So many people complaining on how he does his stuff. He is doing on his way, and the best of all: he is sharing! Adrian, i love your videos, just keep doing what you doing at the way you feels is the best! Thank you!
I like your style as a tech. 50% logic, 35% theory, and the all important 15% "what if I do this?" I've always found that you've got to be willing to improvise. That's the part that a lot of techs don't have. As you know, "what if" is king. Well done! 👍👍
I would be so scared to snip off those legs. Should those new chips choose not to work, you'd be left with nothing, not even a malfunctioning one. But it worked, so thumbs up! Lovely machine.
@@benbaselet2026 Soldering is anything but trivial if you're someone like me - an inept guy with a serving of Multiple Sclerosis on top :D No, seriously. Soldering is a big pain in this state. My hands are almost useless for anything requiring precision or steadiness. So I choose not to cut, for I choose not to solder :D
You are a braver man than I on that chip replacement method! I don't like to damage the existing hardware even when it is expected bad and I have replacements. I try to always maintain the ability to revert back to the original state. Being different part numbers from a different decade on your new floppy controllers had me worried they would be different somehow like CMOS instead of TTL and may not work. But I haven't done any reading on the matter, that's just what popped into my head. Clearly it worked so it was an improvement! I'm really curious to see how that goes with the RAM sidecar! Since mine is only 64kB I should really look into one of those as well.
Bravo on not just jumping straight to electrolytic replacement. That's become a serious pet peeve on a lot of the electronics channels I watch. Almost everything I own (except some Mac stuff) from the late 70s-early 80s has high quality caps that still dont need to be replaced. Throwing a bunch of cheap caps in ensures that a machine that probably didn't need a re-cap in the first place...will definitely need one again in a decade or less.
Bad caps would be much more likely than a fault in an IC. The issue still could be a bad cap that caused the last chip to latch up. Most people that are recapping seem to be using Panasonic high temperature caps. Pretty sure they won't go bad in a few years.
I really like the method of desoldering a bad chip off and replacing it with a socket instead which makes it very easy to swap out chips when necessary.
@@adriansdigitalbasement or even just a pcb with an edgewise push switch on it to stuff in the edge connector 😉saves making holes in the poor old thing 😁
I am sure there would have been room on the back switch plate with the new power supply but whatever. When your hell bent on ruining the case it's not hard to find a reason to.
Fantastic to see it working properly! Akbkuku’s PSU mod is such a good thing for these machines. I know I suggested a different PSU on the last vid. Needless to say, I was wrong. But great work tracking it down to that IC.
Smashing job on that! That was quite the detective work to figure out the error, sometimes desperate times call for desperate measures. Glad that those IC's are easy to come by! I'm not terribly fond of where the reset switch was mounted, but it's easily reversible should that cartridge slot need to be called into use.
If the capacitors are good and the chip is not resetting properly then it could be the resistors in the reset timing circuit. There is usually one resistor to discharge the capacitor on power off and one to trickle power into the capacitor on the reset line so the reset is low on power up but slowly goes high. Of course it could also be the logic itself, though.
He must have intentionally pressed a key during the POST to get it to stop in order to take the screenshot. That is usually (but not always) what causes ERROR B. Press enter and everything should still work correctly, if that was what caused it. I used to have a PCjr myself, so I know.
I always wonder how modern PC gaming would be if we still did booter games. It's almost too bad that modern games rely so much on OS-specific SDKs, drivers, and all of the hardware IO stuff.
This series has been pretty interesting to follow along with. I'm looking forward to seeing how you make out with that sidecar memory expansion in the future. Your diagnostic of the bad IC chip on the floppy controller was really interesting, especially when many in the comments were giving different advice. I like the fact that you replaced the chip rather than going with some other ridiculous reset solution. As for cutting the legs and tossing the bad chip I'd have done the same thing. I don't really subscribe to the theory of saving everything even when it's broken as some have suggested. The chip was bad. You definitely chose the best solution.
Really nice work diagnosing the problem and getting that PC Jr to work correctly again. I am currently working on a Commodore 128 that's giving me fits. Thanks for sharing Adrian.
Great video! But the Reset switch in the Cartridge Port? The right port is where the BASIC Cartridge does into; if you get it. As I remember, the computer does reset when you put the cartridge in or pull it out.
It doesn't matter which slot the cartridge would go into (BASIC or otherwise), but I do like the simplicity of just shorting out those two pins via a push button.
That's a very interesting fault mode for an IC. I wonder what's happening there. I don't know if the 765 is manufactured in CMOS, but it looks like some sort of "soft" latchup condition .. somehow not creating a hard short leading to total destruction of the chip. What fits, is that a latchup condition can only be removed by switching off the device. I think the normal power on reset sequence was just right to trigger it when warmed up a little. Such faults are typically caused by slight ESD damage.
@@adriansdigitalbasement I would totally expect such ESD/latch up damage to be progressive, since they are a literal short circuit somewhere on the chip, heating up that area and damaging it further. I think it would have only been a matter of time till the old 765 would have failed completely. That's why in the industry ESD protection measures are such a big deal. Usually nothing happens without any, but if you damage something it could be latent and only manifest itself after quite a time at the customer. So they play REALLY safe for this reason. But, of course, thats all just blind guesswork. It's ONE failure mode which would fit to the symptoms, I'm sure you could find at least a dozen others if you look for them.
My money is on a power supply sequencing problem. Some rail is probably coming up before or after some other rail and causing the issue. I'm sure the original power supply had protection logic to ensure correct sequencing, and the replacement atx adapter board does not.
@@gorak9000 According to the IBM PCjr Technical Reference Manual, the whole system is +5V single supply. The +12V are only used by the drive motors and extension cards. So I think this is out.
Following your series has been entertaining, but I'm really confused why you would mount the switch and button in the cartridge bays. One of the more interesting things to do with PCjrs is use cartridge programs (Lotus 1-2-3, Colorpaint, Managing Your Money, River Raid, Demon Attack, etc. ).
HEY I love your vids. Always nice to see an old system like this revived. I am curious about what tool you are using at 9:01? Is it like a mini drill to create a hole in the through-hole after you've applied new solder? Looks very useful.
If you get the IBM 128K sidecar you can remove the 16 4164 chips, install 16 sockets and 16 41256 DRAM chips. There's a spot in the middle of the board where you can solder jumper 2 pads or, do what I did and install a pair of .100 pins and used a jumper. You'll need a small TSR to load when booting to recognize the extra RAM in DOS, but that will get you to 640K.
HI Adrian - I don't believe in just shotgun replacing every component either, but replacing 35+ year old electrolytic caps are a no brainer, especially if you plan to keep the machine long term (even Nichicons). It sounds like you tested them in circuit and got expected ratings, but I have still seen ones pass tester tests but act up in use until replaced. I would also like to share that in my experience, late 70s to mid-90s axial and radial full-sized caps generally don't necessarily leak visibly, or burst from the top vent -- they generally just seem to dry out eventually. Makes troubleshooting harder for sure. The video doesn't make it clear how you settled on the one chip being the issue, but if replacing it fixed the issue, then great. I would be very interested to see a voltmeter clipped to that floppy controller chip's voltage input lead (with the other lead grounded) and watch the meter during the PCjr reset button held down -- is it possible the expansion cards aren't fully reset during the computer being "reset", with that chip retaining some state from voltage present during reset ?? We know for a fact the card resets properly when being fully removed and reinserted. Best wishes!
Interesting way to figure out the problem :) I wonder, instead of removing the chip, could you just put the new one on top (piggyback) to see if that helps? I have repaired some c64's and I followed some other youtubers who repair c64's and did that on the chips they suspected was broken. So I wonder, is it always safe to do that?
I have to say that if you have 40 year old capacitors in a unit they are going to fail sooner than later and it never hurts to change them regardless how well they measure. It’s easier to change them then clean up the mess if they leak all over the PCB.
I used to own two PCjrs. I inserted and removed the BASIC cartridge all the time. It seemed to not affect the computer much at all. Nevermind that the Jr was anything but PC compatible. Adrian, one of my Jrs had a Rapport expansion upgrade to add a 2nd 360kB floppy drive, memory expansion, and a sidecar that had a 40-80 column toggle switch and a parallel port. Mine had 256kB on the board. Unfortunately, I accidentally tore a trace on the memory board (imagine a 15 year old kid trying to solder ram chips onto said board at the time).
@@FloppydriveMaestro he has the heated desoldering gun, you go trough all the pins and the chip falls off, its actually faster using the gun and you dont destroy the chip in the process.
@@laharl2k But why do you care? The chip was broken and he was going to replace it regardless. If a chip is broken its easier to just to this. Heated desoldering guns are not perfect and it can often be fiddly to get it all off in 1 go. Why does every one care so much about a broken chip having the legs cut off. IT WAS BROKEN ANYWAY.
@@FloppydriveMaestro it wasnt broken, it was just not working perfectly. but still it was still partially functional. You just dont trow away salvageable stuff, its that easy, desolder it properly, put a label on it that says "reset semibroken" and that's it. save it in case of nuclear catastrophe or something. You never know when you'r gonna need it or if you'll ever get to a point you cannot longer find a replacement. Just like with antique old machines, you just dont throw away broken parts, you save them ust in case in the future you can fix them or something happens and they become usefull again.
In my PCjr we always kept Cartridge BASIC in the left slot. Should the machine lock up and a 3-finger salute wasn't enough, we'd just wiggle the cartridge side to side and that would reset it. I think the fact that the system resets when a cart is inserted or removed is mentioned in the Guide To Operations manual.
If you get a 128K side car, many of them can be modified to use 256k DRAM chips to change them to 512K. I did that for one of my Jrs and have 640K in it now.
I see an opportunity here for someone who likes designing PCBs to make one which offers floppy control and 512kB of RAM, possibly with a CF / SD adapter all on one board. Heck even a cheap flash module would probably be enough space for a PC Jr.
8000 people cringed when you unplugged that floppy card when power was on. Yikes! It seems like there was a dozen other places you could have put those reset switches where they would not have blocked the cartridge slots. I would have either run them out the back or jury rigged a blank spacer that slotted into the cartridge slots with both switches on it. That's just me, though.
Yeah, between pulling the card while it is on (and risking shorting lines on the motherboard together), cutting out the old IC without knowing if it is bad or if the new ones work and installing a switch where it blocks the cartridge slot, its all cringe. There are way better ways to go about all of that.
Cutting the legs of the chip seems to make more work. Now instead of using some desoldering braid and prying it out, you have to cut each pin, use tweezers and remove each one, then use desoldering braid to take the solder out. Not to mention if the chip was good it's now ruined anyways.
Sure it can, higher resistances, signal noise, tolerances that over time are drifting. What I don't get, is he has a desoldering tool and it would have been simplicity to just remove the chip intact. He say's he's against replacing caps without reason but apparently has no issue in all but destroying a chip? seem inconsistent.
@@daishi5571 He destroyed the chip because it was already broken. All testing showed it was broken so why bother leaving it intact if you are going to replace it anyway.
If that's all the troubleshooting he wants to do I guess that's fine, to me that's slap dash. I still don't understand why the need to cut the legs when he has a desoldering tool which he then used afterwards, it's adding work.
I'm not a fan of replacing capacitors either. However, most L/C meters do not check for DC leakage, and only check ESR and capacitance. DC leakage can make an L/C meter think the capacitor has greater capacitance when DC leakage is present. This is because L/C meters use TIME to determine capacitance. The longer it takes to charge, the greater the capacitance. However, if the capacitors are leaking DC, they will give the illusion of higher capacitance, because it's taking longer to charge the capacitor. Nichicons are excellent capacitors, but that does not mean they are immune to DC leakage.
Not sure why you blocked the cartridge port with the reset switch. Why not just punch a whole in the front of the unit and mount (either the switch your had, or a nicer large button momentary contact switch) and add the reset button rather than block off the cartridge port.
A much more elegant solution would have been to make a 'reset cartbridge' with a very simple circuit : a reset button conected to the 2 pins you have to short to reset the computer. no holes no soldering. You insert the cartbridge and you have a rest button.
2:38 Maybe it did not happen, but it'd be fun and ironic to picture the PCjr booting the first time you wanted to demonstrate how it fails to boot, forcing you to shoot another take for that part of the video.
I saw a few other posts that indicate that the problem with the card might be due to the lack of filtering caps on some of the ICs. www.zdnet.com/pictures/cracking-open-the-ibm-pc-jr/16/ (look through the pictures, there's a bodge wire on the back of the card too) I'd give that a try, because if it works, that would be a much cleaner and reliable fix, and .1uF filtering caps are dirt cheap. Of course, might not solve the issue if the controller chip itself is bad.
I cringed when you cut the legs off the old IC, even more so when I saw you had a proper desoldering pump. Why not just flip it over and desolder the old IC out, so you still have it in case of unforeseen problems? It's not like it's a huge hassle with a vacuum desolderer, I don't have any issues with a crappy mechanical pump. Other than that, I really enjoyed the video and look forward to future videos.
I had a similar reaction when seeing that: As long as you are not 100% sure it is broken (and impressions can be deceiving), always try to save the old IC. However, the other side of the story is that these are simply not rare ICs: There is a lot of supply on Ebay and AliExpress prices as low as $1.30 a piece. If it is not rare, why make your life harder?
@@danielmantione So? If it wasn't the problem then he would still have a nice socket and a working chip. If you have gone to the effort of removing the old chip and buying new ones you may as well replace it while you are there.
When repairing/restoring older equipment it is good practice to minimize the damage to potentially working parts, after all, it is not uncommon for such parts to be out of production, and so in limited supply, which might easily mean you are needlessly denying someone else the ability to repair something in the future. There is also the concern about keeping the machine as close as possible to original or maintaining the history of the machine, though this might be more of a concern to museum type restorations it is common for even hobbyist restorers to try to minimize/avoid unnecessarily damaging parts or doing irreversible modifications
mmmm while you can just swap the chip and fix the problem, i'd rather stick an arduino mini to the card and have it detect and reset the chip for me. I rather fix things than swaping out chips, mostly because you never know for how long you'll find those chips until they are all gone.
That 765 was already broken (damaged insulation somewhere in the silicon most likely) and it would have been a matter of time until it fails completely, very likely by shorting out (full latchup) and possibly damaging the rest of the board. On the other hand it was THE floppy controller for all the early PCs (actually, it was in all PCs until they ditched FDC at all, it just got integrated into the chipset later on) so it's still quite plentiful.
So many people complaining on how he does his stuff. He is doing on his way, and the best of all: he is sharing! Adrian, i love your videos, just keep doing what you doing at the way you feels is the best! Thank you!
I like your style as a tech. 50% logic, 35% theory, and the all important 15% "what if I do this?" I've always found that you've got to be willing to improvise. That's the part that a lot of techs don't have. As you know, "what if" is king. Well done! 👍👍
I would be so scared to snip off those legs. Should those new chips choose not to work, you'd be left with nothing, not even a malfunctioning one. But it worked, so thumbs up! Lovely machine.
Soldering the leg back is trivial as long as you don't cut right against the package (which he of course did :-D).
@@benbaselet2026 Soldering is anything but trivial if you're someone like me - an inept guy with a serving of Multiple Sclerosis on top :D No, seriously. Soldering is a big pain in this state. My hands are almost useless for anything requiring precision or steadiness. So I choose not to cut, for I choose not to solder :D
I think you're one of the best retro-themed youtubers, how you fix things is just satisfying tbh
You are a braver man than I on that chip replacement method! I don't like to damage the existing hardware even when it is expected bad and I have replacements. I try to always maintain the ability to revert back to the original state.
Being different part numbers from a different decade on your new floppy controllers had me worried they would be different somehow like CMOS instead of TTL and may not work. But I haven't done any reading on the matter, that's just what popped into my head. Clearly it worked so it was an improvement!
I'm really curious to see how that goes with the RAM sidecar! Since mine is only 64kB I should really look into one of those as well.
Why would you give this a thumbs down? Great video!
Bravo on not just jumping straight to electrolytic replacement. That's become a serious pet peeve on a lot of the electronics channels I watch. Almost everything I own (except some Mac stuff) from the late 70s-early 80s has high quality caps that still dont need to be replaced. Throwing a bunch of cheap caps in ensures that a machine that probably didn't need a re-cap in the first place...will definitely need one again in a decade or less.
Bad caps would be much more likely than a fault in an IC. The issue still could be a bad cap that caused the last chip to latch up. Most people that are recapping seem to be using Panasonic high temperature caps. Pretty sure they won't go bad in a few years.
I really like the method of desoldering a bad chip off and replacing it with a socket instead which makes it very easy to swap out chips when necessary.
instead of fitting that reset switch inside the cartridge slot, why not make up a 'reset cartridge' with a small switch on its front?
I thought the exact same thing
@@adriansdigitalbasement or even just a pcb with an edgewise push switch on it to stuff in the edge connector 😉saves making holes in the poor old thing 😁
@@adriansdigitalbasement 3D-print a replacement enclosure for such a mod, perhaps?
I am sure there would have been room on the back switch plate with the new power supply but whatever. When your hell bent on ruining the case it's not hard to find a reason to.
^^^This times 20. 3D print a case and stick a pcb inside
Nice! I would definitely be quite pumped to have finally found a solution after spending so much time troubleshooting a pesky problem like that.
Fantastic to see it working properly! Akbkuku’s PSU mod is such a good thing for these machines.
I know I suggested a different PSU on the last vid. Needless to say, I was wrong. But great work tracking it down to that IC.
A very nasty bug finally fixed. As always: patience pays ! Very good job, Adrian ! Merry Christmas from germany ;)
I’ve never had an interest in the PCjr but for some reason I’m wanting one now after watching these.
Thanks for sharing!
At least 90 percent of what you said and did are beyond my ken yet I was fascinated watching you do it!
Smashing job on that! That was quite the detective work to figure out the error, sometimes desperate times call for desperate measures. Glad that those IC's are easy to come by! I'm not terribly fond of where the reset switch was mounted, but it's easily reversible should that cartridge slot need to be called into use.
If the capacitors are good and the chip is not resetting properly then it could be the resistors in the reset timing circuit. There is usually one resistor to discharge the capacitor on power off and one to trickle power into the capacitor on the reset line so the reset is low on power up but slowly goes high. Of course it could also be the logic itself, though.
This is a cool video. It is fun going back to these older videos. You've sure come a long way in the past two years. 🙂
The "Error B" on the IBM logo on the DOS prompt bothers me a little... Anyway, I'm glad to see this machine finally working properly!
He must have intentionally pressed a key during the POST to get it to stop in order to take the screenshot. That is usually (but not always) what causes ERROR B. Press enter and everything should still work correctly, if that was what caused it. I used to have a PCjr myself, so I know.
Gotta love those bootable game disks for King's Quest.
I always wonder how modern PC gaming would be if we still did booter games. It's almost too bad that modern games rely so much on OS-specific SDKs, drivers, and all of the hardware IO stuff.
This series has been pretty interesting to follow along with. I'm looking forward to seeing how you make out with that sidecar memory expansion in the future. Your diagnostic of the bad IC chip on the floppy controller was really interesting, especially when many in the comments were giving different advice. I like the fact that you replaced the chip rather than going with some other ridiculous reset solution. As for cutting the legs and tossing the bad chip I'd have done the same thing. I don't really subscribe to the theory of saving everything even when it's broken as some have suggested. The chip was bad. You definitely chose the best solution.
Really nice work diagnosing the problem and getting that PC Jr to work correctly again. I am currently working on a Commodore 128 that's giving me fits. Thanks for sharing Adrian.
All in all another great video. I really enjoy your videos, they are well made, to the point, and made in a friendly manner. Keep em coming :)
No need to apologise Adrian! Life happens! Glad you narrowed down that boot problem to the controller chip.
Love these videos. Sad to think of mid 90s when so much of the stuff was tossed.
Great video! But the Reset switch in the Cartridge Port? The right port is where the BASIC Cartridge does into; if you get it.
As I remember, the computer does reset when you put the cartridge in or pull it out.
It doesn't matter which slot the cartridge would go into (BASIC or otherwise), but I do like the simplicity of just shorting out those two pins via a push button.
That's a very interesting fault mode for an IC. I wonder what's happening there.
I don't know if the 765 is manufactured in CMOS, but it looks like some sort of "soft" latchup condition .. somehow not creating a hard short leading to total destruction of the chip. What fits, is that a latchup condition can only be removed by switching off the device. I think the normal power on reset sequence was just right to trigger it when warmed up a little.
Such faults are typically caused by slight ESD damage.
@@adriansdigitalbasement I would totally expect such ESD/latch up damage to be progressive, since they are a literal short circuit somewhere on the chip, heating up that area and damaging it further.
I think it would have only been a matter of time till the old 765 would have failed completely.
That's why in the industry ESD protection measures are such a big deal. Usually nothing happens without any, but if you damage something it could be latent and only manifest itself after quite a time at the customer. So they play REALLY safe for this reason.
But, of course, thats all just blind guesswork. It's ONE failure mode which would fit to the symptoms, I'm sure you could find at least a dozen others if you look for them.
My money is on a power supply sequencing problem. Some rail is probably coming up before or after some other rail and causing the issue. I'm sure the original power supply had protection logic to ensure correct sequencing, and the replacement atx adapter board does not.
@@gorak9000 According to the IBM PCjr Technical Reference Manual, the whole system is +5V single supply. The +12V are only used by the drive motors and extension cards. So I think this is out.
Nice fix.
When you started summing up what you did till so far, you forgot to mention the power supply fix. Just checking
delighted you got that annoyance fixed. way to go.
Following your series has been entertaining, but I'm really confused why you would mount the switch and button in the cartridge bays. One of the more interesting things to do with PCjrs is use cartridge programs (Lotus 1-2-3, Colorpaint, Managing Your Money, River Raid, Demon Attack, etc. ).
Have you ever seen cartridges for the PC Jr? I'm not aware of very many people who have. They're even rarer than the PC Jr itself.
@@BlackEpyon Neither are very rare... There's always some on eBay
@@JimLeonard Huh. Maybe I just haven't been looking hard enough. Course, I'm more of a Tandy guy, so I'm looking more often for Tandy stuff.
HEY I love your vids. Always nice to see an old system like this revived. I am curious about what tool you are using at 9:01? Is it like a mini drill to create a hole in the through-hole after you've applied new solder? Looks very useful.
nvm, think I found that it is your desoldering iron on one of your other vids (ruclips.net/video/XQVjwPsVFd8/видео.html). very cool!
Really enjoy your videos! Great work. Small suggestion for your health: You should add an activated carbon filter to your soldering fume fan. :-)
Been looking forward to this one -- I've been flying about for work too. Finally have chance to catch up on these videos :)
I've found this very interesting. And it makes me happy to see you fixing up this machine to a state where it can be used again.
If you get the IBM 128K sidecar you can remove the 16 4164 chips, install 16 sockets and 16 41256 DRAM chips. There's a spot in the middle of the board where you can solder jumper 2 pads or, do what I did and install a pair of .100 pins and used a jumper. You'll need a small TSR to load when booting to recognize the extra RAM in DOS, but that will get you to 640K.
HI Adrian - I don't believe in just shotgun replacing every component either, but replacing 35+ year old electrolytic caps are a no brainer, especially if you plan to keep the machine long term (even Nichicons). It sounds like you tested them in circuit and got expected ratings, but I have still seen ones pass tester tests but act up in use until replaced. I would also like to share that in my experience, late 70s to mid-90s axial and radial full-sized caps generally don't necessarily leak visibly, or burst from the top vent -- they generally just seem to dry out eventually. Makes troubleshooting harder for sure. The video doesn't make it clear how you settled on the one chip being the issue, but if replacing it fixed the issue, then great. I would be very interested to see a voltmeter clipped to that floppy controller chip's voltage input lead (with the other lead grounded) and watch the meter during the PCjr reset button held down -- is it possible the expansion cards aren't fully reset during the computer being "reset", with that chip retaining some state from voltage present during reset ?? We know for a fact the card resets properly when being fully removed and reinserted. Best wishes!
Interesting way to figure out the problem :) I wonder, instead of removing the chip, could you just put the new one on top (piggyback) to see if that helps? I have repaired some c64's and I followed some other youtubers who repair c64's and did that on the chips they suspected was broken. So I wonder, is it always safe to do that?
Cartridge shlot.
Don't ever change, your video's are awesome.
Whew! Good work. The PCjr seems to be a temperamental beast. :)
They sure are.
Awesome stuff! Thanks for making these vids!
I have to say that if you have 40 year old capacitors in a unit they are going to fail sooner than later and it never hurts to change them regardless how well they measure. It’s easier to change them then clean up the mess if they leak all over the PCB.
I used to own two PCjrs. I inserted and removed the BASIC cartridge all the time. It seemed to not affect the computer much at all. Nevermind that the Jr was anything but PC compatible.
Adrian, one of my Jrs had a Rapport expansion upgrade to add a 2nd 360kB floppy drive, memory expansion, and a sidecar that had a 40-80 column toggle switch and a parallel port. Mine had 256kB on the board. Unfortunately, I accidentally tore a trace on the memory board (imagine a 15 year old kid trying to solder ram chips onto said board at the time).
(another brainy guy from the west) , thanks for the videos they r better than hollywood movies to me
Nothing crazy if it helps you find & fix the problem. On caps, some companies used good ones. ;)
I'll never understand why you cut the chip off the board. That makes so sense at all considering you have the proper tools.
Plus the chip still worked, it only needed an arduino mini hot glued on top to hack it back to proper operation.
Why does it matter? It was broken. Its much easier to get a BROKEN chip off like this than it is to try and desolder the whole thing in one go.
@@FloppydriveMaestro
he has the heated desoldering gun, you go trough all the pins and the chip falls off, its actually faster using the gun and you dont destroy the chip in the process.
@@laharl2k But why do you care? The chip was broken and he was going to replace it regardless. If a chip is broken its easier to just to this. Heated desoldering guns are not perfect and it can often be fiddly to get it all off in 1 go.
Why does every one care so much about a broken chip having the legs cut off. IT WAS BROKEN ANYWAY.
@@FloppydriveMaestro
it wasnt broken, it was just not working perfectly. but still it was still partially functional. You just dont trow away salvageable stuff, its that easy, desolder it properly, put a label on it that says "reset semibroken" and that's it. save it in case of nuclear catastrophe or something. You never know when you'r gonna need it or if you'll ever get to a point you cannot longer find a replacement. Just like with antique old machines, you just dont throw away broken parts, you save them ust in case in the future you can fix them or something happens and they become usefull again.
Great video, Adrian. I really enjoy your channel.
IBM! Don't panic! Your PCjr will be praised by users!
...in next 35 years
That made me lol for real. Good one!
It's funny where your reset switch is. I just pop a cartridge in there to get it to reboot
I really enjoy your videos; you’ve a great style. Looking forward to more in 2019.
It's true. I used the cartridge for PCjr basic as my reset button. I think either inserting or removing a cartridge would reset the computer.
In my PCjr we always kept Cartridge BASIC in the left slot. Should the machine lock up and a 3-finger salute wasn't enough, we'd just wiggle the cartridge side to side and that would reset it. I think the fact that the system resets when a cart is inserted or removed is mentioned in the Guide To Operations manual.
my first PC was a PCjr, fully maxed out ram, Tecmar Jr Captain/cadet double deck with dual drive mod and 1200 baud modem, all the bells and whistles.
If you get a 128K side car, many of them can be modified to use 256k DRAM chips to change them to 512K. I did that for one of my Jrs and have 640K in it now.
I see an opportunity here for someone who likes designing PCBs to make one which offers floppy control and 512kB of RAM, possibly with a CF / SD adapter all on one board. Heck even a cheap flash module would probably be enough space for a PC Jr.
Patience pays off...and how!!
Cool at least it is fixed, ps love the ansi art, takes me back to bbs days and animation
Believe me, Mr. Black: we hang on your every video!
I certainly wouldn't have snipped a leg of a chip on the floppy controller XD That made me clench my teeth
8000 people cringed when you unplugged that floppy card when power was on. Yikes! It seems like there was a dozen other places you could have put those reset switches where they would not have blocked the cartridge slots. I would have either run them out the back or jury rigged a blank spacer that slotted into the cartridge slots with both switches on it. That's just me, though.
Yeah, between pulling the card while it is on (and risking shorting lines on the motherboard together), cutting out the old IC without knowing if it is bad or if the new ones work and installing a switch where it blocks the cartridge slot, its all cringe. There are way better ways to go about all of that.
I’ve still got my PCjr from 1984. Dad paid $400 for it I believe! It’s in my ex wife’s attic. I’ll have to try to get it someday
Perfect Xmas present!
What monster would thumbs-down this video.
Daventry is prosperous again!
Cutting the legs of the chip seems to make more work.
Now instead of using some desoldering braid and prying it out, you have to cut each pin, use tweezers and remove each one, then use desoldering braid to take the solder out. Not to mention if the chip was good it's now ruined anyways.
nice fix for the drive controller ... personally I like the reset mod ... its very unobtrusive..
That a really odd failure mode for a chip like that. I wonder if it was thermally sensitive? It's always satisfying to fix stuff like that though.
It could have been as simple as a dry joint, but rather than troubleshoot that, just hack it off.
@@daishi5571 A dry solder joint would not cause a consistent fault after power cycling.
Sure it can, higher resistances, signal noise, tolerances that over time are drifting. What I don't get, is he has a desoldering tool and it would have been simplicity to just remove the chip intact. He say's he's against replacing caps without reason but apparently has no issue in all but destroying a chip? seem inconsistent.
@@daishi5571 He destroyed the chip because it was already broken. All testing showed it was broken so why bother leaving it intact if you are going to replace it anyway.
If that's all the troubleshooting he wants to do I guess that's fine, to me that's slap dash. I still don't understand why the need to cut the legs when he has a desoldering tool which he then used afterwards, it's adding work.
I'm not a fan of replacing capacitors either. However, most L/C meters do not check for DC leakage, and only check ESR and capacitance. DC leakage can make an L/C meter think the capacitor has greater capacitance when DC leakage is present. This is because L/C meters use TIME to determine capacitance. The longer it takes to charge, the greater the capacitance. However, if the capacitors are leaking DC, they will give the illusion of higher capacitance, because it's taking longer to charge the capacitor. Nichicons are excellent capacitors, but that does not mean they are immune to DC leakage.
Pulling a card when the computer was on? Wow, you like to live dangerously.
Love it...
Not sure why you blocked the cartridge port with the reset switch. Why not just punch a whole in the front of the unit and mount (either the switch your had, or a nicer large button momentary contact switch) and add the reset button rather than block off the cartridge port.
Side note, love the t-shirt!
A much more elegant solution would have been to make a 'reset cartbridge' with a very simple circuit : a reset button conected to the 2 pins you have to short to reset the computer. no holes no soldering. You insert the cartbridge and you have a rest button.
Looking at all the covered-up IBM branding...could the PC Jr. have been used on-screen somewhere?
Nicely done Adrian :)
2:38 Maybe it did not happen, but it'd be fun and ironic to picture the PCjr booting the first time you wanted to demonstrate how it fails to boot, forcing you to shoot another take for that part of the video.
Well, that was weird. I am a ham radio operator.... when you started to suck the solder from the board at 9:01 it sounded almost like "CQ"
Well done!
next you need that Ram expansion card
Great job, well done.
"Okay, Soos, let 'er rip!" "Oh no! A letter ripped!" "What the 'H'?!" (first thing that sprang to mind when you said "Error 'H'" :) )
Awesome stuff, kudos !
*WOW!* You work *FAST!!!*
I saw a few other posts that indicate that the problem with the card might be due to the lack of filtering caps on some of the ICs. www.zdnet.com/pictures/cracking-open-the-ibm-pc-jr/16/ (look through the pictures, there's a bodge wire on the back of the card too)
I'd give that a try, because if it works, that would be a much cleaner and reliable fix, and .1uF filtering caps are dirt cheap. Of course, might not solve the issue if the controller chip itself is bad.
What was that tool you used to push the solder into the holes.?
Success! Woo hoo!!!
Amazing!
Does the reset button have a different function from just putting ctrl+alt+delete?
An ADB video! Yay! Early Christmas present!
I cringed when you cut the legs off the old IC, even more so when I saw you had a proper desoldering pump. Why not just flip it over and desolder the old IC out, so you still have it in case of unforeseen problems? It's not like it's a huge hassle with a vacuum desolderer, I don't have any issues with a crappy mechanical pump.
Other than that, I really enjoyed the video and look forward to future videos.
I had a similar reaction when seeing that: As long as you are not 100% sure it is broken (and impressions can be deceiving), always try to save the old IC.
However, the other side of the story is that these are simply not rare ICs: There is a lot of supply on Ebay and AliExpress prices as low as $1.30 a piece. If it is not rare, why make your life harder?
Why does it matter. It was broken...
It matters because very you often only know for sure it was broken after you have done the swap. Until then it is just a suspicion.
@@danielmantione So? If it wasn't the problem then he would still have a nice socket and a working chip. If you have gone to the effort of removing the old chip and buying new ones you may as well replace it while you are there.
When repairing/restoring older equipment it is good practice to minimize the damage to potentially working parts, after all, it is not uncommon for such parts to be out of production, and so in limited supply, which might easily mean you are needlessly denying someone else the ability to repair something in the future.
There is also the concern about keeping the machine as close as possible to original or maintaining the history of the machine, though this might be more of a concern to museum type restorations it is common for even hobbyist restorers to try to minimize/avoid unnecessarily damaging parts or doing irreversible modifications
You could’ve just piggybacked the bad floppy controller chip to check.
What the type of IBM you using there is no need resetting button only using control board
Would it be possible to upgrade an old computer to have wifi on it or would it depend on what kind of computer it is?
@@adriansdigitalbasement THX!👍👍👍
mmmm while you can just swap the chip and fix the problem, i'd rather stick an arduino mini to the card and have it detect and reset the chip for me. I rather fix things than swaping out chips, mostly because you never know for how long you'll find those chips until they are all gone.
That 765 was already broken (damaged insulation somewhere in the silicon most likely) and it would have been a matter of time until it fails completely, very likely by shorting out (full latchup) and possibly damaging the rest of the board.
On the other hand it was THE floppy controller for all the early PCs (actually, it was in all PCs until they ditched FDC at all, it just got integrated into the chipset later on) so it's still quite plentiful.
nice!
Sweet, now see how high you can overclock it with watercooling.
^.^
Please use a static safe workstation!
Say's Error H is insufficient power to disc drive or bad connection to controller card
🙂interesting
sounds like NEC CPU time V20/30
You should smash the original floppy controller chip on camera just to piss off all the sperges in here harping on you for clipping those legs.
merry - xmas
throwing away a whole slot for a reset switch seems like a bridge too far for me -- even if that slot is essentially useless