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Author Topic: Pentranic CH-288 Switching 25hz back to 15hz / picture upside down  (Read 2391 times)

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kevinp

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Pentranic CH-288 Switching 25hz back to 15hz / picture upside down
« on: January 05, 2010, 02:59:22 pm »
Hello, I have a switchable Pentranic CH-288 chassis.

The schematic is here: http://arcarc.xmission.com/PDF_Monitors/Pentranic%20CH-288%20Switchable.pdf

It was originally in a 25hz resolution game and I am doing a MAME conversion with a J-Pac.  I have switched the one connector that is marked with an obvious "switchable resolution" label.  I then got a picture that was obviously too high a resolution for the monitor.  I noticed that there is a yoke connector (I think) that appeared switchable to an identical connector below it.  I switched the connector and now have a beautiful picture but it's upside down.

I'm thinking theres another connector to switch somewhere or a jumper wire or something.  This monitor is meant to be switched so I'm thinking I don't have to mess with swapping wires in the yoke or whatever else.  What am I missing?


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grantspain

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Re: Pentranic CH-288 Switching 25hz back to 15hz / picture upside down
« Reply #1 on: January 05, 2010, 03:43:45 pm »
on the first pic you can see the yoke connector-put it on the other header
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kevinp

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Re: Pentranic CH-288 Switching 25hz back to 15hz / picture upside down
« Reply #2 on: January 05, 2010, 04:13:58 pm »
Quote from: grantspain on January 05, 2010, 03:43:45 pm
on the first pic you can see the yoke connector-put it on the other header

Tried that, it gives a correctly oriented picture but the resolution appears out of range like it's in EGA.  Half the screen is wrapped and not within adjustment.  The current header gives a PERFECT picture but is upside down.
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kevinp

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Re: Pentranic CH-288 Switching 25hz back to 15hz / picture upside down
« Reply #3 on: January 05, 2010, 04:40:01 pm »
I switched the yoke connector anyway and now the picture is clear and right-side up.  Strange, possibly a bad connector on the chassis?

Thanks
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grantspain

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Re: Pentranic CH-288 Switching 25hz back to 15hz / picture upside down
« Reply #4 on: January 05, 2010, 04:59:43 pm »
yeah check for a cracked solder joint and also check for any sign of arcing on the plug/pins
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kevinp

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Re: Pentranic CH-288 Switching 25hz back to 15hz / picture upside down
« Reply #5 on: January 07, 2010, 01:56:59 am »
The problem ended up being the horizontal hold trimmer pot on the remote adjustment board.  Was just a coincedence in the end, I guess it must have been flaking out intermittently.  I could feel the shaft had some play in it when compared to the other ones.  I seem to always have to change these pots on newer monitors as they like to use the cheapest nonsealed ones.  I usually replace all with PIEHR brand from Mouser electronics.

Ah well, live and learn..

Kevin
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