Strange 1970's Chip Monitor Test Equipment - LOGIC MONITOR LM-2

I found this really odd Circuit Monitor Thing From the 70's
Livestreams and samples and loads of extra content :-

Paypal :-

Always looking for old gear! to mod or conserve in the "museum of everything else" one day

#electronics #science #retro

[flowmastak]

I don't think there's a single person on the internet that makes this kind of content as entertaining as LMNC

[danielleohallisey]

I’m guessing it was owned by the maintenance department at a DuPont plant in Athens, Georgia?

[Stuartrusty]

Being an old fart Electronics Test Engineer, I remember using something very similar as recently as 6 years ago at work. They were used as part of a fault finding kit. The main difference was that the ones we used were TTL/CMOS specific for 14 and 16 pin logic arrays/gates. They were powered directly from the on board 5V logic supply. There was a sliding window switch over the top of the LEDs for 14 pin or 16 pin device selection.

An invaluable in circuit fault finding piece of kit. Along with LED logic probe (with pulse 'memory') and a high/low tone buzzer for audible logic high or low identification.
Cracking video, brings back memories of many hours spent building projects on copper strip vero board, love it. Thanks Sam.

[Ogaitnas]

Your passion is moving man, as in it moves my ass to work on my projects 👌✨

[harryjohnson]

It ain't in magazines anymore but it is online and in a quantity and quality we could only dream of back in the day.

[justusgronts]

Ahhh yes the good old pre- monolithic devices days! Being able to troubleshoot to component level, a schematic in 6 pica elite type, the size of your kitchen table. Your enthusiasm is commendable
👍👍👍👍👍👍👍👍👍👍/10

[johnpossum]

Great memories from you showing stuff like this. My older friend had that computer and it was his secret stash for his smokes. If his mom smelled smoke he would also blame the computer! 🤣🤣😎
The magazine I was really in to was Radio Electronics and every month they had a circuit or 5 you could build. I still have a stack of them somewhere in storage. Computer magazines like RAINBOW offered programs that you had to type in. But they gave us a learning experience and furthered our understanding of electronics for those who were in to it they were great because it was before the internet. This and Radio Shack was basically all we had. I was lucky enough to have a father that taught electronics after being a WWII Radar Mechanic on the magnetron tubes. The same ones used in today's microwaves were the jamming radars back then and planes would sometimes have banks of them that needed tuning. So my father taught me tube technology as bedtime stories and that is how I got started in electronics. Keep up the great content and I am glad to hear about the second channel!

[bitwiz_]

This is great. I was a kid in the 70s, and saw these advertised in Byte and Popular Electronics, but in all these decades I've never seen one in action. It's amazing! I also was only aware of the standalone models that pulled power off of the chip, like the one in the magazine. This one supplies the op-amp power, and a reference voltage for whatever logic family. I've also found on a google search, an LM-2A by Global Specialties where the clip had ribbon cables, and the LEDs were in the main unit. Definitely not as cool as having the LEDs on top of your chip, but maybe less bulky and more reliable.

I guess the op-amps would be wired up in comparator mode between each pin and a reference voltage for the logic type. There's a bunch of 470 ohm resistors for the LEDs, eight half-chip op-amps, and eight more 240K resistors between each pin and an op-amp. The other board should be much the same. Anyhow, there's enough pictures to trace out the circuit.
UPDATE: each channel is: pin → 240K → - input ; Vref → + input ; output → 470R → LED → LED power (+5V?)

I should try to make one, maybe I can use a regular chip clip and some Arduino headers, or 16-pin ribbon cable headers. Probably two circuit boards with common wires for power and ground, but it might need to be SMT. It shouldn't be hard to wire up a prototype pin circuit. I could even build a 40-pin version. Seeing that blinking on top of a Z80 or 6502 would be awesome, and it really needs to be done.

[cleekersneaker]

The sound of the 1978 drum machine has been my favorite thing about the second channel.

[Gin-toki]

Nice, I have never seen a logic probe integrated into a DIP test clip. Would definetly come in handy when I work on my homebrew 8-bit computer :)

[fissionchips]

I could watch this forever..!! I genuinely had a headache and by the end of the video I felt relaxed.. what wrong with me 🤔 💭🧠

[erikwehn]

Cool Video. Magazines were all we had pre-internet. Love from Detroit

[R.Daneel]

I had one of these when they were new and cool. Mine definitely was a stand-alone clip. There was no support box. As I recall, it got enough use to be worth the cost. As a dead-chip detector, it was a real time saver too. Another must-have was a logic probe and logic "injector". Basically a one-pin version of this. The injector let you pull pins low or high at will fairly safely.

[noexpensespentstudios]

I don't understand half the stuff you do here, but I do enjoy it, and the tunes are great. I'm glad a friend put me on to your channel, it's good stuff. More tech should have lovely red LEDs like those and less ultra-bright blue ones. Back in my day, etc.

[DaveCurran]

Interesting bit of kit. I have a couple of RS versions which are powered by the chip (no external box). I think the op amps on there will be working as comparators, the selector on the box will select the voltage level for a logic one, and the LED will light if it is over that voltage, so 2V for TTL, 2.5V for CMOS etc. The 145 is the keyboard row selector, so the LEDs show the binary of the row being selected. The outputs are open collector, so won't light up. The 138s are the address decoding and show which of the big chips on the board are currently in use. The 00 includes the gate that drives the sounder, so you might see that flashing when sounds are being made. Over on the right, the 393 is the main clock divider and the 166 is the video output shift register, should be a lot of activity on there.

[PACracks]

Dupont Textile is a company in Athens, Georgia. Maint is likely shorthand for Maintenance.

[wisteela]

That is a fantastic bit of kit. I'll have to see if I can find a cheap modern one. Yeah, I was thinking of hooking it up to old computers too. I'd say you got a bargain there.
Also that Lego mount for breadboards is great.

[nneeerrrd]

11:20 literally says "computer" on the case
Sam: where's computer?
🤣😁

[Enjoymentboy]

This brings back so many memories. We had stacks of these magazines in the electronics lab in high school. I built my first strobe light from one of the articles and built a high voltage/low current "joke shocker". It was incredibly funny as long as you weren't the one being shocked. But such a huge mass of great projects in these magazines. Everyone should give it a try.

[StuEvans]

Blimey. I had everyday electronics in the 80's. Building all sorts. I can still smell them now.