[time-nuts] HP/Symmetricom 58535A and 58536A
SAIDJACK at aol.com
SAIDJACK at aol.com
Sat Oct 31 22:46:20 UTC 2009
these are very simple circuits, basically just a voltage regulator from LT,
and an Agilent L1 amplifier MMIC, and a number of SAW/Cavity filters, one
for each output.
Depending on what is wrong (the voltage regulator, or the MMIC) you can
probably replace these two with a host of compatible parts from Mini-circuits
There are also a resistive splitter (made of SMT resistors) and GPS L1
filters on the outputs.
If I remember correctly the voltage regulator prepares a voltage of about
3V for the MMIC, so you can probably use various 3V or 3.3V regulators to
replace that one if it's bad.
The MMIC is a low-noise ~20dB gain block.
If the gain block is bad, you can probably use the Mini Circuits ERA-3+ amp
as a drop-in replacement, even though it's NF could be lower than 2.6dB.
If the SAW/cavity filters are bad, I would just remove it and bridge it
with a wire. It's not really needed, today's GPS receivers have these built-in
already. Removing it would probably increase the output sensitivity by a
couple of dB.
Lastly, they either had the option to be powered by input 1 (via 5V from
the Coax) or via an SMC connector. Most units receive power only from the
SMC. You can also provide power into the unit(!) from the Antenna connector
(3.5V to 5.5V) - that actually works well too. It won't work if you do not
properly provide power to the unit.
You can test this by measuring the center pin of the Antenna connector,
there should be 5V on it. If there isn't, then the amp does not get power
Lastly, if you want to modify the unit to receive power from output port 1,
then just add a small inductor (say 15nH to 33nH) to the footprint for it
right at the output connector.
In a message dated 10/31/2009 15:27:47 Pacific Daylight Time,
jltran at worldnet.att.net writes:
Anyone with manuals or schematics for these units?
Anyone with any experience repairing them?
Thanks in advance.
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