Exploring what's inside a 1980's milliohmmeter and how does it work, repairing it. Please support my channel on Patreon: / diodegonewild Instagram: / savage_danyk
What a beast of machine! Amazing! Thanks for bring to us this kind of content, definitely nothing you see on RU-vid on a regular basis, very interesting content. I hope you get better soon!
Thanks so much for letting us see it work; hard-setting the range was a good idea. This would have been a fairly expensive device with very few built and it uses so much current that it was obviously meant for a particular purpose with high-power shunts or wires. Sorry that you've been sick. I know a ton of people that are getting it recently here in the U.S. (central Kentucky), so I guess that no one is getting shots anymore . It put my cousin in the hospital.
Interesting unit. it looks like a ductor set to check across connection points of equipment and get readings in milli-Ohms. Interesting to have Nixie tubes and LED's in the same unit.
This was quite common back then - individual LEDs were much more available than LED displays. Also 1 out of 10 decoders were easier to get, because Tesla produced them, while 7-segment decoders had to be imported from East Germany.
I knew you would appreciate it, all of a sudden, it appeared in the warehouse that we use for storing discarded electronics in our company, ultimately it would end up taken to the scrap heap anyway
I never taught there was resistance meters like that (which can supply that much current, just for mesuring) - indeed useful to measure things like cables under load (getting the effect of the temperature rise included as well). Very interesting!🙂👍
Found something similar, a "microohmmeter" in a lab, with a variac, big screw terminals, and an LCD display, but this one went up to 600 A at maybe 2 V or so... Good for melting the cables under test if you were unhappy about their resistance.
This thing already has all the expensive parts necessary for converting it into a nice AC power supply - just remove the electronics and add a 230/230V isolation transformer and some switches. That would give 0-230V and 0-12V isolated from mains. Add some lightbulbs with different wattages and some more switches and it could also be used as a dim bulb tester for troubleshooting / restoring old radios etc.
Thanks for the great videos! There is actually an old trick to read the ratio of two voltages: use the normal input and reference input of the DMM/ADC. This is for example possible with the old ICL7107 and similar chips. For an ohmmeter you would put the sensed voltage into the input and sensed current converted to a voltage into the reference input instead of a constant voltage. If AC, it would need rectification of course. Constant current would be the other way :) Fun to see the manual feedback loop in this instrument. Very creative design! Love it...
Maybe the variac together with that LED scale was used to set a known voltage drop across measured resistance, and then it calculated the resistance based on current shunt's voltage drop (and thus the flowing current)?
Actually, the only difference to a modern 10A interference filter capable of filtering relatively low frequencies in addition to relatively high ones would be a soldered stamped sheet metal casing of the newer one (I guess, far east and western produced ones would be of the same cheaper case construction even 40 years ago) which would be a nightmare to review and repair. Anyway, a phase regulated large inductance will always require such a large filter.
Прибор для проверки переходного сопротивления контактов выключателей и т.п., одна из его особенностей - прогрузка контактов током, т.к. это важно для определения их степени износа.
This reminds me about the first high voltage lab power supply made in ussr that called уип-1 it was a tube power supply and it's weight was 46 kilo This was a thing of many purposes - you can generate some high voltage with it, or it could be used as a projectile to break heavy fortifications....
Sorry to hear that the creature has returned uninvited, I hope you feel better soon. What a complex piece of kit. If you don't have a use for it, I'm sure there are some salvageable components
I think it modify the reference voltage of the panel voltmeter accordingly to the current of measurement so it measure the voltage over current ratio instead of the external voltage over the reference voltage
Really nice video as always! One day can you make a video where you modify the 24V 10A power supply into an adjustable one? In one of your videos 4 years ago you said that you will try to make it adjustable but it never happened, maybe you forgot it or it was not worth it... (Dont worry at all!). I was interested on how to modify power supplies because it can be really useful for DIY. Can the voltage even set to be higher like 40V? Anyway i learned so much on this channel so big thanks for all the effort you put in your videos to teach us electronics! Keep it up 😉
Ďakujem za toto video, prístroj ma zaujal, najmä preto že má digitróny (podľa mňa najkrajší typ displejov) a pripomína to amatérsku výrobu, trúfam si povedať, že podobným štýlom bastlím rôzne zariadenia aj ja, akurát nie sú až také veľké a ťažké 😀. Je to pekná ukážka ľudovej tvorivosti ako sa bastlilo z toho, čo bolo zrovna k dispozícií.
Nice vid as always 👍 On one side, I would say leave it as it is since it seems to be pretty rare (judging from the fact that you didn't find any info on it), but on the other side, just letting it sit around collecting dust also seems like a waste. Maybe you can find a way to use it for something useful the way it is. But nonetheless, it definitely is an interesting piece of kit. I'm honestly curious what it was originally used for. Maybe it was used in a factory where shunts were produced to ensure that they are in spec.
This kind of milliohm measuring devices were designed to give reliable protective earth resistance or contact resistance results in high power devices or networks. The measurement can show low resistance with 0.1A or 1A, indicating good contact, but totally fail at e.g. 80A. So these test the circuit with real current level. These are not designed to measure resistors (like current shunts), even they can be used also for that purpose (of course only if the resistor withstands the test current). Quite expensive devices btw.
It seems like such a weird way of operating this machine. They already went to the effort of putting 30kg worth of stuff in there, and every kind of component imaginable is somewhere in there, and yet they did NOT put in a small motor to turn the variac for you instead of the LEDs... Just a simple dc motor and a couple power transistors driving it linearly would have completely automated the measurement, but no, they make the user do that job instead.
17:50 How much would such a meter go for these days? I'm sure that some kind of lab with no space issues might have a use for one - this thing looks like it's built to last 50 or 60 years, unless of course someone drops it...
Yes, not the most useful of test gear (outside of a power station perhaps??). But like a lot of fellow enthusiasts salivating over the wonderland array of functionable discrete components and bomb proof hardware🙂
The uA725 (MAA725?) Is a low drift low offset instrumentation amp. They were hard to come by back in the days... To be honest its a very stupid design using high current over a long time. A more intelligent approach would be to use a storage cap for providing the high current but only for milliseconds , discharging it via a constant current load through the DUT. A simple max detector would hold the measured shunt voltage. Everything would be 28 kilos lighter 😆
Unless the point of the device was to measure resistance under continuous high current, taking into account the resistance change caused by associated heating. (Consider e.g. measuring resistance of a cable that will be used for 80A. You'd then want to actually pass 80A through it.) I'm not sure though if the duration of measurement was sufficient for that.
As someone currently suffering from some sort of energy sapping virus (probably the same one), I really felt for you struggling to care about fixing it. Somehow I knew you would though, you can't keep a good man down!
@@DiodeGoneWild about the creature, sounds funky, because here on Brazil we haven't heard about a single case in ages. I started to thought they finally got it eradicated.
Great methodical troubleshooting; imagine if the device was packed properly and the switch wasn't broken in shipping. I have 6 variacs, one even goes from zero to 240 vac! Keep your videos, including the excellent comments from your cat, coming. By the way, what is your cat's name?
