Test Equipment Anonymous (TEA) group therapy thread

[kj7e]

Look what I found laying around in a cabinet at work, no one even remembered it was there.  I've never seen a Fluke 1953 before.

[mnementh]

So... did it follow you home too? 

mnem
 

[kj7e]

So... did it follow you home too? 

mnem
 

No... (still working).

[tggzzz]

Bugger. I've just bought a Fluke 8125A multimeter. If I can get it working my life will be complete since it has the only common[1] display I don't have: nixies. Now all I have to do is go and pick it up.

While there might or might not be one for for sale on fleabay $688, I paid somewhat less than that, and there aren't any completed listings for me to guess its resale value.

[1] yes, that's the weasel word to hopefully avoid pedants convincing me my life is incomplete.

Well, I went to the end of the world and got it. Google streetview hadn't even got that far, and one of the three bridges there was blocked by a large lump of concrete, probably because the bridge had concrete cancer. I chose the next bridge, 10m / 2miles away, and found my destination amongst the brambles. The Forest of Dean[1] was visible on the horizon, on the other side of the estuary. If I'd gone 10 yards further I'd have been in salt water.

The bloke told me it worked but he didn't have any leads. (So how did he know it worked?) The lack of a mains lead was going to be a problem because the mains enters The Thing via a front panel socket and is screwed in to hold it in place.  Oh well, for the price I paid it was worth it.

So brought it home, didn't hose the grime off the outside because I presumed the seals were buggered, opened the lid, opened the compartment in the lid, and found a mains lead. Joy

Plugged it in, manhandled the on/off switch, a front panel light came on - but nothing else. Drat.

Started disassembling it, looked clean, no defunct caps, batteries where they should be, turned it on and found a bit of the PSU that was literally glowing, went and had some coffee.

Came back, found an "AGC" fuse was deceased. Found a replacement clipped in the lid, turned it on again and applied 9V to the input terminals...


The observent will notice an unusual component near the rear bulkhead.

I'll do more of a teardown in another thread.


[1] for those overseas, the Forest of Dean is strange in many ways. They still have people hacking coal out of mines with pickaxes and pit ponies, and the shops have recently dragged themselves into the 1960s. Much like the Fens, in a different way.

[mnementh]

Looks like a dual-filament light bulb, like they low-profile ones they used to use in some motorcycle lighting back in the day. Effed if I can remember the GE number, tho.

mnem
 

[mnementh]

So... did it follow you home too? 

mnem
 

No... (still working).

So... all you're willing to say is "Not yet..." ?

mnem
He's working on it...

[bd139]

tggzzz: nice win that one. The bulb I reckon is part of the NiCd charger for it. Another application of the old non-linear I-V curve magic trick.

Please post the thread link when you're done posting in it

As for the Forest of Dean, been there, know what you mean. They have smartphones in the Fens. They're still banging rocks together down that way though.

[tggzzz]

tggzzz: nice win that one. The bulb I reckon is part of the NiCd charger for it. Another application of the old non-linear I-V curve magic trick.

Please post the thread link when you're done posting in it

As for the Forest of Dean, been there, know what you mean. They have smartphones in the Fens. They're still banging rocks together down that way though.

Don't think it is part of the charger circuit; I suspect it is a voltage limiter in fault situations. ISTR seeing that technique, but I can't remember the details offhand.

Fenlanders tend to inbreed to produce oxen, Deanlanders to produce dwarves. Fields vs mines and all that.

Daughter found a trip to the FoD quite enlightening. I don't dislike it since it has contours and trees, unlike Fenland and south Lincs.

[bd139]

Interesting. Will have to read up.

They have hills because it stops the dwarves escaping

[tggzzz]

Interesting. Will have to read up.

They have hills because it stops the dwarves escaping

Dwarves tunnel through hills, but water is more of a problem. That's why you don't see them in the boggy Fenland.

[med6753]

Well just spent an hour trying to catch up. Progress here with the deck work is going slower than expected. Monday was a washout because it rained. So today got the brush all cut in the blazing heat. It still has to be chopped up and disposed of. The lumber required for the deck work has been inventoried and purchased. Will start on deck replacement which won't be until after all the cut brush is gone. So probably Thursday. Having 90 degree F temps everyday which is not fun. SPF 50 sunblock required.

Just got the call to supper......bye. 

[kj7e]

So... all you're willing to say is "Not yet..." ?

mnem
He's working on it...

Going to take it home to clean it up and calibrate it, maybe check it out for awhile.  I recently bought a HP 53181a with option 10 for the Engineers here at work, so they wont miss this 1978 relic taking up valuable space.


Meanwhile, yet again admiring the quality construction of vintage HP gear.  Took a few photos while I was calibrating the 3310B Function Gen.







It took me a long time to calibrate, Claire Bear (Lab Helper) was not helping much.

[Specmaster]

It wasn’t that. It was the (measured) dead short across the heater in that handle when pushing the tip in exceeding the SOA of the MOSFET. Boost converter was fine as it wasn’t even in circuit when the second one exploded.

I spotted that potential when I had to rework the 9501 handle I purchased to work on a 4 pin system rather than the 5 pin one that it came configured for and if I remember correctly, yours was a 5 pin system? I always turn mine off if I want to swap tips over and was also another reason for getting a second station as I noticed that the tips themselves were not the most solid ones available being as they were cheap but effective clones and it was all too easy to catch the contact rings when swapping them and then can come undone causing problems. So I keep the most used tips fitted to the handles and switch them both on and use which ever is the most suitable, or just unplug the handle and swap over for the other tip when required.

[Specmaster]

tggzzz: nice win that one. The bulb I reckon is part of the NiCd charger for it. Another application of the old non-linear I-V curve magic trick.

Please post the thread link when you're done posting in it

As for the Forest of Dean, been there, know what you mean. They have smartphones in the Fens. They're still banging rocks together down that way though.

Whats that then, a form of current limiter, rather like a dim bulb tester?

[beanflying]

I had a similar  lightbulb moment when I first opened my Fluke 515A Calibrator. The manual snips below may help.

[ArthurDent]

In post #34191 mnementh showed us his ‘twins’ so not being proud, I stole his idea and am posting a picture of my own  ‘twins’.  I’m not sure how many people would be interested in what the innards of my new GW Instek PSM-2010 programmable power supplies look like so I have only included a short description.

 A few weeks ago I bought my first GW Instek PSM-2010 programmable dual range power supply for cheap. I was impressed by its quality and the features so when I saw another listed on eBay I submitted a ‘best offer’ which was accepted. I finally received the supply today after FEDEX let it sit in one of their depot for 4 long days. It was in good shape and worked as expected. Briefly these supplies are 0-8VDC at up to 20A or 0-20VDC at 10A and you can set the output voltage to about the nearest millivolt and the current to the nearest milliamp.  The dimensions are 230mm (9”)W×140mm(6.5”)H×380mm(15)L  and weight is approx. 10kg(22Lb). The spec sheet shows it is nice and stable and my 6.5 digit HP 3457A shows that it is. There are memories and multiple voltage and current safety features that I never had on my older supplies. The cost for the pair (minus shipping) was under $200.

With the cover removed you can see 3 reinforcing steel pieces going front to back and the front of the middle reinforcing piece has a steel post and screws to connect the front of that plate to the bottom plate of the supply so the plastic front panel isn’t seeing that weight. The carrying handle on the top of the case is fastened to this piece so it has to be strong.

The inside of the front panel on the right shows that there are multiple sub-assemblies used to separate functions and make it easier to service. The stranded wire used for the main current path looks like AWG #10. There are 2 heavy current shunts on the main board right in front of the heatsink.

Plugging into the main board is the board with the 16-bit DAC and 20-bit ADC. Notice that all the main commons on this board radiate from a common star point to prevent unwanted voltage drops from affecting accuracy and stability.

Computer control or logging goes through a GPIB/RS232 interface board and I noticed one of the chips is made by National Instruments so it should work flawlessly with their software.

The fan is controlled by the amount of drop across the series regulator but where this supply has a non-linear pre-regulator that keep the voltage across the series regulator low, the fan never has to run that fast and is very quiet no matter what the output load is.

[mnementh]

mnem
*proud to be an inspiration*

[bitseeker]

When I was a kid a chimp did that, and hit me on the back of its head. They did it because they were bored.

I once played catch with a bored orangutan at a zoo. We tossed a stick back and forth until it was either dropped or thrown out of reach, I don't recall. The orangutan looked a bit depressed that the fun was over.

[mnementh]

And Now For Something Sort of On Topic...



http://s3data.computerhistory.org/brochures/era.magnetic-storage-systems.ca1958.102646316.pdf

I just stumbled across this while looking for other stuffs; a really interesting bit of computer history. It is part of www.ComputerHistory.org's "Selling the Computer Revolution" online collection of brochures dating back to 1948.

https://www.computerhistory.org/brochures/

Cheers,

mnem
*Impairing productivity since nineteen-mumblety-mumble*

[bitseeker]

Look what I found laying around in a cabinet at work, no one even remembered it was there.  I've never seen a Fluke 1953 before.

Cool. I haven't seen one before, either. Added to POI.

[bitseeker]

Meanwhile, yet again admiring the quality construction of vintage HP gear.  Took a few photos while I was calibrating the 3310B Function Gen.

Added this one, too.

[GregDunn]

And Now For Something Sort of On Topic...



http://s3data.computerhistory.org/brochures/era.magnetic-storage-systems.ca1958.102646316.pdf

The first computer I ever got to actually operate / program (Bendix G-15) had one of those as its main memory.  You had to type in a bootloader which loaded a paper tape which transferred operation to the mag storage.  It was filled with logic gates where you could actually see the electrons circulating:

[Ero-Shan]

Came back, found an "AGC" fuse was deceased. Found a replacement clipped in the lid, turned it on again and applied 9V to the input terminals...

Now that's a nice meter! Congrats!

The observent will notice an unusual component near the rear bulkhead.

You mean the interior lighting?

I'll do more of a teardown in another thread.

I'm looking forward to it.

[tggzzz]

I had a similar  lightbulb moment when I first opened my Fluke 515A Calibrator. The manual snips below may help.

Toddles off to do a quick test....

... and it looks like you and bd are right.

I suspect I committed the cardinal sin of changing two things at once: replacing a fuse and disconnecting the NiCd battery. Then I forgot about the battery, concentrated on the effect of the fuse, and supressed my "that's strange" sanity check in favour of my prejudice

Somehow I don't think I'm going to bother with replacing the 21.5V battery, i.e. 18 cells.

I might or might not bother to try to recal it, but the only manual I've seen so far is incomplete. It only describes twiddling some trimpots, and doesn't have a schematic.

There's definite signs that some designed-in bodges have been bodged.

[bd139]

I’ve always wondered if it’s possible to make a NiCd emulator for such a device. Three decent 18650 cells probably has the same amount of grunt these days.