Tandy 2500xl that just keeps getting worse

[falter]

Stupid question.. is there anything other than a fault in the switch that tells the floppy drive that a disk is inserted that would cause a 'Drive Not Ready Error'? Also, can I use a drive from another model of Tandy to test? Ie say a 720k from a TL (this, like the 1.4 mb in the SX, has the power integrated in the ribbon cable).

Or could I use a standard 5.25 drive in this pile?

 

[falter]

I finally got round to fixing this. First, I replaced the RTC with what I presume is a reman unit from ebay (has electrical tape sticking out). I also realized the jumper for CMOS clear was set, so things weren't sticking at all.

With the RTC replaced I was able to program the settings for the hard drive successfully. The BIOS does not allow a cylinder count higher than 1099. But that's enough to set up a 200mb drive from the bunch I had kicking around. I had to use a debug procedure to force it to 'clean' the drive first, then I was able to fdisk and format.

Interestingly the floppy drive worked.. but only after I made a 720k tandy msdos 3.3 boot disk. I guess when the BIOS is cleared it can't read 1.44mb disks??

One issue that kept me tied up was the RAM.. I had 1mb but it would not accept a setting of 640k base and 384k extended without turning shadow ram on. Also, apparently if you have the 'mouse device installed' option set in BIOS it will freak every boot if it doesn't find a mouse there.

That's it anyway.. many thanks for the earlier help.

 

[falter]

May have spoken too soon. My quandary seems to be that while the machine will boot DOS 3.30 just fine off a 720k floppy or the hard drive, when in DOS 3.3 it won't read 1.44mb floppy disks.

I can boot DOS 5.0 off floppy, and I can fdisk and format the drive to 320mb (which is its size), but it will not boot from it.

I'm assuming it's because the Tandy 2500's bios can't handle 300mb+ drives?