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How to read parallel-port POST diagnostic codes?

NeXT

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Check the BIOS Eproms for correct seat in the sockets and content.

It took me the whole damn winter to get back to you but you were correct in that something was wrong with my last burn and both the High and Low EPROMs did not have a valid image on them.
I've reburned Version 1.43 from the images here and verified they are burned this time.

No change in the POST codes, or signs of life, unfortunately.
 

zombienerd

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I'll just hop in to mention that I don't mind doing soldering work for parts or cash :p I was a Navy 2M Miniature / Microminiature soldering tech for 9 years, and can professionally solder and desolder any through-hole stuff with my current hobby setup. I have a nice temperature regulated iron and vacuum desoldering / heated air iron setup at my disposal.

I could do a lot of surface mount stuff too, if I only had a nice scope to work under, but that's not in my budget right now. I'd kill for a Pace PRC-2000 like I had in the Navy, but that's too many benjamins for my blood.
 

1ST1

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It took me the whole damn winter to get back to you but you were correct in that something was wrong with my last burn and both the High and Low EPROMs did not have a valid image on them.
I've reburned Version 1.43 from the images here and verified they are burned this time.

No change in the POST codes, or signs of life, unfortunately.

You may try older BIOS versions, just to be on the safe side. If not, try to grab another board, or go deep into the "Olivetti M24 - Theory of Operations" Manual which describes it's logic on lowest level.
 

NeXT

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Tried again tonight with the 1.21 BIOS set with no change.

Also tried the 1.36 set because what the hell, I just got a new pile of 2764's in. Still nothing.
 
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1ST1

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So it's not related to BIOS and the specific PAL which was shipped sometimes with 1.43. You must start from beginning. Oscilloscope, "M24 - Theory of Operation" and "Service Manual" documents, circuit diagram and analize from scratch, all the signals, etc. Or try to get a working board.

One thing you can easyly check, is look if all sockets on the graphics card are populated, or if some pins are bridged in an empty PAL/GAL socket. If last, then the previous owner has disabled the integrated graphics and put in a better alternative (EGA, VGA), and removed it before giving the machine to you, but without placing the original chip back.
 
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normanator

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ATT 6300 POST Error: DMA 04

ATT 6300 POST Error: DMA 04

The "suberror" for RAM failure during the test is 04, but yours is reporting 01 so I think you need to replace your DMA controller chip.

I have a 6300 that used to work fine, but now fails POST with "DMA Control Fail: 04" and the keyboard lights flash.

According to your previous post, the "04" in my case means it's gotten past the DMA chip and the issue is with RAM access? So that means I should start repair by troubleshooting the first 64K of onboard RAM? Just want to confirm before I start de-soldering things. Would you recommend doing a memory chip piggy-back process first to identify the bad chip(s), or just replace all of the RAM chips and be done with it?

ATT6300 POST Error.JPG

Many thanks to everyone for the POST diagnostic info on this thread. This is one of my most prized vintage units, so it will be very excited to get it running again!


Side comment:
The 25v 4.7uf caps on the power rail and video card had out-gassed and corroded the leads, but thankfully didn't make it into the traces. Replaced with new. Video card obviously still works, so I'm assuming the transplant was successful on the power rail as well.

Bad Caps.JPG

About desoldering:
If you don't already have a desolder tool, I recommend the "Velleman VTDESOL3U Vacuum Desoldering Pump With Heater 30W". Got mine for ~$10 on Amazon. It works better than I expected for light desolder work.
 

Trixter

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I have a 6300 that used to work fine, but now fails POST with "DMA Control Fail: 04" and the keyboard lights flash.

According to your previous post, the "04" in my case means it's gotten past the DMA chip and the issue is with RAM access? So that means I should start repair by troubleshooting the first 64K of onboard RAM? Just want to confirm before I start de-soldering things. Would you recommend doing a memory chip piggy-back process first to identify the bad chip(s), or just replace all of the RAM chips and be done with it?

According to ftp://ftp.oldskool.org/pub/drivers/...T Personal Computer 6300 ROM BIOS listing.pdf it is a failure found while testing the DMA chip in the first 64K. So yes, you have a bad chip in the first 64K. As for piggybacking, I haven't had good success with that, but I haven't had a lot of success troubleshooting drams anyway, so it couldn't hurt to try. You can also try the finger test, to see if one of the chips is substantially hotter than the others.

Side comment:
The 25v 4.7uf caps on the power rail and video card had out-gassed and corroded the leads, but thankfully didn't make it into the traces. Replaced with new. Video card obviously still works, so I'm assuming the transplant was successful on the power rail as well.

Was the system still operational in this state?

Also, I'd never seen that desoldering tool, for $11 I ordered one to give it a shot, thanks for the link.
 

Chuck(G)

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I've got one of those Velleman tools--my gripe is that the little 'sucker' cylinder really doesn't have much power. After using one for awhile, I've gone back to my big Soldapullt.
 

normanator

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Thanks, Trixter! So glad I found this group.

Yeah, the orifice on the Velleman is a bit large for detail work, and you have to make sure the tip is flush with the board. But I suck (pun intended) at coordinating a soldering iron and sucker anyway, so this, along with careful application of solder wick, works better for me. Again, I only to light duty soldering. I should probably practice, practice, practice your technique someday. But you know what they say about someday. ;)

As for whether the system worked with corroded caps, I'm not sure. It's been several years since I've fired this one up, and I only opened it up because wouldn't POST, so...

Thanks again, guys. I've found a few places to buy the the 4864P RAM chips, so I'll get some spares and get to work. Will let you know how it goes.
 
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