Soroc IQ 120: Well, that didn't go to plan ...

[@JohnSmith-is8nq]

It exploded StarTrek style. The shields failed and it made the terminals explode in the operators' faces, sending them flying across the room.

[@PXAbstraction]

In a shower of rocks.

[@JohnSmith-is8nq]

@@PXAbstraction lol yeah, for some reason.

[@terminusaquo1980]

@@PXAbstraction Starships are made out of rocks, didn't you know that 🤣

[@TechnicolorMammoth]

I’m laughing way too hard at OPs comment. What a gem you are!

[@TheSquaredM]

Isn’t Soroc one of Spock’s relatives?

[@jameshearne891]

It was probably a cracked joint or track that started arcing and once the pcb material gets hot enough it becomes conductive itself and starts to burn. This can even happen on car ecu's etc at 12 volts. That is perfectly repairable but you have to grind out all of the conductive carbonised pcb material. Then tape over holes on the bottom side of the pcb and fill them level with epoxy resin. Rebuild any missing tracks using copper tape, either self adhesive or glued down and redrill any holes. I used to repair pcb's in ticket machines for a UK transport company and sometimes we had 1" dia sections of burnt pcb replaced using this method.

[@albinklein7680]

Why use that expensive copper tape? Serious question; I repaired countless broken PCBs with magnet wire.

[@NullReference119]

I agree this is the most likely scenario. However, with older style center tap supplies it's not unusual to find a cap can just like the one here. They can short internally and basically explode just like that. If that happened however Adrian should check the windings on the transformer. That sort of short can absolutely destroy the windings by overdrawing the VA the transformer is rated for. This is why any cap directly across the windings of a transformer should always be replaced, ideally with something that will fail open circuit. Rewatching the segment where Adrian reads the cap marking it doesn't sound like a multi-cap. But, I'd still highly suggest he check the windings before continuing with this power supply. If the windings are toast there is no point in trying to repair unless he wants to do a transformer rewind.

[@sivalley]

Agreed. The amount of heat needed to carbonize FR4 epoxy board is significant and impossible to deposit in a single impulse without traces or components exploding. If there are no dead shorts, cleaning and replacing that capacitor with a modern equivalent should not be too difficult.

[@jayfowler4747]

Gets burnt then the carbon conducts... not the other way round

[@timballam3675]

Looking at the height of that cap I think the "Glue" wasn't enough to hold it in place. Got asked to look at a solar inverter and the damage was almost identical from a damaged contact on a relay!

[@JFo-i4o]

The H/B/F switch is the duplex selection: Half/Block/Full. "Block" is probably Block mode, like IBM terminals.

[@mcosta3810]

From one story told to me, an electronics class teacher stated: All electronics run on smoke. Once the smoke escapes, it stops working.

[@desnick2316]

It is an infamous magic smoke

[@No_Way_NO_WAY]

gotta remember that, the next time im talking to our electrical engineers.

[@froller]

I'm certainly need couple of magic smoke refill cans. Can you tell me if I can buy some of these? :)

[@mal2ksc]

@@froller Doesn't work that way. You have to take the failed part out of circuit and soak it in liquid smoke before re-sealing it.

[@gordonwelcher9598]

Such a hilarious profound statement. This is the first time I have heard this. Please continue with this fresh original humor.

[@computeraisle]

I used to do component level repair on these up in KC. On some models, there was a six-pack of logos, which were actually the tops of Coors cans, of which SOROC is an anagram.

[@VorlonFrog]

Having worked with Soroc terminals in the late 1970s, I can confirm this story. Similar words from our hardware techs.

[@joeobrien5627]

Soroc is an anagram for Coors; the logo is an open beer can

[@AlsGeekLab]

Wouldn't have figured that out myself, but now I've seen it , I can't unsee! Great bit of trivia! No company could have ever been taken seriously though, no wonder they were short-lived!

[@ricardog2165]

Pretty sure I read in "The Soul of a New Machine" that the founders were trying to think of a company name when one of them glanced at the beer can he was holding and the rest was history.

[@Unfinished80]

Lightning maybe. A lot of homes used to have serious grounding issues and transient voltage suppressors were non-existent. Just a guess.

[@mikestewart4752]

And the TV antennas. If yours ever got struck, most your good gadgets were toast. As me how I know. Lol

[@subynut]

Certainly possible! Lightning is known to do some really strange things!

[@ChrisDreher]

I have a sound card + modem that apparently was struck by lightning. Multiple chips literally have their plastic blown off, exposing the damaged silicon beneath.

[@nemesisstormuk]

Good call..

[@sonicunleashedfan124]

@@ChrisDreherthe 8-bit guy had an underground Ethernet cable between his house and his parents house struck by lightning which blew any Ethernet circuitry in any computers connected to the internet

[@pm4466]

I have seen similar damage caused by older electrolytics with the vent on the bottom. I'd pull the cap and confirm whether this is the case. The hole in the PCB could be from the capacitor shorting internally, then sending the hot plasma out the bottom vent hole.

[@adriansdigitalbasement]

I won't spoil the second part but I dig into exactly what you're suggesting. 👍

[@gordonwelcher9598]

Be very very careful. Hot plasma is nothing to fool around with. Wear plenty of protective gear.

[@nickwallette6201]

@@gordonwelcher9598 Oh no worries. It's probably cooled down by now. ;-)

[@amyhughes5574]

In 1979-ish my high school replaced their 40-collumn terminals with these Sorocs, connected to SWTPC computers running the FLEX OS, and in the following year they got a single multiuser computer running UniFLEX, and a bunch of these Sorocs.

[@Clavichordist]

My high school had them also. I can't remember what the computer was or the OS though.

[@r.g.c.3897]

I coincidentally just watched a video on old CRT televisions and they used a hair dryer to soften the glue and remove the protective glass to remedy the "cataracts". They didn't use a wire, simply softened up the glue with heat and pulled the glass away.

[@powerofvintage9442]

Those keyboard switches are the same design as used by one version of the Atari 800 keyboard as well. Very cool!

[@stonent]

My firs thought was they reminded me of the TI/99 keys.

[@Clavichordist]

That's where I saw them before.

[@fritzkinderhoffen2369]

I glad to see you investigating these older systems. The 2102s are 1kx1 bit static memory. It was usual to use 2k by 8 bit like is on that board for a display. That would easily allow for a 80 characters per line by 24 lines. Look forward to seeing you overcome the power supply issue. Glad you are not restricting yourself to the original design as the solution :). The interesting parts hopefully didn't go flash also!

[@jonqu7041]

We sold these and ADM 3a terminals in the 70s for use with a variety of s100 systems (most of all Alpha Micro systems). I used to repair these back then. I wonder if someone tried to discharge the fly back incorrectly with the logic board plugged in. I have seen that take down an ADM 3a… (when grounding to an improper ground goes wrong)

[@NicolaiDufva]

I feel that "Well, that didn't go to plan" is a good general description of this channel. I mean that in a good way. It is so interesting and informative to see Adrian work through unexpected curveballs from the 70's and 80's...

[@rvenden]

Love your forensic work. I look forward to the next episode.

[@kilroy79763]

WOW ! I have a slightly more weathered one just like this one - I have been waiting for the right time to dig into it...this may be - Im looking forward to what you do with it sir!

[@wacholder5690]

8:00 CL - RS = Current Loop (Teletype Mode) or RS232 (Standard Serial Terminal). Guess you'd found that out later / already ... 🙂

[@vintageapparatus]

An IQ120! This was the first terminal we had on our Imsai 8080 back in the day. I carted ours to college and we used it in our compsci dorm. They have as you noted a rattly loud keyboard, but the most interesting part was they had lower case letters. But the letters are not descenders. They sit all on the same baseline, so the 'g' is the same height as a capital G and positioned the same way, it's just a 'lower case' g. Looks funky. I hope you can fix the power supply board, that looks like a hot mess.

[@mal2ksc]

Sounds a bit like the Apple ][+ font with lowercase shoehorned in. The blank line had to move from above the capitals to below before descenders became possible.

[@ricardog2165]

@@mal2ksc I remember adding the shift mod to my Apple II+ by wiring the shift key to the game port.

[@itguydave2164]

Also, try to repair before changing over and keep it genuine. A SMPS might also introduce new issues due to high frequency switching noise if your not careful, so might need some additional filtering.

[@snap_oversteer]

19200bps is pretty fast for 1976! I have Tektronix 4006 vector terminal from '75-76 which must have cost a fortune back then and it can only do 9600bps.

[@andrewdunbar828]

Ooh! Something different. Wouldn't mind seeing more odd old stuff like this on your channel.

[@davida1hiwaaynet]

Adrian; the damage you see is common with this type of board. There was chemical damage which caused the resin bonding the fiber weave to become conductive. The capacitor may have seeped a small amount of fluid onto the board which damaged it chemically and lead to an arc fault, even with low voltage. The repair is to remove all charred areas with a sanding pen or other abrasive and replace that capacitor which leaked. Other possibly causes are use of corrosive soldering flux, or other any water based or caustic fluids on the board.

[@user-nd8zh3ir7v]

I would love to see the old board saved, but I understand the case for new stuff from reliability standpoint

[@andreas9238]

keep the board, toss the linear regulation and the chunk of a transformer

[@sittingstill3578]

Maybe a collab with Usagi Electric with his capacity to make single layer PCBs.

[@KatarinaMelki]

I've encountered damage like that once. In my ThinkPad 701c a ceramic cap shorted and shot out a brilliant orange flame. Burned right through both system boards in a similar way. I know for certain I wasn't supplying any more than 16v DC to the machine at the time, so I'm pretty sure a short plus the chemistry of the cap caused it to go out like that.

[@desiv1170]

The only thing I know about the Soroc 120 is that when I have been playing with CP/M on my Apple //e, one of the terminal types I can choose for compatibility (mostly for some CP/M games like Ladder) is the Soroc 120. Cursor keys and screen clearing matches. Considering when the Soroc was released, I am thinking Microsoft chose to emulate the Soroc for it's CP/M card.

[@adriansdigitalbasement]

Ah that's a cool bit of history! It kind of implies it was more popular than I thought.

[@donaldcongdon9095]

@@adriansdigitalbasement I remember running Lifeboat CP/M 2.2 on my TRS-80 Model II in the early 80's. You had to set your applications that needed full screen control (like WordStar) to SOROC emulation, which apparently worked on the Model II.

[@jamesross3939]

I have two aftermarket keyboards from the early 80's for the CoCo and they use those same keyswicthes. I used contact cleaner and very light sand paper on the contacts and silicone oil on the plastic key mechanism and they work great now.

[@bluerizlagirl]

Remember the formula for energy stored in a capacitor: Joules = 0.5 * Farads * Volts ** 2. 30 000µF is 0.03F and 0.5 * 0.03 * 400 = 6J. That's enough to cause some damage, if something shorted the capacitor while it was fully charged .....

[@adriansdigitalbasement]

That is very true! I guess I'm not used to working on things with quite so much energy stored in them.

[@aivansama6265]

It was 20 volts tho, so 10th of that.

[@robbybobbyhobbies]

@@aivansama6265 Doesn't the equation say Volts to the power of 2? Which would be 20 x 20, or 400 as OP said.

[@bluerizlagirl]

@@aivansama6265 How so? 20 * 20 = 400. 0.5 * 0.03 * 400 = 6.

[@aivansama6265]

@@robbybobbyhobbies Might have been a slight misreading from my part 😶

[@albinklein7680]

I didn't know they still used safety lenses this late. I was sure that implosion-bands were totally common since the early 1960s. In European TVs (I am from Germany) they never used safety lenses. The oldest TV in my collection (a 1951 Philips "Hondehok" TV) already has a "lens-less" CRT with an implosion band.

[@gabrielleeliseo6062]

They were not at all uncommon later in the US, especially in cheaper CRTs.

[@retrozmachine1189]

Last time there was a discussion about the stick on lense a lot of people around the world, me included, commented that they'd never heard of it. It seems to really be a USA thing. The rest of the world used the implosion band method.

[@evensgrey]

The double quote being on shift-2 is a specific feature of teletype-derived keyboard layouts. That's why it was extremely common before the IBM-compatibles began to dominate the personal computer market, bringing with them the Selectric typewriter keyboard layout IBM decided to use. This device does have the ESC and return keys in odd places.

[@TestECull]

What that looks like to me is an external short across the capacitor. IE, a critter of some sort bridged it while it was still charged. The capacitance in that thing is insane and a sudden dump of that energy will make quite the bang.

[@cll1out]

I’ve seen similar blasts in automotive situations, it was probably less than 20 volts but that capacitor had all the amps in one moment to do all that carnage in a fraction of a second. I reckon it was dropped a few inches from the table while running and that heavy cap made the board contact the chassis.

[@subynut]

Caps can hold quite a bit of energy (as you have mentioned many a time when dealing with high voltage power supplies). They can cause quite the arc or burn when they are shorted. Depending on how much support the board has at that corner, perhaps someone leaned enough on that corner of the PC board that it shorted the cap to the chassis?

[@lepompier132]

Adrian, it appears you have the option to create your own PCB and transfer these parts to the new board while replacing any components that have failed. Additionally, address the issue that led to the sparking which caused the blackened area. That's a one side copper PCB and easy to reproduce.

[@Rorschach1024]

Id check to make sure the rectifiers and regulators arent shorted, id clean up the blast damage. Check the transfofmer for shorts dusconnect the transformer and power it up with a variac to make sure it is delivering the correct voltages. Id try to keep it original if at all possible.

[@dru6809]

I think CL and RS stands for Current Loop vs RS-232. Older terminals supported that. Wrt to the blast damage 🤷

[@timradde4328]

I would have to agree with you as many terminals from back then could support both. As many had TTY's and might replace with this.

[@twilliamc3]

I patiently wait for towel-based merch. 😆

[@davidchoi6068]

It's easy to remove the glue between CRT & front protector glass. In the O days, I use a 60W bulb to heat up a 5 " Bunkerramo Teller terminal display, after 5 - 10 minutes, remove the glass, let CRT cool down, use alcohol to clean those residue glue. When studying television in electronics, teacher told us that it is not an easy job to break a CRT at the front, but easy to break at the neck (6.3V bulb ) area

[@kilosierraalpha]

Hi Adrian, my guess is lightning damage or some other over-current event that caused the energy spike. I've never seen a cap burn up like that though. By the way, would love to see you repair that CRT with "cataracts". Never seen it done on video.

[@randyeubanks2934]

A Soroc IQ120 was the first piece of computer gear that I ever actually repaired back in 1978 (It had a TO-3 Voltage Regulator with a heat intermittent issue). I have wanted one for my collection for many years.

[@watchmakerful]

Check the transformer, possibly its windings are shorted to each other and 120 V gets into low-voltage rails.

If that can capacitor leaked (or the CRT goop, maybe?), it is very possible that the PCB started conducting right under the cap. Over time, the current increased, and increased, which turned the PCB into conducting carbon, and on and on...until a fire erupted. I have seen this happen in an HP oscilloscope.

[@katho8472]

Can we also appreciate the Soroc logo on the PCB made from solder? But anyways, yes to the switch mode power supply conversion! Just like you did with the 1541 - did this twice to my drives and that works like a treat! Maybe you can even then add a switch for the the fan that would become useless then, but you can still switch it on, for the full retro noise experience :)

[@RoyceTaft]

I’ve got one of these in storage that I bought in a big lot of vintage electronics. Still need to bring it home and test it out!

[@kilroy79763]

me too hey thats 3 of us...LOL is there a group for this computer?

[@simontay4851]

Boy? Bought - that i bought in a big lot...

[@RoyceTaft]

@@simontay4851good catch. Revised accordingly :)

[@No_Way_NO_WAY]

Im watching a lot of tool/device restauration videos, 27:04 this is usually the point everything goes into a large bucket of evapo-rust for cleaning.

[@retrozmachine1189]

Those types of key switches were known for going dirty on the contacts. The original TRS-80 MI ROM keyboard routines couldn't cope with the amount of bounce after a few years of use and would give multiple characters for a single press. A replacement keyboard routine was available as a system program to address it, as were upgraded ROMs.

[@jeromethiel4323]

The infamous KBFIX. Which was not a fix, it was a work around. They upgraded the switches, and the TRS-80 i had did not have keyboard bounce.

[@stamasd8500]

Gives a whole new meaning to the term "exploded view" :)

[@skunkmyrddyn]

Having seen board damage similar to that on laptop motherboards where the DC jack came loose and arced, I can say that the fiberglass becomes conductive when it's turned to carbon (acts like a carbon resistor) so repairing the board may require removing anything turned to carbon from high heat / arcing to ensure it is not going to conduct.

[@scottdaviesvk2sdx319]

Hi Adrian, I have repaired numerous Ham radios and audio amps where a dry or crystallised solder joint has caused heat which leads to smoking of the polyester resin in the fibreglass PCB which then carbonises and leads to more and more damage until the resistance of the carbonised section eventually becomes too much for the low voltage to cross. The copper track and solder become burnt up in the fibreglass fire. Oh and yes, clean the board and join any missing traces with used solderwick. It carries large currents very well.

[@andreas9238]

I guess my way forward would be to get the logic board hooked up to a 5V bench supply, to see if tehre is life in the data bus (and the video output will also most likely come alive if things ain't blown. As for the Power supplies, i'd guess either the cap has shorted, leaked or there was a broken solder joint beneath it. Even at 12V Fiberglass PCB can char and get conductive itself. Cap juice can make this even more spectacular. The transformer in any case looks like it'd be totally capable to deliver quite a bit of current to help that situation forming. The blast radius might then just be the final piece of already damaged PCB trace burning off. I totally am for your proposal to get rid of both the old transformer, the linear regulator and the huge capacitor altogether. The monitor might just be running off 12V internally, which is relatively common with this size of a tube. That gross glue is really just that: super gross. Hope it did not kill your yoke. Also i'd guess the monitor section will do little to nothing except some DC without sync coming in. Cannot see much beyond output transistors and coupling transformers on there, so i'd guess its solely relying on the sync signals to run both horizontal and vertical deflection. The offboard flyback transformer is a nice twist. Allows to measure around on the board with probably no dangerous voltages around. imho best result from measuring in there would be CRT board using regulated 12V internally, PSU modules with +-12V and 5V are relatively standard.

[@TheRepeatloader]

the board damage was probably that it sat for years collecting rust and moisture, then someone plugged it in to see if it would work and got a huge plume of smoke trying.

[@KosmokratorVideo]

Welding for example uses low voltage but very high current. So that burn marks can easily be caused by the capacitor being shorted. May be a loose screw floating around in the case?

[@button-puncher]

25:50 Acme Electric Corporation. I love it. Ancient stuff branded Acme. It'd be interesting to see a lightweight conversion. SMPS AND a LCD display. BTW, for giant stick on feet, I like to use stick on Wall Door Stops from the hardware store.

[@sjjjvideo1]

I love terminals from the 70s.

[@markorr4423]

I remember Soroc ads in Creative Computing (and probably BYTE) in the very early 1980s. I recall they had a Soroc 140 model with a *LOT* of extra keys.

[@rod370]

Hi, Adrian. The Soroc IQ 120 was a popular dumb terminal produced by Soroc Technology in the late 1970s and early 1980s. It was a relatively affordable and reliable terminal, often used in business and academic settings. Key features of the Soroc IQ 120: 12-inch display: Provided a clear and readable display for text-based applications. 80-column x 24-row character display: Standard display format for the time. RS-232 interface: Allowed connection to various computers and modems. Detachable keyboard: Offered flexibility in workspace arrangement. Cursor control keys: Enabled efficient navigation within the text. Function keys: Provided quick access to common commands. The Soroc IQ 120 was a significant product in its time, contributing to the growth of computer usage in the early days of personal computing. While it may seem primitive by today's standards, it was a reliable and functional tool for its era.

[@Herby-1620]

For all of us, it would be useful to unsolder the big cap, and use your tester to see if it is "good" (even if you replace things with a switch mode power supply). By the way, a switch mode power supply is less than $30. for +5, +12, and -12. Check the schematics to see what it needs. The main board also needs to generate -12, so you will need to wire that up as well.

[@SiaVids]

The PCB in the damaged area got very hot from the rectifier diodes and it carbonised the glass fibre material which then proceeded to combust. I have seen similar on Galaxians arcade PCBs which have a similar style of rectifier.

[@jonnycando]

I’ve used terminals like this as late as 1997 in offices that had no internet and had to rely on modem over telephone dedicated loop. 19200baud, but at least we were connected to z/os mainframe sessions so high speed wasn’t critical.

[@Ea5hyw]

Que bueno escucharlo en mi idioma. Buen trabajo!! Saludos.

[@yohannwilkerson6058]

We used Beehive terminals connected to Computer Automation LSI-4 Scout computers to control some material handling systems back in the early 80's. It's nice to see one again.

[@madscientist15808]

If you pause the video at 29:28 it looks like there is some residue on the CRT socket. Maybe some of that adhesive they used got into the socket, shorted it out and let some high voltage through to the low voltage section. Also I would try to save the original power supply. Maybe first desolder that capacitor, remove every bit of burnt PCB and, if necessary, repair any broken traces. Additionally, I would try to clean the CRT socket with some IPA or an ultrasonic cleaner to make sure that no residue is left in there. And if none of that fixes it, then you can always still go ahead and replace it with a switch mode power supply.

[@andreas9238]

Sure, from a conservation standpoint one could do that, rebuild the linear regulator section. From a "keeping it working" perspective i'd strongly prefer to just replace it with something slightly more modern. If the transformer is still good, a DC/DC from "whatever voltage between 8 and 20V there is" to 5V might be an option. Also reduces the amount of extra heat in there. We currently do not know the current draw from the logic board, but some 2 to 5 Amps sound not far from reasonable if that is all TTL stuff on there.

[@ericwallace4985]

I would clean it with a buffing with a Dremal and see if boge wire would fix. replace both transfers. Reform all transistors and you know how to go after that.

[@wearethewatt2950]

This cap stores lots of charge and should have a pretty low esr. Shorting it can cause an arc that will last until it has discharged. The beefy transformer will help prolong this. A tiny conductive hair can trigger this. I am working with ultracapacitors, and had a fault at a circuit at their output. No way to existinguish the fire, had to wait until they were depleted.

[@TotoGuy-Original]

you could get some tubular spacers to space the cry so it sits more forward or you could use nuts that are too big for the screws or washers also

[@leosmith848]

Adrian, scrub it clean it and repair it. LV can easily do that sort of damage if a component fails or a cap lead goes loose. You should see what happens when big audio power amps let loose. The easy way to sort this is to remove everything and test the parts individually. The carbon will be conductive - grind it out and repair with epoxy/and glass cloth if you have any. I'd pop in and help if I weren't 6000 miles away. Such fun working on 'my era' analog tech. That power supply is a classic example of 'how we did it back then' and needs to be preserved...

[@Gamma67]

Wow what a blast from the past... I had one of those terminals hooked up to a WD pascal microengine - bet you never heard of it... around 1980 worked at a shop that subcontracted assembly and test for the wd/90 system. Pretty cool machine but not much demand for it. This was before WD was in the hard drive business.

[@SimonEllwood]

I have seen the inside of a few terminals from that era and it always amazes me how many 74 series chips they have. What are all those chips doing? If you look just a few years later a similar task is being done with a fraction of the chips.

[@electronicarchaeology]

The blast around the cap is probably due to a lightning strike. I have seen that before on an amplifier.

[@Matticitt]

The ginormous silver capacitor is amazing. I've never seen anything like that.

[@spacewolfjr]

The IQ120 was top of the line when it came to terminals for writing sad poems back in the day

[@sprint955st]

When you took the top off I was reminded of when Robocop takes his helmet off at the deserted steel poant

[@Gattancha]

Ouch - not what I was expecting to see! On a side note, The Beehive terminal you showed at the start of the video kind of reminds me of the terminals used in the Fallout games

[@zebo-the-fat]

A small escape of the magic smoke (very hard to get fresh smoke, most of the smoke mines have closed down!)

[@vadimbich4602]

The best way to get new smoke these days is to install it with new components pre-filled with synthetic magic smoke. Unless old smokeless components have smoke refill valves, but I think they stopped adding refill valves to electronic components in 1976, in an effort to force consumers to buy new components instead of just refilling the old ones.

[@retrozmachine1189]

The HBF switch might be for half / simplex / full with B being some term I don't know for simplex operation, perhaps being 'both way' for dual simplex where two separate channels are used for communications.

[@Colaholiker]

Agreed. I couldn't find an explanation for the b, but the h/f part of the switch yelled "DUPLEX" at me immediately.😅

[@RS-ls7mm]

Baudot?

[@Colaholiker]

@@RS-ls7mm While "Baudot" is definitely an important term in serial data transmission, I don't see it fit in when selecting between half and full duplex... 🤔 After all, it's one kind of encoding (which series of pulses means which character), and is root of the term baud rate for the serial transmission speed. But half or full duplex selection is a completely different parameter.

[@RS-ls7mm]

@@Colaholiker Just guessed it was an alternate operating mode, common at the time. Nothing says the switch only did one thing.

[@50shadesofbeige88]

3:20 Doing foam and foil is like going to the DMV. Nobody really wants to do it, but sometimes its necessary.

[@someguy2741]

I swear they were used in the major utility company my mom worked for... in like 1980 I visited. I comment on it being a computer and there was just one on the floor. One of her coworkers... said no no... thats a terminal. I swear it was the name. The name rings a bell.

[@sikkepossu]

32:01 Voltage surge caused by lightning??

[@OpticalCharacterRecognition]

I love the way, when things go wrong, it makes you laugh. I'd just get angry. Guess I have the wrong temperament for this kind of thing.

[@hugoegon8148]

Do the chassis have that burning marks too? Perhaps a metal piece inside did a short on the fully charged cap. That would spark. 😊

[@kylek6922]

I bet you could use one of your variable voltage power supplies to setup a hot-wire and cut through that adhesave or whatever that crud is holding on the extra glass on the old monitors like this that have it.

[@twocvbloke]

Don't need high voltage for a big kablooey like that to happen, a sudden moment of high current can make such a mess, after all, a welder uses low voltage high current to melt metal, so this sort of bang isn't impossible, the why though, well, that's the burning question... :P

[@somedudeRyan]

Reminds me of the WANG terminals at my dad's work in the 80s. Always thought those were super cool

[@dashxdr]

I had one of those soroc terminals in the mid 1980's connected to my northstar horizon. It had good feeling keys. I think I ran it at 9600 baud... maybe 19200

[@simonlathwell]

At 28:55, the only time I've seen a capacitor with that kind of damage is when either to much voltage was put into it causing it to overload and spark over to nearby metal resulting in that kind of damage. The other option would be if it was struck while running, or shortly after being turned off and it was hit with enough force to make it make contact with the metal shielding, hence massive spark, burning, and the system would have just packed up and no longer working. Glad you didn't turn it on before checking it otherwise there would have been fireworks like crazy or your home electrics would have shut-off.

[@danmenes3143]

You don't need high voltage to cause damage like that--just high current and low resistance. Guessing the low resistance happened when the capacitor started bleeding its juicy innards onto the board below. The 30,000 uF value suggests to me that the power supply was designed to source 1A or so. That's plenty to get things nice and toasty--then the board started to char, which lowered the resistance further. Things progressed until either 1. someone noticed the smoke and turned it off, or 2. the current got high enough to blow the fuse.

[@CthulhusDream]

That "Theory of Operation" manual vertically hatched artwork looks like a Junji Ito horror manga reaction image If I've ever seen one lol.

[@crayzeape2230]

Looks like it was a slow burn rather than a blast. Some resistive heating in a bad joint perhaps.

[@davidemmons8001]

Yeah Id like to see it as much original as possible. Keep as much with out going modern. Great stuff.

[@SysadminJohn]

I wonder if someone moved the terminal while it was on and, because as you said it's not easy to get your fingers underneath, they had to drop it off their fingers from an inch up. The weight of that huge capacitor could've possibly flexed the circuit board enough from a small drop that the solder mask touched the case. Maybe.

[@brucecowgill7672]

I have two of these that are still working. They have a white phosphor crt which I fixed the cataracts for both of them. I am having an issue with the keyboard switches getting stuck down. Apparently the stack pole tower structures crack and cause it to bind up. Unfortunately replacement towers are not available so really only way to fix is to find a donor old keyboard or dremel the towers to create more room for the sliding action.

[@tookitogo]

32:08 Because it’s not the voltage alone that matters, but the power. Consider welding uses low voltage, high current electricity to melt metal. And that we can have multi-kV discharges that cause no apparent damage because the current is minuscule (like an ionizer). So in the end, you can easily cause significant damage with low voltages. And it’s not like you need hundreds of watts to carbonize an area of PCB like that.

[@markmuir7338]

My vote would be for you to isolate the burnt traces and use a bench power supply, just to see whether the rest of the thing works. If the power supply failed in the way you described (shorted transformer), the logic chips are probably toast.

[@froller]

The transformer was beefy enough to deliver the current that made all this damage to PSU. 15V is pretty enough to do some kind of arc welding if power source survives it. So it's all about the current not voltage.

[@kencreten7308]

That was totally cool, Adrian... Oops... looks like ... star destroyer when Picard beamed a photon torpedo on to their bridge.

[@Zeem4]

Somewhere I have a keyboard from a BBC Model B that uses stacked-pole keyswitches, which is pretty unusual as far as I can tell - it's the only one I've ever seen and I've owned dozens of those machines. It's been in pieces for nearly 20 years as it didn't work very well and I took it apart, and never got round to putting it back together again. I assume that the contacts are oxidised - they look like they might be easy to clean, but doing all of them would be a lot of work.

[@atkelar]

I'd remove the cap, test it at least, and scrub the board. Carbon in the sut makes it conductive, so that is a very bare minimum; then, I'd try from there if the input makes for a good output ^^ - My guess is that something shorted out with a bang. That large capacitor can pack a punch. The frame being full bare matel makes it likely. Maybe it fell down while powered up and the +5V contacted the grounded chassis? Hard to tell...

[@dennisbartello7682]

Watching this while eating Haribo! Also - when the capacitor is the size of a Coors Silver Bullet.

[@ronsingh]

Oh man, this brings back memories, IQ120 attached to an Ampro Z80 LittleBoard and a Cromemco Z2. To this day, a vestigial version of Soric continues in Toronto, Canada. I sure miss those simple days of PIPing and STATing🙂 IQ120 attached to a Z2, computing as God intended...

[@donaldcongdon9095]

Wow! It's been a long time since I've used PIP and STAT. Amazing how much functionality they packed into those two little utilities. CP/M was such fun.

[@Pulverrostmannen]

I seen this type of burn damage in car amps too, enough current trough the circuit will heat up enough to catch fire and then the current will keep it going until the circuit opens. you should check if the transformer is still good after such damage before you figure out what to do next. there was probably a poor connection or short in that area or component leading to the burnout to begin that can damage the tranny. begin by cleaning the area to check how bad the damage is and measure the transformer first

[@BarnaAntal]

The cause is most likely a bad solder joint on the lead of the capacitor. It got hotter and hotter, and it simply burned it self thro the pcb. The voltage is low, but judging the size of that transformer obviusly the current was high. Clean it, replace the cap if necesary and it's done.