[R-390] BFO question

[Flowertime01 at wmconnect.com]

Fellows,

Two of you were working on your BFO problems.

It was suggested that you loosen the shaft coupler between the deck and the 
front panel to back the knob off the stop washer so the BFO could be adjusted 
from full end to end. The Idea being your BFO was running fine and just way off 
455.

One of you ask if the BFO had some kind of mechanical center. Sorry not so.
The coil will run from end to end and there is no "center" you just cranked 
the
shaft to move the coil from end to end. Once you found the 455 point, you set 
the
front panel knob and extension shaft up on zero. You adjust the knob, shaft, 
and clamp to not cause undue friction and stop against the stop washer. The 
bushing in the front panel has some play and can be adjusted to give a better 
center. Loosening the green screws on the IF deck and moving the deck a bit may 
improve
the mechanical alignment of the BFO and band switch shafts. 

If these simple checks did not get you in line, there are more things to do. 
Pull the tube and run around the socket for voltage checks. 
Check that the BFO on/off switch is turning the B+ on and off at the tube 
socket. Check your screen and grid voltages. The filaments are good as
they are in series with the PTO and the receiver does play.

Before you go for a coil can replacement, heat all the solder joints.
Cold solder joints are known to happen.
The likely one are on the pins of the coil can.

If this has not got you going the BFO coil can is known to fail.
Back when you just replaced them. 
Nothing actually went bad in the coil can that could not be fixed.
You can get the cans open and do an inspection and repair.
Most problems were in the form of cold solder joints or little
broken wires.

The coils have a good range so fixes will not push them beyond the
range where they will not tune 455 plus and minus 3 as expected.

The coil can is work to get it out and back in. It can be done.
I have done it a few times.

Let us know what you found your problems to be.
Or if you got this far and still need some more help.

Roger KC6TRU






In a message dated 6/29/05 11:30:51 PM Eastern Daylight Time, 
wd8kdg at worldnet.att.net writes:


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