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

[AlfBaz]

Weird... I've never seen these filters blow and now two in a row, these shaffner's must be terrible 
As for the digits the 3457A defaults to 5 and1/2 digits on power up, just select number of digits (forgot the abbreviation) and select 6.
This thing is a 3million count meter which means that it can only go to 3.000000, which is good as a lot of meters (like flukes, I think) 6 and 1/2 means the first digit can only be a 1 befor you loose the sixth decimal place (1 million count ?)

[AlfBaz]

I forgot to ask, I see in one of the pictures you have a gpib cable, do you have a pc interface for it? if so which one?
I was thinking of getting a 82350B PCI card as they seem quite cheap compared to the PICe 82351A but then thought that I should spring for the extra cash and get the 82357B gpib to usb unit so that I can also use it with the laptop. I just need to look into compatibility with these units and the various standard drivers out there

[bingo600]

@AlfBaz

I found the "digits button" , and is now showing 6 digits 

The Gpib I/F you see there is a Prologix Ethernet interface , it works ok but is a bit slow if you want to transfer much.
I'd prob recommend the Prologix USB if you want a Prologix , mostly because there is a lot of source on the net for the USB version.
But in order to use a Prologix you must be into programming , as it doesn't automaticly support the NI or HP/Agilent drivers.

Basically the USB version is seen as a "Serial to GPIB" converter , and the Ethernet version is seen as a "Telnet to GPIB converter". So you have to send your own measurement commands.

If you're using windows , i'd recommend a Card or USB that supports the NI or Agilent DLL's.

I also have a Beiming GPIB (HP Clone) , that i got off Ebay for $50 ... A nice offer from an EU based seller.
http://www.ebay.com/itm/S82357-GPIB-USB-interface-Agilent-82357-compatible-/171021102514

If i should get one from Beiming i'd prob buy the newer version that supports DMA (Like the
http://www.ebay.com/itm/F82357-GPIB-USB-interface-Agilent-82357-compatible-/171021607671

Website : http://bmjd.biz/


Originally i have a NI PCI-Card , that i intended to install in my server (it's on 24/7). But the "only PCI" slot in my Mini-ITX board is PCI-Express 
So it's just doing nothing  right now.

If you just need hobby readings , i'd prob go for an USB based card , and if you're not Linux based as i am.
The Beimings should be Agilent compatible wrt. the drivers used under windows.

/BIngo

[AlfBaz]

Thanks for the info Bingo

[bingo600]

I got my new NON Schaffner mains filters today.

If you look at pic01 you can see the old Schaffner bulge at the back.


Pic02 shows a bit of the black "goo" on top at the front.


Pic04 shows the brand new Schaffner that died after 35 min of 230v.


Pic05 shows my new filter


Pic07 shows the "goo" that leaked to the outside of the meter.


Stay away from Schaffner mains filters.

Rignt now my 3457A is running burn in with the new filter , and i don't expect to have more troubles with the mains filter.

Once again thanx to AlfBaz , for the nice pictures.

/Bingo

[amyk]

Not surprising; you replaced the original with another made in Switzerland, those are the old ones which have problems. The ones made in Thailand should be OK.

[ddavidebor]

or even cheap china ones

[bingo600]

Not surprising; you replaced the original with another made in Switzerland, those are the old ones which have problems. The ones made in Thailand should be OK.

I know i did , because that was the only one i could get in a hurry.
I wrote about only being able to get the swiss ones , in a previous post.

I hoped it would work , does that mean the Schaffner's from Thailand is ok ?

/Bingo

[ddavidebor]

yeah, from thailand are ok.

[Tin Whiskers]

Schaffner mains filters have a short life (an example above is only 7 years, with no time in service) because they employ paper-dielectric capacitors.

Over time, the paper dielectric of a capacitor absorbs moisture even though it may be encased with a resin dip, for example. While mains paper capacitors are usually of the self-healing type, if the current flow due to moisture is too great and widely distributed in the dielectric, the capacitor will explode. This appears to be more likely when a capacitor is left unused for some time.

These days, paper capacitors (which generally have lousy specs) only see service in mains applications. Besides the capacitors in Schaffner filters, commonly seen brands of paper capacitors are RIFA and WIMA. All brands exhibit a short life and are unsafe (despite accreditations which may appear to suggest otherwise).

When paper capacitors absorb moisture they swell. This results in the commonly observed cracks in the resin case of paper capacitors and hastens their demise.

I recommend, for safety and reliability, that you avoid using any paper capacitors, such as RIFA and WIMA, and avoid filters with paper capacitors, such as Schaffner. In addition, these components should be immediately  removed from service - check to see if any of your electronic equipment harbours them.

[SeanB]

Funny enough I find oil filled sealed in a steel can with glass frit seals paper capacitors to be very reliable, at least an order longer lasting then plastic film units. This is in motor run applications, where I have some 40 year old paper capacitors that are still perfect, though the rubber sealed ones only ran 30 years before failing as the rubber seals cracked and let the oil out and air in. I am using polycarbonate caps as replacements.

[Tin Whiskers]

Yes, Sean, the reliability of a paper capacitor is improved if you provide a better barrier to penetrating moisture, and hermetic sealing works best of all.

Unfortunately, providing a better barrier increases the price. If a better barrier is necessary to avoid moisture absorption of capacitors in electronics, the use of paper as a dielectric material becomes uncompetitive. Therefore, necessity dictates that paper capacitors are components with poor performance.

For capacitors in electrical applications, a rugged case may already be an environmental requirement. If the rugged case also provides an adequate moisture barrier, the use of a paper dielectric may be viable, as you note, Sean. Regrettably, the Schaffner filter case does not provide a satisfactory moisture barrier.

[SeanB]

The Schaffners are good only as long as they are powered up regularly to keep them toasty. If you have to use one it would be best to bake it at 120C for 12 hours before use to dry it out. I have some that have been on for decades, though these are much bigger devices and are better sealed with a solder seam, not part of a socket inlet.

[lewis]

I thought those caps were metallised polypropylene? Didn't think they've used paper for years...

[SeanB]

Metallised paper/polypropylene blend is a very common capacitor dielectric. Cheap to make, smooth and can be sputtered on. Normally though I prefer to derate a little for longer life, they assume for self healing that you will have a large energy to clear faults, but not enough to actually blow it to pieces. Some I have unwound were missing more than half of the foil deposit on the plates. The polypropylene ones have a disconnect mechanism in the motor ones, where as it cooks and burns it builds up pressure and plastic foam in the case enough to pop the terminal cap off breaking the connection. Those have a warning that during operation you need a 10mm gap by the terminals for this disconnect mechanism to work. Some I have seen go a lot further than that, basically pooling a foam puddle onto the floor of the cabinet that is both sticky and stinks.

[skipjackrc4]

Wow.  I've never had one fail before, but I've recently bought a few pieces of older test equipment with these filters that I haven't run for more than a few minutes yet.  I'm nervous about relying on them, now. 

What brands of mains filters are safe?  It looks like I'll be buying a few pre-emptively.  I'm getting ready to move in a few months, so I'll have all my equipment off the bench anyway.

[kmel]

Same story here...  Just got 3457A and then Boom.

[Richard Head]

Amyk

Not surprising; you replaced the original with another made in Switzerland, those are the old ones which have problems. The ones made in Thailand should be OK.

We had a product that also blew up the Schaffner filter regularly. The dud units were also only ever the ones made in Switzerland. The eastern units were fine.

Dick

[winfreak]

Holy smokes!

I never knew that this could happen that easily in such expensive devices - I thought they might put a bit better components inside them, but nope, that's just nasty!

[PE1RKI]

are the corcom mains filters ok ? http://www.te.com/en/brands/corcom.html
i found one in a hp 438 from which i have several and maybe in all my other hp gear.

[Edward3121]

The Line Filter in my HP3457A has already ... I was planning to add one.

[Edward3121]

The Line Filter in my HP3457A has already ... I was planning to add one.

[MadTux]

These Schaffners are everywhere!!!!

And they strike with the most nasty and foulest smelling magic smoke that only Satan could have invented. How is it even possible to pack so much stinkiness in such a small space??

This time it came from a HP 3326A that I left running over night for some tests. Slept one room above and the nasty smell woke me up early on the morning and I guessed from the smell that something mayor had burned down. Went down and pulled all plugs. Next some coffee, then I went on to investigate what had burned. From the smell I first feared that the transformer or a big part of some PCB had fried, but fortunatelly the only part that fried itself was the Schaffner mains filter.

Only problem that I now have is that the Schaffner filter is part of the voltage selector and fuse assembly, which probably means that I have to do some Dremel-work to make the replacement fit into the assembly.

[SeanB]

Just use the Dremel to remove the filter and leave the input straps to solder the inside wiring to, then add another filter inside the case or just a simple MOV and 220n 275VAC Class X capacitor across L and N inside.

[WillTurner]

I have just acquired an HP3457A, and suffered the dreaded mains line filter failure within the first couple of hours of power being applied. As white smoke was jetting out of the rear and I was reaching for the power switch, I noted that the meter was still running. Hence the failure didn't cause me too much stress.
  I used a very small drill bit from outside of the case to start a pilot hole in each of the rivets, enlarged them to about 3mm, and the filter popped  leaving the bulk of the rivet in the case, the swarf on the bench, and none inside as far as I'm aware. I didn't think to strip the unit before tackling the repair  . The rivets look like they are brassy, and were quite hard. After squeezing the remainder of each rivet with pliers, I was able to push them out of the case.
  The soldered earth connector didn't impress, although I understand why it was done that way.  I replaced the schaeffer unit with a 6A generic item from the local electronics shop. I didn't re-solder the earth connector.
  Also, while I was poking around inside, I measured my CAL RAM backup battery voltage (3.4V). Not sure how useful this measurement is, since as I understand it the battery voltage drops off a cliff.