Jack the Giantkiller

[lumberbunny]

Recently I found an entire Jack the Giantkiller cabinet. I'm new to these things so I was hoping to get some help on repairs. It's biggest problem is that the sound doesn't work. I've tried the obvious like turning up the volume and making sure the speaker still works (it does) but beyond that, my knowledge is pretty limited. Does anyone have any suggestions as to where to look next?

 

Thanks

Edited August 24, 2006 by lumberbunny

[tta583]

Well, as a pure guess I would try to find the audio amp section on the game board and give it the once over. There "should" be a transistor or 2 that are used as the amp. I would test those first with a meter. As a quick test I have heard of folks that, with the board on, touch the pins of these transistors on the solder side of the board. Supposedly if you and get a little scratchy "pop" out of the speakers then you need to look at replacing the transistor. As I understand it you finger is acting as a conductor to cross a little current over to the emitter of the transistor which then makes its way to the speaker to produce the "scratch".

 

Here is a link to the KLOV article on that game. The Operations and Maintenance Manual is linked at the very bottom. I did not look at it but it may have the schematics.

 

http://www.klov.com/game_detail.php?letter=&game_id=8217

 

You might want to check http://www.crazykong.com/ as well to see if they have any other manuals.

 

bombjack.org is a great place for manuals as well.

[lumberbunny]

Well, as a pure guess I would try to find the audio amp section on the game board and give it the once over.

 

I'm having a hell of a time figuring out which part is the audio amp. There's a 741 op amp on the board, and I gave that a tap but nothing happened. Have any hints?

[tta583]

Not right off my head. That Op Amp could be used for a number of things I guess. I would pull the board and trace the speaker pins from the finger board back and see where you end up.

[colorfixer]

Not right off my head. That Op Amp could be used for a number of things I guess. I would pull the board and trace the speaker pins from the finger board back and see where you end up.

 

 

First make sure that the game has its -5V and +12V supply rails, since the game will still play with only +5V. This is needed in order to make the sound happen. The audio on this game is a MB3712 (the ic located at E1). I have aslo seen these boards without a needed pot at VR1 for some reason.