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RCA Studio II Display Question


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#1 mckafka99 OFFLINE  

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Posted Tue Jan 8, 2013 5:08 PM

I recently picked up a CIB (less manual) RCA Studio II. The unit plays its' built in games as exepcted with one small drawback - there are 'missing' vertical lines in the display for every game. I've attached a picture of what this looks like on the bowling. On all the games, the same vertical lines are missing. I've taken a peek inside the switch box and inside the unit (had to fix channel selector, but that was a breeze) and everything looks pretty good and clean. Does anybody know what would cause this condition? Thanks.

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#2 carlsson OFFLINE  

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Posted Wed Jan 9, 2013 7:00 AM

Hm, it looks like every 8th pixel - possibly bit number "4" when counting 76543210 is missing. The console has four CDP1822NCE chips, i.e. 256 byte x4 SRAM for a total of 512 bytes of which half normally is used for graphics and the rest for programs. Could it be that one of those has suffered "bit rot" while the other chips still work so you don't get any additional issues? It also has a CD4001BE Quad 2-input NOR and a CD4042BE Quad D-type latch to decode ROM and RAM addresses.

The display is handled by a video display controller (CDP1861) but I gather the actual graphics are generated by the 1802 CPU and transferred with DMA to the 1861. I don't know if there is something more simple like old capacitors that might cause this issue.

An archived page of Paul Robsons old Studio II page (the original one is no longer available?)
http://archive.konte...om/techinfo.htm

#3 mckafka99 OFFLINE  

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Posted Wed Jan 9, 2013 1:06 PM

Thanks for the detailed response. It actually doesnt look to bad and for a brief moment I almost thought it was the wa it was supposed to look, the missing lines adding some 'variety' to the otherwise bland display. I'm glad the unit works at all and perhaps if it is along the lines of what you are suggesting, I just need to find another unit to try out. They seem to pop up every now and then but of course never with that switch box so I suspect the 'jewel' of my find was the switch box. Thanks again!

Edited by mckafka99, Wed Jan 9, 2013 1:06 PM.


#4 carlsson OFFLINE  

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Posted Wed Jan 9, 2013 5:57 PM

Since I live in 230V PAL-land, I never bothered trying to adopt power to boot my fully boxed Studio II. Instead I sold it with a few common cartridges to a friend, and instead kept my Conic M1200 clone that is easier to connect, outputs colour on some games but otherwise works the same. I've still got a few doubles of the most common games as I picked up a bunch from various eBay sellers. It seems like Black Jack is the absolutely most common Studio II game - I acquired at least three copies out of a total of a dozen boxed games!

I wonder if those CDP SRAM chips are somehow compatible with other SRAM chips of similar capacities, or if more complex procedures would have to be undertaken if one was proven to be bad and needed replacement. Perhaps it even is something as simple as a cold solder joint, but you mentioned the board physically looks fine - on both sides?

#5 mckafka99 OFFLINE  

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Posted Wed Jan 9, 2013 7:40 PM

As soon as I get the chance, I'll crack it open again and take some pics and post them. Maybe there is something there I missed.

#6 mckafka99 OFFLINE  

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Posted Wed Jan 9, 2013 8:43 PM

Here are a series of pictures of the inside. I probably should have used the iphone to take the pictures instead of the ipad - tough to get too close to get the shots. If there is a particular section you think it would help to have a better picture of, let me know.

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#7 akaviolence OFFLINE  

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Posted Wed Jan 9, 2013 10:52 PM

What a pretty board!
A quick scan and I only noticed one possible trouble spot, but it may just be the way the light is reflecting off it, can you check to see if there is still a good connection at the indicated trace?
Would need much better pics or scans or an in person inspection to really check the board over...

Attached Thumbnails

  • rca studio 2 pic.jpg

Edited by akaviolence, Wed Jan 9, 2013 10:53 PM.


#8 carlsson OFFLINE  

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Posted Thu Jan 10, 2013 5:43 AM

The people at iFixit borrowed a Studio II in 2010 and took it apart. You can compare your images to theirs:
http://www.ifixit.co...Teardown/3527/1

It seems the place where there is a gap between the solder point and the ground (?) area is where the black wire connects. It leads to the reset switch and status LED. It makes me wonder if the reset button and LED work on your machine, or if a missing ground would be an issue. On the teardown pics above, it looks different. Unfortunately I haven't located any definitive schematics on either site.

Edited by carlsson, Thu Jan 10, 2013 5:57 AM.


#9 mckafka99 OFFLINE  

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Posted Thu Jan 10, 2013 6:09 AM

The red status light works and the 'clear/reset' button works as expected. I'll see if I can get better pics ASAP. Thanks for helping.




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