0x0035 - IBM PCjr ATX Power Supply Adapter Prototype

[@moth.monster]

It's a good thing you made that first failure before making a real PCB.

[@TechTangents]

That's why even ghetto prototyping like this is useful!

[@MxArgent]

"Measure twice, cut once"!

[@wellskian5387]

i dont mean to be so offtopic but does any of you know a trick to get back into an instagram account? I somehow lost the login password. I would appreciate any tips you can offer me!

[@chrishouston909]

@Wells Kian instablaster :)

[@wellskian5387]

@Chris Houston i really appreciate your reply. I got to the site through google and I'm waiting for the hacking stuff now. Takes a while so I will reply here later with my results.

[@vega1287]

you get a negative resistance because the multi meter mesures a voltage increse rather then a drop in voltage so the fluc is acting like the electrolyte of a battery

[@BigBoyLies]

this got to be the most ghetto pcb job in the history of youtube lol

[@CyberCreeper22]

this sounds like a challenge

[@Manawyrm]

laughed out loud at the negative resistance. Wonderful, I'll buy 2 of these adapters from you with the negative resistance and then go ahead to build my perpetual motion machine with it :-)

[@ZoomPicard]

I like the fact you show the whole story of all the failed attempts not some edited down version where it appears you got it right first time. This is more like real engineering and electronics where the first design rarely works!

[@osgeld]

white vinegar. table salt, hydrogen peroxide makes a weak hydrochloric acid solution that will etch standard hobby grade pcb's in about 30 - 60 min

[@TechTangents]

I read about a reusable solution you can make a while ago that can be rejuvenated. I'll probably look into that for a long term solution. I'm not super thrilled with the idea of needing to dispose of extremely toxic chemicals.

[@osgeld]

yea that's muriatic acid and hydrogen peroxide, you refresh it by pumping air though it

[@skonkfactory]

You can de-copper used etchant by dumping steel wool into it and leaving it for a couple of days. It's then not particularly toxic. Also, sharpies work as etch resist pens.

[@BEdmonson85]

@@TechTangents That reusable solution you're referring to, muriatic (hydrocloric) acid in peroxide, I'm guessing, generates cupric chloride which will eventually need to be disposed of as well. It's waay more toxic than just using ferric chloride and the fumes are horrible.

[@johnuser5162]

Tandy: Nice graphics and sound you got there, IBM! Would be a shame if someone..... *stole* them!

[@DerekWitt]

Have you seen one of those Racore/Rapport expansion kits for the PCjr? My PCjr had a double-height sidecar that had a parallel port, a PC/PCjr toggle switch, a memory expansion board and a floppy controller that allowed me to have a 2nd 360k floppy drive. My memory expansion board had 256kB of ram on it. That toggle switch was a rather poor attempt to switch between 40 column and 80 column display modes on start up.

[@xephorce]

Love the video. I am just glad to see i am not the only one that runs into issues that make no sense. got to love that negative resistance reading lol.

[@doughboy1966]

I thought that there was going to be a huge plume of smoke from the power supply when it went into flake out mode on the first power up.

[@msthalamus2172]

Thank you for sharing your mistakes, too. It really does help people follow what you're doing!

[@awesome3165]

That cable vs connector mixup has gotten me more times than I care to admit.

[@villeville6838]

That is some admirable resilience!

[@carslayer]

sweet project, props for making it open source

[@watchmakerful]

Does the original power board have a bridge rectifier immediately after the input socket? If it does, simply connect a 19..24 V DC power supply to the input and that's all.

[@herrbatong]

Sweet, doing ghetto soldering together with ghetto pcb'ing Is how we used to do It back in the day. :)

[@gaybrahderpwood]

This is so wonderfully hackish. Love it!!

[@KiraSlith]

Since the PCjr uses such low amperage, you could just add a 7912 to the [-12v] rail and a Pico-PSU (or compatible clone) to internalize most of the power delivery (still need a external 12v power supply, but those are fairly widely available)

[@danagoyette7932]

With the Wide Input PicoPSU, you can even give it 19 volts.

[@askhowiknow5527]

I just came into possession of a PC Jr. and had to come back to this video.

[@JarrodCoombes]

If you order those PCBs, I'll totally buy one from you for my PCjr.

[@Zankuho]

16:18 Thankfully modern PSUs are protected from any kind of... inappropriate usage.

[@TechTangents]

Yeah no kidding. Using that new PSU saved my bacon in this.

[@donpalmera]

I think a cheap ultrasonic bath would make a good investment. I'm not sure what you cleaned with but I've found that isopropyl can't dissolve the flux I use so I use lighter fluid and then isoproyl now.

[@mihumono]

hey, i know the video is up for some time now, but part of those low resistance measurements could be due to the esd mat being conductive

[@ZerodJailbreak]

Awesome video! What software did you do the layout with?

[@TechTangents]

KiCad

[@DavidScheiber]

that high pitch crt wine comes across in the video really well... like really well.......

[@MrHBSoftware]

oh boy the snowflake generation....

[@ZiggyTheHamster]

It also comes across in real life, but since you probably didn't grow up with CRTs being everywhere, it's more perceptible to you.

[@Halterung01]

That resistance measurement with negative Ohms after all that work would have made me question my existence and realize its futility XD

[@electronash]

12:12 I'm fairly sure the click noise you were hearing was just the PSU trying to start up, since the reservoir caps still had some juice in them. (I'm assuming you tied the /PS_ON signal to ground on your adapter PCB, so the PSU will switch on as soon as mains is applied.) I doubt there is a relay in the PSU, and it's just inductor noise for a brief pulse. Props for manually cutting the PCB like that, but personally I would have just used an older / crustier ATX PSU, and chopped the plug off. Or, soldered some wires (plus heatshrink) directly to the pins of the ATX socket, then just scored the edge connector for the PC Jr out of the copper clad. Again though, it was genuinely interesting to watch, as I don't think I've ever seen the box cutter PCB method on KZbin before. ;)

[@electronash]

Ohh - I watched the rest. lol I think we've all done the mistake of reading the reverse pinout once or twice. hehe I now have the strong habit of double-checking the PSU or whatever with the meter (between common grounds or other known wires). I've even seen pinouts on the Interweb that have been reversed from how they are labelled.

[@joeyr9876]

The official IBM PCjr monitor is the only monitor designed to sit on top of the floppy drive. It is a known design issue. Even in IBM's marketing materials, other monitors sit to the side of the computer. This is why you are having that floppy drive issue.

[@kokodin5895]

why didn't you just put the connector from the other side, then the pinout would match the pcb

[@TechTangents]

There is a lot more space towards the side of the case vs. towards the RAM card. The ATX cable would not have fit if I flipped the connector around.

[@kokodin5895]

in that case i would make right angle pcb to pcb solder connection but since this board is so simple it would probably be overkill i wonder if optiplex 755 sff power brick would be any good for that

[@gallowsgryph]

According to my roommate (who's studying to become an EE), you likely got the negative resistance from having your probes backwards. Regardless, congrats on getting this working. The flux issue sounded a lot like an issue David had on 8bitguy when he was assembling the PE6502. He didn't clean off the excess flux like he was supposed to, and it ended up causing problems.

[@mikematkovic3466]

Brilliant idea !! How about adding in a 120vac to 18vac transformer to the board with an IEC polarized cable non grounded power cord to the back ?

[@retrox684]

My two biggest gripes about the pc are the crummy keyboard and external power supply. This is pretty cool

[@zigafide]

I can't wait for part 2

[@PlumpyArts]

wow this is amazing.....

[@perkyzombie]

My first PC, a XT, had one game for the first couple years, GWBasic. Good times!

[@DoRC]

Damn that was a lot of work. I think i would have made the edge connector piece then just used wires to connect it to atx connector.

[@kcinplatinumgaming2598]

Patience of a saint :D i would have gave up within an hour lol

[@uK8cvPAq]

What type of flux pen was that? Wasn't RA or water soluble was it?

[@hikaru-live]

What I have in mind for such power adapters is actually make them run on a 12V barrel jack input. The +12V rail is a direct pass-through (maybe with a fuse, a diode and a TVS as some protection,) 5V is obtained from 12V through a buck converter based on LM2596 (I have the room anyway so bigger components are okay,) and -12V is obtained through 12V through a buck-boost converter based on MC34063.

[@Timmymantwo]

This is a really good mod

[@setoman1]

Congratulations, you've created a diode.

[@jeffm2787]

Looking at the schematic for that PSU it looks like you could just toss in DC and it would work.

[@xBelastianx]

The sweet familiar sound of an Brother HL 2030^^

[@giovannicarovanello62]

Ahaha, I feel so bad for you at the end of the video. You did all that amazing work, and at the end there were no games to be played on the system :( Well, that aside, this video was very educational! Thanks a lot!

[@Space_Reptile]

I'd love one of those boards, pretty sure LGR would too

[@randfurs]

Please add a low pass filter in the parts with the CRT, thanks...

[@eformance]

These are AMP Mini-fit Jr connectors, FWIW.

[@BollingHolt]

Cool!!! It must be nice to actually have patience ;)

[@llugnuto7795]

was the thrift store called "deseret industries"?

[@RainerTrunk]

Once again, great Job.

[@txd]

Water soluble flux will do that to a board. I found out the hard way too on a project. could not for the life of me figure out why i had an almost short. Kept removing components from the board.

[@zodiacsoulmate]

Ur video is too good, keep it up!

[@jussapitka6041]

Do you also put a molex and fan connector on the board so they don't have to be wired from the power supply.

[@dominikschutz6300]

Ready for Pico PSU :)

[@FennecTECH]

So the flux is soaking into the fr4?

[@ToTheGAMES]

Awww yes, a new AkBKukU video!

[@josephnealeUKscratchcards]

awesome video as always

[@jussapitka6041]

How the hell does negative resistant work? Can someone explain?

[@TheAussieRepairGuy]

Never heard of acid resist pen and ammonium sulphate...

[@AdamBouzaneOfficial]

Love it !

[@E-virtuosEu]

this guy's crazy :-P

[@Nitro_0999]

Man where do you learn how to do all of this stuff

[@Koutsie]

At 16:00 you also should use a HFF. My ears are bleeding ouch.

[@TechTangents]

It slipped past me this time. Normally I remove it, but I was kinda rushed on this video.

[@Koutsie]

AkBKukU sorry, im just being nitpicky :/

[@these.are.my.things]

Could you use a 12v ATX power supply like on an HTPC.

[@matt4193]

Some PSUs wont turn on when they dont have any load. If you try to do "the paperclip thingie" to start a PSU, stick a fan or an old molex HDD and see if they spin.

[@eduardoavila646]

Would it be possible to get a 12v power supply, and use a boost converter circuit to bump up the voltage to 18v? A friend is in a simillar condition as yours.

[@TechTangents]

The problem is that it is AC. That is much less common.

[@eduardoavila646]

Oh i see.. I that case here i think its 16v dc. So a boost converter would do the trick?

[@TechTangents]

It could, just make sure it's rated for enough current as well.

[@jacekjagosz]

How did he get -12V?

[@fuentescgabriel]

Jacek Jagosz the atx power supply already has -12V.

[@jacekjagosz]

Gabriel Fuentes Oh. So for my understanding GND on a PSU would have to be +12 compared to actual ground? Could somebody explain?

[@ColdestLivewire]

ground is still earth ground, ac voltage goes above and below ground. it just uses a negative voltage reg

[@BoingoInstaller]

Jacek Jagosz gnd is 0v

[@Manawyrm]

negative voltages can be an unintuitive concept. GND is just an arbitrary point, it could theoretically be anything. In order to simplify things, we commonly use GND as earth ground or 0V to earth. If you now imagine 2 batteries in series, both 1.5V types, and the center point is GND. If you measure a voltage between GND and the positive terminal of the second battery you get +1.5V, and on the negative end of the other you get -1.5V. It's the same principle with the power supply.

[@ManiacalMichael504]

Man, just when you were getting done with that first one I was thinking "no way I would've gone thru all that trouble." And then do it all over again!? Definitely much more patient than me.

[@DuckGWR]

Yeah, that issue with the monitor is a know problem with the PCjr. IBM's ads and promotional material all show it on top, but the paperwork advise against putting the monitor on top of it.

[@redwanhasan1721]

It takes in 19V 2.5A AC? I would probably just get a small transformer and solder those wires directly to the power board(as that connector might not be available). 19V 2.5A DC? I would do the same thing, I mean just hooking up wires directly to the power board but use an Asus Laptop/monitor power supply(they are usually rated at 19V 3.4A).

[@MrHBSoftware]

those power supplies you are talking about are most likely DC and use some type of switch mode power supply circuit so they wont do....he needs 18v or 19v AC...you need an old school power brick with an actual transformer on it and remove the bridge rectifier...and a 19v 2,5a transformer would be quite beefy and heavy....maybe if the PCJR powerboard rectifies the supplied AC immediately right after the input, then you probably could get away with feeding it with DC

[@redwanhasan1721]

Hugo Barbedo well if I can take a look at it I would understand whether it is taking in the AC and converting it to DC and nothing else then feeding DC would be okay. For AC I mentioned about directly using a transformer.

[@MrHBSoftware]

yes i misread it..but a 2.5a "real" transformer(not smps) for cheap would not be easy to find i guess...i have a drawer full of power bricks but most are rated at 1 amp or less. but would be the simplest solution of course

[@redwanhasan1721]

Hugo Barbedo don't know about your place but they are very easy to find where I live, you can easily get 7A rated ones for like 5-6US$

[@MrHBSoftware]

I am in Europe, Portugal. that seems very cheap for a 7amp xformer...are they toroids or "normal ones"?here i can find nice 12 and 24 volt beefy transformers also cheap from used industrial applications but not 18/19v...24v could overheat the voltage regulator at the powerboard or exceed rating for other components...and those cheap industrial transformers we can find here dont come with an enclosure or with a plug and cords...nice thing would be to find a charger for some type of old device, already with a plug, cord and enclosure, just open it and remove the bridge rectifier..

[@LetsPlayKeldeo]

amazing video !

[@boxodoughuts6480]

Random question but what did you go to school for?

[@ToTheGAMES]

+AkBKukU you could wash the board in a alcohol bath just like you did with the Voodoo.

[@turbo5546]

I feel like using a 24 pin extension cable to make an adapter would have been a lot easier, and you could have removed the pins from the connector you didn't need and have the atx connector hanging out of the pc like that

[@Hydr8Man]

I see an akbkuku video notification Me: *REEEEEEEEEEEEEE*

[@610annasinclair]

and the 8 bit guy might want one

[@Koutsie]

What os is that. I cant quite figure out by kde/gnome (cant see close enough on android lol)

[@TechTangents]

Check my channel about page

[@Koutsie]

AkBKukU ffs me

[@TechTangents]

It's no problem I get asked that a lot. I recently made the FAQ to answer some common questions.

[@Koutsie]

AkBKukU Yeah, well i had not checked the channel info for ages... But yeah can't wait to see what thisll become, will it even work well etc Keep up man!

[@monthlyanarchist]

great video!

[@leisergeist]

I wonder if a PicoPSU has enough juice to power one of these.. That'd be pretty much ideal: an entire power supply just a bit bigger than the board you made Edit: beefiest one delivers 160 watts... Might work? No idea what these draw

[@eduardoavila646]

I think it could! I've seen a 386 that had a 120w power supply. Ans these older cpus didnt had a too high wattage

[@leisergeist]

Yeah, I'd bet it would work great. No giant power supply hanging around outside the case. Might as well spend $45 on a nice modern power supply than $60 on a questionable old original from ebay

[@yukisaitou5004]

LeiserGeist The PicoPSU still requires an external AC-DC transformer that's pretty large, especially for the 160W version. It's about twice the size of most Laptop power supplies and costs more than the PicoPSU itself.

[@leisergeist]

Still quite an upgrade from an ATX power supply sitting outside the computer with a mess of wires running in, wouldn't you say? lol

[@colinstu]

Picopsu still requires a 12v dc power brick to power it, but yeah it would be pretty elegant. Not sure if it could provide enough amps on the -12 / 5 / 3.3v rails though.

[@dwoodcob]

@AkBKukU Hey have you thought about using a Pico power supply? They are ATX power supplies that run on laptop style DC bricks. You might even be able to fit one of those in the case, or at best just have a power brick coming out of the PCJr. Here is a link to a 120w one www.mini-box.com/s.nl/it.A/id.417/.f . I have seen these things go up to 300w. Another great project man, keep up the good work.

[@TechTangents]

I will be looking into these for pt2

[@dwoodcob]

AkBKukU Cool, great to see if you can make it look like from the outside there are no shenanigans going on. Look forward to part 2.

[@MakarovFox]

interesting behaviour of the flux ink

[@rasz]

water soluble flux?

[@bombardactyl]

I'm here because I got pretty much the exact PCjr combo you have but with 2 floppy drives and no power supply and refuse to buy one online.

[@sunnohh]

I would have screamed, several times. 🍻

[@greenvm]

Run some electricity through the negative resistance bit and you will get more power on the output than what you gave it :P

[@Skwisgar2322]

you might be able to make it internal with one of those compact ATX psus made for mini itx systems. any modern atx power supply is going to be beyond overkill for that machine.

[@Skwisgar2322]

Or make it more original looking and use one of the 12DC to ATX psu adaptors, replacing the 18vac barrel jack with a 12dc one.

[@Skwisgar2322]

something like this www.short-circuit.com/product/picopsu-90.html#

[@Nanospark0]

3:36 I use that same exact motherboard as a parts donor board. It comes out of a Compaq Presario 5000 (Intel version) and it ran an Intel Celeron SL46T 566 MHz CPU. Nothing special here.

[@anthonyaviles8665]

Count me in for one of those boards let me know I'll get one from you

[@VicGreenBitcoin]

Next time just buy the 60 Dollar Power Supply ;-) Thanks for the Video.

[@HeyBirt]

Finding a transformer with an 18VAC output would not have been that difficult. Since the original power supply is a switch type you might be able to feed it DC as well (as most switch type supplies just rectify the input and then do the switching.) If you rectify 18VAC you will have about 25VDC so a 24VDC supply would probably work. This would be easy to test with the supply out of the computer. If the power supplies in these things are not reliable then you could design a new card to hold a new small switching mode power supply (a fully enclosed type) like a MeanWell RT-50B. That would give you a 120AC~240AC input PS that would fit in the case without a big honking ATX supply taking up space externally.

[@ClanTeamKill3r]

dude you could use a pico power supply for this and you could make it all internal with a standard external power brick

[@Sheevlord]

Actually negative resistance is possible, but it usually requires active circuitry. en.wikipedia.org/wiki/Negative_resistance

[@acmild]

Does anyone have a suggestion for an imac G4 17” Power Supply replacement? Cuz i’m in a country that doesn’t have the market for apple’s old machines, so there are no one sell those here and importing it cost a fortune

[@RetroBerner]

You could probably just throw a cheap pico psu in there with your connector, sweet!

[@JonTheGeek]

Can we talk about how cool it is to make a PCB from scratch?? Really imbodies the tinkering mindset

[@crusaderanimation6967]

13:30 Oh yea... i know this feeling bro. I will just make simple ATX tester i trough... it will be simple i thought ... just diodes resistors wires and one button i trough... even i am not that dump to fu!@ that up i thought. But at leas now i know i'm not first nor last to make that mistake.

[@smallmoneysalvia]

I’d suggest some decoupling capacitors, just because it’s designed to have such short traces from the voltage regulators to the board.

[@rwdplz1]

When you realize $60 would have been cheaper...

[@RanHam]

Cool deal. I just hacked up an atx to power my Amiga 500. I'm stuck on a green screen of death

[@guycrew728]

Ouch! Sorry you had to deal with that wasted time.