Said, Thanks for the reply. This is certainly a starting point. A schematic would be wonderful. I have looked and have not found one yet.
The units both provide about 4.5 VDC to the center pin when any port is connected to my Tbolt. However, the signal amplitude, as measured by TBoltMon, is essentially non existent on the 4 way splitter and divided by at least 2 on the 2 way splitter. Therefore, I suspect the amplifier is dead. Did not know about the voltage regulator. Will open one and get to work. Thanks, Joe -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Saturday, October 31, 2009 5:46 PM To: [email protected] Subject: Re: [time-nuts] HP/Symmetricom 58535A and 58536A 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 etc. 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 properly. 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. bye, Said In a message dated 10/31/2009 15:27:47 Pacific Daylight Time, [email protected] writes: Anyone with manuals or schematics for these units? Anyone with any experience repairing them? Thanks in advance. Joe _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
