[time-nuts] Troubleshooting an HP 58503A

Matthew D'Asaro medasaro at mit.edu
Sat Oct 6 21:16:48 EDT 2018

Fellow time nuts,
     Thanks to a very helpful (and generous) member of this list I now 
have a Motorola VP Oncore for my 58503A. Unfortunatly, there appears to 
be another problem somewhere with my 58503A. With the receiver installed 
it now appears to pass its self test, at least it behaves as the manual 
says it should with the power indicator illuminating immediately, 
followed a few seconds later by the other lights each flashing in turn, 
and then the power light alone remaining lit. At this point it should 
(again according to the manual) present an 'scpi>' prompt on the serial 
port, but it does not. I am sure I have the correct wiring between my 
computer and the unit because I can measure the RS-232 TX line voltage 
coming from the 58503A on my PC's RX line. I have tried the default 
serial port settings (9600 8N1) as well as other baud rates with no success.

Figuring that, if it will lock, I really don't care if it talks to my PC 
I have left it outside connected to an antenna for the last five hours 
or so, but I still haven't gotten it to lock.

1) Has anyone else experienced problems with these HP units failing to 
communicate with the PC? Any solutions?
2) Is there a service manual available anywhere?
3) Does anyone know what the internal LEDs on the back of the board 
mean? After powering it up and letting it sit for a few minutes the two 
red ones on the far left (with the front of the receiver facing me) are 
on along with the green one on the far right. The three red ones in the 
middle all flash on momentarily every 15 seconds or so, then they go off 
4)Do you have any other hints?


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