Finiky H Hold on Pentranic Ch288

[cyork2]

I just bought a new working Space Invaders stand up cabinet.  Someone put in a Pentranic Ch288 monitor (Rodotron tube).  I have lots of numbers off the tube etc if CH288 isn't enough detail.  I think it is 19 inches but I haven't had the mirror out of the cabinet yet so I haven't measured it.

Anyway, nearly every time I power up I have to adjust the H Hold to get rid of a valley in the playing field (the aliens look like they are moving down into a valley then climbing back up instead of moving across a level field).  After 5 to 10 mins the valley comes back and I have to adjust it again.  The valley is generally in the right hand side of the screen, is maybe two aliens wide and extends the full height of the monitor. Any suggestions... is this just life with an older arcade monitor?

I have multi-meter and basic electronics experience but no experience with monitors.  If someone has a specific suggestion and can forward the schematic please send to cyork2@gmail.com.

Is there a standard recommendation on software to run a test pattern with to tweak all the settings? (I bought the arcade vga board and the PC arrived today so I'll have it connected to a PC fairly soon).

Thank you all in advance,
Craig York

[Rickn]

Just sent you an e-mail on the possibilty of repair or a new board,

Just thinking though, few questions:
- Pentranic, is this branded Pentranic USA, what is the manufacture date, this may have actualy been manufactred by ALS ... possibibly wrong tube, yoke and chasis combination.

Send me some pictures and possibly post for others. This sounds like horizontal foldover.

I will be happy to help you in any way possible... I don't want to just sell you a board or do a repair that does not fix the problem.

Good Luck

Rick

[cyork2]

Rick your awesome.... when I need a new monitor I'm buying yours.

Something dawned on me (doh moment)... I tweak the settings right after I turn it on while it is still relatively cold.  Then a few minutes later I tweak it again and by then the tube has had time to warm up.  I'm thinking it just behaves slightly differently cold vs warm and if I leave the warm settings I can just give it a minute to warm up before I play.  I should have thought of that sooner.

If it keeps acting up I'll post some pics and troubleshoot here so everyone can benefit.

thank you,
Craig

[Rickn]

Hey Craig, glad to hear you have found a reasonable compromise,

Nope not the tube, we are likely dealing with a leaky Electrolytic cap and temperature co-efficient.

If I get a chance I will look at the schematic and see what might be the cause,,, but for that I need some pictures,

If I can help you isolate the right one, you can change its yourself and all is well.

For now I will look at it as a closed issue unless you e-mail or post again.

Enjoy

Rick