There's been some funny results too across two mainboards. The first one, my trusty DFI AK70, ran it like a champ.

The second one, a newly polymodded MSI MS-6191 IR2, only got as far as listing the CPU name before freezing. No matter the RAM config. Granted, I suspect the FSC branded BIOS is to blame here... but I'll test out both its retail AMI BIOS and the Award BIOS from 6167, given the strings between 6167 and the OEM 6191 BIOS seem to be very close.

EDIT: Forgot to add - the same MSI that locks up with the 800MHz Athlon, runs properly with two 700MHz chips, an T-Bird and another Pluto.

Thermalwrong wrote on 2025-02-19, 02:02:

Ahh, I fixed the keyboard which was down to 3 of the traces on one of the keyboard sheets being discoloured from what I guess is […]
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Thermalwrong wrote on 2025-02-18, 03:18:

The last few days I've been going at my Toshiba T4400C collection trying to get them all working - I have at last got to enjoy o […]
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The last few days I've been going at my Toshiba T4400C collection trying to get them all working - I have at last got to enjoy one and it's a real speed demon...

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Well, it's an ISA system from like 1991 / 1992, it's fast for its time. This one is running an SX2-50 processor instead of the regular SX-25.

Last week I bought 2 more because I had spare caps leftover from my recapping of the other power supplies. I don't really intend to keep them all but it's been a learning experience.
See this post for the kind of problems I had: Re: Bought these (retro) hardware today
Two out of four had dead motherboards and I tracked it down on both of them, to the clock generator which is a little SPXO like a surface mount version of a clock can like the one wiretap made a replacement for.
One mainboard I was able to use the working 25mhz clock generator from another motherboard that was broken in other ways, which is now just for parts. That's three out of four working but getting a new 5 volt 25mhz (or 33mhz) clock generator that will fit in the limited space is not easy, it's not micro soldering but a can clock would be too big.
There are some 5v 25mhz clock generators I found but that means waiting for parts to come in and I wanted them all fixed today. And they need significant adapting to fit the weird footprint this clock generator used.

Going through my box of scrap boards I found a 25mhz crystal on an office pbx system board, but it seems to be 3.3v - which requires stepping down because the Toshiba T4400 is 5v all the way, 3.3v was not invented yet when this thing was made. Using a 3.3v LDO, a 1uF MLCC capacitor and some cut capacitor leads as traces, it's all bodged into place:

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And that works, hooray. Then I found out its keyboard is broken with the enter key not working, which makes it pretty useless. The keyboards on these, the T4500 / T4600 / T4700 / T4800 / T4900 / T1900 laptops are made by Alps and I can't see a way to fix this keyboard, there's a little 3-leg chip glued to the flex pcb and that connects to the enter-key-pad - I can't fix that like I can a regular membrane keyboard.

Ahh, I fixed the keyboard which was down to 3 of the traces on one of the keyboard sheets being discoloured from what I guess is water ingress since the aluminium backing plate was corroded there. Used the conductive paint with kapton tape masking and hotplate paint curing method again, got all 3 traces within 50 ohms and not shorting each other (which they were, but the excess paint scrapes off with a bit of effort). Tested the keyboard in parts and the Enter key now works, put it all back together and re-melted all the heat stakes that hold the keyboard plastic to the backing plate and that worked, hooray.
But now I think that this T4400C #4 has killed a processor since it's tripping the DC-DC board's 5v low voltage limit...
Of course I need to test this - I have this Taken PCI400 that I 'fixed' a few weeks ago!

Thermalwrong wrote on 2025-01-31, 21:52:

What was the original TIM like? Was it still good enough for the cpu to cool properly or did it need replacing? […]
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AGP4LIfe? wrote on 2025-01-30, 07:00:

I decided to dive into the deep end and replace the thermal paste on a Slot A 600Mhz CPU. I really want to replace the factory […]
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I decided to dive into the deep end and replace the thermal paste on a Slot A 600Mhz CPU. I really want to replace the factory TIM on my 950Mhz Thunderbird, so I used this 600 to "learn" the opening process..

I gotta say it doesn't feel great, those pins are tough and you really have apply a lot of pressure. However seeing the garage factory TIM on the inside of the 600 makes me wonder how hot these things really get, and further entices me to now replace the 950's.

I also found out my 600, has a 700 core. Interesting 🤔.

Everything went well and the CPU still works with no damage to the exterior case.Feels good. I think I'll practice one more time on a 650.

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What was the original TIM like? Was it still good enough for the cpu to cool properly or did it need replacing?

I have been trying to use the motherboard I fixed here, my Taken PCI400-4 which was working after a socket replacement and some loose pins around the southbridge resoldered: Re: Bought these (retro) hardware today
I was trying to test an ISA soundcard on it but it wouldn't boot reliably, getting stuck on / flipping between "C0" and "C1" post codes. Initially I thought it was another loose pin on one of the chipsets so spent ages reflowing the solder on those but to no avail.
Shoulda checked the basics at this point specifically clockspeed, but after some time figured out that the board would boot normally if heated around the CPU / northbridge area which is why I thought it was the northbridge. It would work sometimes when started up but it seemed whenever I left it for a while and it got cold, it would go back to being broken.

Using the hot air with a nozzle I was able to narrow it down to the area around the clock generator, the ARK 915A which has a bash mark on it:

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Checking with the oscilloscope it was showing an unstable ~9mhz on the main cpu clock instead of the 33mhz it's supposed to be. Can't find a datasheet for the ARK 915A or Macronix MX8318 clock generators, but the MX8315 is pretty close. There was no clock on the 14.318mhz crystal so I thought perhaps it was the crystal that was bad, swapped that and no difference 😐

The conclusion seems to be that there's a broken bond wire inside the ARK 915A clock generator since borrowing the MX8318 from my Zida 4DPS has made the board reliable again.
When the ARK 915A clock generator is heated up then it will work with the crystal and do its job properly, but when cold the crystal oscillator is dead so I assume that the XO crystal output pin of the clock generator which drives the oscillator, only has a working connection when warm.
If I heat the ARK 915A then it works and it seems to keep working if it works when it starts up, so a heater atop the chip could work. Mechanical pressure also seems to work so I might try some kind of clip on top of the chip to keep pressure on it.
Or I could look at making some alternative clock generator work, I'd rather not do that and replacements for the ARK 915A or MX8318 both seem to be unavailable. Getting an alternative clock generator working would be a lot of work...

Anyways, now the board works again (albeit at the cost of the 4DPS which I'm not using right now) and it's set up for a Cyrix 5x86 processor I thought I'd try out my 5x86 chips - the IBM one works perfectly and seems to run very cool.
I have another one with the green heatsink and cyrix branding and that works just fine as well. Then there's the one I got on this M919 from a junk lot quite a while back: Re: Bought these (retro) hardware today
I've not tested that chip until now because pin R1 broke off when I was cleaning it, there was only the tiniest little dot of a connection poking through the ceramic. I tried soldering a pin directly to that and making it strong mechanically with superglue, but didn't want to test it because well... I don't think that's going to work.
I tried it this evening and the processor was dead, just "--" on the post card 🙁 As suspected, it did not work. Not possible to solder to something so tiny and have that stay connected to something as big as a cpu pin.
A couple of weeks ago though, while I was trying to go to sleep I was for some reason thinking about this and visualised a new way I could do that repair. I have some scrap PCBs that are 0.8mm thick with 2.54mm spaced through-holes, I used the mini grinder pen to clean off all the traces so now I've got some 6-pin segments of a PCB. Those slide over the pins at each corner of the CPU so that this modified CPU sits level in the socket.

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I've soldered a long single strand of copper wire to pin R1's little silver dot of a connection and checked it's functioning by checking the resistance to ground of this missing R1 pin for Address line 28 and the adjacent address pin, both measure 17mega ohms to ground so the wire is working 😀
To get the PCB with the wire to sit flush there's a channel carved into the backside and a pin from a very dead Pentium 200MMX is soldered into the front-side of the pin repair PCB, which is better for this than a regular CPU pin because there's a larger peg that sits inside the Pentium's organic PCB. That peg gives a bit more mechanical strength and makes alignment easier.

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The little PCB bits are held in place at the corners with superglue. The strand of wire is looped around from the outside of the CPU / pin repair PCB and is soldered to the pin at the front-side, so it now has no mechanical connection to the CPU pin but has an electrical connection.

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Now the CPU works! 😁

edit: ugh now the floppy controller is giving me trouble... not this CPU that's causing it though!!

The floppy controller on this Taken PCI400 board was not working, giving a floppy disk fail message in the BIOS and not even trying to move the heads. The board around the floppy controller area is immaculate, but these faults don't exist in a vacuum so I started comparing my Taken PCI400 against the Zida 4DPS - the floppy controller (super i/o) chip on the 4DPS has a 24mhz crystal by it, but there's no crystal on the Taken PCI400...
Spent a *while* trying to find where the floppy controller's clock input linked to but it seems to go to pin #5 of the clock generator chip, which I'd swapped out with the clock generator from the Zida 4DPS (this kills the 4DPS).

Checking pin #5 of the clkgen with the oscilloscope when it's on shows that with the MX8318 gives out 16.24mhz - there's yer prahblem. That should be 24mhz according to the W83787IF datasheet and the clock crystal on the Zida 4DPS by the super i/o chip.
So it seems that the Ark 915A incorporates a couple more clocks which the PCI400 makes full use of, not possible to swap the ARK 915A for the MX8318 and still have the board 100% working.

Put the ARK 915A clock generator back and it still does that thing where when it's cold it'll give out an unstable ~10mhz to the cpu which causes it to fail to boot up. It gets better and worse as it gets warmer/colder and it seems that pressing on the chip makes it work more reliably. Here I've tried a metal springy clip on top of the chip to apply pressure, it didn't really work...

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Trying another way instead I moved pins 2 (crystal output) and 3 (crystal input or frequency) input out of the socket so that the ARK 915A has no connection to the 14.318mhz crystal that the PLL bases all other frequencies off of. Hooked up the frequency generator to pin 3 and ground and fed it 14.318mhz and it now works every time. This bypasses the damaged connection that I think is on the crystal-output pin that would normally drive the crystal.
Gonna see if I can use some useless microcontroller to use / drive this crystal instead and save this board so it can work all the time instead of only sometimes / only when warmed up.

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Lately it seems all the problems I'm facing are clock frequency issues, I could put an SPXO frequency generator there instead but 5v input simple oscillators are hard to find. I actually broke apart one of the broken SMD SPXO oscillators from one of the Toshiba T4400C mainboards and it's got a little tube type crystal inside along with some silicon that drives it, guess the bond wires melt when it gets overvoltage.

edit: aww heck yeah. Went through my box of spare microcontrollers like atmels and pics and the attiny2313a was the best option to hand. Requires no extra circuitry to run the crystal (PICs do) and has a ckout pin, kind of a cruel fate but it's got no code and just has the fuse bits set to use an external crystal and provide the CKOUT pin - doing the same thing as the SPXO on my T4400C motherboards were doing. That feeds into the Clock Input pin of the ARK 915A, with the ATTINY 2313A piggy backing the VCC & GND of the 74LS244 beneath it, with all its other pins folded underneath.

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Now the board starts every time! 😁 (and the floppy controller works great)

Geez, all my T4400C needed was a recap of the internal power board, a belt for the FDD and a bettery recell. Runs well.
Also, an underclocked Pentium Overdrive(just yeeted the fan off) did help a fair bit over the stock 486SX.

Just been testing a bunch of old systems, old consoles & micro-computers mostly, with some cheap converters ie. Scart to HDMI, S-Video/Composite to VGA etc.

With a very cheap Composite to VGA converter, the CGA Composite output from my IBM XT is usable, albeit not perfect. If it wasn't for some flickering at the top of the screen it would be great. No big deal though, I was only testing it out of curiosity.

Whilst testing multiple systems, I discovered that the keyboard wasn't working properly on my Sinclair ZX Spectrum +2A. It was working fine when last used about 9 months ago, so I feared the worst. But upon opening it up and checking the ribbon cables, they were fine and instead a tiny little dust bunny had worked it's way under the keys and was shorting out a whole row on the membrane. Removed the dust and reassembled and all is well. Good job the membrane is ok, as replacements are near impossible to get hold of. It's also amazing how dust manages to find it's way in there, I even have the machine covered up when not in use. 🤣

Took apart my old GRID 286 "portable" computer because it refuses to power up. Motherboard is definitely getting power and there's definitely a significant draw, so I'm wondering if there's a short somewhere, though everything looks clean and a short is not obvious.

Will have to delve deeper into it when I have some additional time.

Finally got a serial cable made that fits/works with the "PoQet PC" I
acquired several months ago... (For anyone who doesn't know about this system,
the PoQet is a very early (1989ish) tiny handheld DOS system (80C88)
powered by 2 AA cells!)

Wasn't as easy as it sounds, because the PoQet uses an odd/nonstandard
connector for all it's peripherals, and although the pinout is given in the
"technical" manual, signal levels are NOT given, nor is any information
about connecting anything to it other than official PoQet peripherals.

The PoQet also has no "normal" drives - just a couple of proprietary battery
backed up RAM modules which slide in the side, have undocumented connectors...
also, no ethernet port, modem ... so basically the only way to get anything
on/off the PoQet is via the serial port (they apparently did have software to
do this).

Turns out I was able to make a connector which fits enough of the periphal
connector to access the serial lines (from a dead PCI card edge), and measure
them well enough to figure out it actually does +/-10v RS-232 (I had been
concerned that the system itself might only do TTL/3v with a level converter
in the peripheral adapter which I don't have...

Was able to connect it to another PC, CTTY to the serial port, and access
the command prompt.

I had hoped to bootstrap my DDLINK to it, but the serial transfer fails,
probably because the PoQet serial port is "odd", only powered at certin
times... and it's not clear that it's 100% compatible with 8250...

But it does have DOS 3.3 in ROM including DEBUG, which means I can write
a program to "type" something into DEBUG to at least get it there (Takes a
long time!) - remains to be seen if DDLINK will actually work once it's on
(it's worked everywhere else I've ever tried it - but bootstrap does require
"type"ing binary data into a COPY command over a CTTY session... not something
normally done, and the PoQet may not be compatible enough...)

But ... still a major accomplishment toward being able to actually run this
system and see how it works!

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

So turns out I accidentally damaged the 74F245 octal bidirectional transceiver on the ATC-5200 board while fixing a bent in the case. So can I solder a 74F244 instead?

DaveDDS wrote on 2025-02-21, 11:44:

Finally got a serial cable made that fits/works with the "PoQet PC" I acquired several months ago... (For anyone who doesn't kno […]
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Finally got a serial cable made that fits/works with the "PoQet PC" I
acquired several months ago... (For anyone who doesn't know about this system,
the PoQet is a very early (1989ish) tiny handheld DOS system (80C88)
powered by 2 AA cells!)

Why do companies always feel the need to reorganize a perfectly good standard keyboard layout? This always drives me nuts.

Made a Voodoo 2 SLI cable.

Tested out and found out I got a dud Kyro II card.

Damn.

BetaC wrote on 2025-02-12, 00:13:

While volunteering at my local recycler I ended up finding an incredibly dead, and incredibly interesting looking CPU in a completely thrashed by battery leakage Macintosh IIci.

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I don't know what happened to cause this outcome, but the result is damn cool looking.

Yeh... This is the typical damage caused by these nasty lithium/thionyl chloride batteries which Apple used in these older macintosh models. Looks like the acid spit wasn't there long time, or it would have eaten into the motherboard as well.
Clearly Taridan lithium/acid batteries have some uses where them make sense, but on a computer, where the charge/discharge cycles are irregular, isn't one of them.

That reminds me of the old barrel lithium cells that were soldered to the motherboard in early PCs. User-replaceable? What's that?

Kahenraz wrote on 2025-02-21, 16:34:

DaveDDS wrote on 2025-02-21, 11:44:

Finally got a serial cable made that fits/works with the "PoQet PC" I acquired several months ago... (For anyone who doesn't kno […]
Show full quote

Finally got a serial cable made that fits/works with the "PoQet PC" I
acquired several months ago... (For anyone who doesn't know about this system,
the PoQet is a very early (1989ish) tiny handheld DOS system (80C88)
powered by 2 AA cells!)

Why do companies always feel the need to reorganize a perfectly good standard keyboard layout? This always drives me nuts.

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I agree. Some strange design choices made here.

Kahenraz wrote on 2025-02-21, 16:34:

Why do companies always feel the need to reorganize a perfectly good standard keyboard layout? This always drives me nuts.

FWIW, I don't actually find it all that bad (and I've used many small systems where the keyboard
was much worse!

But then again, I've used so many different systems/terminals over the years that you get
pretty used to thing changing as you move around.

Probably the only things that I've "noticed" are the CTRL key being up on the side like a
TAB (and to be fair, I used a number of terminals in the 70s-80s setup like that),
and the "power/sleep" key being right above the ENTER key - all to easy to put it to sleep
(but fortunately you just wake it back up and everything is as it was ... just a bit annoying to
sometimes figure it out and hit an extra key when you weren't planning)
- and I wouldn't mind if the arrows were in a more standard 'T'

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

Haven't got to it yet, but when I get home later I'm planning to do some more inventory of all my acquired PC components and continue filling out my spreadsheet so I can keep track of what I have. I've probably forgotten about at least half of it by now.

I added tweeters to my Nokia, for dramatically improved sound quality. Now if I could do anything about the sub 100Hz side of things too...

Tiido wrote on 2025-02-22, 00:45:

I added tweeters to my Nokia, for dramatically improved sound quality. Now if I could do anything about the sub 100Hz side of th […]
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I added tweeters to my Nokia, for dramatically improved sound quality. Now if I could do anything about the sub 100Hz side of things too...

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Nice!!! That's a great idea for a mod. 😁

As for the sub 100Hz side... I would think that an old subwoofer with an audio pass-through would be a great option. A lot of them will let you pipe the audio into the sub for bass and right back out again to your speakers (monitor).

Of course, the downside is that the volume controls on your monitor won't affect the sub, so you'd have to either adjust both or adjust the output level from the source.

Alternatively, running wires out of the monitor from the amplifier to a sub with speaker-level inputs might work... but most likely the circuit is already high-passing out the bass frequencies so as not to destroy the speakers, so there wouldn't be much left for the sub to work with.

If I really wanted a sub I will have to procure something and it is not difficult to get sound from the monitor to send to the sub, but for now I will enjoy just having a crisp sound 🤣

Updated the bios on the K7N2, and it's now properly identifying the cpu. Next is testing the memory and installing an operating system.

Fixed a Seasonic AT power supply. One of the big caps at the primary side was quite dead, Jim. The other one was fine, but replaced it anyway.

It couldn't even detect it.

PD2JK wrote on 2025-02-24, 12:12:

Fixed a Seasonic AT power supply. One of the big caps at the primary side was quite dead, Jim. The other one was fine, but replaced it anyway.

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It couldn't even detect it.

Caps can be a bit funny with these component detection devices, but a multimeter should solve that problem. My guess is its dried out with age good idea changing out the other but I would go a bit further and change them all since if one has dried out the others wont be too far behind. (even more so since its a Rubycon which are a really good brand of caps)

Also check for reefer caps ....horrible little bastards that go boom when you look at them the wrong way.