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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

Jason A.
 

Question #2 - does anyone have a 1L5 that is working you don't need anymore or one you are parting out?

Thanks and best regards,

Jason

fiftythreebuick
 

Jason, be sure to include the same part for a 3L5 in your searches. I believe they both have the same board in them, and I'm almost sure the discriminator is the same.

And before you give up, I'd open that thing up and see what's going on inside. I fixed a Collins crystal filter that was not too different from what's probably inside that one. You just never know!

Tom

On Thu, Feb 20, 2020 at 10:03 AM, Jason A. wrote:


Question #2 - does anyone have a 1L5 that is working you don't need anymore or
one you are parting out?

Thanks and best regards,

Jason

Jason A.
 

Thanks Tom! I'll open it up and take a look. My fear is that it would be potted inside. It's definitely worth a shot!