HP 58503A EFC error wont lock [FIXED] - Page 1
Forum section: electronics / repair

author: Samogon
author_rank: Frequent Contributor
timestamp: May 05, 2017, 02:35:04 am
content: Hi,I have GPS standard HP 58503A which in past had broken power supply i have fixed it and unit started to work, but fails to lock, it can track birds and even syncs time, but reports health error EFC err (see print of system:status?)Also diagnostic shows no errors.It had problems with +15V being out of tolerance ~19V.I wonder if it could affect some componets that now it has this EFC error.Can someone point me where to dig with this error?Thanks------------------------------- Receiver Status -------------------------------SYNCHRONIZATION ........................................... [ Outputs Invalid ]SmartClock Mode ___________________________ Reference Outputs _______________Locked TFOM 9 FFOM 3Recovery 1PPS TI --Holdover HOLD THR 1.000 us>> Power-up: coarse freq adj [TI +162.0 ns] Holdover Uncertainty ____________Predict --ACQUISITION ................................................ [ GPS 1PPS Valid ]Tracking: 7 ____ Not Tracking: 3 ________ Time ____________________________PRN El Az SS PRN El Az LOCAL 08:17:16 [?] 18 Sep 199710 26 158 30 1 12 273 GPS 1PPS Synchronized to UTC14 56 39 99 3 17 319 ANT DLY 0 ns16 26 191 20 *25 20 41 Position ________________________22 42 304 114 MODE Hold26 55 176 3831 59 358 129 LAT N bla-bla-bla32 46 76 135 LON W bla-bla-blaHGT +20.50 m (MSL)ELEV MASK 10 deg *attempting to trackHEALTH MONITOR ...................................................... [ ERROR ]Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OKEFC: ErrGPS Rcv: OKE-113> DIAG:LOG:READ:ALL?Log status: 3 entriesLog 001:20001016.16:16:27: Log clearedLog 002:20001016.16:22:00: GPS reference valid at 19970918.03:27:55Log 003:20001016.20:37:02: Position hold mode started

author: TheSteve
author_rank: Unknown
timestamp: May 05, 2017, 03:47:49 am
content: Have you monitored the adjust voltage to the OCXO as it warms up and tries to lock?

author: edpalmer42
author_rank: Super Contributor
timestamp: May 05, 2017, 04:22:06 am
content: What's the response to the :DIAG:ROSC:EFC:REL? command? If its near 100 or zero then either your OCXO has drifted with age to the point where its frequency can't be corrected or maybe it has a fault with the oven. Replacement or major surgery is required.Which oscillator is in yours?Ed

author: Samogon
author_rank: Frequent Contributor
timestamp: May 05, 2017, 05:28:43 am
content: Thank you guys, will check it tomorrow.When i was measuring 10MHz output without antenna it was 9999840Hz compared with well known rubidium source used as reference frequency for agilent 53150A.

author: edpalmer42
author_rank: Super Contributor
timestamp: May 05, 2017, 05:43:27 am
content: Quote from: Samogon on May 05, 2017, 05:28:43 am160 Hz doesn't sound like drift. It's about the right error for a dead oven on an SC-cut oscillator.Ed

author: Samogon
author_rank: Frequent Contributor
timestamp: May 05, 2017, 06:38:11 am
content: Is it repairable or needs to be changed?

author: Samogon
author_rank: Frequent Contributor
timestamp: May 05, 2017, 02:30:58 pm
content: Quote from: edpalmer42 on May 05, 2017, 04:22:06 amHere is what it reports +9.99969E+001Oscillator is: hp 10811-60159

author: edpalmer42
author_rank: Super Contributor
timestamp: May 05, 2017, 03:20:13 pm
content: Almost anything can be repaired if you work hard enough at it.There's lots of info online on the 10811 oscillator, including full schematics, so repair is possible. The 60159 version is a bit rare, though. I see that one is for sale on ebay. It looks like the unit is soldered shut. That will make repair a pain. Unsoldering oscillators is a bit of an art. Do it wrong and you overheat the interior.The first step is to pull the oscillator and power it up on the bench so you can do some testing. Check obvious things like current draw, frequency while warming up, response to EFC voltage, etc. Confirm that the fault is in the oscillator rather than the 58503A. You mentioned power supply problems with the 58503A. Maybe the oven isn't getting any power.Ed

author: Samogon
author_rank: Frequent Contributor
timestamp: May 06, 2017, 06:55:58 am
content: There was +12V regulator dead on main board which was supplying power to oven with conjunction of -12V they were supplying 24V of OCXO.Thank you guys

author: edpalmer42
author_rank: Super Contributor
timestamp: May 06, 2017, 07:57:45 am
content: That looks more like it! What's the :DIAG:ROSC:EFC:REL? command give now? You can expect it to move rather quickly for a few weeks and then gradually slow down over the coming months.Ed

author: Samogon
author_rank: Frequent Contributor
timestamp: May 06, 2017, 05:50:21 pm
content: It is +8.68492E+001

author: edpalmer42
author_rank: Super Contributor
timestamp: May 06, 2017, 06:28:07 pm
content: So that's 86.8%. Watch it to see which way it goes.My Z3801A (a cousin to your 58503A) started in Oct. 2012 at about 51.2%. It's now about 55.5%. The numbers aren't directly comparable to yours because mine has a different OCXO, but you should be good for a long time. If your oscillator happens to age down instead of up, you'll never have to worry about it.Another piece of data you might want to record is the response to the :DIAG:LIF:COUNT? command. This tells you how long your receiver has been running since it came out of the factory. Each count = 3 hours of runtime.Ed

author: Samogon
author_rank: Frequent Contributor
timestamp: May 06, 2017, 06:46:32 pm
content: 30864 hours.+8.67462E+001 going down

author: edpalmer42
author_rank: Super Contributor
timestamp: May 06, 2017, 07:05:05 pm
content: Only 3.5 years of runtime? Barely broken in!We're done!Ed