[time-nuts] Troubleshooting an HP 58503A

Mike Cook michael.cook at sfr.fr
Sun Oct 7 01:48:09 EDT 2018

> Le 7 oct. 2018 à 03:16, Matthew D'Asaro <medasaro at mit.edu> a écrit :
> 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.

What voltage are you finding? IIRC RS232 leaves a logic 1 i.e. -ve voltage on the line if not transmitting. You could try putting a scope on the RS232 chip TX driver input to see if the CPU is sending anything during startup.

> 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.
  It may not lock if it has a saved position which is far away. That happened for my Z3801A which is pretty much the same box and had come from China. I had to force it into survey mode. But that needs RS232 working. 

> Questions:
> 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 again.
> 4)Do you have any other hints?

> -Matthew
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.

People have only as much liberty as they have the intelligence to want and the courage to take.

Emma Goldman

More information about the time-nuts mailing list