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

[Tom Frobase]

There is a 100 pf capacitor in the 17 MHz mixer circuit that is notorious
for going bad, it is located in the RF deck.  As I recall it is C286 . ...
tom, N3LLL

On Thu, Nov 11, 2021 at 1:38 PM brianpepperdine brianpepperdine <
brianpepperdine at sympatico.ca> wrote:

> 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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