[R-390] Calibration Osc issues

[Larry H]

Hi Dave,  Yes, that would call for a Jameson's moment.

You are right - no way did that cal osc work without that cap.  But, the
multivibrator generating the markers (free running) probably would
(although most likely a little low in frequency (and it must be low for
proper op)).  Check frequency and then add the cap and see what's going on.

Regards, Larry

On Sat, Oct 6, 2018 at 12:33 PM dog <agfa at hughes.net> wrote:

> So I've replaced that bad choke in the filament circuit to V205 which is
> right next to HR202/Y201/Y203. Then the B+ choke L211 to V205/V206 was
> open. Got a replacement for that. Still no work. So I pull out another
> RF section to test/compare and just looking at the one I just pulled out
> and it has not been disturbed, there is a 1000pf mica from V205-1 to pin
> 8 (the 200KHz crystal) on the octal socket of HR202, part of the calib.
> osc. circuit, just like the schematic. But on the one I repaired, there
> is no mica cap and it looks like nothing has ever been soldered to pin 8
> of the octal socket. Now I have replaced the two 0.1uf, C256/C309 with
> those huge orange drop caps. I'm thinking about getting some different
> 0.1uF caps for them, another issue.
>
> But why does it look like there's never been a 1000pf connected to pin 1
> of the octal socket, that circuit would not work without that and I
> don't remember the calibration oscillator not working and I can't
> believe I never tried it? That's not to say that I ever did try it, my
> memory fails me at the moment. The one without the mica cap is EAC
> #337X, hard to read and the other one is EAC #146. The earlier one also
> has R235, 47Ω. I guess next thing is to try the early RF section in the
> RX I'm working on. Both of these worked at one point and pretty sure the
> calib osc did too.
>
> Any ideas? I'm going to let it rest for a bit, I've been working on
> these all day. I need a Jameson's but I don't have any.
>
> Dave
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