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Coleco with screen out of sync may be...


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#1 Mauro72 OFFLINE  

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Posted Sat Feb 25, 2017 1:41 PM

Hi,

I have a coleco with out of sync i think with all games.

Something like this:

http://derbian.webs....lt.htm?id=c19_1

I have 10,90v in pin 8 of RAMs (the 12v line). Its low?

Any help? Thanks!

 

 

Attached Thumbnails

  • coleco_2.jpg
  • coleco_1.jpg


#2 cdn2a OFFLINE  

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Posted Sun Feb 26, 2017 6:12 PM

So, first off.. it's a PAL Coleco. I don't know too much about those.

 

You can test the VDP, but odds are your getting a signal. (Based on you screen shot.)

Is the a tuneable slug/inductor in the modulator? For channel freq.

The part you have circled is an old shcool inductor.



#3 nanochess ONLINE  

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Posted Sun Feb 26, 2017 6:15 PM

In NTSC Colecovision, checking pin 36 of VDP chip right to center of a composite jack and GND in side should generate a stable black & white picture.

I don't know about PAL, but it could be the same.

If the picture isn't stable then the VDP chip is damaged and needs replacement.

#4 Mauro72 OFFLINE  

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Posted Mon Feb 27, 2017 6:30 PM

Hi guys...

It's a PAL version. nanochess, so i can connect a composite jack to pin36 (center) and the ground of VDP, external side of the jack (pin 1 may be, i need to search schematic of VDP).

Ok, thanks!



#5 Mauro72 OFFLINE  

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Posted Wed Mar 1, 2017 10:48 AM

Anyone know the specifications of that old inductor encircled? I want to change it.

Thanks.



#6 cdn2a OFFLINE  

cdn2a

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Posted Wed Mar 1, 2017 2:40 PM

They are ancient... They are rated by color codes.

PAL is prob different from NTSC check here...

 

If you desolder it you can measure it too.

 

http://www.vishay.co...ode-calculator/



#7 Mauro72 OFFLINE  

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Posted Wed Nov 22, 2017 5:52 PM

Hi again..

Trying with some cartridges, i noticed about sound. Is good, no problem. Here a small video with "Decathlon" game. 

https://youtu.be/JkmGIYVekJY



#8 Jinks OFFLINE  

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Posted Thu Nov 23, 2017 5:06 PM

Mine does the same nfi how to fix

#9 Mauro72 OFFLINE  

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Posted Wed Dec 6, 2017 12:33 PM

Mmmmmmm... suspect discovery. A pnp transistor, 2N3906 near vdp. Anyone can confirm the value of EBC in board?

Thanks!



#10 adamcon OFFLINE  

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Posted Wed Dec 6, 2017 3:14 PM

Mmmmmmm... suspect discovery. A pnp transistor, 2N3906 near vdp. Anyone can confirm the value of EBC in board?

Thanks!

Replace it anyway.  This transistor is a huge problem in the ADAM data drives, and probably many other applications.



#11 Mauro72 OFFLINE  

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Posted Thu Dec 21, 2017 1:15 PM

Fixed!!!! :)

 

Mixed problems, faulty power supply and two bad vrams. Now working!

Thanks!

 

2017_12_21_14_38_03.jpg 2017_12_21_14_38_48.jpg 2017_12_21_14_39_00.jpg



#12 nanochess ONLINE  

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Posted Thu Dec 21, 2017 1:44 PM

Well done! :thumbsup:




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