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Travails with a non working Secam Colecovision console


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#1 zCRP OFFLINE  

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Posted Wed Jul 18, 2018 4:12 PM

Here's a short video I shot about my Secam Colecovision console, which does not work... any suggestions for fixing it are very welcome!!
 
 
Plans for a future follow-up video: some oscilloscope probings on various chips, trying to replicate what is described in the service manual.


#2 youki OFFLINE  

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Posted Thu Jul 19, 2018 6:07 AM

Hello, i can not help a lot here. 

 

But seeing you video i have seen you have a TMS9928ANL as VDP.

 

 

On a SECAM Console , i think it should be  a  TMS9929A   .



#3 zCRP OFFLINE  

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Posted Thu Jul 19, 2018 11:10 AM

Looking at the VDP datasheet, the difference between 9928A and 9929A is that the former has a 525 line format, and the latter 625. Other than that, they should both be perfectly software compatible and pin identical, and both have removed the NTSC output feature replacing it with chroma/luma signals.

The original VDP in the secam console has a heatsink attached and I have found no way to remove it without damaging the chip, so I have no way to be sure what the exact model is, and there are also no schematics for the secam (or PAL for that matter) model around.

What I can say is that I took the secam VDP chip, dropped it into a working pal cv, and it worked perfectly fine. Also, if I take the 9928A chip and place it inside the secam cv, I get the same "artifacts" that I have with the original chip. So I believe that they are for our purposes equivalent.



#4 youki OFFLINE  

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Posted Thu Jul 19, 2018 1:30 PM

The 9929  is 50Hz    , the 9928 is 60Hz.

 

But indeed, i don't think it is the cause of your issues.



#5 zCRP OFFLINE  

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Posted Thu Jul 19, 2018 3:09 PM

Hi, I have fixed the graphics corruption and general system crashing issues, but the video grounding issues remain.

 

Here is the video showing what I did and what is still wrong.

 

https://youtu.be/-2_9etM0eEg



#6 zCRP OFFLINE  

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Posted Sat Sep 1, 2018 5:33 PM

Update: the remaining video issues were due to the fact that the "official" scart cable supplied with the French CV has only one ground connection on the shield. Apparently my monitor needs the other ground connections as well, so I soldered a few bridges inside the connector joining shield with various ground pins and now everything works perfectly ;)






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