Model IIs - Lots of Model IIs

[Gazza]

This is called "Modeltwoitis", a common ailment of big Tandy fans. It only gets worse as you age. I am already planning out the final resting spot for my heavier machines for when I retire.

I've been in a parallel universe since lugging these things around. It was dark when I got home and I couldn't be bothered shuffling cars up and down the driveway, so 1..2..3.. and up on the shoulder - still paying for it.
I'm too old, fat and bald for this.

Are you certain it doesn't have the plastic disc on one end instead of mylar? I don't see how the little plastic fingers on the plunger would be able to hold the pad if it was just mylar. Unless someone tried to rebuild the keyboard incorrectly in the past.

Correct Pete, one side looks to be ex-metalized mylar and the other side is slightly thicker.

Finally managed to take a pic of that mysterious PCB - still none the wiser.
Sorry about the quality of the pics but the cross-hairs on the camera were leaping all over the board - couldn't make-up it's mind what it wanted to focus on.

I was informed today that there is another HD to be repaired and that the collection of 8" floppies I was given is just a small part of what came with these computers - I think he sent you a few jpg's of what's available.

Next question - whats the best option on a 34 pin to 50 pin adapter?
I only have one copy of some of these disks, so the sooner I can get them on the HXC the better.
cheers
Gazza

 

[lowen]

...
Finally managed to take a pic of that mysterious PCB - still none the wiser.

Yeah, this one is new to me, too. Going by the 74LS240's on the board, it is some sort of output port. I haven't looked up the other chip numbers.

...
Next question - whats the best option on a 34 pin to 50 pin adapter?
I only have one copy of some of these disks, so the sooner I can get them on the HXC the better.
cheers
Gazza

NF6X's board, available on OSHPark. Minimum order is 3 boards. See the thread http://www.vcfed.org/forum/showthread.php?48252-Model-II-12-16-16B-6000-8-quot-to-5-25-Inch-floppy-adapter-cable-50-pin-to-34-pin and the Github repository of the design at https://github.com/NF6X/fd50to34. The thread contains links to the OSHPark order page; I ordered three a while back, but haven't built them yet.

 

[Druid6900]

I've been in a parallel universe since lugging these things around. It was dark when I got home and I couldn't be bothered shuffling cars up and down the driveway, so 1..2..3.. and up on the shoulder - still paying for it.
I'm too old, fat and bald for this.

Having worked for Radio Shack Canada as a service depot manager, and worked all the way through the era of the Tandy Business machines, I can tell you that age, weight and hair possession had no bearing on how fast those suckers ruined your lower back...LOL

Finally managed to take a pic of that mysterious PCB - still none the wiser.

That board is a mystery to me as well, and wasn't a Tandy product that I'd ever seen.

Some tips to get the floppy drives (the single sided Shugarts in the main unit and the CDCs in the expansion bays) working well is to swing the head load button arm carefully aside and clean the heads with denatured alcohol several times. The head load buttons themselves (Shugart) can be removed (pinch the two molded "ears" together and it should pop out the front of the arm), rotate it 180 degrees and re-install. It should work like a brand new one because only one edge of it wore down.

On the CDC, I recall something holding it in the arm, so loosen whatever it is, stick a small screwdriver in the slot of the headload button and rotate it 180 degrees for the same reason.

Now, any Mod II has to have either an expansion bay attached (powered on before the computer) or a terminator pack plugged in where the cable from the expansion bay would be attached to operate correctly. The terminator pack looks like a small black and brown harmonica.

With those Shugart 8 MB hard drives, there is a, I'd say, 3 inch diameter screw on plate that contains the physical drive lock plate and the terminator chip that has to be removed if you are adding a secondary hard drive.

As a rule of thumb, power up is all peripherals first and computer last. Power down is the reverse of that.

Hope this helps with your recover of this equipment.

 

[pski]

Now, any Mod II has to have either an expansion bay attached (powered on before the computer) or a terminator pack plugged in where the cable from the expansion bay would be attached to operate correctly. The terminator pack looks like a small black and brown harmonica.

This is only true with the early floppy drive controller. The revised FDC eliminates the need for the terminator if the expansion bay is not attached. I'd say maybe 1/2 of the Model IIs out there have the revised FDC. You can tell if you have the revised FDC by looking for an unpopulated 34 pin J1 connection on the board.

 

[Druid6900]

This is only true with the early floppy drive controller. The revised FDC eliminates the need for the terminator if the expansion bay is not attached. I'd say maybe 1/2 of the Model IIs out there have the revised FDC. You can tell if you have the revised FDC by looking for an unpopulated 34 pin J1 connection on the board.

That is, indeed, true. There was an FDC board redesign, however, replacement in the Model II, which had stopped selling by that time, was not mandatory. I think the number of Model II systems with the new FDC was considerably less than 50% since they still had all those original boards in the replace/refurbish system

The new FDC didn't go into mainstream until the advent of the Model 12 and, if used in a Model II, required a number of modifications to the cardcage motherboard and, I believe, one of the other boards, depending on what was installed in the Model II.

If one or more of those systems were bought with the 8 megger Shugart, then they probably have the original FDC card and would need the terminator or expansion bay attached.

The easiest way to find out is to turn the Model II on with nothing attached to the expansion port and if you get "insert diskette" you're good.

I have the boot error codes around somewhere and I'll look up what you get if you need an expansion bay (or it isn't powered up) or terminator plug when I get the chance.

 

[pski]

That is, indeed, true. There was an FDC board redesign, however, replacement in the Model II, which had stopped selling by that time, was not mandatory. I think the number of Model II systems with the new FDC was considerably less than 50% since they still had all those original boards in the replace/refurbish system

The new FDC didn't go into mainstream until the advent of the Model 12 and, if used in a Model II, required a number of modifications to the cardcage motherboard and, I believe, one of the other boards, depending on what was installed in the Model II.

If one or more of those systems were bought with the 8 megger Shugart, then they probably have the original FDC card and would need the terminator or expansion bay attached.

The easiest way to find out is to turn the Model II on with nothing attached to the expansion port and if you get "insert diskette" you're good.

I have the boot error codes around somewhere and I'll look up what you get if you need an expansion bay (or it isn't powered up) or terminator plug when I get the chance.

The revised FDC was introduced sometime in 1981 so there's a good year or so of Model II production that probably included them. The tech bulletin describing it is dated July 1981. I imagine some of the earlier Model IIs brought in for service were upgraded to the new FDC too, but like you said it wasn't a mandatory upgrade.

Regardless, it's definitely the preferred FDC for your Model II so those that have one are lucky!

 

[NF6X]

My II isn't in a convenient position for me to examine it right now, but I assume that it must have the newer FDC. I don't have a drive terminator plug, and I can boot the system without an external drive bay plugged in.

 

[Chuck(G)]

My model 16 (basically a model II with the 68K add-in) has the revised floppy board with the 34-pin unpopulated header. Stick a real header in there and jumper a couple of pads and you can use PC-type 3.5" drives in one.

 

[pski]

My model 16 (basically a model II with the 68K add-in) has the revised floppy board with the 34-pin unpopulated header. Stick a real header in there and jumper a couple of pads and you can use PC-type 3.5" drives in one.

Yes, by the time of the Model 16 release in 1982 the revised FDC was used exclusively. I've thought about soldering in a 34 pin header in the past but was afraid of ruining a good FDC card with my soldering. I've more practice now so I may revisit that option.

 

[Druid6900]

The revised FDC was introduced sometime in 1981 so there's a good year or so of Model II production that probably included them. The tech bulletin describing it is dated July 1981. I imagine some of the earlier Model IIs brought in for service were upgraded to the new FDC too, but like you said it wasn't a mandatory upgrade.

Regardless, it's definitely the preferred FDC for your Model II so those that have one are lucky!

However, the company policy, at the time, was to replace the FDC board in the Model II with the original FDC board unless you didn't have any and only then were you supposed to do the mods and use the newer FDC.

This was recommended when doing on-site work as the customer didn't want to wait while you did the mods to be able to use the redesigned board. It was fairly time consuming and required an extensive tear-down of the unit.

I made sure we had a number of the older FDCs on hand even if we had to mod in-shop warranty machines to get them. Our original Model II test machine was the first to donate its original FDC.

The new board did have it's plus side as it was easier to align and because the first thing to be lost with a Model II (with and expansion bay) was the terminator. This meant that, even if it was your bay that went down, without the terminator (for the original card), you weren't going to be doing anything. I used to keep a few terminators in stock to loan to customers if that situation arose.

 

[Gazza]

Lowen, thanks for the links, NF6X, thanks for the design, just waiting on the OK to buy the parts. He wants 'me' to build 10 boards. Oh well, my soldering skills were getting rusty.

Druid6900
That board is a mystery to me as well, and wasn't a Tandy product that I'd ever seen.
Yep got me stumped. Tis a company in Anaheim, CA called ACTPCB - don't know if they had anything to do with it.

The drive had a short to gnd on the supply so while I was tracking down the offending component I gave it a good service.
Some of the other drives are going to take more work. A couple look to have seized spindle motors, hoping that they will respond to a bit of TLC.

A pic of the FDC card that's in the Model II.
According to the link below it's a Rev C card and it was connected to an external floppy but "seems" happy running without the terminating pack.

http://fjkraan.home.xs4all.nl/comp/trs80m2/ModelIIBusCardZoo.html

 

[MicrocomputerSolutions]

Lowen, thanks for the links, NF6X, thanks for the design, just waiting on the OK to buy the parts. He wants 'me' to build 10 boards. Oh well, my soldering skills were getting rusty.

Druid6900
That board is a mystery to me as well, and wasn't a Tandy product that I'd ever seen.
Yep got me stumped. Tis a company in Anaheim, CA called ACTPCB - don't know if they had anything to do with it.

The drive had a short to gnd on the supply so while I was tracking down the offending component I gave it a good service.
Some of the other drives are going to take more work. A couple look to have seized spindle motors, hoping that they will respond to a bit of TLC.

A pic of the FDC card that's in the Model II.
According to the link below it's a Rev C card and it was connected to an external floppy but "seems" happy running without the terminating pack.

http://fjkraan.home.xs4all.nl/comp/trs80m2/ModelIIBusCardZoo.html

When the spindle motor seizes on a Shugart SA800 or SA850, the least expensive solution here in the US is a replacement spindle motor. The bearings in the spindle motors live long service lives and when the bearings seize/go, it's time to replace the motor. Taking the motor off the chassis and forcing it to rotate can free it up enough to turn temporarily, but once the bearings seize, they are done. Even if you get them to turn, they will not continue to turn with a load on them. Good used motors currently sell for about $50 with the 50hz pulley, and I don't think you could buy high quality ball bearings, disassemble the motors, and replace the bearings for the same $50.

I have about 6-8 220V motors with 50hz pulleys in stock if you need to buy some. The 50hz motors that I come across on drives here in the US don't have much time on them, because here in the US we don't even have 220V 50hz. The motors usually come out of drives that people bring in for service because they bought them and they don't work. Duh, the 220vac 50hz spindle motor is turning at the wrong speed, and the index pulse and timing will be out of spec on 110vac.

 

[pski]

However, the company policy, at the time, was to replace the FDC board in the Model II with the original FDC board unless you didn't have any and only then were you supposed to do the mods and use the newer FDC.

This was recommended when doing on-site work as the customer didn't want to wait while you did the mods to be able to use the redesigned board. It was fairly time consuming and required an extensive tear-down of the unit.

BTW, thanks, I love these stories from the trenches from back in the day. You guys should write a book about your experiences!

I was perusing the MII tech bulletins last night and II:1 and II:30 mention a number of jumper mods that were necessary for the early FDC to work properly. Apparently, the revised FDC fixed the need for the mods so the steps to get the revised FDC working on an early MII are to remove the jumper mods. It seems that at a minimum you needed to pull the floppy drive to get access to the logic board which is where most of the mods were. This definitely is a significant job on the MII.

 

[pski]

Druid6900
That board is a mystery to me as well, and wasn't a Tandy product that I'd ever seen.
Yep got me stumped. Tis a company in Anaheim, CA called ACTPCB - don't know if they had anything to do with it.

It's very interesting that the board is labelled TRS-80 MODEL I. Curious how many pins are on that header? Also, would you have a shot of the opposite side of the board too? That would help in reverse engineering it.

A pic of the FDC card that's in the Model II.
According to the link below it's a Rev C card and it was connected to an external floppy but "seems" happy running without the terminating pack.

http://fjkraan.home.xs4all.nl/comp/trs80m2/ModelIIBusCardZoo.html

I believe the significant issue with the older FDC was not necessarily that it would not work. I remember reading that if you turned off the computer with a floppy in the drive 0 and no expansion unit turned on or terminator installed then Track 0 on Disk 0 would get zapped thus rendering your DOS floppy disk no longer usable. It was apparently a cause of much pain early in the Model II lifetime.

 

[Gazza]

They measure 11mm and are around 5mm thick. Maybe 4.8mm thick once the flat adhesive pads are removed.

I might be able to send you a few to try out if you like?

Hope this helps.

Ian.

Hi Ian
Postie bought me an early XMAS present and express post too - thanks, I owe you one, actually the big "E" owes you one.
thanks
Gazza

 

[Gazza]

I have about 6-8 220V motors with 50hz pulleys in stock if you need to buy some. The 50hz motors that I come across on drives here in the US don't have much time on them, because here in the US we don't even have 220V 50hz. The motors usually come out of drives that people bring in for service because they bought them and they don't work. Duh, the 220vac 50hz spindle motor is turning at the wrong speed, and the index pulse and timing will be out of spec on 110vac.

Will keep you in mind, we may need one or two down the track. Be a while before I get to those computers.
thanks
Gazza

 

[Gazza]

It's very interesting that the board is labelled TRS-80 MODEL I. Curious how many pins are on that header? Also, would you have a shot of the opposite side of the board too? That would help in reverse engineering it.



I believe the significant issue with the older FDC was not necessarily that it would not work. I remember reading that if you turned off the computer with a floppy in the drive 0 and no expansion unit turned on or terminator installed then Track 0 on Disk 0 would get zapped thus rendering your DOS floppy disk no longer usable. It was apparently a cause of much pain early in the Model II lifetime.

1 pic as requested

 

[pski]

1 pic as requested

Anyone please correct me, but this looks like a rudimentary IO interface adapter. It exposes the 8 data lines and maybe? 7 bits of the lower address byte to a 34 pin header. There is some IOCYC/RD/WR routing going on there but I didn't take time to figure that out. The switches seem to not be hooked up so I think they are non-functional. This must have been for a specific custom accessory. I'm not sure how useful it is as a general IO interface adapter as I don't think it passes the entire lower address byte or the RD/WR/etc. signals.

 

[Gazza]

Update
We now have a fully functioning keyboard.
A roll of self-adhesive open cell foam, a tube of Kwik-Grip, some anti-static bags, an 11mm hollow punch, a big hammer and a good supply of alcohol got the job done.
Many brain cells made the ultimate sacrifice to get this keyboard running.:rip:
1 down, 4 to go.

The floppy decided to play up and wouldn't recognize when a disk was inserted. A quick once over showed the door switch was OK and as quick as it went bad it fixed itself and hasn't missed a beat since.:wallbang:

The slow boat from China has finally docked with all the bitsn'pieces, so I've begun building some of Mark's fd50to34 adapters.

I dismantled the first hard drive only to find it has been got at. The spindle lock wasn't locked, probably a bit late in the day to worry about it now but I put it in it's locked position. Self-tapping screws to hold the boards in place instead of machine screws, threads stripped, jumper pins and test point pins bent, some shorting together - must have been repaired at the local Tandy service centre.:wink:

The two grenades were changed and it was given a good clean and inspection with MK1 optics.
Powered it up, no smoke, funny smells or noises - YET.

I connected the HD to the Model II but unfortunately I'm getting a HN ERROR
HN error is - ID not found, No Boot Track, Re-INIT Hard Drive.
Will try a reformat when I get the HxC connected.
More research (beer) required.

Gazza

 

[pski]

I love the sticker over the power port on the HD! I made the mistake once of powering up with the lock on and couldn't figure out why the disk wasn't spinning for a minute or so. Thankfully, no long term damage. Also, I have one of these that I bought that came without a locking tab engaged and it worked, so you may get lucky.