True. Fixing up these machines is immensely gratifying.

Agreed.

haha, we'll get there eventually!

Ok! I'll keep that in mind, thanks

Entirely depends on the multimeter as to how much "how you doin'" it is. I have a GS Pro-50 DMM that can accurately go up to 30 MHz, and it's so sensitive that it can pick up mains frequency from my bench light with the probe just floating in the air. Also got one of those AliExpress specials, a "Mestek" DMM, and it goes up to 100 MHz surprisingly. I've probed 386/486/Pentium bus clocks with it, and it's fairly accurate. On the other hand, I'm sure one of those Walmart or Harbor Freight $10 specials with a Hz setting will give you a bad time lol.

They are very nice machines. Especially if they are hacked :)

Thanks!

@@Epictronics1 I believe you are the only one hacking the PS/1 board like you are doing. I haven't seen anyone else on KZfaq doing it or read about it on the internet forums. Bravo! Pioneering for us to learn from and do some fun projects.

Thanks John!

I have one like that in a 486 build I made. It’s probably the only OPL3 card that isn’t insanely expensive now.

Problem: Rubber don't last forever and all wet lytics use rubber seals. So it will go bad after some time and leak its fluids all over the stuff..

​@@Stefan_Payne : And if it somehow doesn't leak, it can still go bad from drying out over decades.

Yeah, I have used it in some projects. It's very nice to work with and would probably have been a better choice for this card

Thanks! Yeah, that is one fast PS/1! But I still have an itch to get it even faster :) I'll keep trying until we find the limit

Agreed! This was a success!

Thanks!

Unless you measure the leakage current of the old capacitor you can't say whether it is good or not.

@@felixokeefe In this case we don't need a tester to know that the large caps are _not_ excessively leaky. If they were electrically leaky enough to matter they would be self-heating and likely bulging. Plus leaky capacitors tend to read high when tested with a multimeter which we did not see here.

I'll measure again without it in the socket. Some people may not agree with putting so much work on an ESS card, but I have only good things to say about those cards

I never had one of those. I always had Sound Blasters in the 1990's@@Epictronics1

@@Epictronics1 Having a way to monitor Cpu voltage might be useful as you don't know how much it drops under load, especially if you overclock the cpu, could well be the cause of the instability. If i recall Cpu Galaxy had somewhere around 4 volts when he got 180 and 200 mhz clock speeds.

@@austinmaxi We have checked the voltages in a previous video. The buck gets stable under load at the intended voltage. In the next attempt, I'm gonna try 4v. thanks

Thanks for sharing. I haven't given up on the PSU. Since it started to work after we replaced those six caps, I think the logical thing to do is to replace some more or all the electrolytics. I'll order that diod too in case it's marginal

Ok! I'll give it a try. Thanks

​@@Epictronics1 well really it just needs several pads added for resistors that set the voltage divider and another solder pad to link to each pad then you jump the voltage you want. Basically the same thing that is on most motherboards of that era. Then you can try 3.3 as well as 3.4, 3.5, 3.6, 3.7 etc etc. If you need help redesigning the board let me know and I can make it happen :-)

I'm gonna try with overvoltage and better cooling next time. Jumpers for fixed voltages would require quite a lot of work I think. Maybe something like the mc34063 with different resistors could work, but it's fairly easy to adjust the voltages with the trim pot.

Oh, crap! I'll fix it in the next repair attempt :) Thanks!

@@Epictronics1 Love what you do, please keep it up! I recently got an IBM PS2 Model 55LS that I guess isn't that common - no floppy! It's dead so I am going to start with the PSU. I may need some assistance if you are willing :)

@@TheRetroRecall Thanks. Of course, I'm more than happy to help out. I suppose you'll start by checking for a RIFA or a WIMA cap :)

Thanks!

I considered mentioning the SX20 but decided not to. Because almost nobody had one back then anyways lol

Haha, I believe they call that a burn 😂

Great, I'll give it a try. thanks

@@Epictronics1 try 3.4 all the way through to as high as 4v for very high clocks provided you use good cooling. I found I needed 3.5-3.7v to get these stable at higher clocks.

@@Mevunky That's very useful info. I'll give that a try, thanks

A standby circuit on old AT power supplies? How would that even work?

@@looks-suspicious This AT PSU is a bit unusual. It has a soft start

@@looks-suspicious At the very end of the AT era, there were some weird soft start AT motherboards. I've worked on two myself, one being an FM Towns PC and the other an IBM tower like in this video. You can actually adapt an ATX power supply to work with these soft start boards, I did such a conversion for a customer of mine a few years ago. He had a fully decked out FM Towns Pentium that was overloading the original 200W AT supply. I heavily modified an Antec SL350 to replace the ATX connector with the AT P8/P9 connectors and the 3 pin header for the soft start. One wire goes to +5vsb and the other to the PS_ON, the last being ground. Machine worked great and no longer shut off after a few minutes.

I have a few ATX supplies that make noise in standby, too. AFAICT, it's normal. Probably just a really low duty cycle, or the controller changes the topology under low-load conditions.

If nothing else works, I'll try with external power

You were lucky then. Very nice machines

Same for me. The model 2123 with a 386SX/20 and...2 MB of RAM? Bought it at Costco in 1990 or 1991. I even managed to run OS/2 on it for a hot minute.

I'll check if there are some more small caps between the two large heat sinks, thanks

Just saw that your issue is the noise when the PSU is turned off. And since its weird that the PSU seem to have a 5V Standby CIrcuit for some reason (0,02A, +5VS), I think that might not be an issue... @@Epictronics1

Yeah, lesson learned. I'll just use the scope I have already. The DHO800 is small enough to move around on the bench

Yeah, that would probably have been a better choice here.

That's very useful info. I'll make a new attempt with proper cooling. Yes, the PSU seems to work properly after I had replaced those caps. I would have replaced that coil but I can't find any part numbers or specs. The numbers written on it don't show any results on Google. Thanks!

Could be. The BIOS doesn't have an option for changing wait states. Unfortunately, I am not aware of a way to check wait states without having the option in the BIOS

@@Epictronics1 run cachechk utility. Also you can try to replace cache chips with 15 or 12 ns ones and make sure ram is 60ns

I'm very happy with the UNI-T. I may have a go at the mod. Thanks

yeah, I probably used a too thick wire for this repair. It's not too bad without the 10x magnification. It's not really noticeable when the card is installed :)

No worries, this board is gonna fly safely. Eventually...

Thank you! :)

The thought crossed my mind, that may be the way forward

That can help, but mine worked ok at 150mhz and 3.3 volts instead of 3.45.

@@theALFEST I read somewhere that slower CPUs are just factory rejects of faster CPUs. If that is true, it totally makes sense that most 133 will run happily at 150. I really hope someone will add 50MHz to the interposer. That would be a dream solution for this IBM

@@Epictronics1 Yeah, but a way to add some wait states is definitely needed for 50 mhz. Also good specimens go to 180 or even 200 but these cpus are harder to find and you need different MB for sure.

@@Epictronics1 For later revisions of AMD 486 cpus it is more marketing than tech. Later 486dx4/100 cpus often go up to 150mhz too.

Good question, hard to tell

Ok, I'll see if I can find a 133ADZ. Thanks

Not true, but the ADWs do run a little hotter so you need a heat sink and fan. I’ve found both ADZ and ADW are the best overclockers. The later 5x86s don’t overclock as well.

I've been told in the comments that the multimeter isn't very good at measuring frequencies. It has worked well until this project though

Oh, I should have tested 160 with the onboard graphics disabled. Then we would have known

But didn't it work fine at 120MHz? That would mean the entire motherboard, including the chipset and video, work fine at 40MHz.

@@eDoc2020 Yes, It runs stable at 3x40

Yes, It has a rather unusual design. My only guess is that it was cheaper to manufacture this way

lesson learned, thanks

Unfortunately, there is no such option in bios

Not quite. that socket is specified for a 487 Math co. The ODP has that extra pin you mentioned. the ODPR is a regular overdrive. So, without the hack, you could get to 75MHz with an ODP100. In other words, you can "only" get to 25.88 FPS without hacking the board

Unfortunately, I don't have the PS/1 on the bench to check right now. I can check when I have some more space. Thanks

Oh, yeah, I was meant to ask you if your MB supports hard drives larger than 512MB. Apparently, there was an improved BIOS for this board but it was referred to as 07H1001.

@@Epictronics1 That's a good question. I hadn't officially tried it. Right now I'm running a 512mb compact flash solution. Buuuuut... it might go higher. The original owner had upgraded the computer to a Conner CFS1275A hard drive, which my research says is 1275mb. It was mostly dead when I got it, but it did briefly boot an install of windows 95 before dying for good. So it might be worth experimenting with. Also, perhaps there some sort of reader I could get which would allow me to rip a copy of the bios and archive it? What kind of reader should I buy?

@@vhfgamer Great! I use a TL866 Plus to rip eproms but I think the new version Xgecu T48 is about the same price. If it can do 1257MB HDDs it's definitely a newer BIOS!

@@Epictronics1 Ouch, those are a lot more money than I was expecting. Are there any basic cheaper versions that would read the chip? I'm not as interested in burning anything, I just want to help out.

@@vhfgamer Ok, no worries. I don't think there is anything cheaper. The old TL866 is about the same I think

I suppose I could replace it. But I would prefer to keep the socket 4 machine as original as possible. I'll try some more

I ran out of time. I checked for shorts and continuity but didn't do a proper test. I'll test it and report back

Hey, Unfortunately, no. Good luck with the project!

The clock chips won't allow me to run it at 50 unfortunately. Hopefully, someone will redesign the interposer to give us all that option, on any board!

In general the faster the bus speed the better you will be, quicker ram access and such, of course your other hardware needs to support such speeds. I have been looking into PCI overclocking to 66MHz for a crazy fast 486 system, apparently some of the later PCI chipsets allowed for 66MHz bus as an option. I am just at the research stage on that though.

@@nigelrhodes4330 Sounds like a fun project. good luck!

The IDE controller on these cards is excellent. I tend to use it with MBs that give me trouble with the CD-ROM drive

I'll see if I can find one, thanks

Ok, I'll probably replace them all

Yeah, could be electrically leaky or it was that small cap with 20ohm ESR. Which was the cap I would expect to be the cause before even seeing the footage, because several other KZfaqrs have stated it's the one that "always" goes in these SMPS.... It's close to the heat sink so it gets cooked and has to handle the high-frequency switching noise which is much harder on it than the 120/100 Hz the usually much colder bulk capacitor needs to handle. Mr Carlson's tester would work but you can build a simple leak tester on a bread board with just a bench power supply, the tested capacitor, a resistor and a LED! It won't catch as much as his, but it'd very likely enough for this. IE charge the capacitor with the led/resistor as load over it using the bench supply (at a voltage that's safe with the resistor/LED combo). If the capacitor is really bad the bench supply's load limit may kick and the LED might not light up at all. If it does light up, the actual testing consist of turning of the power and watch the led slowly fade away. Or just go out nearly instantly if it's bad. IIRC with many ESR meters one of the signs of bad leaks is that the measured capacitance is too HIGH because the instrument misunderstand the leak for "more capacitance" - but it's not always there so the lack of this doesn't rule out leaks.

Excellent

Sweet! I hope to get there too someday. What IBM used the 07H1001 BIOS?

It's an upgrade I found in old IBM archives pages. I couldn't link it on youtube.

@@antonioesposito585 Ok, I found the article. Let's hope someone finds a chip someday

@@Epictronics1 I also tried a cyrix 5x86 but unfortunately it crashed with my PS1, while it works perfectly with Aptiva 2144 921.

Check out the comment from @vhfgamer. The BIOS he has might be what you are looking for

Looking forward to comparing 150 to 160 when/if we ever get there. 50MHz vs 40MHz bus

@@Epictronics1 Oh, I missed the part about 50Mhz bus. I didn't even know they made those. Nice...excited to see the results (if you can get there)!

@@ruthlessadmin This MB only goes to 40, but maybe we can hack it :)

Yes, but only if we reach the goal :)

Yeah, most of us threw away our best toys. Who would have thought we would miss them two decades later

Yes, unfortunately, that didn't help

@@Epictronics1 Ugh, what a bummer.

I don't have a wirewrap tool, unfortunately. Sounds like it would be a good choice for this repair. Maybe, I should get the tool. Thanks

There are some caps on the interposer. Five 10uf caps if I remember correctly. Not sure if it's enough though.

Quite possible. I'll try with different chips

Did I miss something? The ESS is for the PS/1. It doesn't need the IDE, but eventually, this card is going to end up in a system that does

@@Epictronics1 Yes, there are more cut traces.

@@nasko8605 I can't see any, where?

@@Epictronics1 Those cut traces are (from what I see in the video) for the IDE port only. But when you talk about older systems that have usually only the IDE1 port on the I/O card, you will want to use IDE2 (from the soundcard) for an optical drive, especially today when SD/CF/SATA to IDE adapters have no way to select master/slave device on an IDE channel.

@@sebastian19745 Yes, the IDE controller on these ESS cards is excellent. I would normally use this card in older systems. I don't really remember why I went with an ESS for this project. I'll probably replace it with a SB16 when I need the ESS for another project.

ESS cards? Have you tried with the drivers at Phil's computer lab? www.philscomputerlab.com/ess-audiodrive-es1868.html

A real treasure now!

​@@Epictronics1 Sorry I meant the soundcard repair! 😂 It's a nice machine I like these PS/1

Great, now we only need to figure out how to set the speed to 50. The onboard chip doesn't have suport for 50

...so we need a new PLL chip. 😅 Maybe a any_pll or what it was called... 50MHz FSB needs fast L2 cache, 12ns tag and rest of the chips 15ns and of course 60ns memory. And still wait states are very likely needed.

@@djpirtu2 I'm an optimist :)

I'll try again with proper cooling. Thanks

That is an international PSU with a switch for 120 or 230v. But now that I think about it, shouldn't those caps be rated for at least 230v? Why 200v rating I wonder

No, they don't need to be rated for 230V. They are in series. The PSU is a half bridge topology and they each have about 175V DC across them. 240V AC rectified is about 350VDC. There is nothing wrong with those high voltage capacitors. Their ESR is actually lower than the new ones.

Really? that quickly? I touched it to check. It was lukewarm. I'll try again with a fan, thanks

@@Epictronics1 I do not remember how long it took. But mine CPU hung at 150 mhz with faulty fan

@@theALFEST That's very useful to know. Thanks!

I'll try to disable it and test with an ISA card

Not necessarily, I had VLB motherboard that had the FSB up to 50MHz and all VLB cards (video, I/O) worked well at any frequency. May be that the memory on the video card is slow; to test what really failed, it should run a mainboard tester (like troubleshooter or check it) to see what fails and where.

@@sebastian19745 Yes, some MBs VLB seem to handle faster FSB better than others

Would you recommend any specific multimeter?

Ok, I've read that some people are getting 160 out of these am5x86s. Unfortunately, not the three chips I have :/

I had mine (in 1998) run at 150MHz. When I tried at 160MHz, I had to add thermal paste, a bigger heatsink and a big fan to run it stable; later I tried a water solution and itworked for months. That was before 2000 when my computer was a 486. The VLB graphics and multi I/O worked perfectly, as well the ISA sound card. I was running Windows 95 at the time.

@@sebastian19745 Do you remember if you ran any benchmarks back then? Higher FSB seems to trump higher speed. I'm guessing it was a few FPS faster at 150 than 160.

@@Epictronics1 I only had ran motherboard testing programs like CheckIt and Troubleshooter to see if the system is in a stable working state. Other benchmark programs I had at the time were Norton SysInfo and ChrisVGA but I do not remeber if I ran them or the results if so. The higher FSB is, the faster the memory access is. If the ISA clock is set as a fraction of the FSB, then the ISA and VLB bus will be faster and of course the whole system will be faster. So yes, 120MHz CPU with 40MHz FSB is faster than 133MHz CPU with 33MHz FSB. If I remember right, VLB bus works at the FSB frequency and PCI at 33 MHz fixed frequency only. TheTroubleshooter program seemsto have dissapeared, mostly CheckIt is used today, I finded it on first versions of HBCD; it is useful because it test all sub sytems of the motherboard like DMA,IRQs, cache, CPU but also sound blaster and video. Try first versions 5 to 7 of HBCD, they are bootable CDs and can even extract old utilities, benchmark, sysinfo tools from there.

@@Epictronics1 maybe they have, but I never knew of anyone that did.

That sounds discouraging. Maybe, there is a better solution

Thanks! I'm not likely to ever play DOOM on this IBM actually. In fact, I tend to use it to take notes, because of the lovely keyboard lol. I just want to know if it can be done. Some PCs got a lot of crap over the years for being slow and un-upgradable, like this PS/1, the PCjr and some PS/2s. I find it extremely rewarding if I can make them fast :)