[R-390] Non functioning BFO

[Jon Schlegel]

Hi Ken,

If you suspect a tube to be bad, try testing/replacing BFO tube V505 
(5749/6BA6W).  If that doesn't pan out, remove V505 and energize the 
receiver.  Probe pins 5 and 6 with a Hi Z input voltmeter (VTVM) and 
you should see something on the order of +250 Volts DC.  Make sure 
BFO is turned ON and receiver is set for normal operation otherwise.

With the receiver turned OFF and UNPLUGGED, probing pin 7 with an 
ohmmeter should show very nearly a dead short to GROUND (BFO 
coil).  Probing pin 1 to ground should show about 150k ohm to ground 
(grid leak resistor).

These tests should turn up most problems occurring "right out of the 
starting gate" and if nothing turns up then we drill down from there.

Regards,
Jon WA3MVM


At 01:36 PM 8/31/2008 -0600, you wrote:
>I have just discovered the BFO is no longer working in my '67 EAC R390A.
>I use a ELDICO SBA-1 SSB adapter so there is no telling how long it has been
>this way.  I have the great Y2K manual out and tube tester at the ready
>where would you suggest I start to get the BFO working again. I suspect it
>is a tube but is there other things to look at.
>
>Thanks much
>Ken DE W7ITC
>
>--
>Kenneth A. Crips, W7ITC Home of the Chew Crew, Red Headed Irish Terrier
>House Ninjas, Chic', Cowboy, and Ladybug 10th degree black belts in Mouch
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