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Newly aquired Tandy 6000HD! Lots of questions to follow...

Chromedome45 said:
well the village idiot struck again...Yes me while I was attempting to isolate the HD problem with the controller I accidently plugged in the Static RAM chip in backwards. ...
Why do I do these things! I know get in a hurry and don't double check.
Click to expand...

Looking at the schematic, you may have done more damage than just the PAL. The SRAM is directly connected to the WD1100-11 (U27), a 74LS244 (U21) is connected, among other chips. You need to look at the schematic, pages 226 through 228 in the PDF of the 6000 SM in the archives (237, 239, and 241 in the hardcopy), and suspect every single chip that touches the SRAM chip. Oddly enough, the PAL at U18 shares no lines in common; just because the system will boot with it out does not mean that it is bad and everything else is good. You really really need to not try to troubleshoot this with just a DVM.

The good news is that these controllers show up more often for sale than the type 2.

For the type of damage that this sort of reversal can cause, look at the thread on this forum:Free to a Good Home (with conditions) (I know it wasn't a chip reversal that caused that, but rather an improper cable, but the type of damage you can see is very similar, and could be difficult to diagnose.) The other bad news here is that the equations for these PALs are not in this manual.

On the bright side, it may only have fried the SRAM chip. But if it won't boot with the SRAM out, that's probably not the case.
 
When I pulled the original 1010 chip it would boot with the PAL. So I figured the 1010 was bad and got a replacement. With the repacement 1010 in there will not boot with the PAL in place. With replacement 1010 pulled will boot with PAL. Scratching head. Hmm so what is it the 1010 or the PAL???? :confused:
 
I see what you mean Lowen. Collateral damage. I am looking at the schematics and will try my best to find the culprit! Also just FYI this is with no cables plugged into the controller board at all.
 
Previous post deleted in this section. Incorrect data.

Ok it is now working. Operator error. Dopey me again!!! I just read to much into things I guess.

When I was attempting to determine the problem I was using the floppy disk access as my indicator of whether the controller was behaving or not.

Wrong! I never had the HD hooked up and totally got lost in my troubleshooting and never bothered to hook up the drive and try the Repeat Break key to bypass HD boot. When I did hook up the HD and pressed the proper bypass keys it booted to the diagnostics from the floppy as it should oh well live and learn and stop messing around.

Now I need to open it up (I dread doing that the case is very dry rotted from being in a non temp controlled warehouse). So each time I open it something else may crack or break off.

Sorry got off subject briefly.

Anyway the on board HD is bad or dead. I have a Seagate ST-251-1 40 Meg I plan on putting in as a replacement. I assume that drive will work in it. I haven't tested the Seagate yet but I will hook it up to the 6000 and run some diags on it!!
 
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More good news Tandon 15 Meg HD is still working no more thousands of ID NOT found errors running diagnostics. That actually did turn out to be a bad receiver chip Part number 3486 at U5. Also as Lowen mentioned the LS 244 was bad as well it is attached to the data bus of the RAM chip I had reversed.
So next to try is the Seagate ST-251-1 with 28ms access time should boot and run a little faster.

So was never the PAL chip or the 1010. Thank goodness the PAL is good. As for the onboard RAM I used a 6116 at 120nS speed as a replacement.

So hopefully no more goof ups by me!

Also watch out for the 20 DATA connector going to the controller board. It is backwards. Blue pin 1 line is going to pin 33-34 so flip it so blue line matches to Pin 1. Didn't find this till I kept getting a drive not ready error under diagnostics and Xenix install.
 
Has anyone here successfully formatted a Hard Drive under TRSDOS 4.2? The version I have gets to the end and then complains disk not ready Disk NOT formatted. I have installed CP/M to the HD and Xenix as well. Is this a TRSDOS bug or hiccup? Bad or corrupt disk image? I don't really know.

Oh that is running it in either TRDSOS II mode or TRSDOS-16 mode. Any hints etc. Appreciated.
 
I saw mention of the three Lisas in your other thread. Cool stuff! My dad had a Lisa when I was a teenager. Nice system.
 
Great news about the keyboard. I'm rebuilding my 6000 keyboard right now as well so let's share experiences.
 
Got mine done and works fine. However it rocks towards the back some like when you put some weight on the back edge of the keyboard it lifts up at the front.
 
So a general question about the "B" series keyboards. M12, M16B and T6000. Where do you place your keyboard? Seems like the 6K keyboard likes to rock backward when you rest your wrists on it. Slide it just under the front edge of the computer? I had thought about adding some small rubber feet to prevent the rocking of it.
 
The 6000 keyboard originally came with 4 thin round 1 inch or so diameter rubber feet that fit in the circular indentations on the bottom. Mine has them and it does not rock. I slide mine as close as possible but that's more due to desk space. Those B machines are so friggin deep and then you need to leave even more space for the fan airflow.
 
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