[R-390] SERIAL # 163

[Gene Beckwith]

*Gents,

I have a recently acquired Motorola...has relay non-stock...not sure yet 
why . . . it's not a hack job...

Did general up dates...caps etc...works great...didn't check out why or 
what the relay does..it's just behind the BFO pitch control inside the 
the filter deck...unit still has a live ballast tube...and is in 
pristine conx....label on rear says Army Security Agency...no other 
history...

73, 

Gene
W8KXR*



Flowertime01 at wmconnect.com wrote:
> 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
>
>
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