[R-390] R-390 Woes

[Renee K6FSB]

Adam looks like a potential mod for SSB.
previous owner may have installed the LEE 6BE6 mod in place of the 6BA6 
for the BFO.
you will need to pull the coupler and take a look underneath. probably 
the mod is not 100% self contained in the IF Deck.
IMO 6BE6 or 6BY6 are not great tubes for SSB too much distortion for me, 
I currently use a 12AU7 PD in place of the reg tube. ( I current 
regulated the fil for BFO/VFO tubes), PD Article to follow soon.
my AGC mod is Hatch.
re the switch, original is B+ for the BFO on/off so if it will do that 
you will be ok.
Renée, K6FSB

On 10/8/25 12:43 AM, Adam Morehouse wrote:
> I might have found the issue.
>
> Can anyone tell me if the white coax in the follow pictures is supposed to
> be there?
>
> https://photos.app.goo.gl/M6Qcr9mXFrZ6sgiRA
>
> It doesn't look original to me, nor does the the resistors and caps in
> front of the BFO. They seem to be hooked to V508 and RT512.
>
>
>
>
> On Tue, Oct 7, 2025, 16:55 Adam Morehouse <morehouse90 at gmail.com> wrote:
>
>> Hey guys,
>>
>> I appreciate the pointers on my R-392, and now that it's buttoned up, it's
>> time to work on my R-390. I only tested this briefly when I first got it,
>> today I threw it up on the bench. Supposedly this was restored by Rick
>> Mish, it is very clean (except the gear train, which has a lot of fresh
>> grease...), and the front panel is pristine.
>>
>> It does pull stations, but the volume is extremely low in AGC mode, and
>> gets slightly louder when placed into MGC.
>>
>> In MGC, with the BFO switched on, it plays at a normal (not super loud,
>> but loud) volume.
>> In AGC, with the BFO switched on, it hums, low volume audio.
>>
>> The limiter seems to have no effect, and varying the BFO doesn't do
>> anything at all no matter AGC/MGC.
>>
>> I have Tom's solid state kit installed, and B+ at the AF deck test point
>> is a steady 180.5vdc.
>>
>> I am going to dig out the TM's later on, I have them somewhere...but maybe
>> somebody here can help point me in the right direction.
>>
>> Thanks!
>>
>> Adam K2AAM
>>
>>
>>
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