Sega/Gremlin (Frogger) Need assistance troubleshooting

[godfrey]

Hello,

I recently came into possession of a Frogger cab that works about 50% of the time.  When you first plug it in, you'll get one of two screens.

One of them is normal, X's that fill the tube and go away as the rom is loading.  I haven't seen it act up even after long periods of time.

The other is a screen filled with blue vertical lines, usually 5 in a column across the screen (left to right).  I wouldn't say its mosaic in appearance.  There are some other colors that pop in and out.  You can play the game (minus the fact you can't see anything on the monitor, so input controls seem normal at this point).

It doesn't seem to be related to the tube and it's boards.  I'm in the process of putting in new caps anyways.

I removed the ram and rom IC's from their sockets and carefully cleaned the pins and sockets as well.  This however did not solve the problem.

Hopefully my photo of it will be visible.  It's been a while since I've posted pictures on a forum.

If anyone has some insight, that would be great and I sure would appreciate it.



Thank you in advance,


Phil Godfrey

[modessitt]

I appears your hold is set right on the edge of locked and scrambled.  A cap kit may help and is a good idea if it looks like it hasn't been done in ages just to give you peace of mind about it.

You need to adjust your holds (horizontal probably, but vertical also, maybe) to move it more to the "center" of it's hold tolerance.  As the caps get older, the window of locked sync gets smaller until it will eventually not lock.  This is whay a cap kit is good if not done in a while.  However, you can try adjusting to see if it will stay locked.  If it does, you can try skipping the cap kit.  Maybe it will stay locked and not mess up again.  It's up to you, though.

[godfrey]

Thank you for the kind reply.  I picked some of the capacitors out of the parts bin at work the other day - the common values anyway.

I was looking at the individual outputs (RGB) on the oscilloscope and they appeared okay.  I'm so used to looking at a waveform monitor and vector scope I can almost tell you what you're watching by looking at it.  (Well I can tell you some detail at least).

I do repair industrial and broadcast equipment - so this won't be a problem.  I see that a lot with equipment that comes in for service at work.  I have the service manual for this arcade as well.

It shouldn't take but an hour or so to remove the chassis and replace the caps.  I will replace the electrolytic caps and look for any damage on the PCB caused by leaky caps.

I will update you with the results.


Thank you again!


Phil

[Kevin Mullins]

I'm leaning towards agreeing with modessitt ..... looks like a sync issue.... horizontal shift, frequency, etc.
A simple pot adjustment might cure that one.
(always recommend a cap kit on a monitor of that age anyways though)

What model monitor is it?

[godfrey]

It is a Wells-Gardner 19K4675.


Thanks again,

Phil

[Kevin Mullins]

It is a Wells-Gardner 19K4675.

That's kinda what I figured..... this might help: http://www.arcaderestoration.com/index.asp?OPT=3&CBT=24

[Pac-Fan]

Frogger boards come in two varieties (actually more if you read all the schematics at the back of the manual)

The primary two are Konami labeled boards, and others that state Sega/Gremlin in the board's silk screen.

One board runs POSITIVE SEPARATE sync, the other variation runs NEGATIVE COMPOSITE sync.

Read the numbers off the board and verify against the schematics and follow the schematics to the monitor and you'll see which boards run separate H+V positive (2 separate wires) and which ones run composite negative sync (single wire)

You need to match up your board, your wire harness and your monitor inputs to get it right.  It's a pain if you're subbing in parts that weren't in the original combination in the cab.

Often Frogger boards will have a tiny Radio Shack home-made daughter board with a 74LS0x chip hacked onto the edge connector and a couple chips to convert the signal as well, which was done by ops to overcome these mis-match problems.

Double check what sync signal it's putting out, what the wire harness is carrying (most only carry one or the other, and you'll have to add a new wire if it doesn't have the one you want), and what your monitor is capable of handling.