Symmetricom/Hewlett Packard 58503A GPSDO 10 MHz Hardware error - Page 1
Forum section: electronics / testgear

author: anilnediyara
author_rank: Newbie
timestamp: June 29, 2021, 05:47:03 pm
content: I have a HP 58503A GPS receiver that came from an used equipment dealer. When powered it’s RED LED on panel lights up. Since I couldn’t find any service manual of information online. I request help from those familiar withThe reply to queries and The status response from it on terminal is given below.DIAG:TEST? ALL+160, +0, +0DIAG:TEST:RES?+160, ALL*STB?+192

author: MegaVolt
author_rank: Frequent Contributor
timestamp: June 30, 2021, 08:05:07 am
content: Have you connected the antenna? For this unit to work properly, a GPS antenna is needed so that it can synchronize with satellites.

author: anilnediyara
author_rank: Newbie
timestamp: July 01, 2021, 05:12:00 am
content: Yes antenna is connected. I will give it more time to sat lock. The manual says the the RedLed flag means hardware error; it is specified that if led is lit contact service !

author: rf-loop
author_rank: Super Contributor
timestamp: July 01, 2021, 05:58:25 am
content: It is nearly same/same as HP Z3801A:https://www.mail-archive.com/time-nuts@febo.com/msg70293.html( "....Z3801 is so easy to convert to 58503 is because it is essentially the same design in different packaging. ... ")When troubleshooting you can go forward using info about HP Z3801AHere you can find LOT of info about Z3801A, also for troubleshooting hw. (yes there may be some differences but this you can see when you compare Z3801A documents/info with your 58503 on your table, and carefully inside there... )http://www.realhamradio.com/GPS_Frequency_Standard.htmLong time ago I have owned both (and not only single ones) but if I have some documents about these they all are in my homeland so not available in near future, even if they exist in my documents "library"..And then nitpicking... what a 10mz. buuh.... it is 10MHz. Period!

author: anilnediyara
author_rank: Newbie
timestamp: July 01, 2021, 09:24:53 am
content: Thank you for the information and leads will work in that direction and get back to you all..Have corrected the typo mz, it was posted late into the night 😴

author: anilnediyara
author_rank: Newbie
timestamp: August 06, 2021, 05:43:48 pm
content: HiThank you for all the leads to above topic. To close this thread I thought of sharing my experience with you allI had checked the power supply and could find that one +12v regulator had failed. Even after replacing it the machine was failing in self test with the error code +192. Which is the error code (+192) for EFC voltage limit has reached.As Mr Tom Van Baak had suggested I checked the OCXO output, it was 55 hz higher. I adjusted it to 10MHz by trimming it and it was very stable after about 6 hrs. Left it running overnight, the receiver was not locking on to GPS satellites and the self test error was still flagged.On further probing found that the EFC voltage was only around 31% and still that error was being flagged. The power supply rails were once again checked and no ripple was noticed. There was slightly more than normal switching noise on all the rails. I removed the EFC supply coax to the OCXO and switched on the receiver and noticed that the error was not flagged, to make sure reconnected the EFC coax and restarted the receiver, surprisingly the error was not getting flagged even after repeated restarts. So I am at loss in tracing what exactly was wrong.The receiver is locking onto gps signal and running the survey fast now. The receiver is up and running for last two days and has been very stable.