[time-nuts] HP/Symmetricom 58535A and 58536A

SAIDJACK at aol.com SAIDJACK at aol.com
Sat Oct 31 22:46:20 UTC 2009

Hi Joe,
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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