Author Topic: HP 34401a Self Test Fail  (Read 3033 times)

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Offline lkmurdoch

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HP 34401a Self Test Fail
« on: July 10, 2014, 07:23:36 pm »
Hi everyone,

My first post so here goes.....

I have a HP 34401a that fails self test. It does measure AC volts, DC volts reasonably accurately (very close to a Fluke 45) but Ohms is way off cal.

The Ohms function measure 00.000 when the leads are shorted, but nothing else. I have checked for signs of obvious damage internally and checked the

power supply voltages which are fine. Any suggestions gentlemen?

Thanks in advance,

Mike
 

Offline free_electron

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Re: HP 34401a Self Test Fail
« Reply #1 on: July 10, 2014, 09:52:11 pm »
error code ?
Professional Electron Wrangler.
Any comments, or points of view expressed, are my own and not endorsed , induced or compensated by my employer(s).
 

Offline Dr. Frank

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Re: HP 34401a Self Test Fail
« Reply #2 on: July 11, 2014, 06:59:18 am »
Hi and welcome..

not possible to figure out. I suggest you give more detailed hints:

- do you run the self test, and then you get an error?
- error code available?
- what does the instrument read in the different Ohm ranges, each 2W and 4W, with shorted leads and with resistors of appropriate value attached?
- did you check the same on the rear connectors?

Frank
 

Online tszaboo

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Re: HP 34401a Self Test Fail
« Reply #3 on: July 11, 2014, 08:15:42 am »
Download service manual from Agilent. Check for your error code in that.
 

Offline lkmurdoch

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Re: HP 34401a Self Test Fail
« Reply #4 on: July 14, 2014, 04:09:38 pm »
Hello all,

No error code was displayed after the self test.

I checked the Ohms current source opamp (U201) for correct supply and reference voltages and they are correct.

Interestingly on a whim I checked for a voltage on the test leads of any kind and the is none.....the Fluke 45 on the bench shows 1.56 volts DC.

Therefore I suspect that there is indeed an issue with the Ohms current source.

I would appreciate any insights any of you my have to offer.

Michael
 

Online tszaboo

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Re: HP 34401a Self Test Fail
« Reply #5 on: July 14, 2014, 04:58:45 pm »
On the ohms, there are about a dozen transistor in a weird configuration. They are that way for protection. I would check if they are good.
 

Offline VK5RC

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Re: HP 34401a Self Test Fail
« Reply #6 on: July 17, 2014, 08:33:03 am »
Front -  rear different ,  2w 4w different? 
Whoah! Watch where that landed we might need it later.
 


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