[R-390] Calibration Osc issues

dog agfa at hughes.net
Sat Oct 6 15:33:26 EDT 2018


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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