Author Topic: Advantest R6551 DMM  (Read 1763 times)

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Offline radhaz

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Advantest R6551 DMM
« on: March 16, 2015, 04:04:00 am »
I purchased an Advantest R6551 bench DMM from ebay. It has an issue in that all modes drift around an offset of 10s to 100s of counts as if there is noise in the circuit. AC volts is the worst.
This was a 230VAC unit, and I powered it up using a step up transformer. I opened the unit and saw a jumper to select the input voltage, so I changed the input to my local 120VAC, but there was no change in performance.
The PCA appears to have not been meddled with with the exception of the battery, which had rosin residue indicating it was changed at some point. The date on the battery is from '03, and it measures 3.7 or so volts.
I wonder if the cal has been lost. Does the drifting fit the description of a lost cal? The user manual has a cal procedure, and I'll try that when I have time.
 

Offline Vgkid

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Re: Advantest R6551 DMM
« Reply #1 on: March 16, 2015, 06:50:13 am »
Do you have the leads shorted when testing?
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline radhaz

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Re: Advantest R6551 DMM
« Reply #2 on: March 16, 2015, 10:58:45 pm »
Leads are shorted in all modes.
 

Offline Testtech

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Re: Advantest R6551 DMM
« Reply #3 on: March 16, 2015, 11:46:47 pm »
Check or replace all the aluminum electrolytic caps. The symptom suggest power supply noise. I would replace them if it were in my shop.
 


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