First post, by keropi

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time for Saturday hackery 😁
The target is my beloved IBM PS1/pro pc.
It has 2 things that need attention:
a. noisy PSU fan
b. IDE led is not working with new large HDDs

After 20 years one would expect that the original PSU fan will become noisy. It is a trivial thing to replace it, with a high quality Noctua 80x80mm fan

Here is the PSU with the original fan still attached:

and here is the new one screwed in it's place:


Two soldered wires and some insulation later, and the PSU is once again quiet and with better airflow , win-win 😁


For some reason (probably IBM's strict standards policy) the onboard HDD led does not work with newer and bigger HDDs. It will light up during boot when the BIOS queries the HDD but activity is simply not showing. In all fairness all HDDs up to ~2GBs work fine, it is when you install larger/newer ones (which need a BIOS overlay driver like DiskManager to work) that the onboard led stays off during access.
I was discussing this issue with a friend and he thought if there was a way to grab the activity signal from the IDE cable. That made me remember that Elbox's FastATA (that's a 3rd party IDE controller for the amiga 1200) actually has a small wire that you attach on pin39 of the amiga's IDE header to get the HDD led working 😀 Some googling later I found this web page: http://www.zapwizard.com/oldsite/Guides/IDE/

the job is fairly simply... you disconnect pin39 from the IDE cable and connect it to the shorter leg of a led. Then you grab a +5v signal , put a 150ohm resistor and connect it to the led's longer leg. And presto! you have an independent HDD activity led 😁
I thought I made a small "pcb" that takes a floppy power molex and powers both the HDD led and a small 12v fan I have installed on the 486slc2 cpu upgrade , 2in1 🤣

Let's take a look on the PS1/pro faccia , the led area that interests us for now:

and from behind:

as you can see there is a yellow led on one side of the transparent plastic thingie: the led powers on and the light travels through the transparent part and finally it shows on the front of the pc.

My main goal here is not to butcher the machine and alter it's appearance. It is too precious to me and I already butchered it as a teenager and made a horrible hole in the one and only frontplate cover the machine has so I can have an external IDE cdrom 🙁 , it worked fine but I wish I did not cut the cover plate, you just can't find another 🙁

Anyway, I discovered that if I add the 2nd led in the following place it works fine 😁

So it is time to get things going!
We begin with the isolation of pin#39 on the ide cable:

we put that aside and place the connectors and resistor on a piece of development pcb (or whatever this is called)

and make solder tracks to connect the parts 🤣

you can see above the 2 straight lines that go to the fan connector (+12v and GND) and the 2 solder joints that connect the +5v power supply to a pin via the resistor.

next it is the led's turn to get connected to the pcb with a 2-wire header (recycled reset cable from a pc case 🤣 )


and that's how it looks connected (the led part that is)

You can see the white/brown wires that come from the led and the single header from the ide cable (a thin black cable)

It works fine 👍 and the HDD activity is finally shown! Plus the fan spins too so it does everything it is supposed to do 🤣:lol::lol:
All that remains is to secure the pcb on some empty space and take a pic of it working 😁

🎵 🎧 PCMIDI MPU , OrpheusII , Action Rewind , Megacard and 🎶GoldLib soundcard website

Reply 3 of 12, by keropi

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really? that's great if you can find it! have a look of the horrible job I did when I was younger...


I cut the expansion cover... not proud of that 🙁
Let me know if you find the machine and we'll arange something 😀 thanks in advance!

@MaxWar: yeah the fan is awesome 😁 only the best for my 1st pc 😊

🎵 🎧 PCMIDI MPU , OrpheusII , Action Rewind , Megacard and 🎶GoldLib soundcard website

Reply 4 of 12, by keropi

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a small update with the finishing touch 😁

a layer of hotglue for insulation:

then double sided tape for mounting:

secured into place:

and final test!


looks great 🤣

🎵 🎧 PCMIDI MPU , OrpheusII , Action Rewind , Megacard and 🎶GoldLib soundcard website

Reply 5 of 12, by Amigaz

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Love these threads, I wonder how people could stand the noisy fans back then.. 😜

Noctua fans is the shit, silent and built to last WW3

Nice, "porno" red HDD light you got there 😁

My retro computer stuff: https://lychee.jjserver.net/#16136303902327

Reply 6 of 12, by keropi

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yeah 🤣 , this is a mature-only audience system 🤣

I added a SW60-XG card, I like the onboard mixer that grabs audio from my CT-1320c....

🎵 🎧 PCMIDI MPU , OrpheusII , Action Rewind , Megacard and 🎶GoldLib soundcard website

Reply 8 of 12, by retro games 100

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Absolutely awesome work. Well done. I really wish I had time to mess about with old hardware ATM. Not to these high standards of course because I'm stupid, but just switching on power to retro hardware makes me feel good.

Reply 10 of 12, by TheMAN

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looks good!
though, I think you could've just heat shrinked directly over each wire's solder points instead of inserting the tubes then heat shrinking over it... it makes for a better air tight seal 😀

Reply 11 of 12, by pleonard

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This thread is a couple years old, but I thought I'd ask if the machine number is "2123" or similar? I believe your PS/1 is a very rare model, which is actually a re-skinned PS/2 Model 30. (It was apparently marketed as the PS/1 Pro in Greece, but a regular PS/1 in the USA.)

The Model 25, which was the other ISA model in the original PS/2 lineup, progressed through a 286 and 386sx version. But the Model 30 stopped at the 286, which makes the 2123 PS/1 essentially the "Model 30 386sx" which never existed. You will find it takes PS/2 RAM, for example. But luckily it includes a standard IDE bus, instead of the oddball hard drive support in the original 25/30 models.

Another key improvement over the Model 30 was finding room for a 5.25" bay in the very bottom of the machine -- a 1/3rd height, I believe. The PS/2 Model 30 never had any kind of 5.25" bay, which hampered upgrade options as CD-ROMs became more common.

The 2123 part number was possibly re-used by IBM for a non-PS/2-based PS/1, which leads to a lot of confusion. For example, this page from IBM is mostly correct but falsely claims the power supply is in the monitor, which was only true for the 2011/2121 models:


There is a gentleman who is selling such a model for $1k (!) on eBay Canada:


Reply 12 of 12, by keropi

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^ yep, it's the 2123 model allright 😀
the monitor was a normal bog-standard VGA one , with the same keyboard as the one in the auction linked above (which is on eBay several years now 🤣)
It does take 72pin simms and not just any simms, normal ones do not work. I had to order IBM branded ones and I currently have the max of 16MB installed. The main problem IMHO is the lack of L2 cache, there is none and there is no place to install any.
Back then I made that cut at the front panel so I could connect a CD-ROM externally (IDE and power cables went through the cut, I was ~12-13 back then 🤣), would really love to get a replacement (along with the keyboard/mouse/monitor as well since I binned them back then 😢 😲 ) but that ain't happening soon....
I do have the complete docs that came with the system, if there is anything you need lemme know 😊

🎵 🎧 PCMIDI MPU , OrpheusII , Action Rewind , Megacard and 🎶GoldLib soundcard website