Tandy 1000 help needed

My recently purchased Tandy 1000 boots to this screen (attached).


It's instantaneous, doesn't even seem to do any self-test. Anyone know if my system is done for or is there an easy fix?

Thanks for any advice!

ianoid said:

My recently purchased Tandy 1000 boots to this screen (attached).


It's instantaneous, doesn't even seem to do any self-test. Anyone know if my system is done for or is there an easy fix?



Thanks for any advice!

Click to expand...

A little more info please. What model 1000? Also, what peripherals, if any, are installed? I would suggest removing the case cover and check to see that all of the chips are properly seated for openers. I would kind of suspect a memory problem right off the bat. Don't give up - there's an army of Tandy folks on this forum. I'm quite sure we can help you out.

Agent Orange said:

A little more info please. What model 1000? Also, what peripherals, if any, are installed? I would suggest removing the case cover and check to see that all of the chips are properly seated for openers. I would kind of suspect a memory problem right off the bat. Don't give up - there's an army of Tandy folks on this forum. I'm quite sure we can help you out.

Click to expand...

It's a straight up model 1000 with the detachable keyboard, not an LX or EX, etc. It has a 256K memory add-on board. I tested it with and without the board. I also pushed on the exposed chips on the motherboard, but I didn't remove the drives that cover up much of the motherboard.

The Tandy 1000 comes standard with 128k of RAM. This error is around the 48k mark.

If you look at http://support.radioshack.com/support_computer/doc1/1253.htm there are 2 banks of RAM, each with 64k.

This error seems to indicate a bad chip in the first bank. Turn the machine on and leave it running for a while. Then turn it off and feel the tops of the chips in the first bank of RAM. One may feel very hot or very cool compared to the rest. That is a good candidate to try replacing.

It was kind of a hassle to figure out how to remove the drive housing since I've never done it and I couldn't find any advice or videos on the web. Finally took the time to find the right screws to remove.

I left it on for maybe 15 minutes. Is that long enough? The two socketed ICs that heated up were not RAM chips. All the RAM chips seemed to be room temp to the touch. There were two chips that ran rather hot that were nearby: MC6845P at position U88 (I think) and R6765P at U52.

Something that caught my eye was that at U9 there is an IC stacked on a black thing that is rather tall, and at U10 there is no IC at all! Is that normal? (picture attached)

On one hand, I'd love to replace any socketed ICs (if y'all would advise it) and try to get it working. On the other hand, if it's going to be a deeper project with soldering, I don't have the time or wherewithal to manage it right now.

Do you guys think this is the best message board to troubleshoot- or would I be better off asking on the Tandy usenet (google) group? I'd bet both you (very helpful) members there too!?

Thanks again!

It was kind of a hassle to figure out how to remove the drive housing since I've never done it and I couldn't find any advice or videos on the web. Finally took the time to find the right screws to remove.

I left it on for maybe 15 minutes. Is that long enough? The two socketed ICs that heated up were not RAM chips. All the RAM chips seemed to be room temp to the touch. There were two chips that ran rather hot that were nearby: MC6845P at position U88 (I think) and R6765P at U52.

Something that caught my eye was that at U9 there is an IC stacked on a black thing that is rather tall, and at U10 there is no IC at all! Is that normal? (picture attached)

On one hand, I'd love to replace any socketed ICs (if y'all would advise it) and try to get it working. On the other hand, if it's going to be a deeper project with soldering, I don't have the time or wherewithal to manage it right now.

Do you guys think this is the best message board to troubleshoot- or would I be better off asking on the Tandy usenet (google) group? I'd bet both you (very helpful) members there too!?

Thanks again!

Based on your photo, I would suggest you have a bad memory chip. What it is trying to say is that at the RAM address BBE0:0000, it wrote a 0000 and read back 0400. This area is used for video memory. First you should try replacing the faulty chip, then see if you can successfully boot. Rather than play hunt the defective chip, you can probably find 16 of the 64Kx1 chips easily enough for $20.

The extra black spacer under U10 is almost certainly a no-slot real time clock. Apparently U9 is a spare socket and is not ordinarily populated.

Looks like U11 is a replacement memory chip. remove it and power on. If you get the same error code than you found the bad chip. Just a guess. Then let us know what you find.

MC6845P is the video chip, which obviously seems to work. R6765P is your floppy controller, and is probably not an issue.

It looks like the ram chip in U11 has been replaced. I can't quite read the text, but it looks like it says -2 or -3, which would not be the right speed. Either way that suggest this machine has had RAM issues before.

I don't happen to know, would this machine work with only 64K installed? If so you could switch around chips to narrow it down.

The result 0400 would suggest that its the third bit that is bad, so I would look at the chips in U27 and U28. You can take chips off the memory expansion board, they should be compatible.

OK, so I did some RAM chip swapping (with some new chips that cost around $30 shipped for 18) and managed to get the system to boot with 128K.

When I put the memory expansion board back in, it started a new problem behavior intermittently which has now become consistent, even after letting it cool down a few hours. So I removed the memory board (supposedly 512K, but never confirmed more than 384K before the RAM got working again) and it boot with 128K a few times, but the problem became worse anyway.

When I flip the power switch (without fan or drives plugged into the PS, which was how I had the unit to troubleshoot the RAM- and how it was working intermitently) all the happens is the speaker makes a loud space age sound like a phaser and then becomes a fixed deep tone. Nothing pops up on the monitor.


Do you think it's the PS, or does this sound like a familiar issue with another chip?

I hope so, I only have so much patience for repair before I buy another unit that is tested and set it aside for parts or sale. I don't do soldering stuff at this point, so once it gets to that point, or to spending more than the machine is worth working, I usually bail out.

Thanks for your help!