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Seequa Chameleon schematics wanted.

O

ogaijin3

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Apr 24, 2025
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Will trade software DOS 1.25 AND other ver. Or chips. I probably have more but need to spend time finding it. My Chameleon has color capability. I don't remember if that was what made it + (plus).
I'm new here and found this forum by chance. My wife is threatening to throw out my old PC stuff because of space needs. So if I can find the one part I need. I can keep it. Most of my other stuff is old IBM stuff and expansion boards (OEM).
 
I saw that in ‘87 in a liquidation sale schem sheets for the Chameleon and the Plus were for sale for 10 bucks a piece, oh to be able to go back.

I hate to toot my own horn but I’d consider myself pretty knowledgeable with the Chameleon (proudly own 6 for archival purposes on Seequa.org), what part or help are you needing for yours? Also, can I see some photos of your color-capable pieces? I don’t think I’ve seen a Color Chameleon yet! Super jealous!
 
My Chameleon has color capability. I don't remember if that was what made it + (plus).
Click to expand...
Here is a rare dealer sheet I procured and scanned, the Chameleon Plus shipped with 256K of RAM, rather than the base model Chameleon's 128K.
There is a Color Chameleon that is advertised on here, which is the only mention I have found outside of a couple magazines of a Color model Chameleon. Is the keyboard labeled as a Plus?

SeequaDealerPricingSheet.png
 
@McJonesTech and I are working on reversing the schematics, but it's sort of a side project as I have a lot of things going on. Hopefully sometime next year!

There are TON of PALs on the Chameleon. If anyone has any experience dumping those, that would be a big help.

If anyone has the RAM Plus expansion card with the extra ROM chip, dumping that would be a huge help too.
 
GloriousCow said:
@McJonesTech and I are working on reversing the schematics, but it's sort of a side project as I have a lot of things going on. Hopefully sometime next year!

There are TON of PALs on the Chameleon. If anyone has any experience dumping those, that would be a big help.

If anyone has the RAM Plus expansion card with the extra ROM chip, dumping that would be a huge help too.
Click to expand...

In principle you could just hook up a PAL's inputs and outputs to a microcontroller's digital I/O lines and build up a 'truth table' from the measurements.

With that data you might be able to come up with an equation that describes the logic and begin to piece together some sort of gate-level schematix.

Of course, there is an obvious problem with respect to the rate at which those inputs and outputs change. Clock speed and sampling rate, for instance.

And if there is a clock directly fed into the PAL you need to be able to measure that clock as the behavior of the internal logic might be dependent on the clock.
 
Istarian said:
In principle you could just hook up a PAL's inputs and outputs to a microcontroller's digital I/O lines and build up a 'truth table' from the measurements.
Click to expand...

This works for simple "combinational" PALs. Registered PALs are very difficult to suss out by trying to build a truth table.
 
Istarian said:
I guess that mean somebody needs to identify the actual chips used on these boards then, because that will dictate the appropriate approach.
Click to expand...

I do have a DuPAL on the way. Where help would be useful is in verification via multiple dumps. Some the PALs on my motherboard are missing (scavenged?) and PALs are also known for just straight up dying.

We are currently working on putting together the BOM for the board and that is just the tedious process of noting every chip, resistor, capacitor, etc and their ids and values. Seequa didn't print U numbers on the silkscreen, but they were kind enough to put grid notation along the edge of the board.

If anyone is interested in helping us build out the BOM, PM me your email and I can add you to the google sheet.
 
I don't know when exactly part placement and soldering began go be heavily automated, but manual assembling of this sort of thing was once common place.

Consequently, I suspect the grid notation was used to help speed up those aspects of manufacturing boards and systems. It may also facilitate a more consistent way of identifying the location of problems on a faulty board.
 
I'm pretty sure the Chameleons were hand assembled. There are paint-pen annotations on most of the PALs - written there after programming to keep them from being mixed up before installation, no doubt.
 
Istarian said:
I guess that mean somebody needs to identify the actual chips used on these boards then, because that will dictate the appropriate approach.
Click to expand...
I have a list of the PALs on my Chameleon for reference:

AMPAL16L8DC
AMPAL16R4DC
AMPAL16R6DC
AMPAL16L8
AMPAL16R6
AMPAL16R8DC
DMPAL12L6NC
DMPAL20L10NC
PAL18L4CNS
PAL20L2CN

All on one board lol.
 
McJonesTech said:
I have a list of the PALs on my Chameleon for reference:
Click to expand...

All the ones with L's in the middle of their model numbers should be easy enough to reverse engineer if you have working examples, it's the ones with Rs that are the problem.

On the bright side: if you can get the equations I think the still-in-production GAL16v8s and GAL22v10s can emulate all, or at least most of, these part numbers.
 
Some interesting discoveries, the two 6116 SRAM chips on the board are font RAM. Yes, the Chameleon has a CGA with software fonts. They're decoded at AF00 and you can write to them at any time. The newer BIOS have the normal CGA font and thin font included - but who knows how you were supposed to switch between them.
 
Made some decently aligned reference images, and started populating the board in KiCad to produce a BOM. Once every component is accounted for, I will be stripping this board (trust me, it is in horrible condition and has very little chance of ever working) so I can get proper photos of the front and back.


1770330091058.png
 
more progress!

nothing makes any sense on this board. i think it was routed by aliens

1770512799714.png
 
This board is a crazy auto-routed mess, but I'm putting the pieces together.

Here we can see how the onboard CGA's font SRAM works:

1770666747443.png
 
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