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zombienerd
August 16th, 2017, 05:06 PM
I recently got an IBM PS/2 Model 25-004, single floppy drive. Boots to basic fine, and occasionally will boot to DOS from floppy.

A few questions -
1st, the floppy drive is iffy. Only reads disks 1/2 the time, if that. I'm reading that bad caps are a common problem, and I'm going to guess that's my issue, but input is appreciated before I go trying to find parts.

2nd, there is no hard drive installed, but I see a ~40 pin header on the motherboard, I'm guessing is for a hard drive. What hard drives are compatible? Is it a standard 40 pin "IDE" cable, or do I need a special cable for it? Should I just go XT-IDE with CF?

3rd, What's the big 1/4" phono style jack on the back for?

Lastly, while the color screen is beautiful, and all the colors seem to show fine with the system test disk, the white text in DOS & Basic seems a bit 'purplish', any ideas if there's an adjustment?

glitch
August 16th, 2017, 05:14 PM
Clean the floppy first, if you haven't. Otherwise, yes, capacitors are sometimes a problem with them.

The drive is a "planar" drive, I forget what the internal signaling is, but it's not 16-bit IDE (it may be XTA, many of the later ones were ESDI). Your best bet is an XT-IDE, as you mentioned. Personally I use industrial Flash modules (DOMs) instead of CF cards, but if you do use a CF card, make sure you get an adapter that supports 5V on IDE pin 20, so you don't need to hack a power cable into the harness. As you probably noticed, there are no Molex power connectors inside!

krebizfan
August 16th, 2017, 05:28 PM
The phono jack really is an audio jack. It only redirects the PC speaker to an external speaker. Don't expect too much out of it.

zombienerd
August 16th, 2017, 06:15 PM
The phono jack really is an audio jack. It only redirects the PC speaker to an external speaker. Don't expect too much out of it.

That's actually kinda nifty.

evildragon
August 16th, 2017, 06:30 PM
The HD is ST-506 if I remember. I have the tech ref manual somewhere. I'm the Model 25 guru. I know perhaps TOO much about these damned things, lol.

The floppy drive, clean the drive if it fails, yes, a recap is going to be needed. I might make a video on this honestly.

lutiana
August 16th, 2017, 06:33 PM
I might make a video on this honestly.


Please do. I have some floppy drives from a Model 95 that need to be re-capped and I've no idea how to do this efficiently.

zombienerd
August 16th, 2017, 06:36 PM
I already cleaned the heads and lubricated everything. Guess it's going to be a recap. Hopefully the values are visible. Evildragon, do you happen to know the ones needed for the job? I would definitely make a video of this procedure myself, when I do it. :P

evildragon
August 16th, 2017, 06:39 PM
This is the hard drive interface..

http://i.imgur.com/Do6VMR6.png

evildragon
August 16th, 2017, 06:40 PM
I already cleaned the heads and lubricated everything. Guess it's going to be a recap. Hopefully the values are visible. Evildragon, do you happen to know the ones needed for the job? I would definitely make a video of this procedure myself, when I do it. :P

The cap values should be on the caps themselves.. Every drive is different, you'll just want to see what values are there right now, and replace with electrolytics of the same value. Mind the polarity! ;)

luckybob
August 16th, 2017, 06:50 PM
Honestly, it REALLY pains me to say it, but as someone with five of these systems, do yourself a favor and give up NOW finding a working hard drive at a reasonable price. This machine is a PRIME candidate for an XT-IDE CF card.

evildragon
August 16th, 2017, 07:09 PM
Honestly, it REALLY pains me to say it, but as someone with five of these systems, do yourself a favor and give up NOW finding a working hard drive at a reasonable price. This machine is a PRIME candidate for an XT-IDE CF card.

And that's why I have an XT-IDE. They all fail, not a matter of if, it's when, if not already.

zombienerd
August 16th, 2017, 07:36 PM
Generally on my XT-class machines, I use a Zip 100 drive with Palmzip as the mass storage.. But with my floppy issues, it would have been nice to have an XT-IDE laying around already :P I'm going to have to pick one up.

evildragon
August 16th, 2017, 07:52 PM
I don't miss those days using a Zip drive. So slow.. I thought it was fast and awesome, but when you pop in that XT-IDE, holy crap does things speed up. You can run GeoWorks with respectable speed!

https://www.youtube.com/watch?v=qsCcykSIU3c

(The only caveat here is I upgraded my model 25 with a VGA card).

Trixter
August 17th, 2017, 10:36 AM
That's actually kinda nifty.

It is nifty until you try to record line-out with it and then find out it isn't line-level output. I had a really hard time trying to use it as a recording source (http://www.vcfed.org/forum/showthread.php?55081-Quarter-inch-audio-output-vs-3-5mm-audio-output-questions) and eventually gave up :-(

lutiana
August 17th, 2017, 11:05 AM
It is nifty until you try to record line-out with it and then find out it isn't line-level output. I had a really hard time trying to use it as a recording source (http://www.vcfed.org/forum/showthread.php?55081-Quarter-inch-audio-output-vs-3-5mm-audio-output-questions) and eventually gave up :-(

Well if it's designed to drive an external speaker or headphones then it'd be a speaker level output (10s of volts vs low single digit voltages for line level and millivolts for mic level) so you'd need to step it down to use it as a line in to a recorder. Did you ever get this to work?

evildragon
August 17th, 2017, 11:21 AM
I've had luck recording my model 25's audio output with a resistor across the - and + of the TS connector, and then put on a capacitor (otherwise it "popped" a lot). I could always breadboard it again and see what values worked.

tipc
August 17th, 2017, 11:42 AM
I don't miss those days using a Zip drive. So slow...

A SCSI Zip is fine though. I used one as a informal h/d on a Mac II years ago. I was lucky enough to find one in a classified ad about the time they came out for beans.

tipc
August 17th, 2017, 11:46 AM
Ditto on the XT-IDE upgrade. I actually have a model 25 h/d cable somewhere. It was actually called an IDE interface iirc but was not standard ide/ata. Not sure if ST-506s were present on many of the hard disk cards of the day, but most of those were also pseudo (xt) ide. Tandy had one also.

zombienerd
August 17th, 2017, 01:08 PM
Ordered a Glitchworks XT-IDE Rev 3 kit. Is there a limit to size? Could I run a 2gb DOM if I'm using Dos 5?

lutiana
August 17th, 2017, 01:14 PM
Ordered a Glitchworks XT-IDE Rev 3 kit. Is there a limit to size? Could I run a 2gb DOM if I'm using Dos 5?

With the XT-IDE installed, then your only limit is dos based, and with DOS 5 and 6 that would be a 2Gb partition (though you could have multiple partitions). The only draw back is it take a bit for a DIR command to finish on an 808x machine (the size calculation takes a bit).

zombienerd
August 17th, 2017, 01:28 PM
With the XT-IDE installed, then your only limit is dos based, and with DOS 5 and 6 that would be a 2Gb partition (though you could have multiple partitions). The only draw back is it take a bit for a DIR command to finish on an 808x machine (the size calculation takes a bit).

Probably go with a 512mb unit then. Really don't need 2gb, I was just curious :) I can say that dir listings take forever on the Zip 100 as-is.

EDIT: Went with a 256mb unit, as it was cheapest on eBay from the US with free shipping. Does pin 20 power, so I'm happy. It'll do the job :)

Trixter
August 17th, 2017, 01:34 PM
Well if it's designed to drive an external speaker or headphones then it'd be a speaker level output (10s of volts vs low single digit voltages for line level and millivolts for mic level) so you'd need to step it down to use it as a line in to a recorder. Did you ever get this to work?

I did not. As that thread shows, my electronics and amplifier knowledge is still in its infancy.


I've had luck recording my model 25's audio output with a resistor across the - and + of the TS connector, and then put on a capacitor (otherwise it "popped" a lot). I could always breadboard it again and see what values worked.

If you could, I'd be quite grateful. I tried several resistors across the - and + of the connector but it didn't change the behavior. (Read that thread (http://www.vcfed.org/forum/showthread.php?55081-Quarter-inch-audio-output-vs-3-5mm-audio-output-questions) for background.)

evildragon
August 17th, 2017, 04:22 PM
If you could, I'd be quite grateful. I tried several resistors across the - and + of the connector but it didn't change the behavior. (Read that thread (http://www.vcfed.org/forum/showthread.php?55081-Quarter-inch-audio-output-vs-3-5mm-audio-output-questions) for background.)

I got you, if I can get to sleep at a semi-reasonable time tonight, I'll grab the breadboard tomorrow morning and figure out what I did to get it line level.. I remember wanting to do this originally to capture "Freddy's Rescue Roundup" title screen song (ironically unplayable now since installing a VGA card, the picture loses v-sync).

zombienerd
August 17th, 2017, 04:49 PM
So, recapping the floppy, do I need to replace all caps, or just the electrolytics? There are like 20 small blue radial lead caps with different designations, but only 4 electrolytics.
One 16v10uf, three 16v47uf. Drive is made by Mitsubishi.

luckybob
August 17th, 2017, 04:53 PM
IIRC just the electrolytics. I know some tantalums can have issues, but it seems to be less common of an issue.

zombienerd
August 17th, 2017, 04:56 PM
Cool beans. I can live with $5 worth of parts. They're on their way.

zombienerd
August 18th, 2017, 11:50 AM
Anyone have an idea on why the white text appears purplish? I tried to take a few photos, but none came out really showing the issue. I'm guessing just the age of the CRT, but if there are any adjustments, I'd like to give them a shot. The Red/Green/Blue appear right (to me), but I have no benchmark to compare to.

evildragon
August 18th, 2017, 11:55 AM
The drive or cut off may need to be adjusted. If it appears purplish, then your green is getting weaker.

tipc
August 18th, 2017, 12:03 PM
Anyone have an idea on why the white text appears purplish? I tried to take a few photos, but none came out really showing the issue. I'm guessing just the age of the CRT, but if there are any adjustments, I'd like to give them a shot. The Red/Green/Blue appear right (to me), but I have no benchmark to compare to.

Convergence maybe. When red and blue bleed into one another you get purple. White, contrary to intuition, is the sum of all 3 colors, r, g, and b. Perhaps just one color is off, red or blue. Or maybe your eyes. Oftentimes white can seem a little blue. And as I recall when I shut off my mono 25, I would see a blue flash. Never understood that as a mono monitor has only 1 gun and white phosphors. You can't have a convergence error on a mono monitor. I also remember a guy many years ago talking about an experiment where a black and white television was made to produce color images by means of pulse modulation. Don't ask me anymore then that, that's all I know, and it's utter heresay.

evildragon
August 18th, 2017, 12:20 PM
Oftentimes white can seem a little blue. And as I recall when I shut off my mono 25, I would see a blue flash. Never understood that as a mono monitor has only 1 gun and white phosphors.

I know what you're referring to. See this video of mine where I fed a Sega Dreamcast into my Model 25's monochrome monitor. You can see that blue/green color effect when things move around fast . Has to do with the phosphors properties.

https://youtu.be/U7hWvBc3nD4?t=2m44s

zombienerd
August 22nd, 2017, 11:18 AM
Recapped the drive, and now it won't read at all. I'm searching for a replacement drive.

evildragon
August 22nd, 2017, 12:49 PM
Did you mind the polarity? This is extremely crucial.

zombienerd
August 22nd, 2017, 03:43 PM
Yes. Triple checked polarity was correct, tested each cap, rechecked values were correct. Reflowed all the connections. Tested again. No dice.

evildragon
August 23rd, 2017, 12:20 PM
Something doesn't sound right them, unless the drive accidentally got knocked out of alignment or something wasn't fully attached.. The fact it was working somewhat before repair and dead after, I've never had that happen.

zombienerd
August 23rd, 2017, 01:48 PM
Something doesn't sound right them, unless the drive accidentally got knocked out of alignment or something wasn't fully attached.. The fact it was working somewhat before repair and dead after, I've never had that happen.

I was thinking it could be an alignment issue, but without another drive to compare to, I'm not sure where to start. The caps all tested good, and polarity is correct. No traces were damaged. The only difference was in physical size of the caps. Due to their length (about 2x the originals), I had to lay them on their sides to install. Nothing shorted, I thought maybe there's some kind of inductive screwyness going on, but I doubt it. My new drive should be here within the week, and is the same make/model, so maybe I'll be able to do further diagnostics then.

evildragon
August 23rd, 2017, 09:23 PM
Trixter, I haven't forgotten about checking this for you. Unfortunately I've been having some heart problems and I haven't even been in my office where my model 25 is.

As soon as I can, I will get to checking this for you. (I really want to do it because it gives me something to do).

Trixter
August 24th, 2017, 11:45 AM
Heart problems are infinitely more important! Take your time!

zombienerd
August 28th, 2017, 05:32 PM
New drive came in, was the exact same model as the last. 601 Disk Drive error.

Crap.

Contacted the seller, he apologized, had tested the drive before storing years ago, didn't test again before shipping. Offered to send me a 1.44mb Toshiba built drive, which was just tested as good. I hope it works in the Model 25, I've heard mixed stories about 1.44 compatibility. Has the same card edge connector. I guess I'll see when it arrives.

On a side note, got the XT-IDE installed, but having issues getting it to boot. Working with glitch in PM's to figure it out. So close to giving it a good burn in test! :D

evildragon
August 28th, 2017, 05:38 PM
New drive came in, was the exact same model as the last. 601 Disk Drive error.

Crap.

Contacted the seller, he apologized, had tested the drive before storing years ago, didn't test again before shipping. Offered to send me a 1.44mb Toshiba built drive, which was just tested as good. I hope it works in the Model 25, I've heard mixed stories about 1.44 compatibility. Has the same card edge connector. I guess I'll see when it arrives.

On a side note, got the XT-IDE installed, but having issues getting it to boot. Working with glitch in PM's to figure it out. So close to giving it a good burn in test! :D

I have used a card connector 1.44MB, Mitsubishi drive on my 25, worked Ok, but wouldn't properly detect disk changes, so if you did a DIR on the disk after changing it, it would show the previous disks contents. I'd have to force a read error by removing the disk, then inserting it, forcing it to re-check the contents.

So far the only 1.44MB drive I can confirm that does work properly on a 25, are the ones with pins on them, requiring a different ribbon.

pcdata76
September 1st, 2017, 02:58 AM
I have used a card connector 1.44MB, Mitsubishi drive on my 25, worked Ok, but wouldn't properly detect disk changes, so if you did a DIR on the disk after changing it, it would show the previous disks contents. I'd have to force a read error by removing the disk, then inserting it, forcing it to re-check the contents.

So far the only 1.44MB drive I can confirm that does work properly on a 25, are the ones with pins on them, requiring a different ribbon.

1.44MB edge connector drives can be used in model/30 without any problem (of course as a 720k drive) so i think they should work in model/25 too.

I've repaired several old drives which can't detect disk change properly by spraying contact cleaner to the disk detection switch and exercising the switch up and down. I usually clean all switches in that region (including write protect and density select [doesn't exist usually in PS/2 drives] switches)

evildragon
September 1st, 2017, 12:37 PM
Hmm, you know I could check the disk change switch. The drive I has however that is edge connector, WILL read and write high density 1.44MB disks just fine on a model 25, and thus should work on the 30 also, they contain the same disk controller. While the tech ref manual was written before the machines were released, it's clear to say we have proven it time and time again, that they CAN read and write 1.44MB with the correct disks.

The best drive I've found however is the pin header type PS/2 drive, it works first try and still works to this day (but could use a cleaning).

See, I proved these older PS/2's can read and write 1.44MB disks just fine: https://www.youtube.com/watch?v=H4y0TPFV_qI

With the right drive, they work great! Not only does the BIOS support it (and I have the earliest known BIOS ROM there is---maybe the only BIOS ROM known actually, my later PS/2 model 25-004 motherboard contains the same exact BIOS, bit for bit), but the disk controller can handle it, and works just as good as if it came with the drive, no mods.

zombienerd
September 13th, 2017, 05:00 PM
So, just ordered a Sony-made 1.44mb with card edge. The last drive I ordered came in broken.

Hopefully this one will work, lol.

evildragon
September 13th, 2017, 05:54 PM
I have never successfully tested those drives in a 25. Hope it works for you.

zombienerd
September 18th, 2017, 11:54 AM
I have never successfully tested those drives in a 25. Hope it works for you.

Indeed, it works! I'm quite happy with it. Everything seems to be 100% working with it, as well. No problems detected so far.

I have one of those preconceptions that Sony drives are better than others. Let's hope this one doesn't let me down :)

This is the drive I puchased: eBay Link (http://www.ebay.com/itm/SONY-1-44-MB-INTERNAL-3-5-FLOPPY-DRIVE-MODEL-MP-F77W-IBM-PN-90x6766/142504542484?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649) I removed the power converter board (not sure what machine uses that, but I have one now if anyone needs it), and the 5.25 bay sled.

40847

zombienerd
September 18th, 2017, 11:59 AM
Interestingly enough, the drive numbers are different than I expected. I expected to use drive 0 in the middle cable position. It wouldn't work, and gave an Error (161 or 163, I don't remember). I put it at the end of the cable, and the error disappeared, but wouldn't boot from that configuration.

I moved it back to the center cable position, and set the drive select to 1, and it worked flawlessly.

I figured Drive 0 should be "A" and boot, but it seems I was wrong in my guess. Drive 0 seems to be "B" and wants to be in that position on the cable as well.

evildragon
September 18th, 2017, 12:49 PM
Sweet, that's awesome. Does it read 1.44MB disks? I had that exact drive model and it would not read high density disks on a Model 25, only double density. Another drive however did just fine, but it was pin headered.

zombienerd
September 18th, 2017, 12:58 PM
Sweet, that's awesome. Does it read 1.44MB disks? I had that exact drive model and it would not read high density disks on a Model 25, only double density. Another drive however did just fine, but it was pin headered.

Reading 1.44 just fine. Didn't test writing. Can swap disks with no problems either.

40851

evildragon
September 18th, 2017, 01:19 PM
Awesome, glad to know!! Now we have verified proof, my drive was just simply faulty then. (I would rather my drive having been faulty, than it not having been incompatible).

evildragon
September 18th, 2017, 01:20 PM
Why is your DOS prompt purple?

zombienerd
September 18th, 2017, 01:49 PM
Why is your DOS prompt purple?

That was my question in the OP :P


Lastly, while the color screen is beautiful, and all the colors seem to show fine with the system test disk, the white text in DOS & Basic seems a bit 'purplish', any ideas if there's an adjustment?

zombienerd
September 18th, 2017, 09:04 PM
You may have seen in the other thread, I got the XT-IDE working properly. So, let's talk further upgrades...

Which V30 should I be on the lookout for? 8mhz? 10mhz?

Is there any RAM upgrade options, or is 640 all she can handle? I'm mostly talking on-board, as I want to eventually find an Adlib board to populate the other open ISA slot.

krebizfan
September 18th, 2017, 09:26 PM
The PS/2 Model 25-004 runs at 8 MHz and therefore it will be easiest to run the V30 at 8 MHz. If you find a 10 MHz V30 for cheap, buy it. It will happily run at the lower speed. I have encountered enough expansion cards that had issues with higher speed buses with souped up XTs that I don't think it would worth the effort to get the minor speed bump of swapping in a faster oscillator to bring the system to 10 MHz.

768 kB is the most on the planar board but the system will only use 640 kB out of that. 256 kB in chips and 2 256 KB SIMMs. Not one of IBM's finer moments of design. What programs are you planning on running that might use any EMS?

Edit: I remember there was something screwy about Model 25 memory but I may have gotten the detail wrong on how. Still limited to 640 kB on the planar.

zombienerd
September 18th, 2017, 09:33 PM
768 kB is the most on the planar board but the system will only use 640 kB out of that. 256 kB in chips and 2 256 KB SIMMs. Not one of IBM's finer moments of design. What programs are you planning on running that might use any EMS?

It's already got the 640k. I just like to max out any vintage system I have, so that answers that ;) No need to go any further.

luckybob
September 18th, 2017, 11:14 PM
I was under the impression, the onboard chips were 128k. in size.

evildragon
September 18th, 2017, 11:41 PM
768 kB is the most on the planar board but the system will only use 640 kB out of that. 256 kB in chips and 2 256 KB SIMMs.

This is simply not true, and a myth by someone who never verified the part numbers.

The chips on the mainboard are NOT 256KB, they are 128KB total.

evildragon
September 18th, 2017, 11:42 PM
I was under the impression, the onboard chips were 128k. in size.

They are. The only person I've seen claim 256K size was uxwbill, but that wasn't really the case on ANY model 25 I've encountered, nor was it even in the Model 25's tech ref manual. It IS indeed 128K size.

evildragon
September 18th, 2017, 11:44 PM
That was my question in the OP :P

Green gun likely might be weak on the CRT. Looking at your chess game pic, it looks like the green drive is weak, as I see no green in the pic.

chulofiasco
September 19th, 2017, 06:35 AM
The PS/2 Model 25-004 runs at 8 MHz ... to get the minor speed bump of swapping in a faster oscillator to bring the system to 10 MHz.

But, if you did want to do this, what exactly would it require? =D

krebizfan
September 19th, 2017, 08:31 AM
But, if you did want to do this, what exactly would it require? =D

I am certain that anyone with the technical skills to try and able find the correct oscillator also has the math skills to multiply frequency by 125% to order the proper replacement oscillator.

Trixter
September 19th, 2017, 09:14 AM
You may have seen in the other thread, I got the XT-IDE working properly. So, let's talk further upgrades...

You've got only one free slot; if you want to play games, any 8-bit-slot sound card is your next (and final) upgrade. Watch the length, as you can't put full-length cards in a Model 25.

luckybob
September 19th, 2017, 09:56 AM
umm, im quite certain you can put a full length card in the bottom isa slot. if not full length, then damn near.

zombienerd
September 19th, 2017, 10:18 AM
I was actually thinking of putting an Adlib card in there if I can ever afford one ;)

luckybob
September 19th, 2017, 10:21 AM
I opted for an ATI stereo F/X in mine. But i like your idea!

evildragon
September 19th, 2017, 02:08 PM
I am certain that anyone with the technical skills to try and able find the correct oscillator also has the math skills to multiply frequency by 125% to order the proper replacement oscillator.

Just note if you do this, the clock itself, will tick faster, so don't rely on the computers time anymore. I was actually working on a different kind of overclock, but I haven't even begun to start working on it yet. But I gotta be honest, it's not much of an improvement so I don't see the need to do it.

evildragon
September 19th, 2017, 02:08 PM
umm, im quite certain you can put a full length card in the bottom isa slot. if not full length, then damn near.

Yes, it can accommodate a full length card. It even has a plastic clip to support the weight.

chulofiasco
September 20th, 2017, 08:41 AM
I am certain that anyone with the technical skills to try and able find the correct oscillator also has the math skills to multiply frequency by 125% to order the proper replacement oscillator.

Nah, that went over my head. lol