Horizontal pot, wavy issues on KT1420A

whitefox

Well-known member

Donor 5 years: 2016-2019, 2024
Joined
Jan 5, 2016
Messages
3,674
Reaction score
330
Location
Hockessin, Delaware
I got replacement pots for what i thought were two problematic ones in this Kortek in my Turbo. After replacing them I'm still having horizontal hold issues, in fact, when I get it stable, the video is wavy. It's possible the replacement could be bad, but maybe something else is going on here? If i press down on top of the pot it does sometimes affect the video. Maybe a fracture on the board?

Ugh...



https://www.youtube.com/watch?v=6DaESuhgb3g
 
Bump for suggestions!

The power regulator has a new recap in the game. I don't think the switching unit is involved in powering the crt.

Here's a longer video of me trying to adjust it in, you can see how fickle the horizontal pot is on it, and that is a new replacement.



https://www.youtube.com/watch?v=r3YJziM7MmE
 
Switching the switch

In troubleshooting this display problem I'm having it was suggested I have weak caps in a power supply. The regulator was rebuilt with new caps, so that leaves the switching unit itself.

With some help I found and purchased this one. I connected it up with just the two AC lines and dialed the two 5V lines in. Connected the rest up, powered it up, and got a lot of noise through the speaker and no video. Checked the voltages, they're good.

I'm going over everything I can think of comparing the two switches, did I miss something, is this the wrong switch?

The original is labeled as AC 100V, 5V, 10A.
 

Attachments

  • 20170126_094053.jpg
    20170126_094053.jpg
    204 KB · Views: 15
  • getimage.jpg
    getimage.jpg
    42 KB · Views: 9
  • 20170126_093439.jpg
    20170126_093439.jpg
    204.4 KB · Views: 15
  • 20170130_194506.jpg
    20170130_194506.jpg
    204.1 KB · Views: 16
In troubleshooting this display problem I'm having it was suggested I have weak caps in a power supply. The regulator was rebuilt with new caps, so that leaves the switching unit itself.

With some help I found and purchased this one. I connected it up with just the two AC lines and dialed the two 5V lines in. Connected the rest up, powered it up, and got a lot of noise through the speaker and no video. Checked the voltages, they're good.

I'm going over everything I can think of comparing the two switches, did I miss something, is this the wrong switch?

The original is labeled as AC 100V, 5V, 10A.
Looks like you connected the ground wires(white) to the -5 volt out. The white wires should be on the ground which is between the +5 volts and +12 volt terminals.
 
Looks like you connected the ground wires(white) to the -5 volt out. The white wires should be on the ground which is between the +5 volts and +12 volt terminals.

this. Sega uses yellow for +5 and white for ground. because they're Sega, and they can do what they want.

a lesson that was bestowed upon me in my early days of game repair: there's no such thing as a power supply wiring color standard. Atari had brown ground wires, Sega had their thing, Midway when they got away from the Williams power wiring scheme started using orange for +12 instead of yellow (which was their -5).
 
this. Sega uses yellow for +5 and white for ground. because they're Sega, and they can do what they want.

Looks like you connected the ground wires(white) to the -5 volt out. The white wires should be on the ground which is between the +5 volts and +12 volt terminals.

Huh, so I'll try that tonight. So on Sega's original switching unit there, why are the white ground wires plugged into a terminal marked V-?

Or is that more of Sega's funny stuff.

Thanks for the replies!
 
really old switching power supplies only output +5. so V+ is +5 and V- is ground.

it's why Atari games will get their +12 from the amplifier board, which gets its power from the transformer as an example.
 
Good news, that was the problem. Got it running! Now I have a couple issues with the display and getting the sizing and hold correct & stable, and the display is slightly crooked, but I'll get to those soon enough.
 
I have a question about rotating the picture 180 so that I can flip the tube. I was reading this post on doing this, but I just want to be sure this DY A & B choice is correct.

Currently, it's in the B connection. Do I simply move this to the A position, or do I need to flip the connecter & then plug it into A like in that post?

Thanks!
 

Attachments

  • 20160725_182345.jpg
    20160725_182345.jpg
    211.8 KB · Views: 7
the monitor is probably installed upside down. on most vertical games the bottom of the monitor is on the right side. you can fix this by snapping your yoke plug in half so that each half is yellow/green and red/blue.

your current arrangement is yellow-green-blue-red. you want to flip the two halves of the plug so it goes green-yellow-red-blue. or you can leave the plug alone and don't cut it and just physically rotate the whole monitor.
 
So plugging that into A and flipping it around does produce 180'd video. It's not solving the one problem i was having.

More importantly, I need to address a basic problem here. I can not get the Vertical Hold pot adjustment to stay set for any length of time. I get it right, play the game for a bit, run into the dark tunnel and it starts moving. Turn off the game. Turn it back on in a little bit, and it's off centered. And starts moving again.

I'm running out of things to check or replace here.
 
Did some searching and ran across this thread about the horiztonal and vertical switches on the board.

Looked at some photos i took before taking the game apart and compared it to a photo of the board as it came back from chad and low and behold, the switches originally should be in the negative position and are both now in the positive setting.

I hope this does it! More searching regardless for other options.
 
Yep, the switches did it. Turned on with a solid video display, no rolling. I'll do a full write up in my resto thread. Some balancing had to be done between horizontal hold and horizontal sub position pots, initially I honed it in and turned the game off, and turned it back on and video was scrambled. That horizontal hold is finicky as anything on this kortek.

But we're solid now. More minor work to be done but at least this part is resolved.

Not sure if I should drink tonight to celebrate or drink to forget... :D :confused::cheers::beerchug::friday:
 
Back
Top Bottom