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fatwizard
December 29th, 2013, 09:18 PM
I bought this Tandon PC XT clone on eBay as a Christmas present to myself. I knew Tandon got into building PC's in the 80's, but I had never seen one. This one is a model TM 6005, made in 1987 (stamped inside the top cover),and it sports 640K, a floppy controller and a parallel port on the motherboard. It has a DSDD 360K TM65-2L floppy drive and a TM262, 20 meg ST506 hard drive. It was filthy, but all in one piece and not banged up. A quick look over and I tried powering it up.

It fired right up and posted normally, but the hard drive only made a small tick sound, and did not spin up. I removed the floppy drive for later cleanup. Attached a test drive I use on the bench, and set out to restore the hard drive to service. A nudge of the spindle let her spin up, and I tried the WD40, then light oil soak on the stepper and was successful in getting it seeking. I massaged it endlessly trying to get the Tandon branded DOS copied from the drive to floppies. I was finally successful, and found later that it was more necessary that I realized. The hard drive controller looks like a stock WD1002A-WX1, but it turns out to have a proprietary BIOS installed.

This meant that the typical drive prep wouldn't work (Debug g=c800:5 did not start the low level format routine). The DOS directory contained the Tandon utilities for hard drive prep, so I dodged that bullet. I might have gotten SSTOR or some other utility to do the job, but it was nice to have the original software. The system is a little odd in some ways, but not as odd as a Tandy or a PS/2, and it has clean styling, if a little dull.

To the "issues" I mentioned in the title. The display adapter doesn't light up the monitor (I put a 16bit, 8bit compatible VGA card in it). The floppy drive cleaned up well, and after my typical workover, it seemed to operate normally (if a little noisy), but I soon discovered that it would occasionally stop during long reads or writes and throw up a "Drive not ready" error. Hitting "Retry" would send it on it's way again and it would finish whatever it was doing. I then discovered that it will not format a disk. It whirs away for a while at head 0, track 0, then says "Format Failure Do you want to format another? Y/N" The test drive formats normally. I've never had a drive act like that really, and I don't have a clue what might be wrong with it. If anyone has any insight on this format issue, I would be very grateful, cause the little guy is just about perfect otherwise.

1661116612

SomeGuy
December 29th, 2013, 10:29 PM
floppy drive cleaned up well, and after my typical workover, it seemed to operate normally (if a little noisy), but I soon discovered that it would occasionally stop during long reads or writes and throw up a "Drive not ready" error. Hitting "Retry" would send it on it's way again and it would finish whatever it was doing. I then discovered that it will not format a disk. It whirs away for a while at head 0, track 0, then says "Format Failure Do you want to format another? Y/N" The test drive formats normally. I've never had a drive act like that really, and I don't have a clue what might be wrong with it. If anyone has any insight on this format issue, I would be very grateful, cause the little guy is just about perfect otherwise.

Check for a proper index pulse output.

I just got done diagnosing a half height 360k drive that has a bad index IR receiver. (That is the sensor that detects the index/tracking hole near the center of the disk) The symptoms were that it could read and write a disk more or less OK but formatting would fail with a "drive not ready" or similar error, without writing anything to the disk at all.

In my case the IR receiver was bad (does anyplace sell a compatible part?), but the index pulse could also fail due to dirt on the emitter or receiver, a bad connection, or failure in the related electronics.

mikey99
December 30th, 2013, 11:49 AM
I have an IBM 5155 Portable PC that had a Tandon TM262 installed. I also recall it took a lot of patience to be able
to copy the contents off onto a parallel port zip drive. I was never able to get that TM262 to work reliably.

modem7
December 30th, 2013, 02:12 PM
In my case the IR receiver was bad (does anyplace sell a compatible part?),
When restoring an 8" floppy drive (Tandon TM848), I accidentally broke a lead off the index receiver. I was surprised to discover that the receiver, an SD5421-002 photodiode, was still readily available (as well as the matching transmitter).

Unknown_K
December 30th, 2013, 04:23 PM
It is a cool looking machine, hope you get it 100% working.

Agent Orange
December 30th, 2013, 04:28 PM
I bought this Tandon PC XT clone on eBay as a Christmas present to myself. I knew Tandon got into building PC's in the 80's, but I had never seen one. This one is a model TM 6005, made in 1987 (stamped inside the top cover),and it sports 640K, a floppy controller and a parallel port on the motherboard. It has a DSDD 360K TM65-2L floppy drive and a TM262, 20 meg ST506 hard drive. It was filthy, but all in one piece and not banged up. A quick look over and I tried powering it up.

It fired right up and posted normally, but the hard drive only made a small tick sound, and did not spin up. I removed the floppy drive for later cleanup. Attached a test drive I use on the bench, and set out to restore the hard drive to service. A nudge of the spindle let her spin up, and I tried the WD40, then light oil soak on the stepper and was successful in getting it seeking. I massaged it endlessly trying to get the Tandon branded DOS copied from the drive to floppies. I was finally successful, and found later that it was more necessary that I realized. The hard drive controller looks like a stock WD1002A-WX1, but it turns out to have a proprietary BIOS installed.

This meant that the typical drive prep wouldn't work (Debug g=c800:5 did not start the low level format routine). The DOS directory contained the Tandon utilities for hard drive prep, so I dodged that bullet. I might have gotten SSTOR or some other utility to do the job, but it was nice to have the original software. The system is a little odd in some ways, but not as odd as a Tandy or a PS/2, and it has clean styling, if a little dull.

To the "issues" I mentioned in the title. The display adapter doesn't light up the monitor (I put a 16bit, 8bit compatible VGA card in it). The floppy drive cleaned up well, and after my typical workover, it seemed to operate normally (if a little noisy), but I soon discovered that it would occasionally stop during long reads or writes and throw up a "Drive not ready" error. Hitting "Retry" would send it on it's way again and it would finish whatever it was doing. I then discovered that it will not format a disk. It whirs away for a while at head 0, track 0, then says "Format Failure Do you want to format another? Y/N" The test drive formats normally. I've never had a drive act like that really, and I don't have a clue what might be wrong with it. If anyone has any insight on this format issue, I would be very grateful, cause the little guy is just about perfect otherwise.

1661116612

Hey Wiz.

Anything that pretty has just got to work. Good job of making it presentable. Good luck on the mechanics.

fatwizard
January 1st, 2014, 02:27 PM
Hello all, and Happy New Year!

A quick update. I tore the floppy drive down looking for hidden dust collections that might interfere with the index system. I found no such issues however. I did do an ohmmeter check on the infrared diode emitter, and found it open! This pointed right to what SomeGuy though might be the problem. I have a couple of Tandon TM100-2 drives that are parts mules, so I robbed an emitter form one of those. This one tested as I would expect a good LED to test (open with one polarity, a few hundred ohms with the polarity reversed). It wasn't exactly like the original, but it fit the hole and wired up the same.

So, I connect the drive full of promise that it's repaired only to find it will now only spin when selected, seeks to the innermost track and back to zero and nothing else. Won't boot, won't read (gives a "Drive Not Ready" error).

Well, so much for my repairs. Some wizard, huh. I will be putting the original part back in it tonight in case there is something about it I don't understand, but I would really like to do more definitive testing. Trouble is I can't find any service info on this model drive. I have found such for the TM100 series and the TM50's, but nothing but a user manual for the TM65's. I don't know what test points are what on this thing. If anyone has, or can point me to some info on the drive, I would be so grateful.

I want to thank all the responders to this post, and all the members period. I have always worked alone, and as such I never had anyone to ask questions of. This forum has been just the greatest thing for me. You all have been welcoming and tolerant of me, and I can share my enthusiasm for our hobby, and share expertise with others of similar stripe. Thanks!

modem7
January 1st, 2014, 05:27 PM
It wasn't exactly like the original, but it fit the hole and wired up the same.
Different photodiodes can have differing electrical characteristics. Examples: Frequency of operation, receiver bandwith, normal versus darlington pair, amount of light used, ...

SomeGuy
January 1st, 2014, 05:53 PM
Did you test the output of the index pin (pin 8) on the floppy connector during operation? A logic probe should visibly show the signal pulsing a few times a seconds.

Can't think of what might be causing that new problem. Perhaps something with the track zero sensor now? Those may use the same kind of sensor and related circuits. Also easily testable with a logic probe.

fatwizard
January 1st, 2014, 06:02 PM
I had suspected as much about the photodiode, but though it might work anyway, and I had it on hand (big temptation for me). I returned the original diode to the drive, but no avail. I really think it's open, but the drive mostly worked before I removed it. I've poured over this thing a bunch looking for something I did to it to cause it to fail completely, but I can find nothing. This drive is desirable because it's faceplate matches the color of the rest of the system. This could end with me sourcing another TM65 and swapping the faceplate (the others I have seen were black). So I am still seeking some service info (mostly test point ID's). I have more luck repairing old hard drives than I do old floppy drives. That seems backwards

Modem7, I see you are in Melbourne Australia. I left my favorite hat in the airport there 4 years ago when I passed thru on my way to Sydney to visit family. What an incredible place Australia is!

modem7
January 1st, 2014, 07:36 PM
Modem7, I see you are in Melbourne Australia. I left my favorite hat in the airport there 4 years ago when I passed thru on my way to Sydney to visit family.
What a coincidence. Slightly less than 4 years ago, I bought a 'Fat Wizard' hat in a Lost & Found auction at Melbourne Airport.
But I then lost it at Indianapolis International Airport whilst travelling through the US.

:)

fatwizard
January 3rd, 2014, 12:32 AM
Too bad cause I'll bet you looked good in it mate. I know I did. :cool:

wesleyfurr
January 14th, 2014, 06:19 PM
I wonder if this machine might be the same thing as the Tandy 1200...I know it was made by Tandon...?

Wesley

fatwizard
January 15th, 2014, 02:23 AM
I wonder if this machine might be the same thing as the Tandy 1200...I know it was made by Tandon...?

Wesley

Spot on Wesley! I don't have access to a Tandy 1200, but I found a YouTube video of one and it is almost identical. The case cover has some minor cosmetic differences, but the frame is just like mine, as well as the power supply. The motherboard is very similar from what I can see in the video. Looks like the parallel port and floppy controller headers are in different positions, and the memory chips are socketed on the Tandy, but soldered in on the Tandon, but they are obviously made by the same manufacturer.

The Tandon accepts a standard PC/XT keyboard, but I assume the Tandy used their proprietary design instead. This is quite a revelation for me. It gives me a new search path as I'm trying to source service information on, or a replacement for the floppy drive. The Radio Shack dealer here in town is a good friend and business partner of mine, and tomorrow I will have many questions for him. :D

vwestlife
January 15th, 2014, 04:46 AM
After taking a lot of criticism for the Tandy 2000's lack of IBM PC compatibility, Radio Shack sold the Tandon-made Tandy 1200 / 1200HD as their 100% compatible "mirror image" clone of the IBM XT. The first version of it only had 5 ISA slots, but a newer revision of it has 7 slots. As far as I know it uses a standard IBM PC / XT keyboard interface.

kb2syd
January 15th, 2014, 05:34 AM
After taking a lot of criticism for the Tandy 2000's lack of IBM PC compatibility, Radio Shack sold the Tandon-made Tandy 1200 / 1200HD as their 100% compatible "mirror image" clone of the IBM XT. The first version of it only had 5 ISA slots, but a newer revision of it has 7 slots. As far as I know it uses a standard IBM PC / XT keyboard interface.

Yes, the 1200 does use a standard XT keyboard.

Havoc
January 15th, 2014, 11:08 PM
I have a running Tandy 1200, your specs & case are similar to mine. Just that all my drives are black faced & my 1200 came with a Tandon 10M HD. I can take pictures of her inside and out to compare. The fact that it has a date stamp realativley close to the same year as the date stamp of my Tandy (Tandon) 1200, (1 year later) would lead me to believe it is the same computer. I find it unusual that Tandon would build 2 different XT's clones just 1 year apart. My 1200 has a original working 8 Bit Sound Blaster Card. I can run Debug on it (G=C800:5} to format my 10M. It has a older WD HD controller. So far it runs all software that runs on my IBM 5150.

Havoc

bettablue
January 19th, 2014, 05:39 PM
That's not a bad looking computer. I hope you get the drive issues resolved and hope to see some pics of it in operation. I'll be following this post too, because I'm working on something similar with my IBM 5160 XT, so your results could be what fixes mine as well.

Nice Christmas gift. Good luck.

Havoc
January 25th, 2014, 07:03 AM
I finally posted my pictures of my 1200 in my Yahoo groups, I hope this link works. link here:

http://groups.yahoo.com/neo/groups/TandyThousands/photos/albums/2130491588

I have made some minor changes to the 1200 since these pictures, all that info is in the description to each photo. After looking the systems look the same as your Tandon. My biggest problem now is the Everex Memory Expansion I/O card. The EV-100, I can find no docs for it anywhere. I want to disable the second LPT port, my Sound Blaster card hates it. I was able to find a clock driver using a old Everex Magic I/O driver. It still holds a charge after all these years.

fatwizard
January 27th, 2014, 11:45 PM
Sorry to take so long returning to this thread, but life is very distracting sometimes. Havoc, your Tandy 1200 is just the spitting image of the little Tandon! I have a different set of expansion cards, but the computer is, as near as I can tell, identical.

One of the delays in posting was my ongoing attempts to repair the floppy drive. I am sad to report absolutely no progress on that front (sorry Thomas). My Radio Shack dealer friend told me the 1200 was not generally offered to franchise dealers, and he never got permission to sell it, as Tandy corporate favored it's wholly owned stores (just crazy). This means he has no service information in his archives for that model.

I was unsuccessful in tracking down any service info, and I just couldn't get anywhere with repairs. The floppy is the only issue left unresolved, but, I got lucky (I think) and bought a TM65-2L drive off eBay just tonight for less than $30 with shipping. I don't really know what it's like as there were no pictures, so I keeping my fingers crossed. I had seen a couple of others on eBay but the cost was "out of sight". All of them I have seen so far have been black faced, and I won't be surprised if the one I snagged is too. I can handle the change of faceplate and lever though.

If repairs are successful, I'll run some photos up the flagpole of her in action, and give her a run at Trixter's Topbench. One of the perks to getting this machine is now, in a way, I have my first Tandy as well!

fatwizard
January 27th, 2014, 11:50 PM
Sorry to take so long returning to this thread, but life is very distracting sometimes. Havoc, your Tandy 1200 is just the spitting image of the little Tandon! I have a different set of expansion cards, but the computer is, as near as I can tell, identical.

One of the delays in posting was my ongoing attempts to repair the floppy drive. I am sad to report absolutely no progress on that front (sorry Thomas :(). My Radio Shack dealer friend told me the 1200 was not generally offered to franchise dealers, and he never got permission to sell it, as Tandy corporate favored it's wholly owned stores (just crazy). This means he has no service information in his archives for that model.

I was unsuccessful in tracking down any service info, and I just couldn't get anywhere with repairs. The floppy is the only issue left unresolved, but, I got lucky (I think) and bought a TM65-2L drive off eBay just tonight for less than $30 with shipping. I don't really know what it's like as there were no pictures, but I have bought stuff from these people before with good results, so I am keeping my fingers crossed. I had seen a couple of others on eBay, but the cost was "out of sight". All of them I have seen so far have been black faced, and I won't be surprised if the one I snagged is too. I can handle the change of faceplate and lever though.

If repairs are successful, I'll run some photos up the flagpole of her in action, and give her a run at Trixter's Topbench. One of the perks to getting this machine is now, in a way, I sort of have my first Tandy as well!

Havoc
January 31st, 2014, 12:40 PM
Since the computers are exact, you can get at least the board dip switch settings here:

http://support.radioshack.com/support_computer/doc1/1962.htm

Unfortunately there is no information on the stock Multi I/O Ram card. Which for me is a problem since I can not adjust Com or Printer ports.
So far my searching has found at least this much information. The cards can go by one of three names. All of which lead to dead ends.

1. Modular Circuit Technology MCT-MF
2. Everex EV-100
2. CRD-RAMXT384 MF

Havoc