[R-390] SERIAL # 163

Thu Apr 2 20:49:39 EDT 2009

Graham,

Tnx  - good lead on why...in my case, performance on ssb is 
excellent...i.e. better than some of my stock 390As...of course they are 
quite good as original as we all know.  I have only limited experience 
with this particular Motorola so far...but find it behalves quite well 
with rf gain close to full on ...plus sig meter seems to be functional 
with ssb . . rcvr is fully assembled and in use presently, but at the 
next tear-down will do some more investigation . . .  ur lead 
appreciated...will advise further if I find more details...

Btw - serial is 906 . . . .

73
Gene
W8KXR

Graham Baxter wrote:
> It may have already been suggested but isn't this the Captain Paul Lee
> product detector mod? I recall that the HT current which feeds the BFO was
> used to energise a relay which switched the audio from the AM detector to
> the product detector. This saved one having to change the switch.
>
> Graham Baxter
> G8OAD
>
> 2009/4/2 Gene Beckwith <W8KXR at neo.rr.com>
>
>   
>> *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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>>>       
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>>     
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