HP/Symmetricom 58503A/Z3805A GPS Time and Frequency Reference Receiver Repair x2 - Page 1
Forum section: electronics / repair

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: August 27, 2020, 07:00:22 pm
content: Hi all,Wanted to share my journey fixing two of HP/Symmetricom 58503A.I have two of those units that are broken. Both of them have bad oscillators which are in my case hp 10811-60212 but another member had 10811-60159 so I guess they are interchangeable.When I power the units up they voltage regulators powering the heaters are getting really hot and the units draws... 1.5A.When the heaters are disconnected the current goes down to about .5AFirstof the units fails the self test, fails also a oxco and efc.. That's what I see in SatStat before it fills with errors so it disables updates.When I look at the log I see "invalid header" messages.reply: -113,"Undefined header"reply: -102,"Syntax error"Sent: *IDN?reply: -113,"Undefined header"------------------------------- Receiver Status -------------------------------SYNCHRONIZATION ........................................... [ Outputs Invalid ]SmartClock Mode ___________________________ Reference Outputs _______________Locked TFOM 9 FFOM 3Recovery 1PPS TI --Holdover HOLD THR 1.000 us>> Power-up: OCXO warm-up Holdover Uncertainty ____________Predict --ACQUISITION .............................................. [ GPS 1PPS Invalid ]Tracking: 0 ____ Not Tracking: 8 ________ Time ____________________________PRN El Az LOCL GPS 06:02:23 [?] 01 Jan 1998* 1 -- --- GPS 1PPS Invalid: not tracking* 6 -- --- ANT DLY 0 ns* 9 -- --- Position ________________________*20 -- --- MODE Survey: 0% complete*22 -- --- Suspended: track <4 sats*24 -- --- INIT LAT N xx:03:04.414*25 -- --- INIT LON W xx:53:37.933*28 -- --- INIT HGT +194.28 m (MSL)ELEV MASK 10 deg *attempting to trackHEALTH MONITOR ...................................................... [ ERROR ]Self Test: Err Int Pwr: OK Oven Pwr: OK OCXO: Err EFC: Err GPS Rcv: OKThe secondunit fails self test, oxco and gps receiver. The serial link is also going up and down, and often I'm getting.. no response from the unit.Sent: *IDN?reply: HEWLETT-PACKARD,Z3805A,3542A0xxxx,3543B-A------------------------------- Receiver Status -------------------------------SYNCHRONIZATION ........................................... [ Outputs Invalid ]SmartClock Mode ___________________________ Reference Outputs _______________Locked to TFOM 9 FFOM 3Recovery 1PPS TI --Holdover HOLD THR 1.000 us>> Power-up: OCXO warm-up Holdover Uncertainty ____________Predict --ACQUISITION .......................................... [ GPS 1PPS CLK Invalid ]Satellite Status __________________________ Time ____________________________Tracking: 0 Not Tracking: 0 LOCL GPS 19:00:00 [?] -- --- ----1PPS CLK Invalid: not trackingANT DLY 0 nsPosition ________________________MODE Survey: 0% completeSuspended: no track dataINIT LAT 0:00:00.000INIT LON 0:00:00.000ELEV MASK 0 deg INIT HGT +0.00 m (MSL)HEALTH MONITOR ...................................................... [ ERROR ]Self Test: Err | Int Pwr: OK Oven Pwr: OK OCXO: Err EFC: OK GPS Rcv: ErrWanted to ask if anybody has any experience fixing the oscillators and I guess heaters on them. When I connect the oscillators themselves... without the heaters they seem to be working.Maybe somebody has those hp10811-60159 OXCOs so I can just get one of them for testing.Second, wanted to know what kind of gps receiver I should get to replace the faulty one or is there a way to fix it?Third, what would be a problem with communication over serial... should I see and how to see what are the serial settings on those devices.What would be a problem with sending commands. It does look like a firmware may be corrupted.Anybody having copy of the firmware I may use?There is command in SatStat to upgrade firmware but I have programmer and adapter, can burn them if needed.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: August 27, 2020, 07:24:27 pm
content: After several tries I've got the response from the first unit:Sent: *IDN?reply: -113,"Undefined header"Sent: *IDN?reply: HEWLETT-PACKARD,58503A,0,3704-Aso... it's missing serial.....Corupted FW?

author: jfphp
author_rank: Regular Contributor
timestamp: August 28, 2020, 02:08:57 pm
content: Are you sure that this old HPIB box knows the query IDN ? Most of my HP instruments don't respond to this question.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: August 28, 2020, 04:02:37 pm
content: reply: HEWLETT-PACKARD,58503A,0,3704-Areply: HEWLETT-PACKARD,Z3805A,3542A0xxxx,3543B-ACommunication is done over RS232 not GPIB, it also uses null modem cable.You can see the response I hope... after several tries I've got the response from either machine.So, yes it does work and it's a valid query.I've started disassembly of one of the oscillators. Not sure how to remove the insulation from the inside...It's very hard from aging... working on it.So, the oscillators are marked as :10811-60212 one of them is LM9611, the other one LM9829. I guess those are the manufacturing dates.