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Cannot Get Tandy 2500 SX/33 to boot from floppy.

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First post, by tegrady

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I have a Tandy 2500 SX/33 that I am unable to get to boot. I was using the original floppy drive, but it would not read any disks, and therefore would not boot. I figured the drive was bad, so I replaced it.

Now when I try to boot DOS (I tried my DOS 5.0 and 6.22 disks) I get the error "diskette drive 0 seek failure". It tells me that the bios settings are wrong and I should correct them. (I have replaced the CMOS battery).

I go into the bios, which is very simplistic on this machine, and I have made sure that I have selected the drive as a 1.44 mb 3.5" drive. I have also selected the boot drive as drive A. I save the bios and re-boot, same error.

I have a box full of 3.5" floppy drives. I tried swapping out 6 of them, they all give the same error.

I then figured maybe the onboard floppy controller is bad, so I installed a floppy controller card. I unplugged the floppy drive from the motherboard and plugged it into the controller.

When the drive is attached to the controller card, it automatically seeks when I boot, so I know the controller is working, but I get the same error message again and it won't boot.

Any idea what is going on here? I'm fairly sure that not all 6 floppy drives are bad. I am also fairly sure that my DOS media is fine.

Is the Tandy not compatible with MS-DOS? Does it need some special version of Tandy DOS to work?

Any help would be appreciated.

Thanks.

Reply 1 of 3, by Deunan

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Can you disable the on-board FDC? Because if not, it will interfere with the add-on card. Chances are that is why all your drives don't work properly in this machine.
Also, this is just a wild guess because I don't know much about the Tandy series, but perhaps the original FDD drive cable is not wired the exact same way as other PCs? Like, does the cable have the "swap" in it? If it doesn't you need to rejumper it to DS0 instead of DS1.

Reply 2 of 3, by tegrady

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Deunan wrote on 2020-03-01, 12:02:

Can you disable the on-board FDC? Because if not, it will interfere with the add-on card. Chances are that is why all your drives don't work properly in this machine.
Also, this is just a wild guess because I don't know much about the Tandy series, but perhaps the original FDD drive cable is not wired the exact same way as other PCs? Like, does the cable have the "swap" in it? If it doesn't you need to rejumper it to DS0 instead of DS1.

Thanks for the suggestion!

You were correct about the cable. The Tandy floppy cable did not have the "swap" in it.

I tried a normal floppy cable using the onboard floppy controller, but it did not work. However, using a normal floppy cable with the controller card did work.

Does the Tandy's onboard controller only work with proprietary Tandy drives???

Luckily, I was able to get everything going by running the floppy and hard drive off of the controller card!

Thanks again.

Reply 3 of 3, by Vynix

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Tandy systems used the drive select jumpers on the FDDs instead of using a "twist" to design the drive A or B. It's a bit complicated.

Also Tandy FDDs were powered by the cable itself... So if you try to plug in a normal drive you can potentially kill it or the motherboard.

Proud owner of a Shuttle HOT-555A 430VX motherboard and two wonderful retro laptops, namely a Compaq Armada 1700 [nonfunctional] and a HP Omnibook XE3-GC [fully working :p]

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