Defender video issue

[hutch1980]

I am having a problem trying to troubleshoot my defender machine. As soon as i can find my missing camera memory stick, i'll supply pictures of the exact problem, but for now i'll have to describe the best i can. The game itself works fine, but the top 1/4th of the screen (horizontally) is scrunched down to a single line. So there is just black empty space at the top 1/4 of the screen, while the bottom is fine.

My first thought was a monitor problem, so i tried adjusting the various pots on the back of the monitor, vhold, hhold, vsync, hsync, etc... with no change in the problem. In fact, when i move the horizontal image up, more of the game screen gets scrunched.

Next, i hooked up a seperate arcade monitor to the defender boards, and it's the exact same problem.

I then tried measuring the voltages of the defender boardset following the schematics, and all voltages are ok. There was only 1 discrepency i'm not sure if it is a problem, but i also measured the voltages  on the bank of the 5 fuses on the power supply. The top 2 fuses which are supposed to be around +5V are now only reading +.25V and the other 3 fuses are around where they are supposed to be. This was the really only thing i could find, and visually the 2 fuses look fine (i.e. not blown).

As far as the built in diagnostic tests, everything passes. The 4 LEDs on the defender board all blink when game is first turned on, indicated ram ok. The built-in game diagnostics that display on the monitor all pass which also indicated the same. I ran it through all the tests and it indicated no errors.

I've run out of ideas at this point and i've tried searching here and the RGVAC for any ideas with no luck. So if anyone here has any clue, please let me know

Thanks

[CheffoJeffo]

Based on you initial description I would have said monitor -- vertical foldover. I had a similar problem with the EZ-20 in my Super Mario Bros. Was a bad cap.

Do you have a spare monitor that you could swap in for testing ?

Cheers.

[hutch1980]

The spare monitor that i tried was not in the greatest condition to begin with. It seemed close to what the defender monitor was doing, so i automatically assumed that it wasn't the monitor. But the spare could have had a similar problem. I use the spare monitor for my jamma test rig and it's had it's own sets of problems too.  I think my next course of action then would be to buy a cap kit for the defender monitor and reset/reheat some of the old solder joints on the monitor board.

[CheffoJeffo]

At this point, don't take my word for more than it its worth (I'm still a complete Williams noob and the multi-board interactions confuse me).

Grab a pic and post in the Monitor forum.

Cheers.

[RayB]

Wow, I wish all tech help requests were this detailed!

Give it a day or so and Mr Layton will post. I bet he know exactly what this problem is... 

[grantspain]

in england we call that fault a frame lapover,usually caused by electrolitic caps,bad solder joints or dirty/maladjusted pots-try your vertical size/hold/shift,then check for bad solder joints on the chassis(give it a tap on the side),then purchase a full cap kit

[SirPeale]

Sounds exactly like bad caps.

K4900?

[RayB]

Isn't it weird though that his other monitor displayed the same thing?

[grantspain]

it would the first time in 20 years that a board would cause that sort of fault for me,the only other thing i can think of is a low 5volts which can cause all sorts of strange problems but the fault described defies all logic unless its a monitor fault

[hutch1980]

Ok, i finally got my camera working. Here are two pics of what i am talking about. I'm planning on re-heating/resoldering the old connections on the monitor board and then getting a cap kit for it.

[grantspain]

that looks exactly like a common fault with pentranics with the partial frame collapse,be nice to know your monitor model number and make

[hutch1980]

It is a Wells Gardner Model 19K4921

[hutch1980]

I'm hoping i can fix this with a simple cap kit as i plan to swap this monitor with a local arcade collector in my town who has the original Defender monitor with slight defender burn-in. It would be a big step up from the one in my defender right now with a really bad burn-in of some trivia whiz game.

[SirPeale]

I'm sure caps will fix that.  Classic bad cap symptom right there.