Eudimorphodon
Veteran Member
I'd definitely agree with not worrying about the drives yet and concentrate on getting the computer itself breathing; you're not going to be able to meaningfully do anything else without video output.
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Tandy 3 in uncertain condition
- Thread starter Tandy_Man
- Start date
Jove
Experienced Member
Tandon is cast as part of the main body and there is a Texas Peripherals sticker on the bottom. Dated 1981
Jove
Experienced Member
Next step, I swapped the floppy controller cards.
Something must have gone right, based on Ian's description it seems the machine is booting into TRSDOS.
Power on goes like this now:
Both drives start spinning,
Drive 0 lights up for a few seconds,
Drive 1 lights up for maybe a second,
there is a pause then Drive 0 lights up for a few seconds
then both drives stop turning
pressing D on the keyboard (directory? I have no idea!) results in a 2-3 second read of drive 0
This tells me that at least drive 0 is working properly (drive 1 has the controller card with missing components)
and also that the keyboard at least works for the letter D.
booting with the break key pressed did not change anything in the boot process so I suspect that key is probably not working.
Edit: I know I said video first then drives but this was too simple of a test to pass up and with seemingly good results I REGRET NOTHING!
Something must have gone right, based on Ian's description it seems the machine is booting into TRSDOS.
Power on goes like this now:
Both drives start spinning,
Drive 0 lights up for a few seconds,
Drive 1 lights up for maybe a second,
there is a pause then Drive 0 lights up for a few seconds
then both drives stop turning
pressing D on the keyboard (directory? I have no idea!) results in a 2-3 second read of drive 0
This tells me that at least drive 0 is working properly (drive 1 has the controller card with missing components)
and also that the keyboard at least works for the letter D.
booting with the break key pressed did not change anything in the boot process so I suspect that key is probably not working.
Edit: I know I said video first then drives but this was too simple of a test to pass up and with seemingly good results I REGRET NOTHING!
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clh333
Veteran Member
The good news: Your computer is essentially sound and probably trying to boot from drive :0. What you describe is a computer in the boot process.
The bad news is that you can't see the messages the computer is sending as a result of trying to boot. You need a video output for that.
The Model III ROM is quite extensive - about 14k including memory mapped output - and contains enough information to run the computer without loading a DOS from a drive. But it gives priority to a disk in drive :0 so it checks that first. If the drive door is open it prompts "Diskette?" reminding you that it wants to boot from a diskette. With the door closed the drives stop turning in about three seconds. With the power on, holding down the BREAK key while pressing the RESET button (orange, recessed in the upper right corner of the keyboard) causes the computer to boot into ROM, skipping the drive search. Then another set of messages asks you about cassette operation and memory values. Both these questions have default answers so you can just hit ENTER in response and you will be left in Level II BASIC at a READY prompt.
Unfortunately, you can't see any messages BECAUSE YOU DON'T HAVE ANY VIDEO OUTPUT. You might wish to solve that problem next.
-CH-
grumpyx
Experienced Member
Send me a PM with your address and I'll ship you a CRT control board. I would hate to see the T3 unfinished.
Malcom
Malcom
Jove
Experienced Member
And work continues. I have a dialog going with a collector on the east coast about the needed video parts.
In the meantime my RIFA replacements arrived and I soldered those in place. I tell you, after 10 minutes in the ultrasonic cleaner the P/S looks almost new!
No drama, everything works just as I did before I did the work.
I did a little more tinkering and thinking about the keyboard and decided the ribbon cable may have been installed backwards.
I checkedd a couple of video sources and sure enough, the keyboard hasn't worked because the plug is on upside. What I was seeing when I hit the D key was a reset.
With the ribbon the right way around I can now boot normally with no input, once the boot sequence has settled down typing DIR and hitting entre results in a 15-30 second read of the disk drive.
Booting with the Break key held, enter, wait, enter, "OUT 244,1", enter as suggested by Ian results in a short drive turn on/seek.
It seems the computer itself is operational with most/some of the keys working.
Now I really am somewhat stuck until the video is sorted.
In the meantime my RIFA replacements arrived and I soldered those in place. I tell you, after 10 minutes in the ultrasonic cleaner the P/S looks almost new!
No drama, everything works just as I did before I did the work.
I did a little more tinkering and thinking about the keyboard and decided the ribbon cable may have been installed backwards.
I checkedd a couple of video sources and sure enough, the keyboard hasn't worked because the plug is on upside. What I was seeing when I hit the D key was a reset.
With the ribbon the right way around I can now boot normally with no input, once the boot sequence has settled down typing DIR and hitting entre results in a 15-30 second read of the disk drive.
Booting with the Break key held, enter, wait, enter, "OUT 244,1", enter as suggested by Ian results in a short drive turn on/seek.
It seems the computer itself is operational with most/some of the keys working.
Now I really am somewhat stuck until the video is sorted.
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Jove
Experienced Member
While I am waiting on the first round of parts to arrive, I decided to look through the bag of 'stuff' that came with the computer.
I knew a bag of screws was in there but I have never actually looked at them or the included 100+ floppy disks.
As far as the disks, nothing of note, only 2 original disks in the entire bunch, mostly data.
There are a few ms-dos disks mixed in. Windows 3.0 on 5.25 and what seems like an entire copy (14 disks!) of Peachtree.
Regarding the screws I do have every small internal screw I need, but am completely missing the main case screws.
Has someone measured the stock hardware to make it possible to head down to the hardware store and pick up what I need? I believe it's 10 screws total for the Model 3/4 cases.
I knew a bag of screws was in there but I have never actually looked at them or the included 100+ floppy disks.
As far as the disks, nothing of note, only 2 original disks in the entire bunch, mostly data.
There are a few ms-dos disks mixed in. Windows 3.0 on 5.25 and what seems like an entire copy (14 disks!) of Peachtree.
Regarding the screws I do have every small internal screw I need, but am completely missing the main case screws.
Has someone measured the stock hardware to make it possible to head down to the hardware store and pick up what I need? I believe it's 10 screws total for the Model 3/4 cases.
clh333
Veteran Member
Jove
Experienced Member
Straight out of the service manual .... I was born too late to ever think service manuals having this kind of information in them!
Thank you
Thank you
Jove
Experienced Member
I went through the machine and properly reassembled using all fasteners so I could document what screws were missing.
While I confirmed I am missing the external case fasteners and have ordered those ....
I have parts left over! Since I didn't take the machine apart I'm not 100% where these go but I suspect they go there together.
I have a small machine thread screw, the same as used to secure the CRT board and a metal bracket, about 2" long and 1/2" wide with a hole in either end.
I will keep reading through blogs, vlogs, manuals etc and hope I stumble on a picture that shows the part, or maybe one of the taken-apart-50-of-these-things guys knows exactly what part I mean!
While I confirmed I am missing the external case fasteners and have ordered those ....
I have parts left over! Since I didn't take the machine apart I'm not 100% where these go but I suspect they go there together.
I have a small machine thread screw, the same as used to secure the CRT board and a metal bracket, about 2" long and 1/2" wide with a hole in either end.
I will keep reading through blogs, vlogs, manuals etc and hope I stumble on a picture that shows the part, or maybe one of the taken-apart-50-of-these-things guys knows exactly what part I mean!
TRS-Ian
Veteran Member
Show us a picture of this 2" long screw you mention
Jove
Experienced Member
One very small screw, one 2" long bracket.
gonk23
Experienced Member
That bracket could be the one which attaches the keyboard cable to the rear shield assembly. See picture from technical reference manual attached.
Jove
Experienced Member
Thats exactly it, thank you.
Jove
Experienced Member
Another step in the right direction. I took the damaged floppy card, really inspected what was broke and missing. Turns out nothing was missing, a few components had been bent/squished and a few legs had snapped. I spent a little time to straight all of the components, resolder legs together and wouldn't you know it, the drive works
At least it works well enough to boot the TRSDOS disk enough to perform a DIR command.
Not much else I can do without working video at this point. Don't fret, a CRT card is on the way.
At least it works well enough to boot the TRSDOS disk enough to perform a DIR command.
Not much else I can do without working video at this point. Don't fret, a CRT card is on the way.
Jove
Experienced Member
And the next small victory. I ordered replacement hardware. It all fits. Not much of a surprise but it's nice to keep moving forward.
Incidentally the price for the hardware in qty 5 was not much less than qty 100. I have a lot of spare case screws now!
Incidentally the price for the hardware in qty 5 was not much less than qty 100. I have a lot of spare case screws now!
Jove
Experienced Member
It boots, it makes pictures on the screen and the keyboard works. HOORAH!
Both drives are working now, I'm able to boot from either one by swapping the ribbon cable around.
every key on the keyboard seems to work, especially the top row '7' key which I replaced tonight
Big thanks to grumpyx who sent over a CRT board and spare key switch & cap. Not for a lack of offers from others, you're all appreciated!
Time to dig through the pile of random disks I got with the system and see if there is anything resembling a game.
Biggest issue now, the display loses vsync after about a minute of being turned on. Not all of the ground are hooked up as I'm figuring out where they all go since this was all apart when I got the machine.
Both drives are working now, I'm able to boot from either one by swapping the ribbon cable around.
every key on the keyboard seems to work, especially the top row '7' key which I replaced tonight
Big thanks to grumpyx who sent over a CRT board and spare key switch & cap. Not for a lack of offers from others, you're all appreciated!
Time to dig through the pile of random disks I got with the system and see if there is anything resembling a game.
Biggest issue now, the display loses vsync after about a minute of being turned on. Not all of the ground are hooked up as I'm figuring out where they all go since this was all apart when I got the machine.
Jove
Experienced Member
Regarding the vsync/vhold,
I will remove the card and reflow all joints tonight, hoping that fixes it, but is there an obvious smoking gun?
From a cold start, the monitor image is usually stable, sometimes with a vertical jitter equivalent to 2 pixels in height.
After 30 seconds to 3 minutes the image then loses v sync and displays the entire image 3 times, overlapping the previous image. No rolling, just 3 distinct images of the entire screen, overlapping each other vertically.
You can kick off this issue also by tapping the top half of the case in which the monitor and PCB is mounted.
Only 2 methods correct the screen once it's having issues
1) cold boot over and over until the screen is correct. waiting longer between power off and power on increases the odds of the image coming back correctly
2) unplug and replug the connector from the computer to the CRT card. This doesnt always work, it is more likely to work the faster to attach the connector.
Horizontal hold/sync is always perfect, the issue is only vertical.
This screams bad solder joint to me, especially the tapping to start the issue behavior, but I am even further from a CRT tech than I am a digital tech.
Anything to suggest to check? I have a scope but I don't even know where to start.
It's been so long since I've even turned on something with a CRT that I kind of forgot what pixels behind glass look like!
I will remove the card and reflow all joints tonight, hoping that fixes it, but is there an obvious smoking gun?
From a cold start, the monitor image is usually stable, sometimes with a vertical jitter equivalent to 2 pixels in height.
After 30 seconds to 3 minutes the image then loses v sync and displays the entire image 3 times, overlapping the previous image. No rolling, just 3 distinct images of the entire screen, overlapping each other vertically.
You can kick off this issue also by tapping the top half of the case in which the monitor and PCB is mounted.
Only 2 methods correct the screen once it's having issues
1) cold boot over and over until the screen is correct. waiting longer between power off and power on increases the odds of the image coming back correctly
2) unplug and replug the connector from the computer to the CRT card. This doesnt always work, it is more likely to work the faster to attach the connector.
Horizontal hold/sync is always perfect, the issue is only vertical.
This screams bad solder joint to me, especially the tapping to start the issue behavior, but I am even further from a CRT tech than I am a digital tech.
Anything to suggest to check? I have a scope but I don't even know where to start.
It's been so long since I've even turned on something with a CRT that I kind of forgot what pixels behind glass look like!