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Milli Vee

Colecovision repair

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HI All

 

I have 2 CV boards - one works but the video is all messed up - so it has bad VDP RAM (one of 8 chips) that I am avoiding changing. The other one has perfect video but never acknowledges a cartridge being installed. What could be the cause of the second one? Is it CV ram (the 2114's) or maybe the connector? It does get wonky if I 1/2 insert a cartridge so something is happening on that connector.

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Posted (edited)

Look closely at the connector.  Are the pins deformed?  Are they multi-colored due to oxidation?  Do you have a cartridge without the case that you can test continuity with?

Edited by ChildOfCv

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2 hours ago, ChildOfCv said:

Look closely at the connector.  Are the pins deformed?  Are they multi-colored due to oxidation?  Do you have a cartridge without the case that you can test continuity with?

I’ll look closer tomorrow

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14 minutes ago, Milli Vee said:

Arg I replaced U16 thinking it was the same as the Adam 

It is the same as on the Adam.  The mistake is that Texas Instruments labels the bits backwards on many of the 99xx series.  Look closely at the bus connections to pins 17-24

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15 minutes ago, ChildOfCv said:

It is the same as on the Adam.  The mistake is that Texas Instruments labels the bits backwards on many of the 99xx series.  Look closely at the bus connections to pins 17-24

Double arg! I forgot about learning that with the VDP - well I’ll replace u11 with a modified 4164 and see how it goes 

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It’s not pretty but it worked!

I figured out which bit was bad by looking  at the skill selection screen 

 

2AD93E51-E112-431A-88C4-FC8491FB7D32.jpeg

6BE2625E-A975-4DC3-967A-B02D0A7761FD.jpeg

E789D41B-E220-4425-ACCC-B23D0D3933E2.jpeg

3464B34E-E98A-47F3-9DAD-E2094FF3BB1A.jpeg

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