Asking the important questions right here!

@UsagiElectric were beard :C

@@UsagiElectric You look a lot younger without it. :)

Some of us beard folks, get tired of dealing with a beard. It gets itchy, all the maintenance, and sometimes you don't want to deal with it, or just want to regrow it. Some just grow one for a bit, and then grow it out and shave, just because...

January must be a "no beard" month

Nah that's a wives tale. That would not be possible.

Yeah I've heard the same back then, when a chain breaks it's spectacular. All that metal is there for a reason. It's like a motorcycle chain at full speed.

Plastic clips on a rubber belt. The most used letters would break all the time. This was only 100 lines per minute printer. Slow... Wait until you had a 1000 LPM printer throw a drum belt. That was always fun.

As of Jan 1, SEVENTIES! Woohoo.

I am on the edge of 60 myself. we have seen alot of things come and go with each decade. things were made so much better, and built to last. I have a 1950's fridge and stove that are still purring along in 2024. tho I really miss the 70's. as a young teen that was a magical time for me. we were so free and truly cared for each other back then. [even strangers]

For a second I thought "are Rasberry Pis really that widely used?" before I realized you were referring to Apple.

@@pancreasenthusiast I also prefer Apple Pie to Raspberry Pie (couldn't help my self) :P

Thank you so much! Also, that's awesome that you were using color thermal paper for your work. That's really wild, I don't think I've ever come across a color thermal printer. I love the technology we saw coming out of the 50s, 60s and 70s and it must have been wild to watch computers change so dramatically during that relatively short time. To go from vacuum tubes to the 6502 in just 25 years must have been wild!

I used to program and sometimes operate IBM 360s and those printers were beasts. The old card readers sounded like a wood chipper. Computer rooms were really loud back then!

Oh man, I can't even imagine how insanely fast that 1,000 LPM printer must have been. The simple 125LPM I have here does essentially two rows per second, but the 1,000 LPM is eight times faster than that!

@@UsagiElectric We had printers that could print as fast as most line printers could do a page eject. Several pages/second. You had to get the paper in just right and there were a bunch of grounding wires to prevent static buildup from the paper shooting by or you would get the biggest paper jam you've ever seen.

​@@ChristopherHaileyYou're right about getting the paper in right. But also all the wire mesh that deflected the paper arc into the collection bin. I once saw the operator restart the line printer after adding paper and the deflection cage wasn't locked in place. The stream of paper displaced a ceiling tile and enough paper was on top of the ceiling to break another tile and come down all over the place.

@@mikebarushok5361 Wow, never saw one go that amok, but i've seen them shoot paper straight out across the room. That must have been a sight!

for some of us the printer was 80 miles away, got result next day (why didnt we invest in a monitor ?) only to find one had input the wrong decimal point and the graph and result was nonsense

@@highpath4776 - for me it was the other way around. The Unisys mainframe was 25 miles away, but the printer was local.

In my "good old days" you would hand your deck of cards through the window at the computer lab and come back a day later to get your print out. Just to find that a misplaced comma crashed your job.

@@KameraShy Been there done that, basically just once as I'm only 59 years old but yeah, just managed to get that experience.

are not some common characters repeated more to minimise chain movement ?

@@highpath4776 The chain or band speed is constant. I do not know this printer, so I don’t know whether it is chain or band. The two types are materially the same in operation. The difference is the band has embossed characters and a chain type has interlocking cast type slugs. Both move the type at constant velocity and fire the hammer when the hammer is over the desired character. Repeated character set allow lower velocity. The advantage of band printers is that end users can change the band when it wears or to change character sets. This printer economizes by having each hammer service two adjacent positions by jogging the rack. Printers like the IBM 1403 had a full 132 hammers and could print 600 LPM. The type chain of a 1403 moves at scary velocity, hence the other comment about a chain stuck in a wall is believable. That is pretty remarkable, considering the 1403 dates to 1959 and was part of the transistor based 1401 system, no ICs. The 1403 saw duty on other systems in laters years up through at least the 1970s and it would not surprised me if some 1403s are still in operation.

@@wtmayhew There is a working 1403 at the Computer History Museum. There are a number of youtube videos of it running.

I've gotten lots of old electrolytic caps like these from the local hamfests. Most of them were perfectly fine after reforming overnight. As long as they haven't dried out or been damaged by applying full voltage without current limiting, they will usually be good.

When I was working in a Lab at my university almost 20 years ago there was a 1mb hard drive being used as an occasional doorstop. The thing was probably the size of a concrete block and weighed 25 lbs or more. Had to be from the 80s. I always wanted to build a wiring harness and see what was on it - even now 15 years later I still sometimes wonder what was on it. Missed opportunities. Strange things we choose to remember

@@FreejackVesa you probably could have bought a decent car for what that originally cost!

Yes the 10V rail should be around 12V, because that is the voltage required for true RS232 voltage levels, though it will probably be fine with 10V anyway. The capacitors really should be tested differently, or at least connected to a power supply via a resistor, and left for 24 hours to reform. 50 year old electrolytics are very much at the end of life, though you will find that some are still within spec after a 24 hour period at rated voltage via a 1k resistor, just in case they decide to short out, so the puff of smoke will not be much, though the resistor should be 5W to survive. 24 hours of rated voltage, then leave open circuit, and measure with the multimeter every hour, and before disconnecting check voltage drop across that resistor is under 1V, saying leakage is under 1mA, which is a rough limit for the leakage acceptable. I have tested some NOS electrolytics, and of the dozen I had 6 were physically leaking when unwrapped, so got tossed immediately, 3 were not dropping down in current even after 24 hours of reforming at 5V, and were also tossed, and the remaining 3 had 2 with a rotted vent, so also failed. The sole good one held charge for over 3 months, checked once a week or so. So the can sizes you have are all still available off current suppliers, and you really should replace, just go for ones in the same diameter can, or slightly smaller, and use a sleeve, common on replacements as well, and use similar capacity and voltage, though you can have a slightly higher voltage, and capacitance within 20% of the nominal is still fine, as those large cans have a tolerance on capacitance of +100%/-80% as still being fine. Yes that 60 000 uF one, used likely on the 30V rail, is perfectly fine, even if the capacitance is anything from 12 000uF to 120 000uF, so anything in that range and voltage is suitable as a replacement. Same for the others as well, though going close to the nominal is better. 85C standard electrolytic, computer grade, none of the low ESR units, your rectifier diodes will thank you. Those large cans make a loud bang when they fail, and can take out the diodes and transformer as well. Though with that power supply, and those power resistors, I would turn the board over, wash it with a new toothbrush and some ethanol, and then apply some liquid rosin flux all over the board, and resolder every solder joint associated with the power diodes, the power transistors and the power resistors, and clean the board again with alcohol to remove the rosin. Will likely fix any dry joints there, and also solve future issues with the power supply. Clean that edge connector, deoxit on both sides, and plug in and out around 5 times, clean again, and apply a last coat. Same for the TTL boards and drivers, and same for any IC in a socket, clean the legs, then plug in again, pull out, clean pin and socket, and put in again. will solve any poor contact issues before you have them, leaving 1000 less problems to solve. Before powering up the printer, get some 24V turn signal lamps, and some 12V ones, and apply the 24V lamps to the 30V supply and the 12V supplies, and the 12V one to the 5V supply, to give the PSU a small load. Off the 30V rail you will draw roughly 2A, the 12V rails around 1A, and the 5v rail same, well below what they likely are rated for, at least for a 5 minute test. Then use your multimeter to measure the voltage out, should be within 10% of what you measured no load. Then take your scope and look for ripple at 60 and 120 Hz, on the output, with AC coupling. Should be under 100mV, and on the capacitors should be under 1V peak to peak of ripple, and at 120Hz, if there is a 60 Hz component you have a diode that is open, or a bad joint, and the 2 peaks for the 120Hz should be roughly the same height, if not you have a failing diode, either nearly open circuit or leaking badly, thermal camera will tell you if a separate diode that it is running at toasty level, or a bridge rectifier block running at 50C above ambient, which under low load should not be the case.

This printer is a Centronics parallel 7 bit wide interface. No RS-232 interface in the Data-100 model.

@@kromaine13Thanks for clarify.

@@kromaine13 No difference in the power supply though, and the 12V rails likely are also used in the hammer drive section to provide bias voltages for the driver transistors, so they turn on and off fast to drive the hammers.

@@kromaine13If there's no RS-232, I wonder what it uses the negative rail for? Centronics is 0 to +5v, iirc, and so are all the TTL, of course. The hammer drivers are probably a simple open collector driver, so no need for a negative rail there, that I can see. Maybe some early NMOS RAM used for a line buffer?

I bet. Pulp + moisture (or oil from the running gear) would for sure gum up those things. It does even today on cardboard or thicker paper printers.

@@aserta yes that and actually (maybe TMI) a lot of human hair. I used to wear gloves which would be shredded by the time I was done.

@@lindoran presumably those with (Acoquisic) covers tended to have less hair in them.

@@highpath4776 you would think that would be true but I found it in the weirdest places. One of the worst dot matrix (not the same I know) that I ever worked on was in a jewelry store. This thing had a noise shroud and was in a drop feed cabinet. It needed to be completely disassembled because hair caused just enough of a clearance issue that the paper would jam nearly every time. I think it matters how the paper is stored and who changes it.

​@@lindoran I used kitchen gloves, one size small. Yup, normal gloves have no chance of survival. Ah, the stuff i used to find inside printers... :)) Worst job i had to pull was chewing gum inside a big Canon printer. Had to clean it, because it was an expensive unit, not like a cheapo these days where you can write it off. That was fun.

@tradde11You know, now that you mentioned this, it DOES ring a bell. Something about header space and vertical 'tab'?!? Maybe it was when we switched from normal 'green bar' paper to shorter 'letter' sized tractor feed. Sorry, it's been a long time... :) P.S. Yeah, i said 'paper tape' meaning that type of punched tape, but you're right it wasn't physically 'paper'.

@@mikefochtman7164 I knew it as "Vertical Forms Unit". The printers I worked on had an electronic version of that or EVFU.

@tradde11Yeah, the one we had, if you had a mixed case band (both upper and lower case) it would do 300 lpm. But if you had an upper-case only, it had all the letters on the band twice, directly opposite and it would print 600 lpm. Paper practically SHOT through that thing. lol

I think it has

The paper tape loop is vertical forms [paper] movement. One paper tape channel is for TOF [top of forms] hole & one channel for Vertical Tab. The paper tape loop is 66 positions long (or the number of lines per page). Being able for the programmer to tell the printer to move the paper to TOF or do a Vertical-Tap was easier than keeping track of line counts.

​@@kromaine13 thanks for the info! Very interesting, and appreciated :)

@@kromaine13 While easier than counting lines, the real reason is the printer could "tab" to the spot much faster than "stepping" to that spot via CR/LF. It's like the difference between the tab key and the space bar on a typewriter. Those engineers used a lot of tricks to get more speed out of their machines.

True! He's not joking.

Right. By the start of 1975 LSI was widely available and we were into the second generation of 8-bit microprocessors, with both the 8080 and the 6800 having come out the previous year, the Altair on the cover of _Popular Electronics,_ and the 6502 less than a year away.