[R-390] SERIAL # 163

[Flowertime01 at wmconnect.com]

Richard,

You own what you own and there is a relay in the BFO circuit.

Accept that this is not original and it is not stock.

As you have a serial number 163 and no one else has seen any of its brothers,
accept that what you have is not some spook modification, because you have 
either the 163rd or 63rd one in the series. And again we have none other like it.

There be only one R390 with manual and one R390/A with manual. The R390's 
were mostly  built by Collins. R390/A were built by every one and even Al Gore 
claims to have had a hand in the early contracts.

Mods may have been for either inboard or outboard changes. Likely BFO mods 
were for SSB. 

Grab a R390/A schematic and start doing a wire by wire pin by pin study of 
the BFO tube and circuit. You will find where the relay was inserted into the 
circuit.

As we Fellows are not familiar with BFO relays, Where is your critter 
actually mounted into the receiver? On the IF deck or some where on the front panel.

I accept the relay looks like mil style. It would have the right voltages to 
operate with the receiver. Is the relay coil about 220 volts B+ or some other 
voltage?

The BFO operated on switched 220 volt B+ to the BFO tube switched by the BFO 
switch. If the relay coil is 6.3, 12.6, 24, 28 volts then the BFO switch has 
been rewired from B+ to the coil voltage. But 200 Volt relay coils do exist in 
mil style, so I can see one of those type relays being used. 

I can see that as the relay is energized, something switches the a load onto 
the B+ line and drops the B+ to low for the receiver to work. Check the 
schematic, pick a B+ point on a RF deck tube and another IF deck tube and see how 
much the B+ drops when the BFO is switched on. If no drop go looking for the 
problem else where. If the B+ drops 10 or more percentage start tracing the 
circuit around the relay.

Good luck with this problem.

No reason you cannot restore the receiver to original and operating condition 
with or without the modifications as you chose.

Believe the schematic you have in hand is good for original and there is no 
@@@RARE@@@ schematic out here some where you need to find.


Please do some digital photos if you can and save some hand drawn schematic 
if you can. Yo may just snap some pictures and have a digital disk done when 
you get them developed. You could then sent that disk to a Fellow here on the 
reflector that could get the pictures up on a web site for us all to view.

Someone put some thought and work into getting that modification into your 
receiver. It may or may not have ever worked. But it could lead to some real 
insight and spark of creativity. A good SSB detector for the R390/A is a much 
sought after grail.

Roger L. Ruszkowski AI4NI