Tektronix 1L5 Crystal Discriminator


Jason A.
 

I recently purchased a 1L5 off of eBay and popped it on the bench and attempted to start calibrating it. 10KHz up seems fine, but it is completely deaf in the 50Hz-9990Hz range. On the oscilloscope screen, setting it for say 20KHz center frequency, it rises just below 10KHz and plateaus as noise all the way to the zero line. Calibration points for the sub-10KHz frequencies seem to have no effect. Checking through the circuit description and schematics, it seems to be a single part responsible for the <10KHz discriminator duty. From everything I am seeing, it is part number 119-0103-01 labeled as a Crystal Discriminator, called out in the schematic as just a rectangle with two terminals (in, out) and an arrow looping back into it on top. It is also is listed as being responsible for the same frequency band 50Hz-9990Hz that is non-functional. I have not disassembled the unit. I am guessing that part is non-existent on the spares market. Checking all the waveforms on the board per the schematic from TekWiki, it looks like everything is pretty close to the waveforms shown, save the one called out between the junction of C180, D200 and the collector of Q200.

I have emailed the person who sold it to me on eBay and will request to send it back unless someone here knows something I don't.

Any ideas?

Thanks in advance!

Jason

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