T1K Mystery: Trackstar, Gotek, and Floppies

[Towmater]

Here's what we know:
The A: Gotek with FlashFloppy works fine, whether connected directly to the MB, or through the Trackstar floppy adapter, the Gotek boots DOS 3.2.
The B: Teac 54B floppies, which have been modified for Trackstar use, show no signs of life other then the activity LED... none of the motors spin.
I've tried the original Teac A: drive, and the second drive that came with the system, none of their motors spin, with or without the Gotek installed.

I built a Kryoflux drive so that I could create the Trackstar utility disk from DeathAdderSF 's site, but can't do much with the T1K not reading physical floppies.

Detectives, please help!

 

[Eudimorphodon]

I have no intelligent suggestions, I just want to say I approve of that big black rocker switch you hacked into the Gotek case. I don't care what it does, I want one in my Gotek.

Okay, well, sanity check: it looks like you have a split/twisted cable emerging from the back of the Gotek, you're positive all the DS jumpers are correctly mapped for how the respective controllers expect them to be on a Tandy? (If you're seeing the activity lights flash then I suppose that's not the problem.)

Do you have documentation for how the drives are modified to make them work with the Trackstar board?

 

[Towmater]

I made a floppy cable with connectors on both sides of the fold, so I could try a straight-through connection as well. I also tried hooking up a 720K floppy to see what happens.

Then the epiphany... how could the entire system work including gotek, and not the floppies? What simple step had I skipped that any bonehead could easily figure out? In my defense, since the entire computer seemed to be working, I didn't think to do the obvious.

A simple voltage check reveals that there is no 12V output, which of course the Gotek doesn't need. Suddenly this is a power supply problem, not a floppy issue.

 

[Eudimorphodon]

Doh!

It *is* interesting to find out that a Tandy 1000 is entirely 12v logic. I guess it makes sense given the vintage of the machine.

 

[Towmater]

It looks as though 12V is used for an audio amplifier, and that's about it. -12V and 12V show up on the parallel port, which I have no desire to use, and on the ISA slot, where anything goes, I guess. I would not be surprised to find that the Trackstar board uses 12V somewhere.

So the T1K PSU manual warns the user not to power it without a load, which could damage it. That's a pretty bad design? This means IIUC that turning the machine on without floppy molex plugged in could damage the PSU. It also makes it difficult to troubleshoot as one has to either build a dummy load, or risk the motherboard being damaged.

I think the best solution might be to find a new supply that offers -12V.

 

[Eudimorphodon]

I hope the EX's PSU doesn't also melt its 12v without a load. I may regret installing that internal Gotek.

 

[seat safety switch]

I hope the EX's PSU doesn't also melt its 12v without a load. I may regret installing that internal Gotek.

On my SX, the technical manual says it needs at least 0.15A, which was sad for me because I couldn't cleanly swap out the super-loud stock 12V "cooling" fan with a 0.035A Noctua. 5V needs 1.25A, which is no problem because the motherboard seemed to suck down almost 1.7A on its own in my testing.

Wouldn't a floppy drive only pull on 12V when the motor is running?

-12V doesn't seem particularly useful (and min load there is listed as 0A); I think it's only intended for RS232, parallel, and ISA. Time for a PicoPSU?

 

[Eudimorphodon]

Wouldn't a floppy drive only pull on 12V when the motor is running?

That's a really good point.

EX manual says the minimum load on the 12v line is .1 amp. The fan is 12v, perhaps that's enough.

 

[Chuck(G)]

It looks as though 12V is used for an audio amplifier, and that's about it. -12V and 12V show up on the parallel port, which I have no desire to use,

That doesn't sound right. Are you sure that's not a serial port? Parallel port are +5 logic.

 

[Eudimorphodon]

For what little's it's worth I've been banging my head on laying out a serial port card for a Tandy EX, and the schematic I'm adapting (one by Sergey) does indeed imply that (...^D^D) the RS-232 transceiver chips at least want a VSS and VDD that are on - and +12v. (Technically the datasheet says 9v is optimum but it seems de rigueur to use 12 on ISA cards.)

 

[seat safety switch]

That's a really good point.
EX manual says the minimum load on the 12v line is .1 amp. The fan is 12v, perhaps that's enough.

On my SX, the stock fan seems to be enough to pull the minimum load. The power supply is stable. I just can't replace it with a super quiet 0.035A Noctua unless I added load resistors or a constantly spinning mechanical hard drive or something.

I would assume most "RS232" devices that you'd want to plug into the back of a Tandy are TTL instead of "high-voltage" RS232, as well.

 

[Eudimorphodon]

I would assume most "RS232" devices that you'd want to plug into the back of a Tandy are TTL instead of "high-voltage" RS232, as well.

It's unlikely the line drivers on a standard serial card will work right without those voltage feeds, though, and RS-232 is bipolar, so a "1" is actually represented by a negative voltage. So if you elected to use a power supply lacking +/-12v you'd probably need to hack your serial cards with regulators.

 

[Towmater]

Amazon's finest, cheapest PSU later...
The Gotek using Flashfloppy firmware doesn't seem to work with the modified Trackstar drives in any configuration. What I ended up doing is to use the Gotek to install the bios and dos files into an XTIDE, then reinstall both original Trackstar modded drives. I think at this point I can concentrate on getting the Trackstar drivers working.