Mar 292016
 

Got a very clean Megazone pcb for a repair.  The board was in near mint conditions but it didn’t boot and also the Sync was missing.

Looking at the schematics available online, I noticed that the quartz responsibile for the CPU clock and sync was the one placed on the bottom board.

Tested with my frequency meter and it was dead.

It is a very rare 18.432mhz OSC which to my knowledge is used only by early 80s Konami boards.

megazone

 

Luckily I had a Double Dribble which I used for spare parts which had the very same OSC.

After changing it, the game booted perfectly.

megazone3

megazone4

For you information, if you try to install the more common 20Mhz OSC, the colours are off and the scrolling is jumping often, so unfortunately it’s not a good replacement.

The board had no sound but I immediately noticed that there was no noise coming out of the speaker which is the evidence of a faulty amplifier.

The amplifier is infact the very unrielable LA4460N, so after confirming the the music could be hear on input pin 2 , I exchanging it and fixed completely the game.

megazone2

 

 

  3 Responses to “Megazone repair log #1”

  1. Nice one !

    Did to exchange the LA4460N by a working one, or did you put another more reliable ? If so, which one

    thanks

    • I used the same one, it is very commonly used on arcade games so I just desoldered one from my collection of junk boards.

      Beware that there is also a LA4461 which is the same but with reversed pinout.