Test Equipment Anonymous (TEA) group therapy thread

[AVGresponding]

Oh yes !!!

You were right the bloody thing somehow needed mains power to get going again, some state machine needed to be reset or something !

Works now !  :-D

I found a 12V battery....  an old car battery I bought 3 or 4 years ago I think. Somehow didn't end up in the car, can't remember why... so from new it sat unused for all these years under the kitchen table.
I remember briefly using it on the bench  nearly 2 years ago now, to power up / test a used electronic ballast module I bought for the HID lights on my car. So I powered the ballast / light for a few seconds, saw that it was working fine, called it a day and put the battery again back to sleep ! Now digging it out again and go figure it's still not dead, measured 12.05 Volts still ! So maybe not dead...tried putting some juice in it with the lab supply.... no problem ! Started modestly at 1A to wake up the battery slowly.. didn't want it to blow a head gasket or something !
15 minutes like that, was going well it looked like.. so I increased the current to 2.85A, the max the power supply will do. Battery was taking it no problems... left it like that for 30 minutes.

Good enough for a quick test of the inverter I thought !

So I plugged it to the inverter... no joy.

Plugged the mains cable as you suggested... ohhhhh, relays clicking briefly !  Turn the (soft) power switch at the back to 'ON'... some more action happening ! 

The main / big transformer now is buzzing loudly and the battery LED at the front panel lights up orange. That lasted for a few seconds then the transformer stopped buzzing, it all became quiet, and the orange LED turned off, and instead the mains status LED lit green, looking good I thought !

So I measured the mains at the OUTlets and.... yeah 250Volts present !!! 

Then I unplugged the mains cable / Input, and bingo, transformer starts buzzing again, inverter working then, and I STILL have 250V at the outputs !

IT WOOOORKS !!! 

Cool, I have meself a nice little industrial Merlin-Gerin inverter ! 

250W / 400VA it says.... might be enough to power my computer, it's not a power house (purposefully so, did want it to be quiet and not draw too much power). And if not.... will still be useful to power other stuff I am sure.

Wow that's cool, some more useful gear in the house !

You might find some old Novell software that will talk to it via the RS232, but you likely won't get much information besides mains ok, batt ok, it's no GPIB. It was mostly used to trigger a controlled shutdown on the server/pc when the mains failed.

Also bear in mind the output waveform on these cheap jobbies is not going to be a perfect sine, and sometimes a very not perfect sine! It should be fine for a PC or laptop, most things that use a wide input range SMPS, but some things don't like it at all and may behave oddly or overheat.

[AVGresponding]

Just bagged a BNIB IR-USB cable for my Agilent U1401B for £19.99 + shipping   

Batch of 34410A's up for ~£700 each:  https://www.ebay.co.uk/itm/363877521046

[bd139]

£700 is a bit steep and too close to new current line units. I'd consider one at £550.

[PA0PBZ]

You might find some old Novell software that will talk to it via the RS232, but you likely won't get much information besides mains ok, batt ok, it's no GPIB. It was mostly used to trigger a controlled shutdown on the server/pc when the mains failed.

Since this thing has no CPU whatsoever I wonder if it is RS232 after all, it looks like there's not enough logic to do something as smart as serial.

[bd139]

You might find some old Novell software that will talk to it via the RS232, but you likely won't get much information besides mains ok, batt ok, it's no GPIB. It was mostly used to trigger a controlled shutdown on the server/pc when the mains failed.

Since this thing has no CPU whatsoever I wonder if it is RS232 after all, it looks like there's not enough logic to do something as smart as serial.

It's not really RS232 i.e. they don't use bytes or a protocol. They use the control pins for signalling various things. usually something like this:

DCD -> UPS reports low battery
CTS -> UPS reports no AC
RTS -> PC sets high when connected
DTR -> PC tells UPS to shut down

Edit: actually one of the first Unix programs I wrote was a C program that shut a SunOS node down when the UPS reported no AC. Sun didn't provide any drivers at all. I had to reverse engineer the thing with a RS232 breakout box and an HP 54645 scope. Those were the good old days 

[AVGresponding]

£700 is a bit steep and too close to new current line units. I'd consider one at £550.

They all include a "make Offer" option...

[tggzzz]

£700 is a bit steep and too close to new current line units. I'd consider one at £550.

At least one is calibrated for another year, others have relatively recent calibration expiries. Corporations like that, of course.

Since they have several, it might be worth making an offer, if beneficial on different items in rotation to keep <3 offers/item

[Saskia]

ordered spare parts for the Bram Stokers Dracula pinball. Almost done stripping the top of the playfield. Lots of gunk, grime, nicotene on that one. Screws corroded, so I will have to check if the contacts are good or not. Once I am done rebuilding the top of the playfield I will need to clean anything a ball can potentially come into contact with ... to prevent it from regunking.
sheeeetloads of work.
Other chores for today:

Clean up living room.
Clean up kitchen
rebuild stereo set after we dood all da work.
make photos of Denon DP 37 to put it up for sale
continue sorting stuff. I am missing my LCR meter. May Odin help me find it.

[Specmaster]

Just bagged a BNIB IR-USB cable for my Agilent U1401B for £19.99 + shipping   

Batch of 34410A's up for ~£700 each:  https://www.ebay.co.uk/itm/363877521046

Be wary, that seller has relatively low feedback score and yet has all of these lovely meters for sale and his recent listings have all been private feedbacks? Seems to be slightly suspect to me.

[Peter_O]

My HP boat anchors able to control the GPIB bus got a slave to play.



This HP7470A slept in the storage of an EEVblog member, who was willing to pack this little friend and send it over for small money.
The HP7470A has no carousel but is able to handle two pens nevertheless. It was the first paper-moving plotter ever.
And - different from the younger brothers - it has the PSU included. Standard IEC13.




It arrived today.
I just chopped a felt marker at hand and printed a makeshift adapter.
The very first try just happened to work quite fine.



This old small guy ist quite fast: The plot was done in far less than minute.

Today I wanted to test the HP54504A Scope GPIB-Output to plotter.
Other than the HP35665A it expects the plotter not to have an address, but to be in listen only mode, which is all address digikeys switched on.
Then it works fine. Except: You can only choose to print or plot. In "plot" you can only chose the plotter model. There is no pen setup like with the 35665. So you need to have both pen positions 'under ink'.

Now comes the problem: My makeshift plot pen above has dried out already. I'm printing a stabilo 88 adapter available on Thingiverse just now and will see how that works.


Does anybody have a better solution for 'non dry out' short HP pens?

[Vince]

You might find some old Novell software that will talk to it via the RS232, but you likely won't get much information besides mains ok, batt ok, it's no GPIB. It was mostly used to trigger a controlled shutdown on the server/pc when the mains failed.

Since this thing has no CPU whatsoever I wonder if it is RS232 after all, it looks like there's not enough logic to do something as smart as serial.

It's not really RS232 i.e. they don't use bytes or a protocol. They use the control pins for signalling various things. usually something like this:

DCD -> UPS reports low battery
CTS -> UPS reports no AC
RTS -> PC sets high when connected
DTR -> PC tells UPS to shut down

Edit: actually one of the first Unix programs I wrote was a C program that shut a SunOS node down when the UPS reported no AC. Sun didn't provide any drivers at all. I had to reverse engineer the thing with a RS232 breakout box and an HP 54645 scope. Those were the good old days 

Just woke up.
Meant to post about just that but you people have already said it all.... not enough smarts for talking RS232, only discrete logic so best it can do is toggle some control lines....

Thanks everyone for the info on how these things work.

I can now button it back up and move on to the next item in the list...

[AVGresponding]

Just bagged a BNIB IR-USB cable for my Agilent U1401B for £19.99 + shipping   

Batch of 34410A's up for ~£700 each:  https://www.ebay.co.uk/itm/363877521046

Be wary, that seller has relatively low feedback score and yet has all of these lovely meters for sale and his recent listings have all been private feedbacks? Seems to be slightly suspect to me.

Either I get my item and it works, or I don't and I give negative feedback, get my money back, and shit-post about them on here.   

[factory]

Thank you for your advice, which I am reading only AFTER the fact, because I had already moved my butt towards the bench to fiddle with this thing... but I more or less did what you suggested....


First I popped the cover, disconnected the battery terminals (couldn't remove the battery itself though, it's stuck in there  ) and measured voltage. 1.0V, not a lot  ! 

So was probably dead. I tried recharging it with the lab supply you never know, but it failed to take any current no matter what voltage I applied... went up to 30Volts the max the supply will do, still not a single electron willing to flow into that battery.

So the battery is dead, open circuit.

So instead I powered the inverter from the lab supply rather than from the battery, limiting the current and increasing voltage slowly.... but nothing happens.
Pressing the button on the front panel doesn't help, no LED activity, and the board just doesn't draw any current at all, it's dead as a dodo.
Of course I checked on the output mains socket, zero volts coming out either.

So.... dead battery and dead inverter board, not a good start ! 

So did some disassembling, pulling wires connectors and unscrewing lugs... so I could flip the board to have a close look at the component side.

Tried to take a half decent pic of the board for your immense pleasure. I know squat about inverters and of course there won't be any schematic.

I looked around... can't see any obvious sign of component failure or over heating...
All I can see if that the buzzer is damaged/missing : its cover/top part came off and inside was... nothing. The piezo bit is not in there anymore... I don't know, guy who hacked that thing probably damaged it in the process 

I can't see any CPU on the board. It looks 100% discrete through-hole design with a bunch of jelly bean DIP ICs as you can see. 9 of them.

- 4001 (NOR gates)
- 4011 (NAND gates)
- 4013 (x2)  dual flip-flop
- 4066 (quad analog switches)
- LM339 (x2) comparators
- Good old LM317 !
- UC3524AN (PWM controller)

As for transistors, we have 5 of them, all 50N05.... 50 Amps 0.022 ohm N-MOSFETs ! Boy at the least I can salvage those !!!
4 come in TO220 packages, organized as two pairs, each pair being mounted on its separate heat sink.
Then the fifth comes in a very large plastic package and is a lone wolf, mounted on a different heat sink, same heat sink as the LM317.

-  A 40A Fuse, in an automotive style package ?! 
- x3 relays
- a small transformer, I guess to power the board and recharge the battery.
- a big ass transformer mounted to the chassis which obviously is driven by the inverter and powers the output mains sockets.


So it doesn't look like rocket science ? Maybe I could spend a couple hours probing around, maybe I can fix it... and even if I can't it's still fun trying to anyway...
Since it's a " No Power " issue at first glance, with some luck it's fairly simple...

Looking at the date codes it's the same age (early 90s) as the three phase motor inverters, we still repair at work. They use the ceramic LM139/LM124, instead of the 339/324 in your UPS, but the LM317 & 4000 series are just the regular plastic versions. 

David

[SeanB]

Powering you need a voltage equal to battery voltage, and a high power capacity, to emulate the battery. 15000uF or so across the leads for the battery, then apply power via the power supply, and it should turn on, probably operating the output stage for 5 seconds if mains is applied, before settling down to connecting through, and trying to charge the battery.  Simple logic, with a power supply capable of 10A, you do not need mains connected, it should turn on with the switch, and provide output into no load, with around 5A draw off the power supply.

Yes the signalling is simple, you use UPSD to control it, or APCUPS, which works with a lot of the serial ones, often using just the regular CH340 IC to make it USB. Very dumb protocol, but it does work well so long as you use it to automatically turn off on loss of power after 10 minutes. No way other than low battery to signal state, and with the small heatsinks there is only around 15 minutes at full load available, or 30 minutes at minimum load. They do kill batteries though, a mix of overcharge, cooking with heat and heavy load draw.

[Vince]

Looking at the date codes it's the same age (early 90s) as the three phase motor inverters, we still repair at work.

Ah yes, can't believe I didn't even think of checking date codes on these chips... 1993 it is then. 25 years old spot on a quarter of century... but still works 

They use the ceramic LM139/LM124, instead of the 339/324 in your UPS, but the LM317 & 4000 series are just the regular plastic versions. 

You are too critical... what's next, you want gold plated traces and conformal coating ?! 

I guess their reasoning was that the electrolytic caps on their board would cause trouble long before the plastic chips would ?

Besides, I don't even know if those CMOS logic chips were available in ceramic packages to be begin with, at least in the '90's they might not ?!

[Zucca]

I am missing my LCR meter

When I read the above line, an immense sadness filled my heart...
It is just a matter or time, if you did not throw away boxes "with closed eyes" 

Hope you fill find it soon, maybe under your nose it a different package?

[AVGresponding]

Looking at the date codes it's the same age (early 90s) as the three phase motor inverters, we still repair at work.

Ah yes, can't believe I didn't even think of checking date codes on these chips... 1993 it is then. 25 years old spot on a quarter of century... but still works 

They use the ceramic LM139/LM124, instead of the 339/324 in your UPS, but the LM317 & 4000 series are just the regular plastic versions. 

You are too critical... what's next, you want gold plated traces and conformal coating ?! 

I guess their reasoning was that the electrolytic caps on their board would cause trouble long before the plastic chips would ?

Besides, I don't even know if those CMOS logic chips were available in ceramic packages to be begin with, at least in the '90's they might not ?!

Usually the first things to die (not including the battery) are the reservoir caps on the charger, due to the heat and huge ripple current.

[Zucca]

My answers would be: Yes, yes, no.

Same here captain! I will wait. A good sniper needs a lot of patience to wait for the right moment.

[Brumby]

Had some good fortune in tracking down a better schematic for my Advance J2E.  This one actually has the output level metering circuit which was missing from the previous best effort ... AND it has a few voltages, to boot!

The only challenge is that it is of poor quality.  You can make out the components, but the values are next to unreadable.  Fortunately, it is almost identical to the first schematic which had much clearer details, so I should be able to dig out enough info to be able to re-draw the circuit.  Time to dust off KiCad.

I will also have to dig out an appropriate meter to take measurements ... It specifies a 20kΩ/V meter.

[mnementh]

...Thanks everyone for the info on how these things work. I can now button it back up and move on to the next item in the list...

Not quite... I know you may already know this, but just in case you don't; these things are designed to use a deep-cycle battery, which has a bit higher IR than your car/motorcycle starting battery there, and the float charge it puts across the battery terminals can cook a starting battery to death.

Once you're back among the gainfully employed, you'll want to invest in a SLA/GMA battery of similar capacity to the one you took out of the thing. Or maybe one small enuf to fit inside. 

Cheers!

mnem

[Vince]

DIODES : now sorting my big " stud " diodes. First, I pick the biggest one of them, because why not, you gotta start somewhere.

It's very clearly marked : " SEMIKRON  SK25/02 "

OK SemiKron / SK.... make sense I guess.

So I google for that sure enough there is a SK25 diode, yay !!!

OR NOT !!!

There is a freaking modern tiny surface mount Schottky diode that's called SK25 !
So I am flooded with that datasheet, can't find one for my old stud diode then !

Not a good start... if someone has it in an old paper catalogue.... please speak up. You will have my gratitude.

In the meantime, moving on to Googling my other diodes... hopefully with better luck.

I think they started adding an extra letter when they expanded their range of components. So it's probably called an SKR25 or SKN25 now.

McBryce.

Finishing up with my diodes today.

Tried to decide what to do with the 4 still unidentifided stud diodes... throw them away to make my organizing easier, or try harder to identify them... or just mix them all in one single "No ID" bag, so I can use them for potentially destructive experiments.... and some fun on my 575 curve tracer.

So I decided to have another look at that SK25/02 from Semikron, as it's my biggest diode by far, the star of the show, would pain me to get rid of it.
I remember what McBryce said about Semikron renaming their diodes SKR / SKN instead of SK... so I gave that a try.

Apparently Semikron is still in business, they have a website. A searched for an SKN or SKR 25 but no luck. They have only SKR/N 20 or 26, not 25.
However I looked at a few of their datasheet and it quickly became evident that their numbering system was extremely easy !

First two digits is the max current in amps, and the last two digits code the max DC blocking voltage in hundreds of volts.

So I could then extrapolate what my SK 25/02 is. It's a 25A 200V diode.

An SK 40 / 12 for example, say, would be a 40A 1,200V diode.

So big thanks to McBryce for the help, this diode is now identified, I can use it potentially  !

[Vince]

...Thanks everyone for the info on how these things work. I can now button it back up and move on to the next item in the list...

Not quite... I know you may already know this, but just in case you don't; these things are designed to use a deep-cycle battery, which has a bit higher IR than your car/motorcycle starting battery there, and the float charge it puts across the battery terminals can cook a starting battery to death.

Once you're back among the gainfully employed, you'll want to invest in a SLA/GMA battery of similar capacity to the one you took out of the thing. Or maybe one small enuf to fit inside. 

Cheers!

mnem

Oh crap, that sucks !  .... or not... means I am done with this thing and I can just salvage it for parts. that will make some room.

[factory]

I acquired this Advance DMM2 about six months ago on the UK vintage radio forum, as received it's completely untested, a little corroded in places inside, but nothing too bad. Also all the button caps have had the fronts cut or filed for some unknown reason, they are glued on too. 
It's been in the repair queue for a while and I've been working on trying to resurrect it for the last two weekends.


The button caps are a non standard size these days and I couldn't find anything to match from the usual sources for new parts. Eventually I found some Isostat button caps from a seller in Bulgaria, they are a excellent fit and have the same offset hole for the switch rod, as the old ones, one is shown fitted to the DMM2 in the above picture.
https://www.ebay.co.uk/itm/133257327505

Here are some pictures of the boards, the power supply is a mains stepdown transformer, feeding a simple switching supply with step-up transformer, this allows allows operation from low voltage DC too. The analog input circuitry uses a μ709 Op-amp, with some transistors and a SL701 amp IC for the AC/DC converter (this is on the small vertical board). It uses a custom IC for the multiplexed display counter & storage functions and a single Fairchild/SGS μLogic 960 BCD display decoder IC, with transistors/diodes for the multiplexing.



The first test had I no display, this was due to low supply rails from the secondary of the switching supply, I eventually found it was being overloaded by the 8uF 350V Erie cap on the +190V rail, it was getting warm, it got a temporary replacement with 4uF 250V (all I had), I quick check of the other caps with the Peak ESR found another that was high ESR, the positive lead fell off on removal (corroded), this will get a full recap if I can get it working.


I now had a display of sorts, but with double numbers showing in the display choobs, a test with an old 3.5V back up cell from one of the Tek scopes, did show a change in the display, the front end is not dead at least. The double digits lit in all displays fault, the manual tells you to investigate IC4 output, then IC3 outputs. These are the 996079 display decoder IC and custom counter IC. 
The BCD decoder outputs of the 996079 are +V for 0 & 0V for logic 1.


Picture of the inside of the fancy custom IC, from the Uni of Queensland Australia; https://physicsmuseum.uq.edu.au/cross-section-display-transistors-and-ics


Last weekend I scoped the BCD outputs from the custom counter IC, two are faulty with some weird negative output pulses (the counter IC does use -12V too for the storage function?). The two faulty output are the lowest, i.e. BCD 1 & 2. BCD 4 & 8 seem to be working OK.



Earlier in the week I disconnected the BCD lines between the ICs, hooked up some test clips and went through the BCD code & see what was displayed. This proved the 960 decoder IC was working fine & for the first time I've got the separate "1" neon to light. The OL lights with the BCD code for 2. The BCD code used is 0V for logic 1 and +V for logic 0.


Yesterday I had a play with some LM741 Op-Amps, to see if I could correct the faulty BCD outputs.
I've had some success, but it's not 100% there. I can get it to Zero now, but my 3.5V battery measures near double it should and using a decade resistor I'm getting good readings on the first two digits, but it goes wrong with strange readings & some double digits with a higher input. I need to draw out the circuit later, comments would be good as I'm not a designer and I'm probably doing it all wrong. 




David

[factory]

Extra pics for above post.

[bd139]

Great post. Very interesting. Looks like the custom IC is a candidate for replacement with an MCU of some sort. Looks like it's just a few 4 bit registers and a counter and tristate mux on the output.