0x0035.2 - IBM PCjr ATX/PicoPSU Adapter Update

[@TechTangents]

I'll put some inventory information here for the remaining external ATX only boards: 8 - total originally available 4 - sold 4 - available Also so everyone can stop recommending it, no a 20pin ATX extension would not be cheaper. 10 new PCBs is costing me $2 total for 10, it would be around $60 to get 10 extension cables.

[@XanatosDavid]

where are you getting the PCB's so cheep?

[@TechTangents]

I don't have a preferred board house, this time they were ordered from JCLPCB

[@BEdmonson85]

Yeah I've heard good things about JLCPCB, haven't ordered from them yet though. PS, if you DL the datasheet for that switch, the dimensions are in there, no guesswork.

[@TechTangents]

I did that of course, that doesn't guarantee I got the tolerances right in my design though. I think I'm going to reprint it with a bevel on the top anyway to make it easier to close the lid. so if it doesn't fit right I'll make an adjustment then.

[@piecaruso97]

i recognize jlc pcb, i used that service to order the pcbs for my custom isa cards

[@djdjukic]

Oh! The experience of waiting for weeks for slick new boards from China and figuring that they need at the very least a bodge, if not a full revision, within 15 minutes of assembly... Very relatable.

[@tekunalogy]

Where did you aquire all this knowledge of electrical engineering, software engineering, etc.? Did you major in computer engineering? It is so cool how you can do any aspect of a project whether it requires electrical knowledge, 3d printing knowledge, programming knowledge, PCB designing, etc. Anyways, good luck for future videos and I am excited to see an update on the new PCB.

[@smallmoneysalvia]

Decoupling capacitors! It’s not so necessary with the tiny power supplies, but there’s some long ass runs out to the full sized psus, and some decoupling caps would provide some brownout protection for super cheap, though you could characterize it with a scope and see if they’re really needed or not.

[@nekoneonneow]

Could you use a 20-pin cable extension to connect the power supply to the adaptor board?

[@TechTangents]

Probably, but I figure that would be too costly and inconvenient. I want my option to be less than half the cost of an original PSU for the PCjr, and at least less than 75% of the cost when you include a PicoPSU. So adding something like that as a requirement would put me outside my requirements.

[@cosminraduta8267]

that would work for this batch, but if he wants to sell them or give them away it would be cheaper to just make the board with a right angle from the get-go

[@TommyAgramonSeth]

How about using a flat connector like in the previous video instead of the angled one? Wouldn't that fit? Or would it maybe stress the slot too much?

[@dkabot]

Is there any particular reason your 3D printed plate has the power jack on top, and the switch on the bottom? The original power supply is reversed from that, and the case is labeled for that layout, so I'm just curious.

[@AshenTiger]

I second this

[@TommyAgramonSeth]

I was gonna guess it's because the switch would fit better but when I looked at it again, it seems like both holes are exactly the same size.

[@TechTangents]

I really badly wanted to put the power switch at the top, but there are two reasons I didn't. 1. The panel mount switch's screw tabs are a lot wider and wouldn't fit well at the top near the lid. 2. I plan on including two versions of the printed part. One that has the barrel jack panel mount, and another with a large slot for the ATX PSU cable to fit through.

[@dkabot]

Thanks for that answer! My curiosity is now satisfied.

[@francoisrevol7926]

Did you try the original boards with a straight ATX connector? the PicoPSU would not be vertical but there seems to be room enough on the side…

[@loganjorgensen]

I'm not surprised that happened even with the Pico coming afterwards, 90 degrees is the standard usually. You mentioned pull on the cable, can't you just add a cable catch to the case hole itself?

[@eduardoavila646]

This was awesome. I was thinking in doing a thing kinda simillar to that in the old at psu connector (the old p12 psus, i dont remember the right name). For when i get a 386. But in my case would be a simple matter of cutting the cables of a old and dead psu that i have from that era and soldering into a atx conector from a dead socket A board that i have here.

[@daviddavidsonn3578]

3:13 why don't you solder a STRAIGHT 24 pin connector to the PCB instead of a 90 degree angled one ? the pico PSU would end up next to the board instead of above it. that might work.

[@leisergeist]

Neat! Glad it worked! People were saying it might not have enough 12v power, bit it looks like it ran everything just fine (and the floppy) It's really awesome how they managed to squeeze so much power into such a tiny footprint huh?

[@TechTangents]

Personally, I find it suspicious. These come in up to 160W which is a _ton_ of power. Also, the 5.5mm barrel jacks these use are rated for less than half the current that one would need from the 12V supply. The people who were talking about it having enough 12V power, were they just in the comments here or were they elsewhere? It's hard to track where you're stuff gets linked, I know there was a hackday article, but that's it.

[@leisergeist]

I suggested the PicoPSU on your last PCjr video, and a few replies suggested it may not be able to supply enough power. I don't know of a way to permalink comments here, but it's kinda near the top when sorting by top Personally I think people underestimate it, but it's been used for media center PCs and low power SFF builds for quite a while... That said, I haven't seen anyone use one in an 80s computer, so you might be a pioneer there. Maybe just see if it gets too warm after loading a big program off disk or something. I think it has thermal and overcurrent limiting anyway?

[@TechTangents]

Ah alright. I did read all those comments. I have a simple IR thermal sensor, so I could see how hot it gets under load.

[@electronash]

@@TechTangents The good news is that almost all of these Pico PSUs just pass the +12V directly from the external power brick anyway, so that can always be upgraded if more 12V juice is required. It would be worth measuring the real current draw of the PCjr, though. Mainly on the +5V rail. I would imagine the motherboard would only draw a few Amps. The highest "peak" power will probably be from the stepper motors on the floppy drives.

[@electronash]

@@TechTangents Oh, and PicoPSUs have been used for many years in retro machines like the Amiga, Sharp x68000, and I've used them just fine in Dreamcasts. ;) The common "160 Watt" version does seem very efficient, you just have to watch out for juicier items like larger / older hard drives, floppy drives, or expansion cards. It's worth comparing the specs of the original PCjr PSU to the Pico, but I personally think it'll be fine.

[@amirpourghoureiyan1637]

the leftover version 1 pcb's can be used as pc jr testers to make sure that the psu doesn't accidentally fry it on first time use

Man... you really love this PCjr! AWESOME !

[@Space_Reptile]

also quick not looking at your redesign , why not make the ATX header vertical ?

[@TechTangents]

It would make the overall design taller i.imgur.com/vYq4M4S.jpg . Which with the connector off to the side like it is now may work out fine. But it would not have fit like that over the card edge like I designed it the first time. So I guess consider the 45° angle a legacy carryover from the first design. Probably not needed, but it doesn't hurt.

[@Space_Reptile]

ah makes sense , vertical would still allow the pico to fit tho as its height is not an issue anymore, also i like rectangles

[@Jackpkmn]

I think the 45 degree angle is a good idea because it accommodates the picopsu but also accommodates a regular ATX psu as well satisfying the requirements of both designs at once.

[@Jackpkmn]

@Galaxy TS2 the ATX PSU does not sit inside the case. It sits outside.

[@Jackpkmn]

@Galaxy TS2 There's nothing wrong about what i said. The ATX power supply does not sit inside the case but that doesn't mean you can't use one did you even watch the video?

[@thedungeondelver]

I know this is gonna sound nuts but I would love to see you come up with a slew of Jr. expansions - more RAM, HD/CF card controller...maybe some kind of gotek-like device that plugs in the cartridge port? :)

[@ZiggyTheHamster]

The jrIDE adds IDE and RAM. The cartridge port is really too limited to be able to add something like a GoTek.

[@Koutsie]

Where do you order your PCB's?

[@TechTangents]

I don't have a preferred board house, this time they were ordered from JCLPCB

[@EdwinNoorlander]

Nice work. Are you using KiCad?

[@TechTangents]

I am using KiCad

[@bikerdave1274]

4:30 anyone else scratching their head over what Floppotron tune this is? 🤔😋

[@Veeb0rg]

Could you have switched the power switch and power brick connector locations on the printed bracket? That way the factory markings on the case match up.

[@danagoyette7932]

I believe the wide-input PicoPSU might be even a bit taller than the regular PicoPSU.

[@kkfdes]

Aww man, you could have soldered the female power connector to the lil green board vertically. Just need to cut the longer pins after sraightening them all and voila! And connect pico vertically afterwards, like an L shape...

[@teh_supar_hackr]

Once the new design comes in, do you have plans on selling these?

[@TechTangents]

That's the plan, I'm going to have 6 left now after I get the next set of boards in. As soon as they are proven to be good I'll order parts for at least 10 more. I'm going to have a listing on my website and sell them directly through pay pal.

[@Jigglenomicon]

Good job! its such a elegant fix imo

[@hanro50]

Couldn't you take your current board design and just mount the power connector flat against the board?

[@TechTangents]

I don't have the standard connectors on hand, just the right angle ones. While it may fit like that, it still doesn't solve the floppy drive power problem that the PicoPSU has. So I need to change the board to have a 4 pin connector anyway.

[@cbmeeks]

Great work! Have you thought about using a thicker PCB? It looked a little loose but maybe it isn't. Hard to tell over video.

[@TechTangents]

The thickness was good It could be a little thicker but the cost to get a basically custom board made isn't really worth it. Cheap PCBs like what I'm are usually created in a giant panel with other boards that are all cut out. So needing a different thickness means you have a much more custom board than usual.

[@Blink_____]

man I had a PC Jr when I was a kid in the 90s, like most curious kids I screwed it all up to hell and ruined a working hard drive unit for it too, lol.... damn I kinda miss that thing

[@RanHam]

So the real question is. Once you get everything set up, what programs are you going to use on the IBM Jr?

[@leadedsolder]

Where are you sourcing your PicoPSUs from? The cheapest I've been able to find in Canada so far is $53-ish shipped on Amazon for an 80W. I have a couple machines that might need a touch of power supply modernization.

[@sickiziu]

@AkBKukU - what software, beside Blender you use to create 3d models for printing?

[@Space_Reptile]

is it illegal to call dibs on one of the 7 ? because DIBS EDIT: actually a board layout to etch would be better , because international shipping and me not QUITE having a PCJR yet

[@TechTangents]

I could always drop the PCB in an envelope with stamps on it if you want to source parts yourself. That would at least save you having to etch.

[@Space_Reptile]

that would be a solution , guess im gonna shoot you an email

[@Motolav]

AkBKukU mailing anything in an envelope isn't a great idea there's a good chance it'd end up bent breaking the PCB

[@leisergeist]

Dave from the EEVBlog tried shipping µRuler PCBs in an envelope some time ago: The PCBs didn't break, but they sliced themselves right out of the envelopes during sorting. People were angrily emailing him wondering why they got empty envelopes lol

[@BEdmonson85]

It would 100% guaranteed be in pieces when delivered, The sorting machines they put standard letter sized envelopes through bend them through rigid rollers as they travel through sorting facilities. If you wanna mail it, put it in a bubble wrap mailer and add a "fragile" sticker (for all the good they do), they go through a different sort process.

[@kcinplatinumgaming2598]

One word !! Excellent

[@cheesewhizz40]

Are you going to continue to use that power switch bracket, or was that just a prototype? The Power plug was where the switch should be. Is the switch you are ordering too big to fit in the original space?

[@skonkfactory]

Why not just fit a straight (non-right-angle) connector? That would put the PicoPSU horizontal.

[@intel386DX]

fantastic project :)! is it any chance to repair the original power supply ?

[@johnuser5162]

What software do you use to design the PCBs?

[@emilalmberg1096]

Metcal FTW!

[@tylrhoot]

Also 3d printing is another option to make a adapter

[@user_romanport]

Hey AkBKukU, why did you put the 20 pin connector at an angle? Why not have it facing the back of the case?

[@TechTangents]

2:56

[@josephnealeUKscratchcards]

great video as always

[@computeraidedworld1148]

Hey what did you use to make that board?

[@piecaruso97]

what about just using the current deisgn with a normal atx connector and the pico psu? will it fit?

[@TechTangents]

I don't have the standard connectors on hand, just the right angle ones. While it may fit like that, it still doesn't solve the floppy drive power problem that the PicoPSU has. So I need to change the board to have a 4 pin connector anyway.

[@beck3k]

Lets start the battle...Vim or Emacs?

[@thedevminer]

you did this really good. . .

[@alexgsdbmx]

Anyone knows what PCB design software did he use?

[@TechTangents]

KiCad

[@AshenTiger]

Hell yeah, KiCAD!

[@Aguyontheinternet]

Do you use Twitter?

[@TechTangents]

Yep! twitter.com/AkBKukU

[@KiraSlith]

I VEHIMITLY suggest you add at least a spot to mount a 7912 along the negative 12v rail! The PicoPSU's rail is too far out of spec, a high rail will likely damage components over time.

[@TechTangents]

The 7912 is a negative _regulator_ not a _generator_ . As an LDO if you take a look at the datasheet for a 7912 you'll see that the dropout voltage is 1.1V, so you would need a -13.1V source voltage at the minimum. The TI datasheet has all the 7912 ratings stated with a -19V input voltage: www.ti.com/lit/ds/symlink/lm79.pdf Also as I stated in the video, it was about -13.6V without a load. I just checked it with it in the computer turned on and the voltage was down(up?) to -11.3V. Which is what I expected.

[@KiraSlith]

AkBKukU Just echoing what I'd been told by (supposedly) better informed engineers. possibly they meant another regulator? point was to smooth out the intake. but if the drop is as you say, then I need to check with better people. From what I understand voltage doesn't normally drop that low under load, thus the fear. possibly something to do with how the PicoPSU handles it's -12v rail?

[@TechTangents]

The -12V rail on the PicoPSU is rather weak, but I don't think that's the main reason. I would not consider a ~6% drop in the rail to be that significant. The LM7912 can go as far out as -11.5V, so a switch mode being a little under that is not surprising. Elsewhere my attention has been called to the system board schematic that for some reasons assumes the negative voltage input is -6V instead of -12V despite the power board schematic clearly showing it outputs -12V. I'm not sure why though because the system board has a SN75188 on it which requires at least -9V. So I think some last minute changes may have been made to the design in the power supply.

[@rudder3084]

Two minutes later "I need another design"

[@_simone.vinci_]

👋👍

[@brenden7158]

oh dear

[@Voltnic]

76th

[@andresbravo2003]

at least i'm not recommend it...

[@BloodSprite-tan]

quick question if you're three-d printing them why not just make a slot that tightly fits the switches you have?

[@TechTangents]

I want to use the other switch because it looks more like the original. Also, the other switches would have to be inside the case because of the size, so they would be difficult to press.