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lucasdaytona
July 28th, 2012, 06:10 PM
Hello everyone, today I got big luck ( a bit expensive, but big luck).

Just got a Brazilian XT, called Microtec MF 88, it's a very interesting XT, only a few things was known by me, I saw a ST238R 33MB 5.25"/HH RLL ST412, full memory banks (27 41256 ICs, how much memory is that?), The cpu is a Intel 1978 SDU8088-IE(didn't found useful info (http://octopart.com/sdu8088-1e-intel-14932101)), have two 5 1/4 drives, looks like 360KB drives, and a lot of dirt inside. I need help with this beast, what are the procedures before the first turn on? I'm thinking to do the usual, take everything off, proper clean, and try to boot with only essential hardware.
I will post pics very soon. Looks like it was on a garage for at least 15 years.

Thanks!

modem7
July 28th, 2012, 06:40 PM
what are the procedures before the first turn on?
Step 1: Remove as much dirt/dust as possible.
Step 2: Look for cards/cables that have become detached, or not connected properly.
Step 3: About five minutes of prayer.


full memory banks (27 41256 ICs, how much memory is that?)
Three banks of nine (8 data + 1 parity) 256K bit chips = three banks of 256 KB = 768 KB

lucasdaytona
July 28th, 2012, 06:44 PM
wow, 768KB of memory is nice!

I'm already doing the step 3 ;)
thanks! I will keep going here.

modem7
July 28th, 2012, 07:04 PM
wow, 768KB of memory is nice!
I see two possibilities:
1. The third bank was meant to have 128 Kbit chips in it, but someone fitted 256 Kbit chips.
2. The third bank is designed for 256 Kbit chips; DOS will see 640 KB of the 768 KB; use of the 128 KB balance is controlled by the motherboard.

lucasdaytona
July 28th, 2012, 07:24 PM
2. The third bank is designed for 256 Kbit chips; DOS will see 640 KB of the 768 KB; use of the 128 KB balance is controlled by the motherboard.

Could you give me an example of that?

modem7
July 28th, 2012, 07:33 PM
Could you give me an example of that?
The motherboard manufacturer could for example, provide a DOS driver that enables the 128 KB to be used as a RAM drive.

lucasdaytona
July 28th, 2012, 07:43 PM
I see, thanks for the info. I'm currently taking a deeper look into the system, the video card have 8x4164 ICs, this results in 64KB video RAM? A DB-9 and a RCA connector, this is a CGA?

modem7
July 28th, 2012, 08:05 PM
the video card have 8x4164 ICs, this results in 64KB video RAM?
Yes.


A DB-9 and a RCA connector, this is a CGA?
64 KB suggests (repeat: suggests) EGA. Look at the motherboard switch block. Assuming that the switches are set correctly, then if motherboard switches 5 and 6 are both on, then you can be very confident that you have EGA.

A better method would be to do a web search with the card's part number, seeing what that search reveals.

lucasdaytona
July 28th, 2012, 08:19 PM
Yes.


64 KB suggests (repeat: suggests) EGA. Look at the motherboard switch block. Assuming that the switches are set correctly, then if motherboard switches 5 and 6 are both on, then you can be very confident that you have EGA.

A better method would be to do a web search with the card's part number, seeing what that search reveals.


There's no part number that could be found on databases, the entire system was made on Brazil, and the things here aren't well documented...

The system don't boot, no beeps, fan spins, keyboard blinks when powered on, there's power on the motherboard, 5 1/4 drive spins a little then stop. Tried it with a known good VGA (configured to 8 bit bus), and same results. Removed the Seagate controller, same results. I think I will reseat the CPU.

lucasdaytona
July 28th, 2012, 08:29 PM
still nothing...
by the way, there's no switch block no the motherboard, a few jumpers over the board, but no switch blocks, or anything related.

The power on led (that cames from the motherboard) on the computer front panel is saying the system is on, also the "speed light" is on.

modem7
July 28th, 2012, 08:52 PM
Some things to try:

1. Swap the first two RAM banks. Chips in second bank into first bank, and chips in first bank into second bank.
2. Reseat anything that can be reseated. Example: ROM chips.
3. Minimum hardware: power supply + motherboard + video card
4. Measure the voltage on the power supply's POWER GOOD line.


keyboard blinks when powered on
Most keyboards do that when they receive +5 volts (the keyboard's self test blinks the LEDs).

lucasdaytona
July 28th, 2012, 09:37 PM
Some things to try:

1. Swap the first two RAM banks. Chips in second bank into first bank, and chips in first bank into second bank.
2. Reseat anything that can be reseated. Example: ROM chips.
3. Minimum hardware: power supply + motherboard + video card
4. Measure the voltage on the power supply's POWER GOOD line.





1 - I will do this tomorrow, is almost 3 AM here, and I'm a working like a zombie, I will sleep first.
2 - should I remove and put it back or just a gentle push?
3 - Ok ! (but the system will beep if the motherboard is ok? I mean, even without a video card?)
4 - The power supply connector only have 10 pins, named:

1 NC(but there's no wire here, maybe NC = Nothing connected?)
2 12V+
3 12V-
4 GND
5 GND
6 GND
7 -5V
8 +5V
9 +5V
10 +5V

All the voltages are fine, even the 8088 is receiving +5V.

The keyboard accepts Numeric lock, caps lock, etc.
I can't stop thinking in a dead CPU.

Thanks for the help, tomorrow more results!

modem7
July 29th, 2012, 12:21 AM
1 - I will do this tomorrow,
There is the possibility that the BIOS author tests the first bank of RAM (or part of it), and simply halts the computer if that tested RAM is bad.
If that is the case, and if there is a bad chip (or multiple chips) in the first bank, then swapping the banks will reveal that problem (but only if the chips in the second bank are good).


2 - should I remove and put it back or just a gentle push?
In some situations, I do not think that a gentle push on a chip will be good enough. I lever the chip out by about 2 millimetres, and then push the chip back in. That is the way I do it.

Some other people prefer to remove the chip altogether. If you do that, you need to be very careful that you do not bend a pin when you place the chip back into its socket, and be careful not to place the chip in the the wrong orientation.


3 - Ok ! (but the system will beep if the motherboard is ok? I mean, even without a video card?)
The writer of the BIOS decides whether or not to beep the speaker at the end of the POST (Power On Self Test).
The author of the BIOS on your motherboard may have decided not to.


NC(but there's no wire here, maybe NC = Nothing connected?)
Yes, NC typically is 'Not Connected' or 'No Connection'.

It is not clear. Is 'NC' marked on the motherboard connector, or on the power supply's connector?

If NC on motherboard:
That would mean that the motherboard does not require a POWER GOOD signal. The IBM PCjr motherboard is an example of a board that does not require a POWER GOOD signal.

If NC on power supply's connector:
Maybe the motherboard requires a POWER GOOD signal (to start) but someone has fitted a power supply without a POWER GOOD signal.


I can't stop thinking in a dead CPU.
That is only one possibility of many.

lucasdaytona
July 29th, 2012, 07:33 AM
The NC is marked on the motherboard.

Today, when I got up, I did the step 3 again, but with more faith.Tried my luck again, and the system beep, and then tried to boot from floppy. All of this without touching the motherboard. Well, then I realized that the monitor have problems, but I will fix this later, I'm using a spare monitor here (a cute 12" paper white), and no booting, can't reads disks, I will clean the drive, and try again.

I have another question, there's a way to change the boot order, like Hard Drive before Floppy?

Stone
July 29th, 2012, 08:04 AM
I have another question, there's a way to change the boot order, like Hard Drive before Floppy?Yes, don't put a disk in the floppy or leave the door lock open and it will boot from the HD. :-)

lucasdaytona
July 29th, 2012, 08:34 AM
Yes, don't put a disk in the floppy or leave the door lock open and it will boot from the HD. :-)


Thank you, as you said, it booted using hard drive, but sadly there's some error in the drive (but the seagate controller recognizes the drive), I will clean the floppy drive, and then try again!

Crypticalcode0
July 30th, 2012, 01:12 PM
Thank you, as you said, it booted using hard drive, but sadly there's some error in the drive (but the seagate controller recognizes the drive), I will clean the floppy drive, and then try again!

clean the guide rail and if the mechanics are dirt clean them but do not forget to use a single drop of machine oil if you do that to prevent mechanical problems in the future.(wear on the mechanism can cause that the header gets misaligned, I use sewing machine oil)

Clean the header with something you know cannot get stuck of leave residue behind.(a can of air usually does the trick, if you do use that check it on something else if there is no moisture in the canned air.)

lucasdaytona
July 30th, 2012, 06:37 PM
clean the guide rail and if the mechanics are dirt clean them but do not forget to use a single drop of machine oil if you do that to prevent mechanical problems in the future.(wear on the mechanism can cause that the header gets misaligned, I use sewing machine oil)

Clean the header with something you know cannot get stuck of leave residue behind.(a can of air usually does the trick, if you do use that check it on something else if there is no moisture in the canned air.)

Thanks for the tip.
Update:

The hard disk is ok now, formatted without any bad sector(using Debug from another Hard Drive (using an IDE adapter))! But the Floppy drives are very bad, the heads are clean, but they don't read nothing! I'm willing to install Dos on the machine, but without a good drive this won't happen. The floppy drives don't have any mechanical problems, at least this is what I think.

Crypticalcode0
July 31st, 2012, 01:26 PM
can you hear the header move around and does the floppy spin after being inserted and locked?
What is the state of the electrolyte components in the power supply and on the board?(Capacitors, Elco's you should keep a close eye on when testing a system that hasn't been used in a long time)

lucasdaytona
July 31st, 2012, 01:47 PM
can you hear the header move around and does the floppy spin after being inserted and locked?
What is the state of the electrolyte components in the power supply and on the board?(Capacitors, Elco's you should keep a close eye on when testing a system that hasn't been used in a long time)


I cleaned the heads of the floppies for 15 times, one of them is fine now, the another is still bad. Both drives (mechanically) behaves good, like they should (Chapter 10 of IBM Personal Computer Troubleshooting & Repair - by Robert C. Brenner, a GREAT book.) The components on entire system are on good shape, in fact this system have a lot of hand writing sticks from factory quality tests, what mean that this system have never been jammed (I don't know the correct word, I want to say the system is in like factory shape, but dirt). I've managed to make a boot disc, and using an IDE drive I had almots loaded the entire RLL HD, even played Prince of Persia on it :cool:. The system is booting from floppy or hard drive, and I'm now trying to give some focus on the another parts, like deciding if it's safe to use the video card that came with the system using my spare monitor. I'm currently using one small CGA/printer card, with 16KB in video memory. The video card that came with the system have 64KB in video memory, and have a RCA connector and a DB-9, the monitor that came with it was an regular monochrome(green/black) 9 pin (that have sincro problems). Sadly the video card have no name or ID, and I have no way to read what is on her bios.

Crypticalcode0
July 31st, 2012, 02:04 PM
Lucasdaytona there are several ways to read a BIOS chip one is directly off the chip but can also be read from the bus or by the host system in several ways.

it's however wise to check if the addresses do not overlap if you want to use dual video card setup.

lucasdaytona
August 1st, 2012, 07:27 AM
can also be read from the bus or by the host system in several ways.


Could you please give me an exemple?

Crypticalcode0
August 1st, 2012, 09:11 AM
A dumb way to do it manually would to use Debug and load each address one by one from the ROM into a register and print them one by one.

I am not a software guy, give me a heap of IC's and I'll build you a working system.

lucasdaytona
August 2nd, 2012, 08:07 AM
The video card is a CGA with 64KB of video memory, just used some games and utilities to find out. The turbo mode is working perfect using the usual key combination. Just want to thank to everyone! I will post some pics very soon.

lucasdaytona
September 28th, 2012, 06:39 PM
After a long time, I got back to this computer. I'm having serious trouble with the floppy drives, tried the usual, cleaned heads, some oil on the trails, etc, but the drives doesn't work well. only one works, but with a lot of problems. The drive A: is the worse, almost never works. The drive B works sometimes, but only see 180KB of the disc, it can format 360KB, and the format.com says formatting 360KB, but I always get 180KB in total disk space. The computer could boot from the floppy drive, but happily the Hard Drive is 100%. What more I could try? I'm surely using reliable disks. I tested these disks on high density drives, with 100% of sucess.

patscc
September 28th, 2012, 06:44 PM
Dumb question, but are you using 360k disks, not 1.2M high-density ?
patscc

lucasdaytona
September 28th, 2012, 06:48 PM
I'm using 360k disks. I tested the 360k disks on high density drives, for read purposes only.

patscc
September 28th, 2012, 06:56 PM
The 180k might be only one head working.
When you do a format, does the head travel all the way, or does it look like it gets stuck ?
Which drive seems to work best, mechanically speaking ?
patscc

lucasdaytona
September 28th, 2012, 07:00 PM
The head travel all the way, without retention, in both drives. Also, the two drives are mechanically ok (the worse drive have a small repair in the door close mechanism, looks like the plastic broke, and someone did a repair).

patscc
September 28th, 2012, 07:20 PM
Is the termination pack correctly installed ?
patscc

lucasdaytona
September 28th, 2012, 07:25 PM
I don't see any termination pack in the drive, where should I look?
I'm using a cable that allows two drives, with a twist.
The drives have a lot of jumpers, with one clearly marked as drive number select. Drive A is set as number 1, drive B is set as number 2, there's no number 0.

patscc
September 28th, 2012, 07:56 PM
It's near the drive select jumpers.
http://upload.wikimedia.org/wikipedia/commons/d/d6/IBM_Floppy_Drive_With_DOS.jpg
It's the thing that looks like a blue chip.
While I'm at it, the connectors in the foreground on the right are the connectors to the actual heads. Do your drives have two connectors ?

patscc

lucasdaytona
September 29th, 2012, 07:15 AM
Only one drive have a terminaton pack, I put it on the end of the cable, set this drive as drive 1 (was drive 2), set the another as drive 2 (was drive 1), and then the miracle happens, the drive 1 is working ok, I was even able to do a six disk install of Indiana Jones, the drive 2 can't read anything. A few minutes latter, the drive 1 stopped working, I did a head clean, but still don't work. Now the head remain stuck, in both drives.
Some questions:

What this termination pack do? What drives should have it? I need to buy this (http://www.ebay.com/itm/5pk-8-x-4-7K-DIP-Resistor-Pack-D8X4-7KSP-/370624128395?pt=LH_DefaultDomain_0&hash=item564aeb658b)?

I've found the answers to my questions(termination pack) on earlier post (http://www.vintage-computer.com/vcforum/showthread.php?1671-IBM-360K-Floppy-T-RES-Terminator) by patscc, thanks!

lucasdaytona
October 2nd, 2012, 07:19 AM
I'm going mad here. I tried to clean the heads again, but this time I disassembled the heads, and did a great job, almost 30 minutes of cleaning, now the head is looking clean. I was able to read/write on some more disks, but when I do a format, I always get 180K per disk. I never heard of a double sided single density drive. I must assume that I have a software problem? I'm using MS-DOS 6.22.

patscc
October 2nd, 2012, 07:36 AM
And you've definitely got two heads, right ? What version of DOS are you using ?
patscc

lucasdaytona
October 2nd, 2012, 07:42 AM
Definitely two heads. Using MS-DOS 6.22.
If I use the /8 switch, it says formatting 160K, and then the disks get 160K
If I use the /1 switch it says formatting 180K, and then the disks get 180K
If I use no switch it says formatting 360K, and then the disks get 180K.
If I use /T:40 /N:9 it says formatting 360K, then says Parameters not supported, and exits.

patscc
October 2nd, 2012, 08:00 AM
Do you know how to use debug.com ?
patscc

lucasdaytona
October 2nd, 2012, 08:04 AM
I only used once, for entering into Seagate ST11R setup. I don't know how to use.

patscc
October 2nd, 2012, 08:23 AM
Try formatting like this: (assuming you're using a: )

format a: /U /C /F:360

patscc

lucasdaytona
October 2nd, 2012, 08:39 AM
Thank you man! Now it sees the full disk. I tried the /U in the past, but no luck, also the /F:360. I think that testing the clusters marked as bad did the trick!

Now I'm going to clean the other drive.

patscc
October 2nd, 2012, 09:27 AM
Glad it worked. Now, since you have DOS 6.22, run scandisk on it.

SCANDISK A: /AUTOFIX /NOSAVE /SURFACE /MONO

If you get prompted for an undo disk, continue without it. (You won't need the undo for a blank floppy).
The summery at the end will give you a nice indication of how everything's working.
patscc

lucasdaytona
October 2nd, 2012, 12:15 PM
I'm doing that, it's working like a charm.
I did the same cleaning process with the other drive, and now it works. It's very interesting that the heads (both drives) wasn't never disassembled(I removed the ink seal on the screw), the entire drive wasn't never really touched. This computer is from 1986~1988...

Keep in mind that I when I bough this computer, the seller said it was a 386 or a 286. And the computer was into a wet place and hot place, surrounded by mouse nests. I still don't believe that the computer worked, and the Hard Drive (don't have auto park) was perfect...

I'm uploading some pics, take a look folks!

10459104611046210463

lucasdaytona
October 4th, 2012, 05:11 PM
I'm having some trouble with EDIT.EXE, it hangs the computer. Anyone had this problem with any XT?

ibmapc
October 4th, 2012, 05:38 PM
I'm having some trouble with EDIT.EXE, it hangs the computer. Anyone had this problem with any XT?
I've seen this on my 5155. Can't remember what caused it. I'll see if I can make it happen again.
I seem to remember that EDIT requires QBASIC to run. Is QBASIC in the current directory (or a directory listed in your path statement) when you call EDIT.EXE?

patscc
October 4th, 2012, 07:19 PM
That's a neat looking clone. What's the game ? It looks familiar, but I can't quite place it.
Alternately, try running QBASIC and see if it loads. How much memory are you showing ?
If you need to just quickly edit a text file, you can use EDLIN, a bit of a pain, but in a pinch.
patscc

vwestlife
October 4th, 2012, 07:29 PM
I've seen this on my 5155. Can't remember what caused it. I'll see if I can make it happen again.
I seem to remember that EDIT requires QBASIC to run. Is QBASIC in the current directory (or a directory listed in your path statement) when you call EDIT.EXE?

The Windows 95 and newer version of EDIT requires a NEC V20/V30 or 286 or higher processor. If you try to run it on an 8088 or 8086 it will hang the system.

The MS-DOS 6.22 and older version of EDIT requires QBASIC.EXE to run, and in fact EDIT.COM does nothing more than call QBASIC with the undocumented /EDCOM switch. Thus typing QBASIC /EDCOM (must be in all caps) will bring up the MS-DOS Editor.

patscc
October 4th, 2012, 07:48 PM
Actually, why don't you try running edit /b
The /b forces edit to run in monochrome mode, and see what happens.

/EDCOM only came about with DOS 5.0

patscc

lucasdaytona
October 4th, 2012, 07:54 PM
Tried edit/b, also hangs. Tried QBASIC works ok, /EDCOM brings the EDIT! Thanks!

lucasdaytona
October 4th, 2012, 07:56 PM
That's a neat looking clone. What's the game ? It looks familiar, but I can't quite place it.
Alternately, try running QBASIC and see if it loads. How much memory are you showing ?
If you need to just quickly edit a text file, you can use EDLIN, a bit of a pain, but in a pinch.
patscc

The game is Prince of Persia! Runs great on turbo mode. MEM reports 736KB of conventional memory, dos uses 60KB, I have plenty of free memory :D!

patscc
October 4th, 2012, 08:03 PM
I wondering if you have a corrupt copy of QBASIC. You ran SCANDISK earlier with out any trouble, right ?
Yeah, Prince of Persia, that's it!
Try running DOSSHELL and see what happens.'
Oh, and you might want to try chkdsk on the floppy edit and qbasic are on.
Oh, also, try everything you already tried with TURBO mode OFF.
patscc

lucasdaytona
October 4th, 2012, 08:11 PM
Honestly, this DOS install is a real mess. I don't have any DOS in 5.25 disks, so I used a XT IDE with a hard drive from a 386 (installed dos 6.22 using 3.5 disks), then copied to the RLL hard drive, did a few things, and everything worked. Now that I have working 360K drives, I will put one drive on a 486, and make install disks from images. And thanks for the tip, I always test with TURBO OFF (and ON later xD).

patscc
October 4th, 2012, 08:17 PM
Okay, then I wouldn't worry to much about it until you get a clean and coherent dos version together. At least in the meantime you can play Prince of Persia !
patscc

lucasdaytona
October 4th, 2012, 08:23 PM
Yeah, I have more than 40 games in it!
By the way, does using TURBO ON does any harm? I have a 486 board that used to work ok with TURBO ON, but with time the board can't work with TURBO, everything hangs immediately.

vwestlife
October 4th, 2012, 08:23 PM
Tried edit/b, also hangs. Tried QBASIC works ok, /EDCOM brings the EDIT! Thanks!

Then you probably have the Windows 95+ version of EDIT.COM. The DOS 5.x/6.x version is only a few hundred bytes, since all it does is call QBASIC, while the Windows 95+ version is 69 KB in size, since it is a complete program all by itself, and does not require QBASIC.EXE to run.

lucasdaytona
October 4th, 2012, 08:30 PM
Indeed I have a EDIT.EXE, 69kb, dated year 94.
That was a headshot vwestlife, perfect aim ;).

patscc
October 4th, 2012, 08:46 PM
No, TURBO on doesn't really do any harm, some games might be odd; the suggestion was while we where still troubleshooting, now that the replies/posts and what not have all caught up, I've finally figured out what's going on, you should be all set.
patscc