Check the turbo switch cable routing. The one on my XT turbo ran under the mobo and caused a short of some kind when turbo was selected. Took a while to figure out what the issue was but in the end I disconnected the connector on the mobo and all was right again. Couldn't be bothered pulling everything out to reroute the cable and I can select the 3 various speeds by a couple of key presses anyway.

Very nice. I have the same case and the same (or very similar, but those TurboXTs all look the same to me) board. I'm saving the parts for long winter nights having a plan to build some cool XT (this will be my third XT, but first built by me).

It's nice to see this Samsung monitor is working! 😀

Caluser2000 wrote:

Check the turbo switch cable routing. The one on my XT turbo ran under the mobo and caused a short of some kind when turbo was selected. Took a while to figure out what the issue was but in the end I disconnected the connector on the mobo and all was right again. Couldn't be bothered pulling everything out to reroute the cable and I can select the 3 various speeds by a couple of key presses anyway.

There is no turbo switch connected at all. The old case had a reset button, but neither case had a turbo switch.

There's a jumper on the board to switch between a mechanical switch and a keyboard switch "Control + Alt + -" I believe. It's in the keyboard position right now. I think you could probably set both, but neither are.

I'll be pulling the board from the case entirely to check for shorts.

HanJammer wrote:

Very nice. I have the same case and the same (or very similar, but those TurboXTs all look the same to me) board. I'm saving the parts for long winter nights having a plan to build some cool XT (this will be my third XT, but first built by me).

It's nice to see this Samsung monitor is working! 😀

This is my first XT ever, I just got real lucky and ended up with a lot of parts for it.

Samsung is pretty good, it produces and EXTREMELY bright picture. Needs some adjustment and cleaned pots / switches, but it's great!
I've got a nice color monitor coming in the mail as well.

It's great if you get one with a few spares. My Redstone XT Turbo flip top had a TVM EGA monitor with it but the hdd was dead. Just put it storage for a bit then decided to fit an XT-IDE hdd card in it. I got mine from MonoTech PC here in New Zealand. He was local and no shipping costs. Fitted a 2gig BigFoot IDE drive I had laying around doing nothing. Works wonderfully and certainly recommended. Saves hunting around for RLL/MFM matching hdd/controllers. I was lucky enough to get the mobo manual with it along with the complete system guide. If the monitor ever dies I've got a couple of 8-bit vga cards for it.

They're certainly big beasts. I hope you get plenty of enjoyment from yours.

I won't be getting any enjoyment if it's not working at all - Like I said, it just makes one tone on power up. Flip the switch, keyboard lights flash, and it makes a beep. Nothing else.

Does anyone have a list of beep codes or any troubleshooting advice for this DTK board? Maybe a replacement I could buy for cheap if it's pooched?

UPDATE: I took it out of the case and put the original MDA video card back in. Also plugged the original power supply in (Even though they are identical)

The machine now boots!

I get this message on boot:

1Phoenix ROM BIOS Ver 2.27
2Copyright (c) 1984,1985,1986 Phoenix Technologies Ltd
3All Rights Reserved
4
5
6Keyboard Bad
7
88087 NMI at F000:E35E.
9 Type (S)hut off NMI, (R)eboot, other keys to continue_

I shut it off, reseated the 8087-2, and lo and behold I get a RAM count!
It still says "Keyboard Bad" (I'm using an IBM Model M - I thought they auto switched to XT mode?), and now I get a RAM error.

It will count to about 512K and says:

140 RAM Bad 80040
2Error. Press F1 key to continue_

First of all, how do I put a model M into XT mode? Second of all, how do I figure out which RAM chip is bad and replace it?

RAM chip - use Landmark diagnostic (if you can) - it will show you the address with failed chip - it's pretty easy to locate it then. If you can't do that - take some other DRAM chip (which you know is good) and remove chips one by one replacing them with this good one (trying to boot after every replacement) - eventually you will stumble upon a bad chip (ie errors will stop). You can also leave as little RAM as you can and test single bank - if you stumble upon error - it contains bad chip - replace half of the chips with chips you removed - no more errors - bad chip is in the half you removed - then replace any chip with one of the chips you removed and test... Without proper software tools or DRAM tested it's basically trial and error.

HanJammer wrote:

You can also leave as little RAM as you can and test single bank - if you stumble upon error - it contains bad chip - replace half of the chips with chips you removed...

That is what I was going to suggest. Take all out but bank 0 and test, if passes then install bank 1 and test, etc. Also you might try gently pushing down on each chip to make they are snug in the sockets first

Does the Model M work in other systems? Could have some bad caps whitch is not uncommon. One of these might be useful in the long run https://monotech.fwscart.com/PS2_to_XT_Keyboa … 4_19714002.aspx Even if it's just for testing purposes.

Well, I tried the BIOS from my parts motherboard and now it... "Boots"

I think I like this "TURBO XT" BIOS better, it's pretty neat. It displays the list of expansion cards it can detect and the RAM counter at the bottom.
It doesn't tell me the keyboard is bad, but it does ignore any input from it. It also doesn't find any error with the RAM and gets through all 640K just fine.

With the DTK multi I/O board installed, it will seek both diskette drives and it will even attempt to boot MS-DOS from the 360K diskette I made! Granted, it seems to lock up after "Starting MS-DOS..." and gets stuck on a flashing cursor. The diskette drive is still spinning but I can't hear it seeking anymore.

The first 512K are all 41256 DRAMs, and the last 128K are 4164 DRAMs, so I'll try swapping the two banks of 4164s to see if it changes anything. If bank 3 is bad, then moving the chips to bank 4 should give me 576K before it throws the error with the Phoenix BIOS.

I don't have the Landmark BIOS, nor an EPROM programmer, nor the appropriate EPROM to put it on. If I had one, I would try. My hope is that I can make it boot into DOS with 512K and then I can use CheckIt or something to go from there.

However, to do that, I need it to:
A> Not lock up trying to boot DOS with the Turbo XT BIOS and
B> Get the keyboard to work somehow.

If I can get the keyboard working, I can try booting DOS with the Phoenix BIOS as well, since it halts with a memory error.

The model M works perfectly well with my modern Dell Optiplex 7010DT, which has onboard PS/2 ports, it works with my turbo AT clone using a PS/2 to AT pin adapter, and it works with my Compudyne 3SL/25 laptop no problem.

The problem with one of those adapters is that not only is it out of stock, but it's coming from quite far away, and I'd like to have something working right now. I can live with the wrong keyboard if I can just get it to work. Besides, I have a real model F somewhere, but it will take some digging in storage to find it. I bought it a long time ago to use with an AT class machine, which it didn't work with correctly, so I stuffed it in my attic somewhere at my parent's house and never went back for it. I'm thinking I'll grab it next time I'm in the area.

EDIT: I used some other diskette drives and it does the same thing regarding the MS-DOS diskette. Either it's incompatible with the BIOS or DOS 6.22 doesn't like an NEC V20 and an 8087-2.

There is so much you can improve with these XTs and related devices, but you really need some programmer (cheapo TL866-II from ebay and you are good!). Since I got TL866-II I'm able to do so much things and repair/test thing in a few minutes which otherwise took me several days (visitng friend with a programmer and so on) - worth every cent spent on it.
For example you can replace the BIOS with this: https://www.phatcode.net/downloads.php?id=101 which is pretty much the ultimate XT BIOS with many cool features.

Anyways - this replacement BIOS probably skssp the RAM error but it show up during DOS boot and system just hangs...

I'm running "Turbo XT version 3.1" already, it shows all the same information at boot as the one you linked. The Phoenix BIOS is much different, but this unbranded one works fine.

I'm going to set it to 512K on the switches and see if it will boot properly from there.

I just want to get to a DOS prompt. Any suggestions for the keyboard? I've hears Model Ms can switch to an XT mode, but I don't know if this is true or how. Any help?

Should auto detect but is isn't unusual for them to flake out because of a bad cap.

Caluser2000 wrote:

Should auto detect but is isn't unusual for them to flake out because of a bad cap.

Any way to force it into XT mode? I'm not opposed to taking it apart and putting a wire across something for now.

UPDATE: Pulling the chips from bank 3 and 4 and installing bank 4 into bank 3's positions got it to boot to DOS 6.22!

I guess one of my 4164s is bad or something. I'll put them into bank 4 and try the other BIOS again, maybe it will tell me what chip it is.

UPDATE (Again):

Putting the bad chips into bank 4 caused it to stop booting entirely. I pulled the 4164s from an old "Magitronic" MDA / Parallel card I won't be using and stuck them into bank 4. I was one chip short so I picked one at random from the original bank 4, and now I have a full 640K on the board! Both the Turbo XT and Phoenix BIOSes boot the machine to a DOS prompt now, but I still can't get anything from a keyboard. I think I'll put it back into it's case for now while I look around for advice on the keyboard situation.

Good job FAMICOMASTER ! Think I would stick with the original BIOS until you get the KB thing figured out.

In my experience, the model Ms don't really work properly on XT computers. I had the same problem with my turbo XT board...the keyboard worked intermittently. I ended up having to use an AT to XT keyboard converter to get it working properly.

There is a special model M for XT computers that doesn't have LEDs. It was sold with a later XT motherboard that had a BIOS that supported the extra keys. Not sure if that particular keyboard works on normal XTs, or if that motherboard supports regular model Ms, but maybe both are required to work.