PCChips M921 486 motherboard repair

[@s1201]

I'm so happy for finding your video, i have the same motherboard with the same issue (it won't boot or show up anything), although i don't have your equipment nor your knowledge... so i will directly order a new transistor and replace it! Thank you and sorry for my poor english. Greetings from Argentina! PS: i'm a big fan of Vogons

[@tony359]

Hola and thank you for your kind words! I'm very happy to hear that my video is helping someone else in fixing their board! Please do let me know if the repair is successful!

[@necro_ware]

Very nice repair! Thumbs up!

[@tony359]

Thanks a lot!

[@RetroTinkerer]

I just discovered this channel and was thinking, hey this repair looks very similar to another one I saw recently from Necroware! Cool to see a CPU powered by a bench power supply. 😯

[@tony359]

@@RetroTinkerer ahah yes indeed! Not sure who made one first though! Necroware is one of my favourite channels indeed! :) Thanks for watching!

[@retrocomputeruser]

That motherboard is an absolute gem. The UMC 888 chip set (as far as I know) is the best you can get as the most overclocked 486 systems had that chip set. Together with built in IDE, parallel and serial interface and PCI slots make this a remarkable motherboard. I also like it's compact form factor compared to others which also lack the said extra interfaces. I just wish I could find one.

[@tony359]

it's indeed one of my favourite boards. Once I find a compact AT case, it may be the chosen one for my Retro PC! :) Thanks for watching!

[@rheffera]

Move over Gillette, the UMC 888 is the best a man can get :)

[@helifynoe9930]

Here is something funny. Way back a long time ago I was as poor as a church mouse. So I could not afford a decent computer. My 486 was so slow that whenever printing, it would slow the whole system down dramatically. So I got my hands on a second 486 motherboard, and put it in the same desktop casing. The second 486 motherboard now took care of all the printing and thus made a huge improvement in operating speed of the first motherboard. Via slicing power cables, I had both motherboards powered by the same power supply.

[@tony359]

Amazing! My first PC was a 386 DX with only 2MB of RAM and no cache. It was painfully slow! (I didn’t know church mice were poor? 🙂 ) thanks for watching!

[@pawelklosinski]

Nice troubleshooting Tony, thanks!

[@tony359]

You’re welcome! - this is a very old video, sorry for its poor quality 🙂

[@julianpacheco1]

Excellent video, please keep this kind of repair videos coming !!

[@tony359]

Thank you Julian, I’m glad you liked the video, thanks for your nice comment!

[@PatricksRetro]

Great video! Thanks for putting it up. I did some repairs already as well and I am learning more about electronics. Videos like these help me so much because, as so often, you learn the most when fixing something.

[@tony359]

Thanks for watching! Yes, it's by spending hours and hours on schematics and PCBs that I learnt the little I know. I have many other boards in the queue but I'm a bit late with everything... watch this space! :) (Looking forward to watching your repair videos!)

[@PatricksRetro]

@@tony359 I know the feeling of being late but at least I do prefer interesting videos over frequent videos 🙂 I did not consider doing repair videos yet but you’ll never know…

[@Fredjoe5]

I believe the extra row of CPU socket pins was for the Overdrive processor, a replacement for the 486 had gave some of the advantages of the Pentium processor. They proved to be a short-lived, transitional technology which didn't end up making financial sense in most cases.

[@tony359]

Ah. interesting! I watched some videos about the Overdrive processor! As you say it didn't make much sense - maybe if you had a fleet of computers and you wanted to keep them alive for a longer time? Technology was running so fast back in the days, even a 100% update would not make much sense :)

[@Fredjoe5]

@@tony359 It wasn't really something that was marketed towards large companies as it would disrupt the earnings made on warranty replacements of corporate PCs. Intel and the system manufacturers really didn't want their corporate partners not doing their usual 2 to 3-year replacement cycle, which was and still is a main source of income for many brand names and OEMs. Most PC owners decided to upgrade their machines to the new Pentium (or at least their motherboard/CPU) rather than buy an expensive new CPU and still not get the benefits of the newer motherboard features. This left the Overdrive without a really solid market to support it.

[@RichMye-wx1ob]

Great vid. Regarding the heatsink for that 486, I worked as a technician in the RMA dept of shuttle in West London in mid 90s, we would only put a heatsink on an Intel 50mhz, nothing on a 25 or 33 but for 66mhz or more in production you really must use a fan plus headsink and that goes certainly for any CPU which also has a 3.x volt ;) Ps great to see the anti static strap, I think I last used one at the beginning of the 90s :)

[@tony359]

That was an OLD video, sorry for the poor audio/video/editing quality! :) I tend to wear my antistatic strap more or less all the time, I am very paranoid about that, particularly in winter when I make sparks when touching anything! Thanks for watching!

[@JohnnyUtah488]

That GUI BIOS setup screen was pretty sweet! Never seen that before.

[@tony359]

Yes pretty unusual even though I think I have two boards with the same one! Thanks for watching!

[@angieandretti]

Oh my goodness! I pulled this exact motherboard out of an eWaste PC a couple weeks ago! I've never built a 486 PC before myself but I figured looking at it that this would be a really good board. Guess I should test whether or not it works... just gotta jerry-rig an ATX-AT adapter to power it up.

[@tony359]

Amazing! I hope you can make it work! Let us know!

[@markg3506]

Nice motherboard! I have a similar one, the Jamicon KM-S4-1. It has 4 memory sockets though.

[@ctiborkoza8944]

nice video, i like error when trying MB without RAM :D

[@tony359]

Thank you! Ahaha yes, was wondering why it did not boot up 😂

[@magnum333]

Cool video bro! There's an Award BIOS for this motherboard and it's a bit faster with EDO ram.

[@tony359]

Thank you! I didn't know you could use a different brand of BIOS! Sorry for the shockingly bad editing/recording of this video, it's very old, early stage :)

[@magnum333]

@@tony359 It's not bad at all, actually I'm impressed by it's quality. The way you can zoom in to the components and the way the camera doesn't appear to be bothering you at all... I tried to record some videos of me fixing an old motherboard but it's very uncomfortable to find a correct angle for the camera, and to actually do stuff at the same time. Do you have any advice?

[@tony359]

I think that was my old iPhone 7 (if memory serves). I used to shoot with the tripod in the way, so uncomfortable. I've recently moved to an overhead stand. The bottom line is: I fixed that motherboard in a very uncomfortable way I'm afraid! Overhead is much better as it's always out of the way. If you have a solid shelf you can use, you can clamp an arm to it?

[@magnum333]

Thank you for that @@tony359 I'll try to produce some related videos and see how it goes 🤝

[@marc26110]

Great video! Thanks for the upload :)

[@tony359]

Thanks Marc for watching!

[@nm0490]

Very nice repair video. Subscribed!

[@tony359]

Thank you!

[@za_ozero]

Base-collector was saturated so you read a value

[@tony359]

Indeed! I'm learning as I go :)

[@stefanvanweerden1217]

Nice video Tony359!

[@tony359]

Thanks Stefan - this is a bit old and less polished than newer ones! Thanks for watching!

[@Shmbler]

Nice content! Hope you will make more. I may have overheard it, but is there a reason why you didn't connect a speaker? As you obviously know what you're doing it seems kind of odd to me that you didn't want to hear the beep codes ;-)

[@tony359]

Thank you Marco! More content will come - I'm just not the fastest at making new stuff! :) What you say about the speaker is absolutely correct. I think I was going to connect one but then I noticed the CPU voltage was incorrect so I stopped and looked into that first. But you're right, maybe it could be a good idea to plug a buzzer in the first place! I should also get one of those boot diagnostic cards at some point. Thanks for watching!

[@vpfaustino]

Good job, nice video

[@tony359]

Hey thank you! That is an old video, editing and sound were a bit meh! Thanks for watching!

[@Thomaszarofka]

I had a similar problem - the voltage regulator stuck the PC a few seconds after powering on.

[@tony359]

Regulators on older motherboards are like Capacitors on other boards... They tend to fail a lot :)

[@LeoGitarzysta]

An idea: Is there any chance you could dump the BIOS from this board and compare against known images and post it if it's new? Just got the same board off of auction site, it was in fact in my very first computer, and I'll be looking to reanimate it very soon, and get the BIOS dump as well. I need to submit BIOS from my first board, as it's chip is only thing that survived back from this day.

[@tony359]

Hi there - the bios is likely available on The Retro Web page. If not, I can upload it there. Thanks for watching and good luck!

[@LeoGitarzysta]

@@tony359 Taking a look at The Retro Web and at your screen - quite probable. The dump from my old board doesn't match any of the dumps, so I'm going to submit it to The Retro Web. Maybe I can get that BIOS running on my new board, I want to try it first.

[@tony359]

@@LeoGitarzysta I shall check my version I didn’t know TRW at the time I think. If you need mine before it’s online, give me a shout!

[@LeoGitarzysta]

​@@tony359 Got my board working after a friend volunteered to resolder the northbridge, in exchange for helping to diagnose his 486 mainboard, which started up as well. Two of four sides were loose, and yesterday after finding just one unconnected pin, the board sprung back to life on the BIOS it had. In the meantime, I managed to run both BIOS dumps in 86box, so I guess, that my BIOS dumps are coming to The Retro Web as well. For both boards and additional XT board, the other board didn't have any dump available over the interwebs ;-) Next step is replacing the fake cache I definitely have, after I test it out more thoroughly.

[@WinrichNaujoks]

Is that a cinema movie projector in the back?

[@tony359]

It is! :) I'll make a video about that sooner or later! :) Thanks for watching one of my first videos, not really the best in audio, video and editing :)

[@mikerogers7071]

👍

[@georgievvladimir]

Can you, please, share the URL to the manual ? I have the same MB

[@tony359]

I didn't know the RetroWeb at the time. Searching online this is another awful "PCChips" motherboard and the documentation can be found here: theretroweb.com/motherboards/s/pcchips-m921-486 - I hope this helps!

[@georgievvladimir]

@@tony359 Excellent. Thanks 👍

[@cecofuli]

Non ci capisco molto, anche se so assemblare PC. Ma trovo i tuoi video, in qualche modo, rilassanti =) Fare qualche video in italiano? =)

[@tony359]

Il mio primo commento in Italiano! :) Ad un certo punto avevo pensato di ridoppiarmi in Italiano, ci ho provato ed ho immediatamente abbandonato l'idea :) L'inglese purtroppo ha una audience piu' vasta e il mio tempo e' quello che e' . Mi dispiace perche' chiaramente mi piacerebbe farlo. Pero' chissa'. Intanto grazie per il commento e per la visione!

[@cecofuli]

@@tony359 Ah ah ah .. come il primo commento?| Si, in effetti con l'inglese puoi raggiungere più persone. Però è comunque un peccato. Potresti giusto doppiarne uno a settimana, per vedere come va.

[@tony359]

@@cecofuli uno a settimana! Se le giornate durassero 48 ore volentieri! 🙃

[@za_ozero]

What do you do with boards you repair?

[@tony359]

Good question... :D I like repairing them but I don't really have a RetroPC. I guess I'll have to find a new home for some of them at some point (alternatively I will have to find a new home for myself LOL!). Thanks for watching!

[@za_ozero]

@@tony359 so i guess you film your learning curve and won't be interested in some old CPUs and videocards donation?

[@tony359]

@@za_ozero Let's talk about that! :) My address is on my profile! Thank you!

[@Marsandrey]

Why not to use the speaker?

[@tony359]

VERY early repair - minimum edit and poor recording! :D Absolutely, I should have used the speaker. That said, I soon realised the voltages were not right so... Thanks for watching and sorry again for the poor quality of this video :)

[@colorbydeluxe900]

what are the odds me as a cine guy watching a random mainboard repair video and suddenly there's an fp20 in the back

[@tony359]

ahahaha KZbin Algorithm WIN! I will make some videos about that and my 12 Cinema Sound Processors! :)

[@colorbydeluxe900]

@@tony359 I already watched a lot of mainboard and computer related videos from other youtubers and I think the youtube algo suggested your channel because of that. It seems it was pure coincidence that I spotted a film projector on a mainboard video 🙂 also youtube did not suggest this specific video, I watched a few of your other videos before I came across this one. Btw. here's my home setup: kzbin.info/www/bejne/n2bWk5yrrM6mgZY

[@tony359]

@@colorbydeluxe900 Amazing, I wish I had that space. I think I hear a German version trailer? I have a friend in Germany with a very similar setup at home: FP30, platter, DD, DTS, SDDS. Either you are the same person or there are two of you! My projector is a philips branded very old FP20. It has the 500W Xenon "shoebox" lamphouse, single phase, no extraction required. I can basically plug it in a living room! I refurbished and commissioned it during the pandemic, it's fully working with DD-DTS and SDDS. But it has to live in the garage unfortunately. In the pipeline there is a video about a DTS-6D I've recently picked up. I wanted to show what that is about - hence the idea of the multiple camera video you did which is amazing. Thanks for watching anyways and hope to chat again soon!

[@colorbydeluxe900]

@@tony359 Thank you! I also had a Philips FP20 which I replaced a few years ago by the FP30D. I'm actually from Austria but I know some Germans with similar setups. Keep making your videos, love to watch them! 🙂

[@tony359]

@@colorbydeluxe900 Shall do and thank you! Bear with me, the projector video might take a while to come out :) My FP20 is old and crusty but is also so convenient because of size and the fact that it's fully single phase. BTW, comments are disabled on your video: such an impressive and super tidy setup! It's absolutely amazing!