Test Equipment Anonymous (TEA) group therapy thread

[Cerebus]

better is to use a seperate filter bec. this all in one plugs are in front of the fuse, when they begin to burn like a RIFA you will have a lot of smoke on the bench.

Another argument for using filters that go after the switch is that the filter caps retain a charge for several seconds after the plug is pulled out (depending on exactly where in the mains cycle the break was made). This fact is known to many who've tried to re-route a mains cable behind a bunch of gear and stuck a finger into an IEC socket to figure out what orientation the plug needs to be. Ouch!

[Specmaster]

better is to use a seperate filter bec. this all in one plugs are in front of the fuse, when they begin to burn like a RIFA you will have a lot of smoke on the bench.

Another argument for using filters that go after the switch is that the filter caps retain a charge for several seconds after the plug is pulled out (depending on exactly where in the mains cycle the break was made). This fact is known to many who've tried to re-route a mains cable behind a bunch of gear and stuck a finger into an IEC socket to figure out what orientation the plug needs to be. Ouch!

Yes this is very true as bd139 will vouch 

Another reason of course is that with the filter where it is, the filter is constantly under stress from the mains even if the equipment is switched off and as such could let go at anytime, day or night as long as the unit is plugged into a live supply. With the filter after the switch, then it can only let go while the equipment is in use and hopefully you'll be there and can deal with it before it fills the house with smoke and stink.

[bd139]

Yeah fucking metcal bites me at least once a week on that!

Edit: to note it’s better for noise if the switch is after the filter which is why the filter is always first.

[Cerebus]

I can't speak for the newer Metcals like BD139's, but the older SP200 and MX-5 have the switch after the transformer, so the transformer primary is always live whenever the thing's plugged in.

[Specmaster]

I can't speak for the newer Metcals like BD139's, but the older SP200 and MX-5 have the switch after the transformer, so the transformer primary is always live whenever the thing's plugged in.

Thats a crap shoot, it means that your drawing power for no reason at all. Most devices designed to have a soft start usually have a separate very small transformer to provide 5V to power the switching functions which switch on the main devices via a relay.

[Brumby]

..... have the switch after the transformer, so the transformer primary is always live whenever the thing's plugged in.

I do not like products that are wired up like that.

I like a power switch that disconnects the mains.

[Cerebus]

Ditto.

The relevant standards that cover electrical safety for the same even insist on a means to isolate the mains. Unfortunately "pull out the IEC cable" is deemed to satisfy that requirement.

[mansaxel]

My shack /lab has too much metal (TE you know!) and quite a distance from the run-of-the-mill router/modem/wifi etc - a tp link ac 1750 type. For 150 aussie pesos - I got an extender and FFS it was actually easier to get going than they said!

I put another Cisco 2702 access point in the shack/workshop/machine room, where the old solution with only one AP didn't work at all. Now I have 5 access points spread around the house, and I can get 80megabits/second both directions to measurement servers on the Internet, and that's only because I cheaped out and chose 100Mbit bidirectional, the fibre is linking up at 1Gbit, but the ISP throttles it. Bandwidth is not a problem. ;-)

[tggzzz]

I can't speak for the newer Metcals like BD139's, but the older SP200 and MX-5 have the switch after the transformer, so the transformer primary is always live whenever the thing's plugged in.

The Tek 2901 is like that; the OCXO's oven is permanenly powered when plugged in.

[URI]

I dig out filter from my Fluke PM6685, looks promising  I have to find replacement that has connectors/cable exit underneath, there is not enough space for Schaffner FN9222-1-07.

That's not very much space. Perhaps you can use a FN9226-1/02. You can solder the old wires to it.
it's length is 35.15mm as per datasheet (I have attached it here).

This is a finding on ebay:
https://www.ebay.com/itm/322644207169

Tanks for the hint. I think that those 90° angled connectors won't fit through the IEC connector opening in the backplate.
I'm also looking for a drop-in replacement but haven't found one yet. 

[bd139]

BTW all the switched IEC inlet filter combos are the answer to all these zapping and exploding and filtering problems!

[McBryce]

I can't speak for the newer Metcals like BD139's, but the older SP200 and MX-5 have the switch after the transformer, so the transformer primary is always live whenever the thing's plugged in.

The Tek 2901 is like that; the OCXO's oven is permanenly powered when plugged in.

For a device with an OCXO that's quite common. My Agilent 53181 does that too, because you don't want to be waiting for the oven to come up to temp after you switched it on. But if the device has no reason for power to be available when switched off, then the power switch should be switching before the transformer.

McBryce.

[bd139]

Same with my 5334B as well.

[URI]

BTW all the switched IEC inlet filter combos are the answer to all these zapping and exploding and filtering problems!

Yes, indeed. -If you are present all the time the damned RIFA is on the mains.   

I use those individually switched Schuko-multi-outlets like this:

(Linked from www.pollin.de)

I use them since my first RIFA exploded inside my HP 3325B while it was warming up and I wasn't in the same room.
Only the mains fuse rescued the device from burning up -and that was how a became aware of the disaster.   

[Specmaster]

BTW all the switched IEC inlet filter combos are the answer to all these zapping and exploding and filtering problems!

Not if access to the rear is restricted, i.e. in a stack or rack mounted then you back to the original problem.

[Cerebus]

True, in that respect the old HP pushrod and switch trick is a better solution.

Also, the range of [switch + filter + (ideally) fuse holder + (optionally) voltage selector] units that are available are relatively small and, compared to separate component parts, expensive, and physical geometry can be a challenge too - even on a 'clean sheet' design -  if you're after something to fit a box smaller than about 3U.

[tggzzz]

For a device with an OCXO that's quite common. My Agilent 53181 does that too, because you don't want to be waiting for the oven to come up to temp after you switched it on. But if the device has no reason for power to be available when switched off, then the power switch should be switching before the transformer.

M pretty sure I have some HP equipment like that, but I can't be bothered to et it all out and check!

[mnementh]

   Some of the Sawdust and Shavings are starting to pay off. Still some Dog Holes to drill but a very flat, true and square 40mm thick second bench has emerged from the work. It will double as extra TEA Bench space as needed but it is primarily designed for accurate 90 degree cuts using the Track Saw.
Planing up the Oak to the match the MDF top was satisfying with sharp blades. The MDF is the reference edge while the Oak is just protection for me from the sharp edges and bumps and bruises in use. Gratuitous FUSION 360 screenshot just for @bd139 

Hmmmm... looks to me just the right size to hold up 4 pints and a bowl of peanuts.     Always a bonus.

mnem
*totally hating Rocket League right now*

[mnementh]

BTW all the switched IEC inlet filter combos are the answer to all these zapping and exploding and filtering problems!

Not if access to the rear is restricted, i.e. in a stack or rack mounted then you back to the original problem.

No, you guys are just not thinking in the right mindset; that of a commercial equipment designer. 

These instruments are ALL intended for use in a commercial/laboratory environment. They expect you to be plugging them into a proper workbench, which will have power bar(s) with a common main switch to kill EVERYTHING when you go home at night for safety's sake. A good bench will have more than one power bar; so you can plug things in that need to stay hot separately, yet still be able to kill power quickly in event of electrical evil or turn those things off as well when you expect to be away for a week or three over the holidays.

They do NOT build this equipment with amateurs and home labs in mind.

mnem
*gifted amateur*

[Cerebus]

You're making the assumption that all this is going on an electronics workbench, it isn't. Just as much test gear ends up scattered around in physics labs, chemistry labs, and even biology labs where they don't end up on a purpose designed workbenches. And then there's the 1000s of units permanently installed in racks as experiment/process specific jigs. And then there's the field engineer up a ladder/tower, down a hole/pit/mine, in the back of a van at a well head, ...

A decent commercial equipment designer has to consider all the end use cases.

[mnementh]

No, they have to design within the SOW. Which is pretty globally EXACTLY as I just described. They don't care if it's inconvenient to YOU the edge-case buyer.   They care about fulfilling the needs of their "Buys by the 1000" clients, which expect exactly that operating environment. They have "ruggedized" and customized products for the kind of use cases you suggest.

mnem

[Specmaster]

No, they have to design within the SOW. Which is pretty globally EXACTLY as I just described. They don't care if it's inconvenient to YOU the edge-case buyer.   They care about fulfilling the needs of their "Buys by the 1000" clients, which expect exactly that operating environment. They have "ruggedized" and customized products for the kind of use cases you suggest.

mnem

I'm not so sure that those kinds of customers exist any more, or if they ever existed even. I really struggling to think of any company large enough to purchase in those quantities, 100's maybe, but there again I'm struggling TBH.

[mnementh]

Okay, so the numbers are smaller now. They make up for it by charging 10x more per copy. 

In today's cookie-cutter world, everything is planned for the convenience of the accounting department, which likes neat little rows of THINGS that correspond with neat little rows of LINE ITEMS on an inventory sheet. This is why there are millions of dollars spent every quarter on specialty workbenches that get used for a year or three then replaced with newer, nearly identical specialty workbenches with a slightly different layout, which functionally makes no difference to the technician using them.

NOT because it's worn out or makes the work easier or better; but because it helps pinheads with clipboards check things off a list at inventory time.

Gear for pretty much any other SOW will start with that "intended for use on a purpose-built bench" basic design and modify it; very little is designed from the ground up "for-purpose" any more. Things like those portable TDRs are such a fascination to folks like us for just that reason. 

mnem
 

[bitseeker]

better is to use a seperate filter bec. this all in one plugs are in front of the fuse, when they begin to burn like a RIFA you will have a lot of smoke on the bench.

Another argument for using filters that go after the switch is that the filter caps retain a charge for several seconds after the plug is pulled out (depending on exactly where in the mains cycle the break was made). This fact is known to many who've tried to re-route a mains cable behind a bunch of gear and stuck a finger into an IEC socket to figure out what orientation the plug needs to be. Ouch!

I resemble that remark. I haven't been bitten, yet. However, it does cross mind when I check orientation that way.

[Specmaster]

I do the same with the gear in my stack, and so far I have not been bitten yet, just don't say it too loud or else the equipment might hear and devise a plan to get me next time