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RGB TFT VGA Color Panel 6-Bit to 3-Bit wiring help

R

rimmeruk

Experienced Member
Joined
Jul 24, 2019
Messages
100
Location
UK England
Good New Year to All!

I've replaced the tired TFT VGA color screen in old laptop (Amstrad portable) with an almost identical screen. I was unable to find an exact replacement.
Using the datasheets for the new panel, I have managed to wire it up to existing LCD cable and I've got a colour image. The original TFT panel
was 3-Bit RGB data signals for R0-R2, G0-G2, B0-B2. The new panel is 6-Bit RGB (supports more colors) with data signals R0-R5, G0-G5, B0-B5.
I'm not bothered about having the extra colors, just the standard 256 that the original had is more than enough for the vinatge software that I use.

Because the older TFT screen cable does not support 6-Bit colour, what is the best or correct way to wire the 3-Bit RGB data wires to the the 6-Bit RGB data wires?
At the moment there are some strange color artifacts and interference which I think may be caused by the extra 3 RGB data signals being unconnected or floating.
Not really sure how to wire the extra 3 bits of color signals from each RGB channel., I've tried tieing them to GND but the display image becomes very dim.

Here are the pinouts for each of the panels signal connectors.
Original Panel with 3-Bit interface
SHARP PANEL PINOUT.JPG

New Panel with 6-Bit interface
NEC PANEL PINOUT.JPG

Thanks for reading.
 
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I found the solution for the extra signal bits here if anyone happens to be interested.

http://www.hantronix.com/page/index/resources/tft_application_notes

Still not sure what to do with the unused DE (Data Enable) signal wire. I've left it floating at the moment and seems to be working fine
without it connected. Not sure if it would make any improvement to the display quality or timing ?
 
Yes I was interested to see a solution. My only gripe is you took too long. Please be less tardy in the future.

IT'S A JOKE :)

I have a set of Ampro LittleBoard style SBC's that take a Pentium MMX. While I shouldn't have any issues similar to yours, the instructions state it readily interfaces to a host of (contemporary) panels, it's useful that have the info on speed dial. The manufacture is IAC, Industrial Automated Computers or something close. I've had them forever, and never got around to building all the necessary cabling. Every interface except the 4 pin molex power connector are headers. Not necessarily looking forward to building all that crap but I'm determined to get it all done soon.
 
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tipc said:
Yes I was interested to see a solution. My only gripe is you took too long. Please be less tardy in the future.

IT'S A JOKE :)
Click to expand...

I don't mind jokes! I had been putting this off for quite some time though. You know when you start something, then decide to finish later (8 months to be exact :sleepy:)
Good luck with your Ampro (I thought they were Z80 based boards?).
 
Not Ampros (though I have a LittleBoard/PC), but a similar form factor. I'm sure Ampro had something similar. But maybe I shouldn't assume.

Anyway they seem to be nifty enough. They came with a small baggy of snappable header connectors. Not nearly enough to get the whole kit operational. They were clearance items I got from Weird Stuff around 15 years ago. 8 months. HA! I wish I could get things done that fast.
 
Here are the results of my quick "bodged" wiring and the lovely colorful BIOS setup screen on the newer VGA panel.
Just go to tidy up all that wiring now and put her back together. Oh yeah, I do all my work on the cooker top at the moment but the wife
can tolerate me just about. :)

DSCF7478s.jpg

DSCF7477s.jpg

The portable is an Amstrad ACL-386SX from the mid 80's. Quite rare to find here in the UK.
The Mono Model is similar in design to the Color Model here by oldcrap.org
https://oldcrap.org/2020/08/24/amstrad-alt-386sx/
 
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rimmeruk said:
I'd have to look them up, I'm looking for something like that. Got any links ?
Click to expand...

when I went looking I never found much in the way of specifics for the IAC boards I have. I do have the manual. I thought for a long time they were made by Vox Technologies. Maybe it's possible they had a similar product or sold it under their name. Or maybe I'm just a total fool. In any event the damned company logo was right on the cover of the manuals I had. I scanned them, but tossed the manuals .. .go figure. I did see an IAC item on ebay recently. Some sort of ITX or mini ITX form factor thing. I'd have to go looking for it.

When I've made progress with getting them up and running, I'll post.

LCD photos look good. I was a Research Machines and Apricot fan for a long time. I actually owned a Nimbus-1 motherboard. The cost to ship it to NJ was at least 20x what the item cost. Then decided to sell it to a bloke in Sweden. But not to worry they pop up all the time. Then again maybe NOT.
 
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tipc said:
when I went looking I never found much in the way of specifics for the IAC boards I have. I do have the manual. I thought for a long time they were made by Vox Technologies.
Click to expand...

Is this what you are talking about: https://www.ebay.co.uk/itm/Vox-Technologies-IAC-H668A-Intel-Celeron-TM-366MHz-66x5-5-32MB-RAM-/152539026032

I'm looking for something like that but it would have to 100% support booting to DOS and also have at least SoundBlaster compatibility.
Yeah, Apricots very rare but RM laptops popup all the time on ebay.

The old girl is back together now, just fixing a floppy drive issue and then it's time for a new harddisk.
 
rimmeruk said:
Is this what you are talking about: https://www.ebay.co.uk/itm/Vox-Technologies-IAC-H668A-Intel-Celeron-TM-366MHz-66x5-5-32MB-RAM-/152539026032

I'm looking for something like that but it would have to 100% support booting to DOS and also have at least SoundBlaster compatibility.
Yeah, Apricots very rare but RM laptops popup all the time on ebay.

The old girl is back together now, just fixing a floppy drive issue and then it's time for a new harddisk.
Click to expand...

That's Vox, my boards are IAC. If they're related in anyway I can't say. The IAC item I saw on ebay I'm still looking for. I'll be back!
 
rimmeruk said:
Is this what you are talking about: https://www.ebay.co.uk/itm/Vox-Technologies-IAC-H668A-Intel-Celeron-TM-366MHz-66x5-5-32MB-RAM-/152539026032

I'm looking for something like that but it would have to 100% support booting to DOS and also have at least SoundBlaster compatibility.
Yeah, Apricots very rare but RM laptops popup all the time on ebay.

The old girl is back together now, just fixing a floppy drive issue and then it's time for a new harddisk.
Click to expand...

Ok no those are not close enough to the boards I have at all. Mine for 1 don't have any means to connect really anything right out of the box. No vga port, although there is a header to which a vga port can be wired to, presumably 1 that'll mount on the cabinet. But mine do have 1 PCI connector, so the expansion capability exceeds that of the board in your link. The sbc's in the previous post while don't have a pci connector per se, they can be plugged into a backplane, and you can expand to your heart''s content. And they're not 500$.

I guess I should post photos of what I have. But that auction should have everything you need I would think. And a lot less hassle.

RM laptops on ebay all the time you say. I'll have to be more diligent and perhaps pick 1 up. Assuming they want to ship it.
 
@rimmeruk
I too am expecting one to arrive here within the next week, an ACL in unknown condition. Neither the seller known the type that he was selling, and gave it as ALT-386SX one.

I really hope to be repairable and also that it will arrive with no missing parts.
Is so sad that no service manual exist anywhere, contrast to monochrome model ALT-386SX. Looking the internals of alt-386sx seen to have many differences.

Anyway I am very impressed with your work with the new alternate TFT panel, and I am sure that is the better way to go, contrary to change the fluorescent bulbs, even if the old TFT screen work.

Looking hard some days now, I found the datasheet of the Sharp LQ10DH15 panel which included on this laptop. I think the original is LQ10D015 but look to be the same exact.
I found also the service manual of ALT-386SX monochrome laptop, in case who someone need it.

https://archive.org/details/manual_ALT286_SM_AMSTRAD_EN
 

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rimmeruk said:
Still not sure what to do with the unused DE (Data Enable) signal wire. I've left it floating at the moment and seems to be working fine
without it connected. Not sure if it would make any improvement to the display quality or timing ?
Click to expand...
For your information, the original Sharp Panel used on the Amstrad ACL-386SX laptop, have the below monitor interface.
Now I suppose that you know where to connect the "data enable" signal. :)
SHARP PANEL PINOUT.JPG
 
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