Just got 3457A and then Boom

[AlfBaz]

My HP 3457A finally arrived today, well packed, neat looking unit, opened it up, very clean, new battery, 44491A relay card installed  .

Visually inspected mains section, adjusted from 120 to 240V plugged it in and all was good. Ran the self test, no errors, 149 cals!

Sitting with the unit on for about an hour looking over the manual then, fzzzz... flames shot out the back. I got up blew the fire out and unplugged the chord from the wall.

Don't know if the internals have been damaged. So far its looking like the IEC socket on the back of the unit has failed. I'm hoping live to neutral/earth is were the energy went and the rest is unscathed. I will power up the transformer and see if all the voltages are good and pick up another IEC socket tomorrow before finding out the fate of this meter

[Jay_Diddy_B]

Hi,

It looks like a line filter failure to me. You might be lucky. It has certainly made a mess of the back of the unit.

You may need to get a new fuse holder. I can't really tell from the photographs.

Good luck !!!

Jay_Diddy_B

[AlfBaz]

Thanks Jay

The fuse holder seems OK, mostly covered with tacky gunk I'll wack 1000V on it from my insulation tester before re-using it.

As for the line filter, I suspect after years of operating at 120VAC in the US, the 240V here in Australia finally killed it.

[Ed.Kloonk]

Thanks Jay

The fuse holder seems OK, mostly covered with tacky gunk I'll wack 1000V on it from my insulation tester before re-using it.

As for the line filter, I suspect after years of operating at 120VAC in the US, the 240V here in Australia finally killed it.

And also because of the gigatrons on the wire running back to front down here, definitely.

[amyk]

It's those bloody Schaffner line filters again... they're potted with a tar-like substance that makes a horrible smell when the caps inside blow up. Apparently NOS ones are no good either, so you should get a new one to replace it.

[dimlow]

Sorry but this makes me happy. I just got a Solartron meter, but i took the option of replacing the mains filter before i used it. So i'm happy i changed it. Not happy about you loss hopefully its only the IEC filter that blew and it has not damaged the meter. I read that the gunk it real hard to get off. I wish you luck with the repair.

[AlfBaz]

I had it sitting where my keyboard normally sits when it went off, it sprayed gunk all over the lower left hand side of my monitor. Managed to get it off with some light scrubbing and hot soapy water. Hopefully the same result with the back meter panel. Yeah it was definitely a weird smell!

I'll go into town tomorrow and pick up one of these for $10 from jaycar and the right size mains fuse while I'm at it. Can't quite make out the brand but it should do the trick. I'll have to drill the rivets out of the original one

[free_electron]

Right, that's it.. I'm checking all my machines for those schaffner thingies and swapping em all out. Bloody swiss junk...

[AlfBaz]

Considering that leaving these things running unattended would not be uncommon, it's definitely a fire trap!

[alm]

I guess exposing them to 240 Vac doesn't help. The big US manufacturers like HP and Tektronix would sometimes use components that were reliable at 110 V but marginal at 240 V (although I'm sure they were specced to work at 240 V, these engineers weren't stupid). But I'm not sure how big a role voltage plays in killing these EMI filters.

[ddavidebor]

I had it sitting where my keyboard normally sits when it went off, it sprayed gunk all over the lower left hand side of my monitor. Managed to get it off with some light scrubbing and hot soapy water. Hopefully the same result with the back meter panel. Yeah it was definitely a weird smell!

I'll go into town tomorrow and pick up one of these for $10 from jaycar and the right size mains fuse while I'm at it. Can't quite make out the brand but it should do the trick. I'll have to drill the rivets out of the original one

you're luck that your is the cheap filter type (7-8€)

i need to change 2 37€ filter

[bingo600]

Dammm  (Thanx)

I have a 3457A @ "Customs" right now ...

Have just ordered a new 230v filter unit.

Had to get another (newer) schaffner 

That was what i could get ....

/Bingo

[lewis]

I had exactly the same problem with my 3457 just after I got it, managed to catch it in time before leaving the workshop overnight. No damage to the unit, just a horrible smell and plenty of black smoke. Thought it was a one-off, but might go through and replace the filters in everything after your experience.

[lowimpedance]

I guess exposing them to 240 Vac doesn't help. The big US manufacturers like HP and Tektronix would sometimes use components that were reliable at 110 V but marginal at 240 V (although I'm sure they were specced to work at 240 V, these engineers weren't stupid). But I'm not sure how big a role voltage plays in killing these EMI filters.

I have a TEK 2235 that was new at the time way back ! and its filter 'went boom' when it was in for cal at Tektronix!  , They replaced it and all was good --- for a few years at least. Got it out of storage some time back at powered up for a run and a short time later 'boom' again with that horrid smell  . Quick check and yes the bloody filter again. Replaced with a different brand and appropriate ratings and so far all good.

@AlfBaz nasty looking mess, but should clean up okay, smell might take a little longer, but its most likely the meter is still fine. good luck. (maybe change your back up battery at the same time!).
LowZ

[Rufus]

I guess exposing them to 240 Vac doesn't help. The big US manufacturers like HP and Tektronix would sometimes use components that were reliable at 110 V but marginal at 240 V (although I'm sure they were specced to work at 240 V, these engineers weren't stupid). But I'm not sure how big a role voltage plays in killing these EMI filters.

Modern class X and Y capacitors for use in mains filters are very conservatively rated. They are specified and tested to withstand voltage spikes of 2.5 to 8kV depending on class so the difference between 110 and 240v should be trivial.

I find these stories of mains filter failure surprising. That is exactly what they are supposed not to do because it can be a shock hazard, but, who knows what they were built with 'back then'.

The only mains filter failure I have seen was due to a badly wound common mode choke where a turn from one side crossed over a turn from the other.

[Bored@Work]

Modern class X and Y capacitors for use in mains filters are very conservatively rated.

Yes, modern ones, maybe. But these ones are old crap. I have had them going boom on me, too. Last one was the notorious filter of a Solartron 7150. And second to last going boom was a singel X cap, not a filter module, on a Tek 2446. And if we talk about other things than measurement instruments, just last week a cap in a old Bosch angle drill went boom on me.

They simply don't age well.

[AlfBaz]

It lives! 

[dimlow]

It cleaned up rather nice too

[bingo600]

It lives! 

How hard was it to get the old filter out ?
I mean it looks like it was riveted in , and one might need a drill.

I would like to avoid toremove all the plugs on the backplate , and drill it out if it's possible ....

Any hints for my upcomming meter (still @Customs)

/Bingo

[AlfBaz]

You are going to have to drill them out and unfortunately, its best to drill them from the inside out, which means that if you don't remove the back panel you run the risk of getting filings everywhere. From the outside, the rivets are flat and larger in diameter than the rivet holes, so you run the risk of drilling off centre.

There's only 3 plugs to pull out, 1 to the acquisition board, and 2 on the digital board. Follow Dave's video on the dismantling.

You will have to remove the top shield off the digital board as this allows the bottom shield to move a little. Remove the 2 screws just above the coms port.
Slightly lift the back panel and when it clears the groove in the plastic casing you should be able to flex the centre of it out enough to disengage a tab from the lower digital boards shield.

Its late here now but if you like I could take some pictures tomorrow and post them for you

[bingo600]

You are going to have to drill them out and unfortunately, its best to drill them from the inside out, which means that if you don't remove the back panel you run the risk of getting filings everywhere. From the outside, the rivets are flat and larger in diameter than the rivet holes, so you run the risk of drilling off centre.

There's only 3 plugs to pull out, 1 to the acquisition board, and 2 on the digital board. Follow Dave's video on the dismantling.

You will have to remove the top shield off the digital board as this allows the bottom shield to move a little. Remove the 2 screws just above the coms port.
Slightly lift the back panel and when it clears the groove in the plastic casing you should be able to flex the centre of it out enough to disengage a tab from the lower digital boards shield.

Its late here now but if you like I could take some pictures tomorrow and post them for you

Ohh yes  please ...
I'd like that very much.

I'm always a bit shaky when disassembling a unit for the first time.
I'll check the battery voltage after i have changed the Mains Filter unit.

Thanx a lot

Ohh and nice cleanup job 


/Bingo
 

[AlfBaz]

Here you go
1 Remove the top lid


2 Remove the shield covering the digital board


3 Locate the three power plugs and remove them




4 Remove the two screws holding the HP-IB port


5 Gently lift the back panel. As it clears the groove in the bottom plastic lid, pull the back panel until the tab disengages.


6 You should now be able to lift it out


7 You will have to desolder the earth lug and resolder it to the new filter. You may want to unbolt and remove the transformer so you can get decent access to the rivet in between it and the filter

[bingo600]

@AlfBaz

Thanx a million ... For the pics , and detailed hints 

And it seems like Customs has released my 3457A to the "Mail" .... Hoping ...

/Bingo

[bingo600]

@AlfBaz

Using your nice pictures, as a guide. I have now changed my mains filter 
Now i finally had a chance to use my new Bosch Drill-stand (notice the laser cross) 

The hardest part was actually to get the soldered earth plug off the mains filter.

But as i wrote further up .... I could only get some other Schaffner mains filters , with such short notice. 

And guess what happened after approx 35 min of power-on with the new filter ....
Mini "boom" , and that "smell" of burned electronics .....
The new filter had leaked a tiny bit of "goo" , but only outside the meter ...
A bit on the mains wire , a black spot on the wall , and a tiny bit on the alu back-frame & on the plastic top.

Schaffner products sucks big time 

I opened it up , and it was totally clean inside , so i cleaned it up and closed it again.
But i don't trust it , and don't know if i should be worried about fire or the likes.
Even though i use it right now with the new mains filter , i don't dare to let it be powered on unattended.

So i have ordered some new "NON Schaffner" filters , and will do my best to warn against those Schaffner products when using 230v mains.

I measured my battery and it was at 3.479 volts , so i won't change it for now.

I am getting good at opening the meter , and will have to do it again in a few days when the new mains filters arrives.

So guyzz  keep away from Schaffner products , even the NOS filters explode.
So it wasn't about them getting 120v first and then 230v , they can "implode" even when they have only seen 230v.

Ohh i checkked my A11R644 & A11R645  - pict 0037 -
They have been adapted to the new 3.4v battery levels (it's in a service note in the manual)

The Keithley shows 2v on my "Not yet restored & calibrated" EDC E100C voltage ref.

Btw: I would have expected another digit on the 10v (Geller reference) measurement on the 3457A (NPLC 100) , but it seems drop a digit after 3+v  .... Any hints would be welcome.
Strange ... The Keithley doesn't , and have 5 digits after the decimal point when measuring 10v.

/Bingo

[bingo600]

Here is some picts i took , as an archive

/Bingo