[R-390] Having issue with 2nd Crystal Oscillator in R-390

[Flowertime01 at wmconnect.com]

Patrick Nelson,

Welcome,

I agree that the symptoms are what they are. I think you are looking for 
the problem in the wrong circuit. As the receiver changes the crystal for each 
MHz in the 2nd crystal oscillator it is not likely that every one of them 
would have spurs with the same spacing.

The wave form looks typical for a 2nd crystal harmonic.

Go to WWV at 15 or 20 MHz or one of the CB frequencies at 27 - 28 Mhz and 
see if you get images on incoming signals. Or check with a signal generator. 
If no images that way then think the calibration oscillator has a spur. At 
higher frequencies images should get further away. Below 14 they may be close 
and not noticed. Or not have enough power to be apparent.

Possibly the VFO has a spur, Below 14 Mhz the RF filters are sharp enough 
so the multiple cal tones and signals do not get through the receiver and the 
receiver sounds as if it is working below 14Mhz.

Once you get the problem isolated a shot gun cleaning is the first step. 
Deoxit the crystal sockets, tube sockets and connector pins. In the R390 
grounds are soldered direct to the module so poor ground lugs are not an issue. 
Check all the other mounting hard ware for crud that may provide a ground 
loop in the circuit.

If this fails you could have a flaky cap. You want to be sure what stage is 
the real problem as inspection is not likely to isolate the problem critter 
and just changing caps until the problem goes away is tedious especially if 
you are in the wrong stage.

If you have a signal generator then you can pull a crystal and inject the 
generator across a cap (for isolation) into the oscillator grid and see what 
the results are. You may want to go for injection into the mixer with the 
crystal pulled. 

Good Luck

Roger Ruszkowsk</HTML>