Author Topic: Restoration : HP 4262A LCR meter  (Read 10973 times)

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Online TiN

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Re: Restoration : HP 4262A LCR meter
« Reply #25 on: July 26, 2016, 10:28:09 am »
No, just soapy water :) Well, perhaps that would be a problem if we had test set, but since there is none here, not an issue.
I already have cheapo probe for 4263B which using BNC's so I'll just use same one here for testing and comparisons.


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Offline TAMHAN

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Re: Restoration : HP 4262A LCR meter
« Reply #26 on: July 27, 2016, 01:00:06 am »
Tin, sorry I do not want to sound disrespectful. But Fail 1 is "normal" in that it points to unhappyness with the DUT. For self test, some ranges need to be shorted dead.

Wait, ill look it up for you *stands up*

L and R need all four binding posts shorted! The resistance must be VERY low - I managed to get my 4262A to bicker if the cable resistance is not low enough.
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Offline cncjerry

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Re: Restoration : HP 4262A LCR meter
« Reply #27 on: July 27, 2016, 03:39:06 am »
tamhan,You beat me to it.  If you don't have the shorting bars on or good leads with low resistance from cur to pot you will get the fail1 error.
 

Online TiN

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Re: Restoration : HP 4262A LCR meter
« Reply #28 on: July 27, 2016, 04:14:15 am »
That doesn't fix fail 2 ones though. I'll have a check after, currently time not allowing more on this.
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Offline TAMHAN

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Re: Restoration : HP 4262A LCR meter
« Reply #29 on: July 28, 2016, 12:55:20 pm »
Hello,
on mine, I always get some self test errors in the C range after start up. The self test of this unit is really complex. I am thinking about making a video.

Tam
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Offline cncjerry

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Re: Restoration : HP 4262A LCR meter
« Reply #30 on: July 29, 2016, 04:22:20 am »
I had a Fali2 as well, can't remember what it was, it was a simple fix though.  That unit is very, very picky about the either the shorting straps or test leads.  You must have a good 4-wire connection.  Actually your tweezer setup looks pretty cool.  Thinking back, as I'll never have a test set either, I should have put BNCs on it when I replaced the banana jacks as that would have provided a shield.

I have the comparator on mine, it works well, I've used it for sorting and it is pretty handy.  You can set it to 1/10th a picofarad.  There is a asian guy on ebay that is selling the GPIB cable and what looks to be the adapter card.  I was thinking of grabbing it to have a fully configured box but then again, I doubt I would ever use it.

Let me know if you need any voltages tested.  I don't use mine much so if you need to swap some cards for trouble shooting we might be able to work something out.
 

Online TiN

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Re: Restoration : HP 4262A LCR meter
« Reply #31 on: September 17, 2016, 07:45:06 pm »
Worked a bit on this forgotted box. Got cables are replaced, so since -12V was faulty, time to get on power supply repair.
It's simple linear regulator, so after checking power transistors Q2 and Q3 (which were OK) only few parts remain to troubleshoot.

Replaced electrolytic capacitors C1,C2,C3,C4,C5 and U3 opamp (used far too good Linear LT1007 here, since usually don't have much stock for DIP8 opamps).
As result negative -12V rail powered up fine, just like new.

Schematics for those thinking at home:



Now front panel is responsive and LED displays are working. I think some buttons still flaky as it does not reliably react to key presses/sometimes lockes up.
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