A1ST Turbo-R back from the DEAD!

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By 3rdman

Supporter (13)

3rdman's picture

05-08-2021, 19:17

I've been wanting a Turbo-R for a while but prices are just FAR too much for me to swallow so I've put it out of my mind until I stumbled onto a broken unit on Yahoo Auctions. The A1ST was advertised as non-functional...The seller apparently had gotten it broken and tried fixing it by swapping capacitors "and to practice".

Needless to say, he didn't get it working and sold it as "junk". I figured that perhaps I could buy it and could keep it for parts for a future project. In any case, a broken unit is what I bought and that is exactly what I received. The system, when powered up, simply had a black screen but it was outputting a video signal so it wasn't wholly dead. So then, I decided to see what I could do...maybe it can be revived?

Upon opening it, it did indeed have a recent recap but it wasn't done very well...there was some bad solder joints and at least one via was torn (this turned out to be the RED line on the RGB output). It also appeared that either the seller or the previous owner had attempted to expand the memory to 512K and had left behind the dip sockets and the various resistors and capacitors that are needed for the upgrade. It was also apparent that whoever installed these bits had run their soldering iron at 1000 degrees and left scorch marks on the board. The "new" memory was missing though so the best I could hope was to get it to boot with 256k.

I started with checking the capacitor swap...I printed out a copy of the schematics and verified continuity to every single capacitor. Surprisingly all of them checked out except for the one mentioned above. This took a couple of nights. Once done, I put my attention on the memory upgrade mods done...I started with checking continuity across the memory chip pins and found that pin #8 (address line #2) is supposed to have continuity across all of the four memory locations wasn't showing continuity. Upon close inspection, one leg as floating in air and the pad was completely missing! This surely as the reason for not working.

I ran a wire to create the continuity between the memory location and then proceeded to remove all mod work related to the memory upgrade as the work was very suspect. In fact, removing some of these pieces led to accidentally removing 3 pads off the motherboard...they were likely barely hanging on as there was evidence of scorching around them.

In any case, I cleaned everything up, slapped it back onto its base and plugged it in...and it immediately came to life! I'm absolutely thrilled that I somehow got my hands on a Turbo-R at a very reasonable price! I really did not expect to have a working unit! I spent the next few hours testing various games and making sure it boots to DOS and to its internal BIOS image...so far all good!

Now that she's working, I've got other deficiencies to worry about as the machine has clearly been scavenged for parts. I am missing the rear microphone adapter, floppy drive, floppy mount, and the keyboard (although complete) has a few letters that aren't working. In this state, I only have my MFR SCC+ SD with cart (with Sofarun) to run titles from and I can't seem to run ANY Turbo-R titles. I suspect that the issue here is simply that I don't know how to launch TR titles from my cart but perhaps something more is wrong with my machine and I don't know it.

If you made it this far, thank you and I have a few questions that I would love an answer for but please keep in mind that I know next to nothing about the Turbo-Rs.
1. The LED next to the "FDD" access light (I learned) shows the "CPU Mode" but what does the LED indicate? If lit, is it in Z80 mode or Turbo mode?
2. I recently purchased an A1WX machine that has a functioning floppy...can I pull it and slap it in the A1ST for testing?
3. Is there a rom/dsk image I can run from my flashcart that can test the various systems of my machine?

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By raymond

Hero (532)

raymond's picture

05-08-2021, 19:41

1. Then the R800 is active.
2. Yes, that should work.
3. There is a test program, however I do not recall the name...

By Alexey

Guardian (3165)

Alexey's picture

05-08-2021, 19:41

3. TESTRAM, MEMTEST, TESTMAP, MSXDIAG

By Grauw

Ascended (10022)

Grauw's picture

05-08-2021, 22:41

Nice fix! I had seen the auction, this one right? You certainly got it for a nice price! I was tempted too, but I already have a turboR and the mention of the recap certainly made it very suspect of a fucked up repair. The capacitors of the turboR are good quality and it shouldn’t need a recap normally. Nice to see only a few weeks later that the lucky buyer has managed to get it to work :).

I wonder if anyone has a 3D print model of the missing battery cover?

As for the keyboard, if it can’t be cleaned, this person is selling new membranes recently.

As for the floppy drive, I think I have a loose original turboR floppy drive laying about…

The most easily accessible R800 turbo application is MSX-DOS2 (Nextor), so if you can boot into it and the turbo LED lights up, as seems to be the case, you know that the CPU works without issue.

By 3rdman

Supporter (13)

3rdman's picture

06-08-2021, 03:59

Thank you Raymond and Alexey. Floppy swapped and worked without issue and my system passed all tests so I am very relieved!

Grauw, yes! That's the one I won...it looked far worse in person if that makes you feel any better. LOL. I'm not too worried about a batter cover but yes, I saw a replacement on ThingVerse I believe. I assume the keyboard membrane can't simply be dirty? I'll take a peek and buy a replacement if I have to so thank you for the head's up.

If you wish to part with that spare floppy, I'll be interested in buying it off you...I'll send a PM and thank you!

On another note, I am able to load TR games via floppy but not through the flashcart...I'll have to figure this out.

By Manuel

Ascended (18092)

Manuel's picture

06-08-2021, 08:04

Which games are you trying and in which way?

By 3rdman

Supporter (13)

3rdman's picture

06-08-2021, 15:30

Undeadline, Illusion City, Fray, Etc...there aren't many games exclusive to the TR and none of them will load for me. I'm sure its my fault...I have the DSKs collected on the flash cart and using Sofarun as my front end but so far they either freeze during load or dump me out to DOS.

By Grauw

Ascended (10022)

Grauw's picture

06-08-2021, 16:31

3rdman wrote:

If you wish to part with that spare floppy, I'll be interested in buying it off you...I'll send a PM and thank you!

I replied to your mail.

By 3rdman

Supporter (13)

3rdman's picture

17-09-2021, 04:02

I'm still coming to grips with the machine and running games on it. I have better luck running things from disk but that isn't very convenient. Focusing on SD Snatcher and using my Megaflashrom, I have no issue playing the game on my other two MSX2+ machines, but it locks up during its initial load on the A1-ST. Any ideas what the issue may be?

By sdsnatcher73

Prophet (2153)

sdsnatcher73's picture

17-09-2021, 07:08

Make sure you set the CPU mode to Z80 in SofaRun settings. R800 can cause issues in games. If a game supports R800 it will enable it itself. Which version of SD Snatcher are you trying to load? Original or translation? In case of translation which version? There is also a patch for SD Snatcher for MFR (the problem may be the memory mapper in the MFR and the SCC being in a subslot).

By 3rdman

Supporter (13)

3rdman's picture

18-09-2021, 02:05

Its appropriate that you should me, thanks. Ive tried multiple versions including two different translations. Could you point me to the patch you mention? I'm not sure that's the issue as it works with my other machines, but I'd like to try.

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