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globeron

How to see if a chip is for PAL or NTSC? VDP TMS9929AN / TMS9918AN NTSC/PAL 50Hz/60Hz ?

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The issue:

I used my TMS9928A (?) Chip of my European TI-99/4A in my European TI-99/4 computer to fix the VDP

so these chips run on 50Hz and have the PAL Output  (and the RGB / YPbPr).

 

I ordered Chips from eBay (China ?)

* TMS9918AN - https://www.ebay.com/itm/1PCS-TMS9918ANL-Video-Display-Processor-DIP40/320857330410

* TMS9929AN - https://www.ebay.com/itm/320853018123?ViewItem=&item=320853018123

 

Result on my European TI-99/4A - white stripes on the screen (looks like sync. issue).

but I just tested in my USA TI-99/4A version (NTSC / 60 Hz) and got the TMS9918AN working okay (colours, etc.)

but the 9929AN only outputs in Black and White (for the rest it is okay).

 

Questions:

1. What is the reason for the Black & White output?   Bad Chip?  (cannot be the crystal as it works with 9918AN -

     or something else Frequency 50Hz/60Hz? 

 

2.  How can I identify a TMS99xx chip that supports PAL 50 Hz output for my European console ?

     (I asked already someone in Europe I send a lot of broken consoles to, to see if he has a spare TMS99xx chip for me)

 

This table is a bit confusing, then the 9929A should not output Composite signal ?

(https://en.wikipedia.org/wiki/Texas_Instruments_TMS9918)

image.thumb.png.15856dbb8e523483879aea51d5546c41.png

 

Also I look around to figure out what the 9929 chip is:

 

 

 

 

 

First I thought it are fake chips I have to deal with.

 

Detecting Fake chips:

 

 

 

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TI-99/4A USA console with composite cable output.

 

TMS9929AN  outputs in Black and White

 

TMS9918AN outputs in Colour

 

20210107_191724.thumb.jpg.875ffb8ef8473c3c9b940871722221c6.jpg

 

20210107_190221.jpg

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20210107_190936.jpg

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Posted (edited)

The 9918 outputs colour composite on a single pin. The 9928/29 outputs video on three pins - luminance (the 'black and white') on one, and colour difference on the other two - and these are combined into a single colour video signal in the (external) PAL UHF modulator. There are some links on the board that you set according to the VDP in use. So with a 9929 plugged into a board set up for a 9918, you're only getting the luminance signal, with no colour information.

Edited by Stuart
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11 hours ago, Stuart said:

The 9918 outputs colour composite on a single pin. The 9928/29 outputs video on three pins - luminance (the 'black and white') on one, and colour difference on the other two - and these are combined into a single colour video signal in the (external) PAL UHF modulator. There are some links on the board that you set according to the VDP in use. So with a 9929 plugged into a board set up for a 9918, you're only getting the luminance signal, with no colour information.

Thank you!  So the reason 9929 does not work in a PAL European version of the TI is the frequency 60Hz ?  

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2 hours ago, globeron said:

Thank you!  So the reason 9929 does not work in a PAL European version of the TI is the frequency 60Hz ?  

No, it *should* work. A PAL EU TI-99/4A needs a 9929A (50 Hz) and a NTSC US TI-99/4A needs a 9918A (60 Hz). The 9928A is not used.

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4 hours ago, Asmusr said:

No, it *should* work. A PAL EU TI-99/4A needs a 9929A (50 Hz) and a NTSC US TI-99/4A needs a 9918A (60 Hz). The 9928A is not used.

Thank you, maybe something wrong with the chip maybe not a 9929, because in the PAL system it does not give any result. 

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As Asmusr noted, you have to change some jumpers on the PCB if you change between 9918 and 9929.  The PAL version was made to output to SCART, if I recall correctly, and will not give you color on the tuner output.  That requires extra hardware to modulate the colors at a certain frequency (which is different between PAL and NTSC) and then combine it with the B/W signal.  That composite signal then goes through the tuner box which also adds in the sound (at another frequency which is different between NTSC and PAL).

So if you have an NTSC unit, you can convert it to PAL, but you will not be able to just drop in the 9929 chip.  You'll have to change jumpers, and even then you'll have to use SCART.

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Given it apparently works at 60 Hz but not at 50 Hz... it seems likely your 9929 is actually a 9928.

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