Author Topic: 53131A repair/upgrade  (Read 822 times)

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Offline ZGoodeTopic starter

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53131A repair/upgrade
« on: August 30, 2024, 01:53:13 am »
I bought some parts to upgrade the timebase in my 53131A and have some problems.  I'm thinking it might be a PSU problem since the OCXO is an extra 1.5A load, but I'd love some input.  I am using the 53131A upgrade board from CircuitValley.com with an MV89A OCXO.  My counter works and turns on with no problems without this board connected.  But when I do connect it the counter turns on with the screen displaying "FAIL: GPIB", and none of the keys are responsive.  If I remove the timebase it goes back to normal.  Any thought where to start?
 

Online Qw3rtzuiop

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Re: 53131A repair/upgrade
« Reply #1 on: August 30, 2024, 08:53:19 am »
I would start checking the power supply output. You can check the voltages on the main PCB.
With an RS232 cable you could also get the full error messages.
 
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Offline DeepLink

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Re: 53131A repair/upgrade
« Reply #2 on: August 30, 2024, 01:28:48 pm »
The 53131A power supply is very likely to be the problem

Start be replacing all electrolytic capacitor right away
Even if the power supply seems to work, it is only a matter of time before it breaks

Also replace the fan, while you are working on it

The reason is that the power supply runs as soon as the power cable is attached (to keep the timebase running 24/7)
The 53131A is getting old and all the ones I have seen have there share of capacitor problems

I have repaired many power supply's and ended up making a PCB for a "hard power switch" as I don't use a build in timebase. I'm using a external house 10 MHz reference

schematic of power supply attached
 
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Offline TERRA Operative

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Re: 53131A repair/upgrade
« Reply #3 on: August 30, 2024, 05:00:06 pm »
I'll 2nd the above. Of the various models of this series I've had come across my desk, they all needed replacement fan and capacitors in the PSU.
Where does all this test equipment keep coming from?!?

https://www.youtube.com/NearFarMedia/
 
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Offline ZGoodeTopic starter

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Re: 53131A repair/upgrade
« Reply #4 on: August 30, 2024, 06:37:39 pm »
Ok, that sounds like a good starting point.  Seems like this mostly confirms my suspicions so I'll order some new capacitors and start there.
 

Offline ZGoodeTopic starter

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Re: 53131A repair/upgrade
« Reply #5 on: August 30, 2024, 06:52:03 pm »
I just measured the power rails as shown on page 2-47 of the assembly level manual and all of the voltages are spot on, within +/- 0.05V.  Is it still likely to be a PSU issue?  I'm still planning on replacing all of the electrolytics since they're known to fail anyways, but if it's a PSU issue I feel like at least one of the rails should measure out of spec.

Also, is there some official list out there for the capacitors?  I made this list based on the schematic, but want to make sure I am getting the right lead spacing/shell sizes.
150uf 400v   c1
47uf 50v   c699
330uf 25v   c3333
470uf 16v   c202
220uf 50v   c7
220uf 50v   c14
22uf 50v   c9
10uf 50v   c10
1000uf 16v   c153
1000uf 16v   c152
1000uf 16v   c103
1000uf 16v   c104
2200uf 16v   c102
« Last Edit: August 30, 2024, 07:01:44 pm by ZGoode »
 

Offline ZGoodeTopic starter

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Re: 53131A repair/upgrade
« Reply #6 on: August 30, 2024, 07:45:21 pm »
AWell here's something unexpected.  I think the MV89A I bought from Ebay is dead.  When probing the 10MHz point on the board I get absolutely nothing and my scope does not see any recognizable signal.  That might be the problem since all the voltages test within 0.05V of their expected values.  I'm going to be ordering a new MV89A from a different seller to test this theory out.
 

Offline ZGoodeTopic starter

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Re: 53131A repair/upgrade
« Reply #7 on: August 30, 2024, 10:54:24 pm »
Thankfully I had purchased two MV89A's.  I just swapped in the second one and it appears to work since it booted up with selftest pass and uncalibrated.  It took a little surgery since the second one was missing the ground pin, but I machined a new one from brass on the lathe and brazed it in place of the old pin.
Now I just need to either finish my GPSDO or find someone local with one who can help me.
 

Online Qw3rtzuiop

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Re: 53131A repair/upgrade
« Reply #8 on: August 31, 2024, 06:23:54 pm »
My 53131a had a fatal high voltage incident with blown ICs and transistors. Thats why I replaced the PSU with another one. I think you just need 5V, 12V and -12V. The 9V of the original PSU aren't used.
 

Offline ZGoodeTopic starter

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Re: 53131A repair/upgrade
« Reply #9 on: August 31, 2024, 07:33:03 pm »
I might replace the power supply eventually, but it appears my unit is one of the final ones produced of the latest revision, so it actually looks fine.  I pulled out all the electrolytics on the power supply and they all tested well within tolerance for the moment.
 

Online Qw3rtzuiop

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Re: 53131A repair/upgrade
« Reply #10 on: September 01, 2024, 10:02:04 am »
I might replace the power supply eventually, but it appears my unit is one of the final ones produced of the latest revision, so it actually looks fine.  I pulled out all the electrolytics on the power supply and they all tested well within tolerance for the moment.
Yeah no need to replace if it a set of new caps will do the job. I just wanted to show that it can be easier and cheaper to replace the PSU if the original one is badly damaged.
The replacement PSU is a Meanwell RPT-60B.
« Last Edit: September 01, 2024, 10:04:06 am by Qw3rtzuiop »
 

Offline DeepLink

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Re: 53131A repair/upgrade
« Reply #11 on: September 01, 2024, 04:24:26 pm »
If you want to run your counter 24/7, as you now have an internal OCXO, do get high quality 105°C long life electrolytic capacitors with low ESR

 
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