix the BFO oscillator.

First pass these days is to deoxit all the tube sockets in the suspect circuit.
 The problem is looking like The BFO switch and function switch wafers come to mind 
as oxide problems. Last but not least every little ground lug is starting to give
intermittent operations.

None of it is serious. But yes it may be time to just shot gun all the hardware 
connections in the IF or Oscillator section of the RF deck.

Your looking for fried out of spec resistors. 
A tube died
It almost killed a resistor before the tube was changed.
No one has looked at the bottom of these decks in a long time.
The receiver worked for 30 seconds after the tube was changed and the
receiver declared fixed. 

Regular PM may have gotten a tube pulled and left marginal charred parts behind
that have now finally gone over the edge.

Eye ball Eye Ball Eye Ball finds most problems.

Good luck and
Keep with it. The receiver can be fixed in a couple hours of bench time.

Roger Ruszkowski  AI4NI KC6TRU old timer now and 33C4H in the past.
 





 
 
-----Original Message-----
From: Rick Roxx via R-390 <r-390 at mailman.qth.net>
To: r-390 <r-390 at mailman.qth.net>
Sent: Wed, Feb 22, 2017 7:15 pm
Subject: [R-390] Intermittent Calibrator Signal !

I’m having an issue with a R-390A I'm working on - TheBFO/ calibrator signal is random - sometimes it's there, other times it's not andsometime it's there and then just fades away. Any suggestions on the best place to start digging ??  Thanks ! Rick Popovich______________________________________________________________R-390 mailing listHome: http://mailman.qth.net/mailman/listinfo/r-390Help: http://mailman.qth.net/mmfaq.htmPost: mailto:R-390 at mailman.qth.netThis list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.html