Empathy List Archives

DC

David C. Partridge

Wed, May 2, 2012 5:04 PM

Thanks to a very kind gentleman, I received in the post today an Itron FG209C2 VFD and an ER-3400 NVM for my ailing 7081.

Naturally, it is still unwell even with these parts fitted, and getting it working will clearly be a labour of love.

I issued a calibrate,zener,103 and received in return a "Cal incomplete" message. Power off followed by initialise also gets me a "Cal incomplete" message to it looks like the new NVM is OK - yippee!

When I then try

calibrate,vdc=0.1,zero

I get a "Zero too large" error message so there's clearly still a fault on the floating boards. Mrs. Murphy said (*) that it would still have problems even after replacing the display and NVM, and boy was she right! Clearly it will be a labour of love to get this working again!

If anyone has any suggestions as to what is likely to be causing the "Zero too large" error, I'm all ears!

(*) Mrs Murphy's law: Murphy is an optimist.

Thanks
Dave

Thanks to a very kind gentleman, I received in the post today an Itron FG209C2 VFD and an ER-3400 NVM for my ailing 7081. Naturally, it is still unwell even with these parts fitted, and getting it working will clearly be a labour of love. I issued a calibrate,zener,103 and received in return a "Cal incomplete" message. Power off followed by initialise also gets me a "Cal incomplete" message to it looks like the new NVM is OK - yippee! When I then try calibrate,vdc=0.1,zero I get a "Zero too large" error message so there's clearly still a fault on the floating boards. Mrs. Murphy said (*) that it would still have problems even after replacing the display and NVM, and boy was she right! Clearly it will be a labour of love to get this working again! If anyone has any suggestions as to what is likely to be causing the "Zero too large" error, I'm all ears! (*) Mrs Murphy's law: Murphy is an optimist. Thanks Dave

DC

David C. Partridge

Thu, May 3, 2012 2:08 AM

It looks like the fault is in the input amplifier which is logically part of the DC ranging circuit. The error seems to appear at the output of IC402. Did anyone find the patent for this circuit - it is actually quite a complex circuit surrounding an LM343 with a discrete chopping arrangement using FETs an OP05 and LH0052 all of which I think is there to cancel the offset of IC402.

Dave
-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of David C. Partridge
Sent: 02 May 2012 18:04
To: 'Discussion of precise voltage measurement'
Subject: [volt-nuts] 7081 calibration "Zero too large"

Thanks to a very kind gentleman, I received in the post today an Itron FG209C2 VFD and an ER-3400 NVM for my ailing 7081.

I issued a calibrate,zener,103 and received in return a "Cal incomplete" message. Power off followed by initialise also gets me a "Cal incomplete" message to it looks like the new NVM is OK - yippee!

When I then try

calibrate,vdc=0.1,zero

I get a "Zero too large" error message so there's clearly still a fault on the floating boards. Mrs. Murphy said (*) that it would still have problems even after replacing the display and NVM, and boy was she right! Clearly it will be a labour of love to get this working again!

If anyone has any suggestions as to what is likely to be causing the "Zero too large" error, I'm all ears!

(*) Mrs Murphy's law: Murphy is an optimist.

Thanks
Dave

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and follow the instructions there.

It looks like the fault is in the input amplifier which is logically part of the DC ranging circuit. The error seems to appear at the output of IC402. Did anyone find the patent for this circuit - it is actually quite a complex circuit surrounding an LM343 with a discrete chopping arrangement using FETs an OP05 and LH0052 all of which I think is there to cancel the offset of IC402. Dave -----Original Message----- From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of David C. Partridge Sent: 02 May 2012 18:04 To: 'Discussion of precise voltage measurement' Subject: [volt-nuts] 7081 calibration "Zero too large" Thanks to a very kind gentleman, I received in the post today an Itron FG209C2 VFD and an ER-3400 NVM for my ailing 7081. I issued a calibrate,zener,103 and received in return a "Cal incomplete" message. Power off followed by initialise also gets me a "Cal incomplete" message to it looks like the new NVM is OK - yippee! When I then try calibrate,vdc=0.1,zero I get a "Zero too large" error message so there's clearly still a fault on the floating boards. Mrs. Murphy said (*) that it would still have problems even after replacing the display and NVM, and boy was she right! Clearly it will be a labour of love to get this working again! If anyone has any suggestions as to what is likely to be causing the "Zero too large" error, I'm all ears! (*) Mrs Murphy's law: Murphy is an optimist. Thanks Dave _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.

DC

David C. Partridge

Thu, May 3, 2012 10:39 AM

And just to annoy me, half way through checking the circuit, after taking voltage and signal readings off a good 7081, it all started behaving normally. I hate it when faults go and hide like that when you are trying to hunt them down!!!

Maybe a capacitor that had gone leaky had re-formed?

Dave
-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of David C. Partridge
Sent: 03 May 2012 03:09
To: 'Discussion of precise voltage measurement'
Subject: Re: [volt-nuts] 7081 calibration "Zero too large"

It looks like the fault is in the input amplifier which is logically part of the DC ranging circuit. The error seems to appear at the output of IC402. Did anyone find the patent for this circuit - it is actually quite a complex circuit surrounding an LM343 with a discrete chopping arrangement using FETs an OP05 and LH0052 all of which I think is there to cancel the offset of IC402.

Dave

And just to annoy me, half way through checking the circuit, after taking voltage and signal readings off a good 7081, it all started behaving normally. I *hate* it when faults go and hide like that when you are trying to hunt them down!!! Maybe a capacitor that had gone leaky had re-formed? Dave -----Original Message----- From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of David C. Partridge Sent: 03 May 2012 03:09 To: 'Discussion of precise voltage measurement' Subject: Re: [volt-nuts] 7081 calibration "Zero too large" It looks like the fault is in the input amplifier which is logically part of the DC ranging circuit. The error seems to appear at the output of IC402. Did anyone find the patent for this circuit - it is actually quite a complex circuit surrounding an LM343 with a discrete chopping arrangement using FETs an OP05 and LH0052 all of which I think is there to cancel the offset of IC402. Dave

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7081 calibration "Zero too large"