Hi. I have an Atari 1985 Gauntlet-II Arcade. It has a vertical hold issue. I bought it, knowing this issue, thru an auction out of state a few months ago. The CRT and CRT board had been replaced before I bought it. My guess is the upgrade occurred 15-20 years ago or used that technology from then around 2003.
Altho all adjustments work, I cannot get the Vertical hold to stop. The best that I can adjust it, is to slow it down. Rarely locking in.
What the previous owner replaced:
1). CRT is a 19 inch Samsung type A48KRD82X01. Vision Pro. Happ Controls MTG-1901CN.
2). The board is a Vision Pro. Happ Controls MTG-2901.
The service manual:
https://www.arcade-museum.com/manuals-monitors/Vision_Pro_(MTG-XX01_Series_13in_and_19in_CGA).pdfI did the following in various stages, WITHOUT ANYTHING IMPROVING.
1). Recap the entire board.
2). Replaced chip i301 (LA7851) because the VH was affected by cold spray.
3). Various Mylar caps around that area because the VH was affected by cold spray.
4). Replaced the 200k VH pot VR303.
Again, there was NO CHANGE.
So I bought a new "working" VisionPro Happ Controls CRT board that was identical to the board I had.
And guess what, NO CHANGE.
My only thought at this time is the VH problem is originating from the main game board.
On the upper left side of the Happ VisionPro CRT board are the inputs from the main game board. R,G,B, gnd, V/S, H/S.
Does anyone know the video pinout for the Atari Gauntlet II game board?
Both the V/S and H/S are connected to pins on this board. If I remove either of them, the picture gets scrambled. If you refer to the link at the top, it was suggested that the V/S (yellow wire) should be disconnected which scrambled the picture.
or Is it possible that the V/S is not working properly? I have a fairly new LED Oscilloscope. But my expertise ends here.
Thank You. Pete.