How to safely swap my drive A and drive B in TANDY 1000 HX

[kiyotewolf]

I've got a Tandy 1000HX, and my A: drive is worn out.

My B: drive, hardly used, I can only assume, is in much better shape.

I'd like to try cracking it open, and just swap the two myself, but I'm worried about mucking it up.

Tips? Hints?



~Paul

 

[Eudimorphodon]

Here's the installation manual for the second-drive kit in a Tandy 1000HX:

ftp://ftp.oldskool.org/pub/tvdog/tandy1000/documents/25-1065.zip

I believe the main "quirk" of the tandy machines is that they require setting the drive select switch/jumper on the drives, unlike most PCs where a twist in the cable takes care of that for you. This manual has a picture showing where the select switch should be. Assuming your drives match it just change the switch positions on the drives and you should be good to go.

The other thing you need to worry about when swapping drives is "termination". Regardless of how the drives are selected the last drive physically on the cable needs to be "terminated". Termination can be selected either by a jumper or by physically adding/removing a resistor pack to a socket. It's not clear from that thin documentation whether that select switch *also* changes the termination setting or if that's done separately. Never been inside a 1000 HX so I can't comment on the drives it ships with. If no one else can comment from memory posting photos of the circuit board side (and possibly the rear) of the drives could probably lead to some educated guessing.

If you get the termination wrong it probably won't damage anything, but the drive on the wrong side of the terminator won't be reliable.

 

[billdeg]

Not to get into a details thing here, but it does not usually matter with this class of machine which drive has the terminator as long as one of them does. At least my experimentation shows me this to be the case.

I would start by swapping the jumper settings. Make sure you write down what they were for each drive and then reverse them. Try that. Jumpers are switches. Some drives have a little set of 5-7 on/off switches, some drives have little clips that fit over exposed pins. You'll see them with labels "DS0/DS1, etc. If changing jumpers does not work or the jumpers for each drive are the same, then you will have to swap the drives physically so that they're at different points in the drive cable.

And if that does not work, swap the terminator. It will be a usually colored differently than the rest of the chips.

My concern is that you only remove drives and chips if you have to, jumpers are not easy to break, and you can always put things back the way they were.

 

[Great Hierophant]

3.5 drives almost always auto-terminate. The instruction manual describes the switch, but not having to change a terminator pack.

Assuming you do not have the particular drive which Tandy intended you to install in the HX, if it does not have a drive select switch or jumper it will be drive B. Modern drives usually have the switch soldered to DS1 because they are expecting the twist in the cable. You will need to break the connection to make it work as drive A.

To the OP's question, just swap the drives and adjust the switches as shown and you will be fine.

Not to get into a details thing here, but it does not usually matter with this class of machine which drive has the terminator as long as one of them does. At least my experimentation shows me this to be the case.

I would start by swapping the jumper settings. Make sure you write down what they were for each drive and then reverse them. Try that. Jumpers are switches. Some drives have a little set of 5-7 on/off switches, some drives have little clips that fit over exposed pins. You'll see them with labels "DS0/DS1, etc. If changing jumpers does not work or the jumpers for each drive are the same, then you will have to swap the drives physically so that they're at different points in the drive cable.

And if that does not work, swap the terminator. It will be a usually colored differently than the rest of the chips.

My concern is that you only remove drives and chips if you have to, jumpers are not easy to break, and you can always put things back the way they were.