[R-390] R-390 (non-A) - Low RF Gain or bad Antenna relay?

[Barry]

When I was looking into this a couple of months ago, Don Heywood suggested looking at the screen and/or plate resistors.  Mine are running high.

V401 Pin 6 : 109k instead of 94k

V402 Pin 6: 92.6k instead of 80k

Both are approximately 16% high and presumably that's mostly coming from R409 and R410.  Those are fairly difficult to get to but looks like I will need to try.  Hopefully that will get the output of both oscillators in range.

PTO output looks low as well.  I haven't checked the resistance values there but plan to do that when I get the radio to where I can get to that tube socket.

Thanks,
Barry - N4BUQ

> I recently replaced all the mixer tubes with ones that checked at the
> 1000 um level.  Some of mine were well under that.  I realize that the
> tube checker is but one data point and it _could_ be tubes but I need
> to do more checking.
> 
> I'm using an HP410C so it should be sufficiently decoupled.
> 
> Thanks for the reply,
> Barry - N4BUQ
> 
> On Sat, Nov 9, 2024 at 4:20 PM Jordan Arndt <Outposter30 at shaw.ca> wrote:
>>
>> My first instinct would be to try some different tubes and make sure you're
>> making the measurement with sufficient decoupling...
>>
>> 73...Jordan VE6ZT
>>
>> ----- Original Message -----
>> From: "Barry Scott" <72volkswagon at gmail.com>
>> To: "Larry Haney" <larry41gm2 at gmail.com>
>> Cc: <r-390 at mailman.qth.net>
>> Sent: Saturday, November 09, 2024 3:13 PM
>> Subject: Re: [R-390] R-390 (non-A) - Low RF Gain or bad Antenna relay?
>>
>>
>> > Larry,
>> >
>> > Your document prompted me to check the three oscillators in my R390/URR.
>> >
>> > On page 46 of TM 11-5820-357-35, the expected voltages of the three
>> > oscillators is defined as being -3v to -11v.  I just checked those and
>> > the 1st oscillator is probably good enough (~ -4.8v) but the 2nd
>> > oscillator and the PTO are both quite under spec.
>> >
>> > I had scoped the outputs several months ago and I thought they were
>> > stronger than that (or, at least, good enough) but checking just now
>> > while in STANDBY with the VTVM tells a different story.  Looks like I
>> > have work to do.
>> >
>> > Thanks,
>> > Barry - N4BUQ
>> >
>> > On Thu, Nov 7, 2024 at 2:21 AM Larry Haney <larry41gm2 at gmail.com> wrote:
>> >>
>> >> Jerry,  Because I found many different 'specs' for the oscillator
>> >> voltages
>> >> in the A, I wrote a doc about it.  The 390 voltages should be very
>> >> similar to the 390As in my doc: R390A Oscillator Output Level Affects
>> >> <https://www.r-390a.net/R390A%20Oscillator%20Output%20Level%20Affects.pdf>
>> >> .
>> >>
>> >> Regards, Larry
>>
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