As
some may know already, due to f1lthy xmas time now I jumped into time-nuttery. What else it is, if one who don't even have frequency counter (any!) buys no less than five broken rubidium standards? Oh, well..
Units in topic are TEMEX / SpectraTime LPRO, which are basically LPFRS with heatsink and little coupling PCB. Quick googling revealed next useful links:
http://www.spectratime.com/products/isource/http://www.egidy.de/temex_lpfrs_lpro/https://www.eevblog.com/forum/projects/building-a-rubidium-freqency-standard-at-home/http://time-nuts.febo.narkive.com/ssfEAnts/temex-lpfrs-01-analog-frequency-adjustementHere's what I received today (lightning fast DHL shipment, yesterday I paid for them, today 3pm I got them delivered!).
Rather bulky and heavy things, 500gramms each. I still confused about purpose of those heatsink fins and frame, as whole thing is ovenized, so why to add extra mass?
All five are same units, with minor changes in labels, specced to power at +24VDC, have 10MHz output and RS232 TTL interface, as well as adjustment and lock pins.
Removing some screws allow to easily take mu-shield off:
Two rather dense populated PCBs interconnected by in-core flexible layer and mechanically locked together via Rb chamber outer case.
Chamber is heater from both sides with TO-220 FETs.
Here's look on PCB from outer sides:
And inner sides:
Motorola 68000 series MCU, DAC8800 and bunch of logic chips around.
Closeups..
There are two XO's glued to side of Rb chamber, 20.000MHz (bigger can) and 90MHz (smaller can in center). Some SMT trimpots and adjustable inductor(?) are nearby as well. Smaller part of chamber is lamp, bigger one is Rb cell with photodetector.
How do I know? Well, I turned this one in to see magic atomic glow...
In darkness:
It's not so bright, but definately visible in normal dim room lights.
I tried connecting serial console to it, set speed 1200 bps, 8N1 mode, but only garble came out:
Where should I start this repair? I tried 3 modules , two drift hundreds of hertz in just seconds, compared to my 33120A, and lock never come low, while one is locking (signal goes low) but still drifts.
Chassis getting about +50-53°C, and power current stabilize at about 0.515Amps with +20VDC (don't have powerful enough +24v source).
As usual, full worklog
will be here.