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Just got a TRS-80 Model III, and I have questions


DistantStar001

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I just got a TRS-80 (Trash-80, not Coco) Model III, and I have some questions.  It is in somewhat rough shape, but, cosmetically, the case is intact, with a few scratches and wear marks.  The nameplate between the disk drives is missing. Also missing is the ",<" keycap and the stem to the switch is broken off. Which leads to my first question: Where do I get a replacement switch? If it helps, the original owner left a note in the keyboard identifying the part number as AS-7567. I suppose question two is: Where can I get a new keycap?

 

Operationally, I really can't say much, as it failed its smoke test just as I was writing this. Nothing serious, one of those notorious yellow safety caps blew out with a fizzle and a lot of bad-smelling smoke. However, the computer itself was still going when without a problem when I turned it off. Still, I think I'll replace them (there's another that seems fine, but why risk it) before I power it up again.

 

On power-up, the computer did boot from the lower floppy drive (marked "Drive 0") and loaded the TRSDOS system disk that came with it. However, the drive makes a loud high-pitched grinding noise when in use. Question three: Will lubricating the drive fix this?  So far, I haven't tested the upper drive ("Drive 1"), but it does light up, and DOS recognizes that the drive is there. 

 

On the keyboard, the following keys are nonfunctional: "E", "T", "Back Arrow", "S", "C", "V", "B", ".>", "/?" and the "Enter" key on the main keyboard (however, the one on the numeric pad does work). The "Up Arrow" and "Down Arrow" keys cannot happen confirmed.  I'm assuming that some alcohol or contact cleaner might bring these keys back?

 

When powered on without a floppy in Drive 0, all I get is a blank screen (no BASIC prompt). Honestly, I wasn't sure if this machine even has BASIC, but Google seemed to suggest that it should. Which leads me to my fourth question: Does this even have BASIC?  No big deal if it doesn't, but I'd like to know.  Maybe there's some sort of key combo or something to get there?  

 

My last questions are: How do I get software off the internet and on to disk for this thing? But obviously, I need to get it fully working first.  Also, What software and accessories would you recommend?  Can't wait to see what this thing can do!

 

That's it for now, thanks for reading, and any help would be appreciated. ?

 

One last question: Where can I find a replacement name badge?  I'd like it to proudly display it's "TRS-80 MODEL III" badge again!

 

Edited by DistantStar001
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The Model III has the same Level II BASIC as the Model I with some small exceptions. 
The CPU is a little faster, so things like timing loops are different (cassette).
The hardware supports lower case, and some hardware was moved from memory mapped to the Z80 IO space if I remember right, so it was modded to support that.
Seems to me there were a couple other differences, but I can't remember what they are.

It should be able to go to BASIC without booting the DOS (hit the reset button?), but I haven't touched one since 1983, so...

I think there is a torrent with software for the model III, there are a few pages dedicated to the TRS-80s with software, but I don't frequent them so I don't know where to send you.
There is a discord server here:  https://discord.gg/mWYezW
 

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Hold down BREAK while turning on or pressing the orange reset to go into BASIC.

 

It's going to have one of two different ALPS keyboard.  One style has keys soldered in with two legs and the other 4 legs.  The one with the stem broken off will need to be replaced and if it has 4 soldered legs, you'll probably have a hard time finding a replacement.  If it has 2 legs, I should have a spare I can send you.

No matter which you have, you'll need to unsolder each key, disassemble it and clean the bottom contact point with something like a pencil erasure where the carbon pad makes contact.  DO NOT JUST REMOVE THE KEY CAPS AND TRY TO WORK IN CONTACT CLEANER!  It will destroy the carbon pads in the later style keys with 4 legs and I wouldn't try it on the older 2 leg keys either.  It did work great on my old 2 leg keys, but when I tried it on a late Model III with 4 legs, I ruined a bunch of keys.

Also, the keyboard circuit board can develop cracks, especially from the center which can take out a vector of keys.  Easy to repair with jumper wires if needed.

 

Jay Newirth will most likely have everything you need.  http://plaidvest.com/newsoft/ 

Very nice guy and his prices are more than reasonable.  At the 2018 Tandy Assembly, he was giving away free key caps.  He also has excellent repro emblems.

 

Disk drives probably need to be taken apart and gone through.  Definitely need to clean any old hardened grease from the rails and re-lube.  The fact that it boots from a disk is a good sign.

 

Getting files off the internet and onto the III is a chore.  You can download them to your PC and then attach your III to the PC with a null modem cable.  You'll need a host program on the PC and a terminal program on the III and then download like an old school BBS.

 

FreHD is basically a modern hard drive for the III that uses an SD card.  You can copy cmd files onto the card from your PC and then pop the card into the FreHD and use the import2 command and they'll show up.  A FreHD setup is around $130 and a must have imo.

Orchestra 90 is really cool but difficult to find; however, Ian Mavric makes new ones (along with FreHD kits).

The ultimate cool accessory is the hi-res graphics card (see my avatar) but good luck find one.  Had a search string setup on eBay for years with no luck, but managed to buy one from Jay at the 2018 Tandy Assembly.

 

Here's a pic of my FreHD on the top case.

 

Edit...

You can get the replacement X capacitors from Digi-Key the part # is: 399-7483-ND

 

 

trs10.jpg

Edited by Turbo-Torch
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So I replaced the safety caps (took a while since I had to practically take the whole thing apart to get at the cap that blew), switched it on and so far it seems to be working as it did before.  However, the screen seems to dim periodically.  So I'm guessing that further recaps will be necessary.

 

I can also safely say that I am not the first to open this thing, as there appears to be a screw missing on the lower disk drive (screen side), and the hole for the screw on the upper drive (case side) is stripped.  No biggie.  I'm sure this thing has had a long full career.  So there should be a few blemishes and such.  It boots, and seems to work, and that's what matters!

5 hours ago, JamesD said:

There is a discord server here:  https://discord.gg/mWYezW

Thanks!  I just signed up and am having fun exploring!

5 hours ago, JamesD said:

It should be able to go to BASIC without booting the DOS (hit the reset button?), but I haven't touched one since 1983, so...

Tried this, sadly no luck.  It just rebooted the computer to the same blank screen?

3 hours ago, Turbo-Torch said:

Jay Newirth will most likely have everything you need.  http://plaidvest.com/newsoft/ 

Very nice guy and his prices are more than reasonable.  At the 2018 Tandy Assembly, he was giving away free key caps.  He also has excellent repro emblems.

Thank you for this!  I checked out his site, and right away I saw the name badges!  Didn't see the key switches, but then, I guess I have to email him for those.

3 hours ago, Turbo-Torch said:

DO NOT JUST REMOVE THE KEY CAPS AND TRY TO WORK IN CONTACT CLEANER!  It will destroy the carbon pads in the later style keys with 4 legs and I wouldn't try it on the older 2 leg keys either.  It did work great on my old 2 leg keys, but when I tried it on a late Model III with 4 legs, I ruined a bunch of keys.

Also, thank you for the warning!  That would have been awful!!  Is it possible to dismantle the switches to clean them?  And if possible, what about using some conductive paint on the carbon pads?  I've done this on a Commodore 64 once and had great results.

 

Also, I did manage to get the "Back Arrow", "T", "/?", and "Enter" to work, but I had to apply a fair amount of pressure and wiggle the key side-to-side to get it to respond.

3 hours ago, Turbo-Torch said:

It's going to have one of two different ALPS keyboard.  One style has keys soldered in with two legs and the other 4 legs.  The one with the stem broken off will need to be replaced and if it has 4 soldered legs, you'll probably have a hard time finding a replacement.  If it has 2 legs, I should have a spare I can send you.

Sadly these appear to be the 4 legged variety, but thanks for the offer.

3 hours ago, Turbo-Torch said:

Hold down BREAK while turning on or pressing the orange reset to go into BASIC.

I did try this, but all it did was ask for a cassette?

3 hours ago, Turbo-Torch said:

Disk drives probably need to be taken apart and gone through.  Definitely need to clean any old hardened grease from the rails and re-lube.  The fact that it boots from a disk is a good sign.

Absolutely the drives need to be taken apart, but weirdly, the high pitched grinding is gone. No idea why?

3 hours ago, Turbo-Torch said:

You can download them to your PC and then attach your III to the PC with a null modem cable. 

 I'm guessing that I'm going to need some sort of adapter for the cable as the only ports are the cassette, and three edge connectors on the bottom.  the good news is that the original owner was kind enough to write "Printer" in sharpie next to the one closest to the power cord, so at least I know where to plug it in.  

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Just figured out BASIC!  Holding "Break" during startup, then "Enter" when it asks for cassette until it asks "Memory Size?", "Enter" again, then it gave me a BASIC prompt!  

 

Also the dimming seems to have gone away for the moment.  Maybe the capacitors needed to charge after being idol for the past who knows how long?

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It's pretty common for the contrast and brightness pots to have problems.  Usually they just need a little lubrication to be loosened up.

 

The Cass? prompt is actually asking if you want the BASIC cassette routines to operate in high or low speed mode.  Type <ENTER> or H<ENTER> for high speed, L<ENTER> for low speed.  High speed is "Model III" mode, 1500 buad, low is "Model I" mode at 500 baud allowing you to save and load tapes that can be used on a Model I.

 

They didn't have the ROM space to put in a more informative message.  Or felt like adding a command to switch cassette modes inside BASIC.  Though you can do so with a POKE.

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For the dimming...spray DeoxIT into the brightness and contrast controls.  There is a video board in the upper shell next to the CRT, remove that edge connector and clean up the connection.  The fingers on the board can also be built up a bit thicker by adding thin layers of solder.  Lastly, clean and re-seat the power supply connectors at the top left of the motherboard as viewed from the front.

 

The keys will need to be unsoldered and removed.  You can then easily disassemble each one with a small screwdriver.  Inside will be a gray rubber cup with carbon pads and a spring.  I would first take an ohm reading to see what you have (probably over 1K).  Then disassemble the key and clean the lower contact portion with a pencil eraser and clean the carbon pads with a soft cloth.  Some guys even rotate the cups 180 so that contact is being made in a fresh area.  Reassemble and test again.  The reading will probably be down to a few hundred ohms and good for another 30 years.  Don't expect to see 0 ohms like a switch.  If some of the carbon pads are ruined, one of the repair coating kits should work fine.  I used some foil dots on my spare Model III that I picked up on Craigslist...that was the one with the newer keys that I messed up with DeoxIT cleaner. 

 

Underneath you should have four connectors.  You found the edge card for the printer port, next to it and inward is the bottom edge connector of your floppy controller card, you can add two more external floppy drives off of it.

The large edge card towards center is for expansion, that's where things like a Hard Drive or Orchestra 90 would attach...they can also be daisy chained with a special cable.  Sharing that same cut out area will be a standard 25 pin RS232 serial connector for your modem.

Now, if your III started life as a 16K cassette based model (as mine did), it did not have the floppy controller board or RS232 board.  It's possible that you still don't have the RS232 board...that was my first upgrade in 1984 and I believe I paid $100 for that kit from Radio Shack.  Later on I added the floppy drive kit.  RS also sold other odd configurations such as 32K and one floppy which may also not have the RS232 board.

 

On the rear, you'll just find the cassette port.  Even if you're not going to use cassettes, you'll definitely want the cable since that port is also used for sound output.  You attach one of the cables to the aux input of an amplifier and now you have surprisingly good sound effects and speech, especially in Big Five Games.  If you look back up at my photo, you can see the little amplified speaker that I use.

 

 

Edited by Turbo-Torch
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Looks like you have a big project on your hands lol.. clean everything inside and look for any capacitors that leaked or are bubbled  up .. change them and any others that look old.. look for any broken solder traces.. as for programs you can easily download some wave files and transfer them using the cassette port.  Then save them to your diskdrives.. and yes with the machine unplugged spray any switches or pots with contact  cleaner an move them back and forth especially those 2. Video brightness  and contrast wheels..

Good luck

 

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3 hours ago, Turbo-Torch said:

Now, if your III started life as a 16K cassette based model (as mine did), it did not have the floppy controller board or RS232 board.  It's possible that you still don't have the RS232 board...

Looks to be the case, as there is no 25 pin port on the bottom, just an empty space.  The good news is that it does have a floppy controller and two drives.  Also, if the badge on the keyboard is to be believed, then it was updated to 48k.

 

The keyboard is going to be a major project, but I was able to get it to do a looping BASIC program (filled the screen with "Hello There!").  No easy task given that the "T", "E", and "Back Arrow" keys are less than responsive.  I never really thought about how much I use the T in BASIC programs.  However, I have found that their performance has improved with use, so I'm guessing that the switches are salvageable.  Also the board isn't warped and I didn't see any broken traces! ?

3 hours ago, MrDave said:

Looks like you have a big project on your hands lol.. clean everything inside and look for any capacitors that leaked or are bubbled  up .. change them and any others that look old..

Definitely a big project!  But good news!  I checked all the capacitors, and aside from the two (filter/safety) caps I replaced, internally everything seems to be good and in excellent shape. ?

3 hours ago, MrDave said:

as for programs you can easily download some wave files and transfer them using the cassette port.  Then save them to your diskdrives..

 Thanks.  But is it possible that you have any instructions on how to accomplish this (either in DOS or BASIC)?  I'm a total noob to this.

 

Additional Question:

Is the Cassette cable/port the same as a Coco 2?

Edited by DistantStar001
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I'm almost certain the cassette cables are the same across most Tandy computers so don't pay more than a few bucks for one.

 

The serial board is going to be difficult to find and it requires a special mylar flex cable.  Jay or Ian may have one to sell and I know Jay had the flex cables reproduced too.

 

You have several other options on getting files to the III.

As mentioned earlier, FreHD is awesome.  It's like having 6 hard drives from back in the day (at $2K+ each) attached to your computer.  You can also get an auto boot ROM for a few bucks and not even need to boot from a floppy anymore...they'll just be along for the ride like booting to C drive on an old PC.  You'll have around 40mb of available storage after bootup between drives 0 to 5 (floppies become 6 and 7).  And of course many other sets of images can be kept on even the smallest SD card. 

HxC floppy emulator is another option and inexpensive, so something to look into.

I've never tried it, but if you have an old MSDOS PC kicking around, there is also a way to write TRS-80 compatible floppies using an emulator on a modern PC and then moving files to the old PC with a 360k floppy drive and writing the disk. The computer has to be running MSDOS (not through Windows) and the drive cannot be a 1.2 mb.

 

Only a tiny fraction of software came on cassette.  I don't see trying to convert disk programs to a WAV file, loading it into the cassette port and then converting and saving it back to disk as an option.  Unless someone has come up with a special program that can load in segments of code (into the limited 48K RAM) and then stitch it back together using multiple operations, it's going to be next to impossible.

 

This is some of the software out there available for your Model III.

http://www.classiccmp.org/cpmarchives/ftp.php?b=trs80%2FSoftware%2FModel+III

I think I have a bookmark on another computer to a site with even more than that.

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15 hours ago, Turbo-Torch said:

I'm almost certain the cassette cables are the same across most Tandy computers so don't pay more than a few bucks for one.

Excellent!  I already made one for my Coco.  ?

15 hours ago, Turbo-Torch said:

The serial board is going to be difficult to find and it requires a special mylar flex cable.  Jay or Ian may have one to sell and I know Jay had the flex cables reproduced too.

I found one on eBay (cable included), but with shipping it's around $100 US.  That's as much as I spent on the computer itself.  Honestly, I can't even say if that's a fair price or not since I've never looked into it before, and I haven't found anything to compare it to.

15 hours ago, Turbo-Torch said:

You have several other options on getting files to the III.

As mentioned earlier, FreHD is awesome.  It's like having 6 hard drives from back in the day (at $2K+ each) attached to your computer.  You can also get an auto boot ROM for a few bucks and not even need to boot from a floppy anymore...they'll just be along for the ride like booting to C drive on an old PC.  You'll have around 40mb of available storage after bootup between drives 0 to 5 (floppies become 6 and 7).  And of course many other sets of images can be kept on even the smallest SD card. 

HxC floppy emulator is another option and inexpensive, so something to look into.

I've never tried it, but if you have an old MSDOS PC kicking around, there is also a way to write TRS-80 compatible floppies using an emulator on a modern PC and then moving files to the old PC with a 360k floppy drive and writing the disk. The computer has to be running MSDOS (not through Windows) and the drive cannot be a 1.2 mb.

I think the PC option is going to be my best bet.  The FreHD looks awesome, but it's a little out of my budget right now.  And honestly, I can't even find a seller for the HxC (at least not one for a TRS-8).  

 

I have a friend who has offered me an old PC, but he's not sure what kind (just not an IBM).  It's either a 286 or a 386 and has 5.25 drive.  Worst case, it's high density and I'll have to find a 360k to install.  The real question is how do I get disk images off of my surface and onto 286/386?

15 hours ago, Turbo-Torch said:

Only a tiny fraction of software came on cassette.  I don't see trying to convert disk programs to a WAV file, loading it into the cassette port and then converting and saving it back to disk as an option.  Unless someone has come up with a special program that can load in segments of code (into the limited 48K RAM) and then stitch it back together using multiple operations, it's going to be next to impossible.

I know this is possible on an Apple II, but I think in this case, the idea is to load the program into RAM without executing it, and then saving it to disk.

15 hours ago, Turbo-Torch said:

This is some of the software out there available for your Model III.

http://www.classiccmp.org/cpmarchives/ftp.php?b=trs80%2FSoftware%2FModel+III

I think I have a bookmark on another computer to a site with even more than that.

Thank you so much for this!!!  Figuring out how to put software onto disk is great and all, but what good is it if I don't have any software! ?

Edited by DistantStar001
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So I've been trying to test my cassette cable loading from an old Android tablet.  I've had a lot of success with this on my Commodore datasette using a program called tapDancer, and have even managed to convert .tap files (and others) to physical cassettes with a TI Program Recorder.  Sadly this tape deck has a lot of noise on the playback, so I haven't been able to load programs with it directly. But at least it records well, and the tapes it makes load on my C2n.  Unfortunately, tapDancer appears to be Commodore only, as I've never been able to get it to load to another make of computer.  The new program I found is called MSX2Cas.  However, while it seems to recognize .bas files, it won't recognize .cas?  (At least not TRS-80 ones in any event)  Weird, since the program sat it does, and Cas is literally in the name.  

 

I've tried to load a program into my Model III with a "CLOAD" command (tried "CLOADM" too, but the computer doesn't seem to understand that and just gives an error message).  The curser disappears (much like an Apple II does with "LOAD"), so I'm guessing that the computer is listening, but after the file finishes playing, nothing happens.  It just sits there, giving no indication that a program was received.  Eventually, I hit Break and it went bad to its BASIC prompt.  So I know it didn't lock up or anything.

 

I checked the jacks on my cable to the pins in the port and everything seems right.  Also, I've used this cable successfully with both of my Coco 2s, so I know the cable works (with Cocos anyway).  So now I'm wondering if it's my program?  Maybe the .bas file is bad?  Or maybe because it's a .bas, MSX2Cas doesn't know to tell the computer that the file has finished?  Maybe it's the Android?  The cable I made has mono jacks, and the headphone jack on my tablet is certainly stereo.  I was using a stereo aux cable and cassette adapter with my Commodore files, and I understand that can be a problem sometimes as the contacts don't always line up.

 

In any case, I was hoping someone out there could direct me to an archive with .wav files?  Or maybe a program that can convert .cas to .wav?  My hope is that I can try to load from another device or computer that isn't so finicky.  Maybe my old iMac, since that's what I use with my Cocos.

 

Thanks again, and as always any help or advice is appreciated.  ? 

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1 hour ago, Turbo-Torch said:

The III will load 1500 baud default or 500 low speed. 

MSX2Cas seems to be going at 2400 bps and there's no option to change that.

1 hour ago, Turbo-Torch said:

Also what kind of program are you loading?  You may need to use system instead of cload.

I was trying to load batlstar.bas with MSX2Cas.  But I have now moved on to PlayCAS and am attempting to load Sea Dragon over the headphone jack on my Surface Pro.  It is a .cas file, and PlayCAS converted the file to wave and the program recognizes it as a TRS-80 Model 1, III, and 4 cassette.  I've checked to make sure that the .wav it generated plays sound over the speaker.  It does.  However, when played over the cassette cable nothing happens.  I did check the port again, and there seems to be some minor continuity between two of the pins on the port.  Both have brown wires attached to them, and since this is my first TRS-80, I really don't know if this is correct or the source of my problem?  Whatever it is or not, I don't think it's my cable that causes the short as it still works with my Cocos?  

 

I just ran a continuity test on my cable and it checks out with no sorts between pins.  So I'm going to check one of my Cocos to see if the short exists on their ports.  Otherwise, maybe I've found my culprit???

Edited by DistantStar001
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OK.  So new issue.  I had a bit of a brownout, followed by a total blackout.  This happened while the computer was on, and I was again (unsuccessfully) attempting to load an .cas file through the cassette port. 

 

I turned it off and unplugged it as soon as I could, but the screen was flickering during the brownout when I got there, and the drive was spinning until I turned it off.  After the power was restored (and I was sure it wasn't going to go out again), I plugged back in and turned it on to see if there was any damage.  

 

The drives seemed to initialize, but the computer didn't boot.  (both drives lit up, but drive 0 kept spinning until I removed the disk or reset into BASIC.   Then I entered a simple two line looping program, which worked as expected.  In fact, as far as I can tell, everything seems to be working as before.  I even tried resetting into BASIC, typing "H" at the "Cass?" prompt, entering 120k at the "Memory Size" prompt, and with a disk, I got the same behavior that I got at power-up.  Following the same procedure, I removed the disk, and got the standard "Diskette?" message, when the door is open, and it spins for about a second with the door closed, then stops.  So pretty much what it was doing before.  It would seem that the drive knows when there's a disk inside, and mechanically, it seems to function.  

 

Just to be certain, I did a partial disassembly and observed the drives in action.  The read head didn't move much, but then again it appeared to be at track 0, and I've never heard the same knocking sounds that I get out of my Apple or (sometime) Commodore drives, so there's a possibility that that's normal.  I also swapped the drives, as Drive one wasn't spinning during the brownout, and is largely inactive since I only have the one disk.  When swapped, Drive one behaved exactly like Drive zero, so if there is any damage, my guess would be that it's on the controller card, and not the drives, since even if both drives were damaged, I would seem that both drives suffered the exact same damage.  

 

At this point I can only guess what's going on.  But my two prevailing theories are that either, A: The brownout caused an under-voltage that damaged either the drives or the controller card, or B: The brownout activated the write function on the drive head, and my one and only disk was corrupted as a result.  Any ideas on how I can tell one way or another?  Or am I missing something else?

 

Edit: I'm starting to think that it might be the controller card.  I just repeated the "H" "120K" test and now it's giving me endless "Read Error in 50095" messages (disk or no disk).  Also, there seems to be another part of the error message, I'm not sure what it says since it's going so fast, but I think it's "?SN ?".  Any idea what that means?

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Start with the most simple.  Remove the mylar flex ribbon that connects the disk controller and motherboard.  Gently clean the ribbon contacts with a pencil eraser, spray contact cleaner into each board's connectors and reassemble.

There's also a longer and narrower ribbon that jumps two areas on the motherboard that should be cleaned too.

If either of those have a flaky connection, it will cause the system to crash in a million different ways or not function at all.

I eventually hard soldered mine with real stranded ribbon cable years ago.

 

Another test is to simply disconnect the flex ribbon from the controller and turn on the computer.  It should instantly boot to Cass?  If you still have issues at that point, check your voltages...if good, I'd next move on to RAM.

 

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On 2/11/2020 at 5:39 AM, Turbo-Torch said:

Start with the most simple.  Remove the mylar flex ribbon that connects the disk controller and motherboard.  Gently clean the ribbon contacts with a pencil eraser, spray contact cleaner into each board's connectors and reassemble.

There's also a longer and narrower ribbon that jumps two areas on the motherboard that should be cleaned too.

If either of those have a flaky connection, it will cause the system to crash in a million different ways or not function at all.

I eventually hard soldered mine with real stranded ribbon cable years ago.

 

Another test is to simply disconnect the flex ribbon from the controller and turn on the computer.  It should instantly boot to Cass?  If you still have issues at that point, check your voltages...if good, I'd next move on to RAM.

 

I'm still in the process of going through all of is (cleaning and going over the boards).  There are two boards behind a metal shield covered in a thin yellow plastic I haven't gotten to yet.  So far everything seems to be working right, so I think my problem is probably just a corrupted floppy disk.  Unfortunately I don't think there is a way to tell one way and or another without a working disk.  So I've turned my attention to the cassette port.  

 

I've moved away from the cassette cable I made and am now using a "test cable" (basically, a bout a quarter of an Atari 2600 power cable with two nails soldered to it).  I used this on my Cocos before I was able to build a proper cable, so again, I know it works.  Since the "test cable" "pins" are free from a din, I can check different combinations of pins to map the port.  Unfortunately, so far nothing works?  And my computer isn't loading.  I've checked continuity on all the pins in the port, now I have to check the connection to the motherboard.  There's still intermittent contact (not a full short) between two of the pins, but different pins after cleaning the port.  Now it's pins 1 and 5 (the outer two).  I still don't know if this is normal, but so far I haven't gotten it to load anything.  I figure that I should disconnect it from the motherboard and then check continuity on both ends to see if the issue isn in the cable or the board.  Any ideas?   

On 2/11/2020 at 9:58 PM, George Phillips said:

Regarding booting into ROM BASIC, just press <ENTER> on both the Cass? and Memory Size? prompts.

Putting in 120k for Memory Size? will cause BASIC to crash.

Thanks.  That explains the error messages I was getting.  I actually did try 48k thinking that the message was referring to the RAM, but got the same error.  So I tried the approximate disk size (I know I got it wrong).  When defaulted, BASIC reports the correct RAM, so this "Memory Size" prompt is just a something I don't understand yet.  First TRS-80, so a lot to learn! ?

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"Memory Size?" is definitely a misleading prompt.  It's really the address of the last byte available to basic.  If no answer is given BASIC will detect the available amount of RAM and set the address to the top of the RAM.

 

RAM starts at 0x4000 (16384) so for a 16K machine RAM ends at 0x7FFF (32767).  Besides storing the program, BASIC needs some working storage so on a 16K machine the maximum available memory for a program is about 15,300 bytes.  If you type in 32467 to "Memory Size" the available program memory will be about 15,000 bytes.

 

But why would you want to give BASIC less than all the RAM?  Some BASIC programs require some memory be reserved for machine language subroutines and BASIC has no way to do that.  A BASIC program would typically come with instructions as to what you should answer to "Memory Size?" before loading the program.  A typical answer for cassette systems with 16K is 32000 as that reserves more than enough space for little machine language subroutines and is easy for the user to remember and type.

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New question: I ran across THR-80.com and just discovered that the site offers a service to create physical system and utility disks for the Models I, III, 4, and 4P, but they're asking for a donation in return.  I have no problem with this, but they didn't specify or even suggest what would be an appropriate donation.  So I was wondering if anyone here has taken advantage of this, and if so, how much should I donate to cover their costs?

 

I'm still working on getting the Cassette port to work, but I did read that I was supposed to be using the "SYSTEM" command for machine language cassettes, not "CLOAD"?  Honestly, it hasn't made much of a difference as the computer still doesn't seem to be receiving anything from the port.  I tried cleaning the contacts on the motherboard a while back, but had no luck.  then again, I still haven't had the opportunity to disassemble the computer again since my last post, so it's possible that there is something physical that I've missed.  Any ideas what that might be?

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He sent me LDOS and NewDos80 disks several years ago.  I gave him $20 bucks.

 

Unless you know that you're converting an original cassette program to a WAV, know how to load that program and that it's at 1500 baud (and probably a million other factors), you're wasting your time trying to use the cassette port.  And if you're trying to load something that was a disk program, it ain't gonna happen.

For example, Dancing Demon is a mix of BASIC and machine language and you have to jump through a bunch of hoops to make it load.  I can't remember the details but I think it involved peeks and maybe changing the Memory Size at startup.  I got that program when it was released and the proper information wasn't in the manual.  Local RS computer center was stumped too as they couldn't load any of their copies.  They called back the next day (after hearing from Fort Worth) and told me how to load it.

 

Furthermore, cassette use was flaky at best even when using the proper cassette deck and commercial software.  The volume had to be just right and if you had the cassette deck too close to the side of the computer, the load would fail due to RF interference.  I can only imagine the added garbage in a WAV file.

Get a good tape deck and buy some commercial RS games off eBay and then give it a try.  All of mine are nearing 40 years old and still load fine.  Or find some sealed data cassettes, write a BASIC program, CSAVE it and then CLOAD it back into the machine.  Of course, finding a good cassette deck may not be easy.  I've had my CTR-80A since new, never stored it in a harsh environment and still had to recap it and replace the belt.

 

For disk drives:

You need to hit eBay and buy a cleaning disk that comes with a fluid solution.  New 5¼" floppies haven't been made in many years and even good floppies will leave oxides behind on the heads...and when you get a bad one, it'll really contaminate the heads.  Also, when you get some good bootable operating systems, make about a ½ dozen backups of each...you won't regret it.

For any disks that you buy, look at the disk surface under a bright light.  If there are faint white splotches, don't even try to use the disk.  It's mold and will often smell like it too.

Lastly, only use SSDD or DSDD disks, 1.2 mb HD will not work.  If your drives are aftermarket, they may be double sided, so use DSDD and LDOS to take advantage of them.

 

 

Edited by Turbo-Torch
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On 2/13/2020 at 12:01 PM, DistantStar001 said:

There are two boards behind a metal shield covered in a thin yellow plastic I haven't gotten to yet.

 

Can you post a photo of what you have?  You should only have the motherboard and a disk controller which is about ½ the size of the motherboard.  If you had the RS232 it would take up the remaining space.

I'm curious to know what has the yellow plastic shield as I've only seen that on the factory hi-res board.  You may have a really cool holy grail hidden inside.

The hi-res board comes mounted on a new RF shield cage that replaces your old one.  It's a single large horizontal board that's the same width as the motherboard but the shield cage over it makes it look like two boards.

It connects to the 50 pin expansion connector with a special short cable that tightly loops and connects from within the computer's case.  From there it daisy chains and exits out the opening to rear of the computer with another 50 pin card connector so you can still expand with other accessories.  That piece could have been tossed by someone years ago and unfortunately they are made of unobtainium.  It's a pain in the ass but you can build one if you have decent soldering skills and patience.

 

 

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15 hours ago, Turbo-Torch said:

I'm curious to know what has the yellow plastic shield as I've only seen that on the factory hi-res board.  You may have a really cool holy grail hidden inside.

The hi-res board comes mounted on a new RF shield cage that replaces your old one.  It's a single large horizontal board that's the same width as the motherboard but the shield cage over it makes it look like two boards.

Here are the pictures of the board.  From what you've described, this seems to be a match, but I'm not an expert (yet) ?

image.thumb.png.ae078e04f130627940748a1abf48bbeb.pngimage.thumb.png.22cd77832d71ae8c7ca7d9af81fb1921.png

15 hours ago, Turbo-Torch said:

It connects to the 50 pin expansion connector with a special short cable that tightly loops and connects from within the computer's case.  From there it daisy chains and exits out the opening to rear of the computer with another 50 pin card connector so you can still expand with other accessories.  That piece could have been tossed by someone years ago and unfortunately they are made of unobtainium.  It's a pain in the ass but you can build one if you have decent soldering skills and patience.

I'm guessing that this is the cable you were talking about?  I was wondering what it was, but was too afraid to mess with it.

image.thumb.png.58c60523d9265697f91dc8862501edc9.png

I actually haven't attempted to get to the floppy controller yet.  I was going to, but when I ran into this board, I decided to hold off until I could figure out what it was and how to detach it without doing any damage.  Right now the computer seems to be fully functional, aside from the keyboard.  But for now, I'm holding off fixing it until I've sourced a replacement keycap and switch.  

 

The computer could use some cosmetic restoration as well.  A new paint job, replacement badges, maybe putty up some of the deeper scratches, and sand down the shallows?  On the other hand, I might just replace the missing badge and leave it with its battle scars intact (I'm sure its earned them).  

 

I haven't haven't had a chance to contact Jay Newirth yet.  I'll get to it, but I figure that I should make a list of everything I need before I do.  Also I need to decide just how much of a restoration I'm planning, since the "48k" badge has a small crack in it, and he doesn't seem to have that on his site.  So I probably should decide if I need it before I go and bug him.

Edited by DistantStar001
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That's the hi-res graphics card!  ?

Imo, that's the ultimate Model III peripheral and I can't tell you how many years it took to find mine.  It came out in '82 and allows graphics that were mind blowing for the time.  My avatar pic is an actual photo I took of my screen.

 

You definitely need to get the system up and running, and I'm guessing once you get a few good disks, it'll be fine.  Mine has been with me since I was a kid and it has a few battle scars but that's just part of the patina.

 

The graphics board will be a whole new animal to learn about later on with its own commands and version of BASIC.  Normally it sits transparent and won't get in the way of anything else you'll be doing.  Now if you decide for some reason you don't want it and remove it, there's a mod to the motherboard that needs to be undone.

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  • 4 weeks later...

Hi again.  Sorry for the long delay in posts.  I had to put aside my Model III until I could get a working solution to write some disks for it.  I'm almost there, but I've run into some confusion.  I've decided to go with the DOS PC option as I was recently given a working 486.  There's a post in the classic computing sub-forum if anyone's interested.  It's the one with the 484 typo (should be 486) in the title that I don't know how to fix.  

 

Long story short, I've managed to install MS-DOS 6.22 on the 486, and it does have a working 5.25in floppy drive.  However, it's high-density.  I thought about extracting one of the drives from my Model III and making an adapter cable to hook it into my 486 just to get started.  But that would mean extracting the drive.  Which needless to say, would be a major pain, not to mention possibly risking damage to my Model III (the more important computer to me) either in extraction or reassembly.  And then I'd need to make a working cable as well that I would have no use for after.  So I'm holding off on that.

 

I'm still looking for a working 360k drive, but no luck so far (at least not in my eBay price range).  However, in doing so, I stumbled upon this website: https://www.tim-mann.org/trs80faq.html#[7]

And according to this site, the drive in my 486 might work.  This contradicts what I had been told earlier in this post (seen below).  So I have to ask: Can anyone confirm this one way or the other?  And if so, has anyone ever tried this before?  And perhaps more importantly, were you successful?

On 2/8/2020 at 7:09 PM, Turbo-Torch said:

I've never tried it, but if you have an old MSDOS PC kicking around, there is also a way to write TRS-80 compatible floppies using an emulator on a modern PC and then moving files to the old PC with a 360k floppy drive and writing the disk. The computer has to be running MSDOS (not through Windows) and the drive cannot be a 1.2 mb.

Even the website recommends a 40 track drive as the best option.  But it goes on to state that an 80 track will work?  If true, I'm guessing that the 40/35 track image is probably unstable from the 80 track drive.  But if an 80 track drive will work to write the disk, then maybe I can write the initial disk with my 486, and make a more stable copy with my Model III? Or an I fooling myself, and the new disk will inherit the flaws of the old?

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