Author Topic: HP 58503A EFC error wont lock [FIXED]  (Read 2235 times)

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Offline Samogon

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HP 58503A EFC error wont lock [FIXED]
« on: May 05, 2017, 12:35:04 pm »
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     3
   Recovery                                   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 1997
 10  26 158   30     1  12 273                GPS 1PPS Synchronized to UTC
 14  56  39   99     3  17 319                ANT DLY  0 ns
 16  26 191   20   *25  20  41                Position ________________________
 22  42 304  114                              MODE     Hold
 26  55 176   38
 31  59 358  129                              LAT      N  bla-bla-bla
 32  46  76  135                              LON      W  bla-bla-bla
                                              HGT               +20.50 m  (MSL)
ELEV MASK 10 deg   *attempting to track
HEALTH MONITOR ...................................................... [ ERROR ]
Self Test: OK    Int Pwr: OK   Oven Pwr: OK   OCXO: OK  EFC: Err  GPS Rcv: OK
E-113>  DIAG:LOG:READ:ALL?
Log status: 3   entries

Log 001:20001016.16:16:27:  Log cleared
Log 002:20001016.16:22:00:  GPS reference valid at 19970918.03:27:55
Log 003:20001016.20:37:02:  Position hold mode started
« Last Edit: May 06, 2017, 11:46:17 pm by Samogon »
 

Offline TheSteve

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Re: HP 58503A EFC error wont lock
« Reply #1 on: May 05, 2017, 01:47:49 pm »
Have you monitored the adjust voltage to the OCXO as it warms up and tries to lock?
VE7FM
 

Offline edpalmer42

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Re: HP 58503A EFC error wont lock
« Reply #2 on: May 05, 2017, 02:22:06 pm »
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
 

Offline Samogon

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Re: HP 58503A EFC error wont lock
« Reply #3 on: May 05, 2017, 03:28:43 pm »
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.
 

Offline edpalmer42

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Re: HP 58503A EFC error wont lock
« Reply #4 on: May 05, 2017, 03:43:27 pm »
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.

160 Hz doesn't sound like drift.  It's about the right error for a dead oven on an SC-cut oscillator.

Ed
 

Offline Samogon

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Re: HP 58503A EFC error wont lock
« Reply #5 on: May 05, 2017, 04:38:11 pm »
Is it repairable or needs to be changed?
 

Offline Samogon

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Re: HP 58503A EFC error wont lock
« Reply #6 on: May 06, 2017, 12:30:58 am »
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
Here is what it reports +9.99969E+001
Oscillator is: hp 10811-60159
 

Offline edpalmer42

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Re: HP 58503A EFC error wont lock
« Reply #7 on: May 06, 2017, 01:20:13 am »
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
 

Offline Samogon

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Re: HP 58503A EFC error wont lock [FIXED]
« Reply #8 on: May 06, 2017, 04:55:58 pm »
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
 

Offline edpalmer42

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Re: HP 58503A EFC error wont lock
« Reply #9 on: May 06, 2017, 05:57:45 pm »
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
 

Offline Samogon

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Re: HP 58503A EFC error wont lock [FIXED]
« Reply #10 on: May 07, 2017, 03:50:21 am »
It is +8.68492E+001
 

Offline edpalmer42

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Re: HP 58503A EFC error wont lock [FIXED]
« Reply #11 on: May 07, 2017, 04:28:07 am »
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
 
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Offline Samogon

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Re: HP 58503A EFC error wont lock [FIXED]
« Reply #12 on: May 07, 2017, 04:46:32 am »
30864 hours.
+8.67462E+001 going down :)
 

Offline edpalmer42

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Re: HP 58503A EFC error wont lock [FIXED]
« Reply #13 on: May 07, 2017, 05:05:05 am »
Only 3.5 years of runtime?  Barely broken in!

 :-+ We're done!   :-+

Ed
 
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