I'm still looking into my TR-4's 9 MHz oscillator. Earlier, I said I could wrap a coil of wire around the oscillator tube (V16) and measure the frequency but apparently I was misremembering something because I tried that last night and I could not get the counter to trigger on anything close to 9 MHz so I just used a 10:1 oscilloscope probe which worked fine.
Unfortunately, I am not able to get the oscillator exactly on 9 MHz. C130 will adjust it down to about 9.000280 MHz but I presume I should be able to swing the oscillator very slightly above and below 9 MHz leading me to believe the crystal has "drifted" upwards just a bit and because of this, I'm not quite able to get one of the filters to respond correctly. IIRC, the LSB filter will respond down to inaudible as I approach zero-beat with the calibrator; however, USB fades out long before zero-beat and I think that's due to the CO being too high.
Any suggestions on a fix? I presume baking it might bring it back down but if that doesn't work, then I'd like to replace it. They're available new in that form factor (HC-49) but I'm not sure about what other characteristics I'd need to consider. I presume this isn't a series crystal and should have an appropriate load capacitance but perhaps other factors may need to be considered.
Anyone know the specs for that crystal?
Thanks,
Barry - N4BUQ
