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TANDY 4000 Needs love...

Patrick.B (TTR)

Patrick.B (TTR)

Experienced Member
Joined
May 11, 2011
Messages
496
Location
Houston, Texas, USA
So I have a tandy 4000 EGA card and CM8 (more on that later)
At first, all I got out of this setup was a white blank screen on the CM8. so I pulled the EGA card and used a restored working Cm5 instead and tested those two on a Tandy 1000 to ensure they work

so I put my tested tandy EGA/CGA card with a tested monitor and powered up the T4000,
I got the boot Bios message on the monitor, but it hangs afterwards with no beeping. the system only has a video board in it right now.

Please Note, the only cards the system has in it are the Tandy EGA/CGA and Tandy Multi i/o card, there aren't any MFM or Scsi cards in it (though I have but need to test them first).
also the Biso battery is dead, I need to replace it.

Does anyone have suggestions or maybe have the service manual for this one?
 
Thanks about the cm8/cm5 information, I guess I'll have to find a COCO3 to test it with.
found the T4000 Manuals in the end, and that link doesn't load in Edge, Chrome nor FTP voyage so not sure whats up with that link.

the hunting begins
 
well the 80287 was terribly hot so I removed it and reconfigured the system for no co-pro, even switched the ega/CGA card for an SVGA /LCD monitor to see if that was the "hanging up issue" nothing
so I plugged in the floppy drive and found after bios information displayed on the screen, there is no "floppy accessed at all. " so I am looking for a WD 37C65-PL to see if replacing may make it move forwards
does anyone knows of a set of bios (paired of course for the 4000 (not A, LX/or SX) files I could download and burn the 27c128-20 Epproms perhaps that is the issue at hand. ?
 
Make any progress on this? I've been working on a 4000 and a pair of 4000LXs on and off for a year or so. Got one of the LXs working, but I'm really trying to get the 4000 going again. I'm the original owner, and the MB is practically pristine, so I'm tracking down what is apparently a particularly difficult failure. Interestingly, the 4000 and the non-working 4000LX both blew the same tantalum cap on first power-up after decades of no use--also the same one that I saw someone else had popped on a 4000. I don't have the board in front of me, but I think if you're facing the machine, it's the left-most 33uF/16v cap in the back. I'm mildly curious if blowing that cap tends to take out something with it when it goes, or if it blows because of a common failure elsewhere. Really odd that 3 machines popped the exact same one. The 4000trm.pdf isn't great quality. Any luck tracking down better docs?
 
well I got the 4000 to work up to a point its complaining about memory error no matter what cpu or ram stick I put in it. (no matter what size always same error) its on the table on the side. annoyingly I will have to scrutinize the board and probably just recap the old betty to make sure I am not missing on something.
 
I recently got a tandy 4000 sx with ega card. I cant seem to get the memory error message to go away either. And i cant seem to get the 1.44mb drive to work either(5.25" mb drive works fine).
 
Patrick.B (TTR) said:
well I got the 4000 to work up to a point its complaining about memory error no matter what cpu or ram stick I put in it. (no matter what size always same error) its on the table on the side. annoyingly I will have to scrutinize the board and probably just recap the old betty to make sure I am not missing on something.
Click to expand...
This is kind of unlikely, but on mine something must have been a bit off at the factory because there is one column of pins across the simm slots that look like they were soldered by hand, and the joints don't look great. Might reflow those if your board is similar. Also, I can take a picture of mine and you can see if any of the bodge wires got yanked off. I'd be curious if you happen to know the exact memory error. Mine isn't even getting to the point of POSTing, which I _think_ it should be able to do even with no memory. Considering the condition of mine, I'm surprised it's not faring better. I'm getting some (what I think are) unusual voltage readings around some of the 74240 and 74245 chips, but I really need to drill down on it to get a better idea of what's gone bad.
 
First pic is overall view, next 3 are closeups of wires, 5th is a pic of the simm solder points that look like they were modified by hand (at the factory).

I guess Tandy didn't believe in cleaning up flux...

.20240507_012843.jpg20240507_012900.jpg20240507_012905.jpg20240507_012911.jpg20240507_012919.jpg
 
When replacing the RTC battery on the 4000, is the original rechargeable? Do you need to add a diode in line if not using the same type of battery?
 
VERAULT said:
When replacing the RTC battery on the 4000, is the original rechargeable? Do you need to add a diode in line if not using the same type of battery?
Click to expand...
The 4000 SX might have a different motherboard, so I'm not certain. The 4000 and 4000 LX use a non-rechargeable 3.6V lithium battery. There are several alternatives for replacement, and I've read somewhere (but haven't tried) a pair of AA batteries will also work.
 
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