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dongfeng
May 30th, 2006, 01:39 AM
After a long wait, I finally received my XT today! Looks really nice, but she's going to need a bit of TLC to get running again...

It's fitted with a whole host of cards, including a "Tiny Turbo 286" board and VGA adaptor. Anyway...

When I turn the computer on... nothing. The power supply whirs into life, but that seems to be it. After I removed the unncessary cards, the hard drive span into action, but still a blank screen.

So... I'm thinking something must be up, and removed all the cards except the 286 card (as it has the processor) and the VGA card. Still the same! Also tried it removing both the drives.

Any ideas? I've also removed the 8088 from the 286 card and put it back where it should be, still no luck :(

mbbrutman
May 30th, 2006, 05:42 AM
How long did you wait for it to boot up?

Did you carefully examine the machine to make sure that nothing is being grounded by accident? How about the capacitors - are they all intact? Other physical damage?

Terry Yager
May 30th, 2006, 06:20 AM
The Orchid TinyTurbo jacks into the mainboard's processor socket. You'll need an 8088 to place there if you want to remove the '286 board and test again.

--T

dongfeng
May 30th, 2006, 07:26 AM
Thank you for your replies :)

I've had it running for about 5-10 minutes and nothing appears on the display. I've checked the board and nothing seems to be out of place - but I'll post a photo of it in a moment just in case one of you can spot something I've missed :D

The 8088 was on the TinyTurbo board, so I have removed that and put it back in it's correct place. The 286 is missing the cable that connects the 8088 socket to the 286 board... which makes be think the seller was lying to be when he said that it worked when taken out of use 15 years ago . . .

I have a feeling that it might be something wrong with the display - I've tried two different VGA displays with no luck. I also put the VGA card from my Epson AX2e in it (set to 8-bit) and get swirly blue lines on the screen. I'll dig out a suitable computer to check the cards...

dongfeng
May 30th, 2006, 08:04 AM
The mainboard:
http://www.howard81.co.uk/upload/vcf/xt/xt_mainboard%20(Medium).JPG

Mainboard in very high resolution (http://www.howard81.co.uk/upload/vcf/xt/xt_mainboard.JPG)

Cards 01 (http://www.howard81.co.uk/upload/vcf/xt/xt_cards01%20(Medium).JPG)
Cards 02 (http://www.howard81.co.uk/upload/vcf/xt/xt_cards02%20(Medium).JPG)
Cards 03 (http://www.howard81.co.uk/upload/vcf/xt/xt_cards03%20(Medium).JPG)

dongfeng
May 30th, 2006, 08:37 AM
VGA card tested in another machine and it's fine...

When an XT boots up... how long, and what sounds does it make? any beeps and such?

mbbrutman
May 30th, 2006, 08:57 AM
At XT booting up will count memory, so it will be obvious. An older 5150 PC might not count memory, but you will at least get a blinking cursor while it goes through POST (Power On Self Test).

Make sure the CPU is in the correct socket. :-) A technical reference manual would be helpful here.

A bare XT (no slots except for video) should boot into BASIC. You might want to ditch the VGA card and use a known workingCGA card (and monitor) just to be safe. VGA should work, but the machine was designed back when Monochome and CGA walkied the Earth.

mbbrutman
May 30th, 2006, 08:59 AM
One more note .. it looks like you have a Monochrome/Parallel adapter. So if you have a true monochrome monitor, you can flip a switch on the motherboard and have it use that display adapter. (You can probably find the XT switch settings online .. if not, I can give you a sane set of settings when I get home.)

Which brings up another point .. you need to verify the DIP switch settings on the motherboard.

Luke
May 30th, 2006, 09:39 AM
http://www.uncreativelabs.net/xtreview/xtreview.htm - useful informations about XT's.
http://www.uncreativelabs.net/xtreview/xtdip.htm - DIP switches stetting.

Terry Yager
May 30th, 2006, 09:43 AM
Also, removing the 'extra' 256K memory board may require another change in switch settings:



Switch # Function Settings

1 Test On = loops on POST, Off = normal operation

2 Coprocessor On = yes, Off = no

3 & 4 System board RAM On On = 64K
Off On = 128K
On Off = 192K
Off Off = 256K

5 & 6 Display adapter On On = no adaptor
Off On = CGA 40 columns
On Off = CGA 80 columns
Off Off = MDA or more than one adapter

7 & 8 Floppy drives On On = 1
Off On = 2
On Off = 3
Off Off = 4

...or mebbe not.

--T

dongfeng
May 30th, 2006, 10:58 AM
Unfortunately I only have VGA monitors available to me, no monochrome or CGA :( But the VGA card came in the XT and apparently was working fine when it was last in use...

Tried the switch settings, but no luck.

Even if there was no monitor attached, it would still try and access the floppy when it boots up, yes? My XT doesn't even try to do that. I have a nasty feeling it's a dud board...

The hard drive is very noisy when it spins, is that normal?

atari2600a
May 30th, 2006, 11:23 AM
Since you think the problem's the VGA card, have you tried removing it?

dongfeng
May 30th, 2006, 11:24 AM
yup... tried booting without it, and even replacing it with a different 8-bit VGA card...

I know they both work... I've tested them in another machine...

atari2600a
May 30th, 2006, 11:29 AM
Hm, will if it doesn't even check for a floppy, then it might be the BIOS/motherboard.

carlsson
May 30th, 2006, 11:39 AM
The hard drive is very noisy when it spins, is that normal?
I don't think it affects how the motherboard works, unless there is a problem with the power supply such as it delivers bad voltages that would cause the hard disk to make noises and has fried the motherboard. :confused:

atari2600a
May 30th, 2006, 11:45 AM
Yeah, a bad PS would sound probable...

dongfeng
May 30th, 2006, 03:07 PM
Ahh it doesn't sound good. I'll try plugging the hard drive to another power supply to see what it sounds like.

Another thing I have noticed is that the floppy drive was connected to the same card as the hard drive, and not the floppy controller card... correct?

It seems the previous owner really liked to modify their XT!

Any way to test the floppy drive in another (more modern) computer? And the HDD?

Any way to test the power supply for correct voltages? Theres a few clone XT boards on eBay which may do the trick, providing the PSU is ok...

Thanks for your help so far :)

modem7
May 31st, 2006, 01:02 AM
Try the most basic configuration: Motherboard with just the power supply and the speaker connected (no cards at all). With the motherboard switches set for Monochrome (5=off, 6=off), you should hear beeps as soon as the power supply is turned on.

If no beeps, then consider:

1. Dead motherboard.

2. Are the two connectors from the power supply in their correct sockets (ie. P8 into socket closest to keyboard connector). I can't remember what the symptoms are if the plugs are reversed (and I'm not willing to try this on my XT).

3. Bad PSU.

For a quick check of the PSU (assuming you don't have a POST card):
On power up, when the XT PSU believes the voltages to be correct/stable, it puts 5 volts onto the 'power good' line (and that takes the motherboard out of its reset state). Measure that line with a multimeter. It's the orange wire. It will take less than a second for the line to switch from 0 volts to 5 volts.

dongfeng
May 31st, 2006, 02:57 AM
Thank you, I have tried that but still there is no beeping from the speaker :(

In testing the PSU, it does not appear to have an orange wire, and there are several red ones. Which ones should I test?

http://www.howard81.co.uk/upload/vcf/xt/xt_psuwires.JPG

modem7
May 31st, 2006, 03:42 AM
The standard colour coding is shown at http://www.epanorama.net/documents/pc/pcpsu_connector.html

The 'power good' line in your case is the white wire.

If your 'power good' line isn't reading 5 volts, the power supply might be good but is being loaded down by a short (or partial short / heavy load, etc.) on the motherboard. To test for that condition:
1. Disconnect the motherboard from the PSU
2. Disconnect all other devices from the PSU except for one (i suggest the floppy drive). You need to leave one device connected because the XT PSU won't power up unless at has a load of some sort.
3. Turn on the PSU and see if the 'power good' line is now 5 volts.

dongfeng
May 31st, 2006, 09:01 AM
Plugged in I am getting 4.99 volts, and the same for when the PSU is disconnected, so I guess it's good.

Is there any way to diagnose if it is the motherboard that has gone, or the 8088? Since the 8088 had been moved to the 286 card in the past, I wonder if it has been damaged...

Chris2005
May 31st, 2006, 09:09 AM
later PCs and XTs were said to ignore the dip switch settings (to some degree). Remember that it's the code imbedded in rom that does the "checking", so therefore with mulitiple upgrades, the importance of those dip switch settings can vary. The first thing you should do in any instance of a seemingly dead cpu is check the voltages coming off the power connector. Unplug it from the mobo, and verify that you got +5v, +12v and whatever else present on those pins. Don't worry about how those connectors get reattached to the mobo - the black wires are always adjacent and on the "inside" (on every XT or AT power supply in existence if things were done right). A fan spinning doesn't necessarily equate to a functioning power supply.

Black is always ground. Red is +5v IIRC. Yellow is +12v. One or the other lol. You're just checking, so there's no danger (if you do it right).

O right you'll need a multimeter and learn how to use it. Radio Shlock, Home Depot, even Walmart will have something in that department. With the test probes plugged in to take a voltage measurement (NOT a current measurement), connect the "hot" (usually red lead) to the pin you're curious about, and obviously with the power supply plugged into the wall and on, touch the ground (usually black) lead to the p/s case, thereby grounding it, and providing a reference (and circuit) to measure the voltage. I know this might sound confusing at first. I can *try* to assist further if you're going to try this. I could even give my phone number lol.

If the voltages are there (and not allowing for each voltage not having sufficient current to do it's job, not all that much of a likelihood I guess) your problem is on the system board duh. You can then resort to substitution (each chip at a time) or invest in some test equipment. Logic probes can still be found around, and probably cheap (have to be able to work with at least 5mhz signals or better yet 10). It would take significant work to trace down the problem by "logical" methods. Probably the best thing to do is find a spare mobo and keep the other one for parts. They can readily be had on ebay and such practically any day of the week.

I think regardless of dip switch settings you would get some notification from the speaker within 30 seconds of hitting the switch.

Another thing to do, and it's tedious, and not necessarily even a likely problem, is to inspect the traces on the mobo. One or more could have been severed I guess. Hope some of that helps.

dongfeng
May 31st, 2006, 09:11 AM
this is how the drive sounds when starting up (8mb) (http://www.howard81.co.uk/upload/vcf/xt/xt_drive.wmv)

dongfeng
May 31st, 2006, 09:17 AM
Thanks Chris, I have checked the PSU and the voltages all seem to be fine and as expected.

Unfortunately early IBM's, let alone system boards on their own are a little hard to find over here in the UK :( but it looks like that's my only option! Given that the hard drive sounds awful, I think it would be better to look for another XT if I cannot resurrect this one...

Anyone in Europe with a working XT board (or even a clone board) they want to sell or trade??? :D

Chris2005
May 31st, 2006, 09:18 AM
of course like an ass I missed the whole second page of the thread. Since you know how to check voltages, try check them while the the connector is connected to the mobo, and also try when it's not connected. There maybe be more then just +5 and 12v on some of those pins. They are color coded. If you get something strange, let us know. Some computers have weird voltages, like -5 and -12v. Some components require negatives for reasons I can't recall.
Sometimes to check a pin while the p/s is connected to the mobo, you might need to utilize a paper clip or somehting, by shoving it down between the wire and the plastic of the connector. Be gentle and be careful not to short (connect to metallic points that were never meant to be). Common sense will be your guide.
If you're say reading 5vdc on a particular pin when it's not connected, but something different when it is, the problem could be the p/s. Or a short somewhere as been suggested. That would require a visual examination of the circuit board (got an eye loupe handy?). It usually doesn't take too much investingating to determine if the power is bad though. Usually.

Chris2005
May 31st, 2006, 09:22 AM
now this is just my own opinion, but in nearly all cases I avoid bothering with the older hard drives. I suppose I have 1 or 2 working ones in my stash though. They're too prone to crap themselves at any point. I'd prefer to plug and IDE hard drive (usually requires an older one though) even into an XT. A better solution in my book, though nowhere near as "authentic", is to uitlize a flash card reader - but though they're out there for things like the Commodore 64, I personally am not aware of such a reader for a PC. Can anyone enlighten? Flash card are becoming real cheap.

atari2600a
May 31st, 2006, 12:03 PM
This guy I know, Benjamin Heckendorn (I'm sure at least one of you have heard of him) used a Compact Flash reader in his custom-built Atari 800 laptop. They can be put in anything!

Anyways, I used to have a hard disk that sounded like that (about 5 years ago; when I was too young to diagnose it). I don't remember hwat happened, but I think I might of torn it apart out of boredom. Sounds like a head came loose in it or something... Can't be the cause though, since the BIOS controlles everything during startup. But maybe it could've generated a random code that could've reflashed the BIOS with crap! Just a thought...

dongfeng
May 31st, 2006, 01:00 PM
now this is just my own opinion, but in nearly all cases I avoid bothering with the older hard drives. I suppose I have 1 or 2 working ones in my stash though. They're too prone to crap themselves at any point. I'd prefer to plug and IDE hard drive (usually requires an older one though) even into an XT. A better solution in my book, though nowhere near as "authentic", is to uitlize a flash card reader - but though they're out there for things like the Commodore 64, I personally am not aware of such a reader for a PC. Can anyone enlighten? Flash card are becoming real cheap.

Now that is a good idea! You can buy a gadget that converts a Compact Flash to an IDE connection. I wonder if that would work? However, it seems rather hard to find an 8-bit IDE card.

dongfeng
May 31st, 2006, 01:02 PM
of course like an ass I missed the whole second page of the thread. Since you know how to check voltages, try check them while the the connector is connected to the mobo, and also try when it's not connected. There maybe be more then just +5 and 12v on some of those pins. They are color coded. If you get something strange, let us know. Some computers have weird voltages, like -5 and -12v. Some components require negatives for reasons I can't recall.
Sometimes to check a pin while the p/s is connected to the mobo, you might need to utilize a paper clip or somehting, by shoving it down between the wire and the plastic of the connector. Be gentle and be careful not to short (connect to metallic points that were never meant to be). Common sense will be your guide.
If you're say reading 5vdc on a particular pin when it's not connected, but something different when it is, the problem could be the p/s. Or a short somewhere as been suggested. That would require a visual examination of the circuit board (got an eye loupe handy?). It usually doesn't take too much investingating to determine if the power is bad though. Usually.

It's a bit late here now, so I'll get on to checking those out tomorrow and report back then :D

dongfeng
May 31st, 2006, 01:04 PM
Regarding replacement mainboards... how about this one?

http://cgi.ebay.co.uk/CPU-NEC-V20-8086-8088-KOMPATIBLE-MIT-BOARD-NEU-SELTEN_W0QQitemZ6878950090QQcategoryZ164QQrdZ1QQcm dZViewItem

modem7
June 1st, 2006, 12:21 AM
[QUOTE=Chris2005] "Some computers have weird voltages, like -5 and -12v. Some components require negatives for reasons I can't recall."

From the IBM XT technical reference: "The -5 Vdc level is used for analogue circuits in the diskette adapter's phase-lock loop. the +12 Vdc and -12 Vdc are used for powering the Electronic industries Association (EIA) drivers for the communication adaptors."

The communication adaptors referred to will be synchronous/asynchronous cards (eg. RS-232, RS-422, etc.).

modem7
June 1st, 2006, 12:23 AM
[QUOTE=dongfeng] 'this is how the drive sounds when starting up (8mb)"

Most experienced readers will tell you that the 'rattling' sound coming from your HDD is not normal.
I have the same drive (an ST-412) in my IBM XT and so I can definately state that for an ST-412, the 'rattling' sound isn't normal.

modem7
June 1st, 2006, 12:29 AM
Although the 'power good' signal is a very reliable indication of PSU serviceability (particularly with the PSU under load), it is definately worth checking the voltages on P8/P9. For example, one of the wires out of the PSU may be broken.

You've relocated the 8088 from the "Tiny Turbo 286" board to the motherboard. I can see by your motherboard picture that it's in the correct socket and oriented correctly. Probably worth checking that none of the pins got bent on insertion.

Probably worth checking the all other socketed chips for bent pins as well (ie. you don't know the history of the board). I presume you already tried reseating all socketed chips.

If someone has earlier 'played' with the board, maybe the two ROM chips (U18/U19) were removed and accidently placed back in the wrong sockets.

modem7
June 1st, 2006, 01:37 AM
Pointers to XT technical information were given earlier.

You may also find the attached document useful (eg. discusses the special requirement for cards plugged into slot 8).
The document specifically covers the genuine IBM XT.

dongfeng
June 1st, 2006, 07:50 AM
Motherboard plugged in only:

P8:
01 White: 5v
02 n/a
03 Yellow: 11.59v
04 Brown: -11.58v
05 Black: 0v
06 Black: 0v

P9:
07 Black: 0v
08 Black: 0v
09 Blue: -4.58v
10 Red: 5v
11 Red: 5v
12 Red: 5v

Hard Drive plugged in only:

P8:
01 White: 5v
02 n/a
03 Yellow: 10v
04 Brown: -10.25v
05 Black: 0v
06 Black: 0v

P9:
07 Black: 0v
08 Black: 0v
09 Blue: -4.03v
10 Red: 5v
11 Red: 5v
12 Red: 5v

dongfeng
June 1st, 2006, 07:53 AM
I have reseated all of the chips on the motherboard, and I swapped the ram about too incase it was a faulty bank. ...but as you guessed... nothing.

The Technical Information guide is really interesting - reading it now!! Thank you :)

Terry Yager
June 1st, 2006, 08:10 AM
The board in the eBay auction is not TrueBlue IBM, so all bets are off, compatibility-wise. (Also somewhat overpriced, IMHO).

--T

dongfeng
June 2nd, 2006, 02:36 AM
Ahh nevermind! The hunt is on for a working XT board!

dongfeng
June 2nd, 2006, 02:45 AM
Wanted: IBM XT parts (http://www.vintage-computer.com/vcforum/showthread.php?t=3363)

Chris2005
June 2nd, 2006, 09:16 AM
that board is a late model XT clone. It squished alot of functionality of a the original desigin (chips) onto that asic or whatever it is in the upper left quadrant (surface mounted). Terry could be right that there could be issues. In fact, I didn't study it though, it may be a different form factor altogether. Although I do own a few things with custom ic's, I tend to shy away and at one time would avoid them altogether. If I can't fix it, I may very well have no interest in keeping it around.
What you might want to do is place a (more or less) local ad in a newspaper or these little booklets they often give away (at least over here across the pond) for nuffin. There's bound to be people not too far away with old puters serving as tenements for silver fish and whatnot.
AND IF IF YOU SHOULD COME ACROSS A RESEARCH MACHINES NIMBUS PUTER PLEASE PLEASE SNIFFUL KEEP ME IN MIND. They're pretty common over there as far as things go I'm told. I'd love to see you find one. You could scrounge one of those GASP for parts, but I wouldn't advise it. Incompatible as all hell too lol, like a Tandy 2000, and n fact uses the same cpu (80186).

Chris2005
June 2nd, 2006, 09:17 AM
if you're in an absolute bind, let me know. I keep a small stockpile of mobos around. If all else fails, I could test em and send it to you. You'd have to pay the postage though. Don't ask me how much that would cost.

modem7
June 2nd, 2006, 05:54 PM
The TTL chips on the motherboard require +5 volts. I've seen different tolerances listed for TTL chips (eg. +/- 0.2V, +/- 0.25V, +/- 0.5V) but personally (I used to repair personal and mini computers) I wouldn't be happy with anything below 4.9V. Remember too that there'll be some voltage drop across the motherboard.

Anyhow, an authoritive source for the IBM XT system is IBM's technical reference for the XT. For the IBM 130W PSU, the tolerance on the +5V is +5%/-4% over the allowable current range. Thus the +5V should be +4.8V minimum.

Earlier I thought, the HDD is making a rattling sound but there's still a chance it will work. But with the HDD dragging down the PSU voltages as you've indicated, you can safely write off your HDD.

Well, unless you've got an under-powered PSU. I presume your PSU is at least 130W (what was supplied with the IBM XT).

I can see an ST-412 advertised at "http://www.labx.com/v2/newad.cfm?CatID=65&Page=254"

With only the motherboard (with no cards) connected to the PSU, the voltages (and 'power good') are fine.
And in that configuration you heard no beeps at all.

How unlucky - a stuffed motherboard and a stuffed HDD ?

modem7
June 2nd, 2006, 07:45 PM
According to the Seagate web site, the ST-412's power consuption ranges from 26W (typical) to 50W (max).
Therefore (even allowing for inefficiency ratio of the PSU), if you do have a 65W power suppy, it will be able to power just the ST-412 alone (assuming the ST-412 is serviceable).

Looking back, with only the HDD attached, interesting that your PSU is generating a 'power good' signal with the -5V sitting at -4V, the +12v at +10V, and the -12V at -10V. If it's a clone PSU you've got, it wouldn't surprise me. It's possible that within the PSU, only the +5v is looked at when generating the 'power good' signal.

In my IBM XT 130W PSU and ST-412 configuration (the HDD uses +5V and +12V), the +12v rightly stays at +12V. You could just have a cheap PSU where the +5V is regulated but not the other voltages. That would explain why the -5V and -12V has dropped as well (neither is supplied to the HDD).

And so on reflection, I wouldn't right-off the ST-412 just yet. Yes, it's making a 'rattling' sound (loose screw?), but all the other sounds it's producing are normal. However, with it dragging the +12v down to +10V, it doesn't look good. I'm sure even an engineer designing a cheap PSU wouldn't design the PSU so that the +12V dropped to +10V under normal load. But does that indicate that the PSU has failed in strange way.

Re your motherboard. Another test. See if it works when removed from the chassis.

Luke
June 3rd, 2006, 01:01 AM
Check the drive on the other computer. Connect only power input and you will see: it's power problem or disk problem.

dongfeng
June 3rd, 2006, 03:01 AM
What you might want to do is place a (more or less) local ad in a newspaper or these little booklets they often give away (at least over here across the pond) for nuffin. There's bound to be people not too far away with old puters serving as tenements for silver fish and whatnot.
AND IF IF YOU SHOULD COME ACROSS A RESEARCH MACHINES NIMBUS PUTER PLEASE PLEASE SNIFFUL KEEP ME IN MIND. They're pretty common over there as far as things go I'm told. I'd love to see you find one. You could scrounge one of those GASP for parts, but I wouldn't advise it. Incompatible as all hell too lol, like a Tandy 2000, and n fact uses the same cpu (80186).

RM Nimbus? Most old schools had those, sadly I haven't seen any for years but I'll keep an eye out :) My University still used modern RM machines, and probably still do.

dongfeng
June 3rd, 2006, 03:05 AM
Hmm it doesn't sound good for the hard drive. But at least you don't NEED one of those to use the XT :)

The power supply has a sticker on it saying 150W, how to check if it is a clone one or not? Maybe I should try doing the voltage tests again with another drive attached? Will try and test the MB removed from the case later on today.

dongfeng
June 3rd, 2006, 03:22 AM
Just tried the HDD on my 333MHz AMD, and it still sounds the same. The grinding sounds have stopped now though, on both computers.

modem7
June 3rd, 2006, 03:53 PM
I don't ever recall seeing a genuine IBM PSU for the XT that differed from the 'standard' wiring colours. Most genuine IBM equipment will have a 7 digit part number on them. The part number is either the actual part number or the Field Replaceable Unit (FRU) part number. Some parts I've seen had both. My 130W PSU has a grey sticker labelled 'IBM 1501438' on the top.

Why did I suggest removing the board from the chassis? In the late eighties, I saw a few clone computers where someone's attempt to assemble a computer, or upgrade the motherboard, failed. Sometimes it was because something had been shorted out on the motherboard: In some cases a screw with an oversized head was used. In some cases the manufacture required that a non-conductive washer be used with the screw, and no washer was used. Sometimes the shorting was caused by a metal standoff under the motherboard.

Something else worth mentioning. I also saw the occasional genuine IBM that had problems after someone replaced the genuine XT motherboard with a clone AT motherboard. From memory, the boards started up okay but were unstable. Replacing the IBM PSU with a clone 'AT' PSU (one that fitted in the XT case) fixed the problem. I recall hearing that in moving to the AT, IBM changed the design of the 'AT' PSU so that certain voltages came up before others (because of something on the genuine AT motherboard.) Maybe some reader can elaborate.

dongfeng
September 21st, 2006, 10:47 AM
Thanks to Jorg who sold me his old XT mainboard, this XT is back alive :D

The mainboard is a 256-640 version, but only has 256kB (four banks of 64k) so I have pushed the total up to 640kB with a couple of expansion cards as I don't have any spare 256K RAM chips to swap in. Had a few problems with bad memory on the cards, but luckily there were a couple of good banks on the dead mainboard I could salvage.

10MB Seagate ST412 is out of my 5150 (which is getting a hard card when it arrives) booting to DOS 2.10. I don't have any spare working FH drives, so the HH drive is good for now, and besides, the later XT's did come with HH drives so it is not all incorrect ;) I'll have to look in the spares box at work tomorrow to try and find a blanking plate to fill the gap!

One weird thing I noticed is that the mainboard is dated 8647 but has a BIOS date of 11-8-82, whereas the 640k mainboard in my other XT is dated 8611 and has a BIOS date of 1-10-86?!?

http://www.howard81.co.uk/upload/vcf/xt/xt_working01.JPG
http://www.howard81.co.uk/upload/vcf/xt/xt_working02.JPG
http://www.howard81.co.uk/upload/vcf/xt/xt_hellovcf.JPG

Jorg
September 21st, 2006, 02:17 PM
I'm not sure if to laugh or cry :) :| :(

Nice job, and I'm happy it found a good home!

I'll post some pictures when I am done with my building-an-Asus-txp4+Pentium 233-in-my-empty-XT5160-case.

Its going to have 192 MB ram, FAST SCSI harddisk and cdrom, and a wireless card- looking to run it under FreeBSD 6.
Oh, and Hercules graphics on a 5151 monitor :D

Picky thing is to find a wireless card that goes in a 5V PCI slot, is supported by FreeBSD, and does WPA.
But I think I found one, just have to order it.

IBM Portable PC
October 19th, 2013, 03:17 PM
Where is the schematic for the IBM 1501438 power supply located?

A parts list (electrolytic, foil and tantalum capacitors!) would be even better.........


Okay, I have a schematic on Pages 8&9 of Sams Computerfacts for the 5150, the parts list as per above would be better.

Somone must have recapped it?