[volt-nuts] HP 3456A -3 Fault - re-cap info
cbrown at woods.net
Sat Dec 27 22:32:03 EST 2014
No problem, I just remember how much time I wasted trying to diag
intermittent fail 3, 4 and IIRC 10 or always fail but alternates which
test fails, etc before I noticed a bulging cap and ran across a posting
over in hp_agilent_equipment that set me on the re-capping path.
Then I was frustrated by being able to find all the value/spec info for
all of the caps but not being able to find original data sheets with
lifespan, dimensions and lead spacing...
Ended up pulling all the caps from one and measuring while taking notes
on available space.
Then sat down and spent the evening browsing mouser looking for approp
caps from the same series all long life high temp low esr type.
A good de-soldering station or gun (I have Hakko gun) and a temp
controlled iron will make re-capping easy.
I am in the habit of cleaning with isopropal after removal and again
after install of new caps. Local grocery pharma section usually has 99%
iso in hermetically sealed pint bottles on sale for 99cents every 90
days or so, and I keep a liter of 99.999% anhydrous lab grade for final
rinse of high impedance circuits.
Not exactly a big deal in a PS, but leftover flux can be corrosive and
often absorbs moisture.
The PS voltages can be checked in place, and you do really need a scope
Remember you have + and - supplies, pay very close attention and check
voltage/ripple before and after.
Make sure to check the large caps as well
A10C5 4000uf +100/-10 15vdc (Fat stubby large can on mail supply board)
A3C6 12,000uf +75/-10 16vdc (Large axial Sprauge over on A3 5v board)
Both of these in all 6 of mine were good, but is worth checking.
Outside of a regulator fail with burnt parts involved I have never head
of the glass sealed Ta caps (little silver axials) failing.
Another common issue is dirty/intermittant on the guard and front/back
With top/bottom panels and the adjust panel on is easy to deal with.
Dripping iso through switch while slowly cycling switch (cases off unit
up on end so drips out) followed by re-lube with deoxit D5 seems to work
well. (Deoxit D5 and D10 are 5%/10% deoxit 95%/90% iso). I have small
bottle of D100 and mix with iso when needed, generally about 98% iso.
Makes application easier, cause I can just apply 10ish drops to switches
like the gaurd and 20ish to the larger F/R switch while cycling to make
sure to fully penetrate and reach all contacts, but 98% evaps leaving
only a very light lube film.
On 12/27/14, 15:56, David Smith wrote:
> Wow Christopher, Thank You! I'm blown away by your kindness!
> I will get two sets of these caps ordered on Monday and see if I can get these two 3456's back in operation.
> Thanks again!
> Dave - W6TE
>> Date: Sat, 27 Dec 2014 15:08:04 -0900
>> From: cbrown at woods.net
>> To: volt-nuts at febo.com
>> Subject: Re: [volt-nuts] HP 3456A -3 Fault
>> First suspect is always the small electrolytics on A10, followed by the
>> large one on A10, and large one on A3, but those last 2 are large/high
>> qual and seem to last much better.
>> All 6 of my 3456As had or developed issues with one or more of the small
>> All 6 have been re-capped with
>> <part id>
>> <original P/N and spec>
>> <replacement P/N>
>> 0180-3009 47uf ±20 50vdc Al
>> Nichicon UPM1J680MPD6
>> 0180-2803 100uf +50/-10 50vdc Al
>> Nichicon UPM1J331MHD6
>> 0180-2635 1000uf +50/-10 35vdc Al
>> Nichicon UPM1V152MHD6
>> 0180-3014 330uf ±20 50vdc Al
>> Nichicon UPM1J391MHD6
>> 0180-3008 470uf +50/-10 35vdc Al
>> Nichicon UPM1V681MHD6
>> These are all direct match for lead spacing/etc except C8, where the
>> replacement is wider leads _but_ has a thick slotted base so you can
>> dog-leg the leads to match the original spacing.
>> All are long-life ± 20% parts, all are larger but fall within the
>> original range spec except C8, where going from 150uf (originally
>> selected part) to 330uf reduced p-p ripple from .45v to < .2v
>> DO check voltage and ripple, but if it comes down to it, the re-cap
>> takes about 20 minutes, including removing A10, pre and post recap
>> cleaning and re-install.
>> On 12/26/14, 14:34, David Smith wrote:
>>> Hello Friends,
>>> I have two HP 3456A's that have the same "-3" fault in the "test" mode. Both DVM's started exhibiting this same fault about the same time. I've troubleshot one of the DVM's to a failure in the Isolation Logic "Transmitter." I have no waveform at the output of A3T1.
>>> Before I continue with troubleshooting I thought I'd ask a question of the group. Is there a common mode failure of these DVM? Is there something in particular or area that I should be looking at/for?
>>> It's probably coincidental that they would both fail at about the same time with the same -3 fault.
>>> Your input is greatly appreciated.
>>> Best regards,
>>> Dave - W6TE
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