[R-390] no signals below 8 mhz, crystal oven removal for xtal testing etc

[Barry]

Hi Brian,

I'm going on very fuzzy memory, but I think that symptom can be linked to faulty mechanical alignment of the band switches.  I don't recall exactly which one, but I think there's a mechanism that can be just slightly out of alignment and it will cause the switch contacts not to close for the 8MHz and under bands.  Loose/slipping geartrain clamps can cause this.

Of course, it could just be the 17MHz oscillator as well.

Thanks,
Barry - N4BUQ

----- Original Message -----
> From: "brianpepperdine brianpepperdine" <brianpepperdine at sympatico.ca>
> To: "R-390 Mailing List" <r-390 at mailman.qth.net>
> Sent: Thursday, November 11, 2021 1:38:42 PM
> Subject: [R-390] no signals below 8 mhz,	crystal oven removal for xtal testing etc

> It was suggested that I bring my question to this List, so I have joined up...
> here goes...
> 
> My R-390A lost reception below 8 mhz. This is the triple-conversion operation of
> the receiver, thus I have turned my attention to the first mixer area etc.,
> which includes the 17 mhz injection via the crystal oven.
> 
> I swapped out the 6C4 and another 6C4 in the mixer chain (interchanged) and it
> runs still OK above 8 mhz in Double Conversion mode, so the 6C4 is fine I think.
> V207 (5654) tube is bit hard to get at... so the other issue to be looked at is
> the 17 mhz crystal in the HR202 crystal oven. If I take out the oven in theory I
> can swap in (temporary) a 17 mhz xtal from elsewhere in the receiver xtal bank.
> 
> Based on a suggestion, I do not see 17 mhz at the P221 jack as per my frequency
> counter.
> 
> 
> However, the xtal oven seems resistant to being pulled out... the Y2K 390A
> manual talks about a spring retainer on top of HR202 (I have none). It seems to
> me that HR202 is sort of in a tube socket kind of thing (as per diagram) but
> with any gentle tube removing kind of movement (gentle rocking and pulling) it
> does not seem to budge. I don't want to really 'wrench' on it. It IS in a socket
> arrangement, right? Not hard wired....?
> 
> In any case, having the xtal swapped in would help diagnosis or fix.. but even
> so
> its lack of presence would also help me in getting my fingers into the tight
> space to remove V207  5654 tube out to test it (it does glow, but what does that
> really
> mean in the Grand scheme sometimes).
> 
> Anyhow any opinions on the xtal oven removal would be appreciated...
> or ideas on loss below 8 mhz reception.
> I hope its not a transformer (one other possibility) because then we are
> getting way beyond my level of competence ( and obvious lack of spare parts).
> 
> Tnx
> Brian VE3HI
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