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-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...] On Behalf Of xyloeye
Sent: Saturday, January 19, 2013 10:07 PM
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Re: HP 3468 DMM battery change





I finally had time to get back to it tonight. Joe mentioned power supply
voltages. I had checked random points to make sure the power supply was
running but I failed to check all the voltages at the service jumpers. When
I did, all but the -15V rails were very low. I disconnected the jumpers one
by one but nothing past them was dragging the voltages down. I thought I had
it narrowed down to one of the temperature sense resistors. I was looking
over the board with magnifiers when I spotted a small piece of solder
shorting two pins of the main regulator (U701). I didn't see it before
because it was hidden under the heat sink. Must have happened when I did the
battery change.

So I'm up and running. All I have to do is calibrate it and I think it'll be
good to go. So thanks, all of you who made suggestions. I broke the cardinal
rule of checking all voltages first. I really appreciate your help.

Ken

--- In hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com> , "J. L. Trantham" wrote:

Did you check the power supply voltages?



Joe



-----Original Message-----
From: hp_agilent_equipment@...

<mailto:hp_agilent_equipment%40yahoogroups.com>

[mailto:hp_agilent_equipment@...

<mailto:hp_agilent_equipment%40yahoogroups.com> ] On Behalf Of xyloeye

Sent: Friday, January 18, 2013 1:52 PM
To: hp_agilent_equipment@...

<mailto:hp_agilent_equipment%40yahoogroups.com>

Subject: [hp_agilent_equipment] Re: HP 3468 DMM battery change





Yeah, I disconnected the battery overnight and shorted the RAM chip Vcc to
gnd to clear any leftover capcitance, etc. That had no effect. I'm kind of
thinking maybe something was on the verge of failure and I pushed it over
the edge. Problem is, even if I narrow it down to a component, all of the
chips are unobtainable now.

Thanks again for your help Jeff.

Ken

--- In hp_agilent_equipment@...

<mailto:hp_agilent_equipment%40yahoogroups.com>

, Jeff Machesky wrote:

You may need to disconnect the battery again to allow the RAM to "zero"
out. Well at least not be in it's present state.

Just a thought,

Jeff

On 1/17/2013 5:16 PM, xyloeye wrote:

Thanks for your reply. You're right, error 1 is calibration RAM. I
tried to calibrate it but since the display is dead, it's hard to do.
When the lead fell off I'm positive it didn't touch anything else. I
just can't figure out how disconnecting the battery would cause a dead

display.

Ken

--- In hp_agilent_equipment@...

<mailto:hp_agilent_equipment%40yahoogroups.com>

, "J. L. Trantham" wrote:

I tried to remove and read the contents of the ROM on my 3478A. In

the

process, I apparently shorted the 5 V line to ground, which somehow

killed

the contents of the CALRAM. In any event, there was a message about
Calibration. I then replaced the battery and went through the

recalibration

steps and all was well.



According to the manual for the 3468A, Error 1 is 'Calibration RAM

Error'.

Error 2 is 'RAM Error'.



I suspect that the issue is that you lost the RAM contents for the
Calibration RAM. Have you tried to calibrate the unit? Have you

checked

the power supplies?



The alternative is once the lead slipped off, it 'connected' to

something

else and took out something. Was it the + or - lead?



Sounds like you need to go the service manual and start with the

trouble

shooting section, probably Service Group E, and go from there.



Good luck.



Joe



From: hp_agilent_equipment@...

<mailto:hp_agilent_equipment%40yahoogroups.com>

[mailto:hp_agilent_equipment@...

<mailto:hp_agilent_equipment%40yahoogroups.com>

] On Behalf Of xyloeye

Sent: Thursday, January 17, 2013 2:06 PM
To: hp_agilent_equipment@...

<mailto:hp_agilent_equipment%40yahoogroups.com>

Subject: [hp_agilent_equipment] HP 3468 DMM battery change





I'm having some trouble with a battery change in a 3468 DMM. You

would think

I could handle that without incident! I kept 3 volts on the

terminals while

soldering in the new battery but one of the leads slipped off and

there went

the calibration. No problem - I can calibrate it again or so I

thought. The

display flashed "error 1" (ram error)and then went blank. It's been

blank

ever since despite all the resetting procedures I've tried. Could

corrupt

ram cause this? Or is could I have somehow damaged the controller?

Any

thoughts would be appreciated.