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rpiguy9907

Help identify mod made to Commodore 128

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I am attempting to resurrect a modded 128 that I acquired on the cheap (yes it is filthy to boot). See the picture attached.

Ignoring the normal bodge wire on the z80 from the factory, what is the other mod with wires going into the board near R27 in the middle, down by U37 at the bottom, etc.

These wires are attached to a switch, also pictured.

I have never seen this mod before anyone know what it is?

 

It is not a JiffyDos mod as this is nowhere near the ROMs, and there is already one of those installed as well :-)

post-45042-0-15331800-1548967525_thumb.jpeg

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Without tracing where exactly the wires connect in relation to other components, I can make a guess: One wire connects to R47, which is part of the Z80 clock output. Another on that same pole from the switch goes down to the glue logic at the bottom. This looks like a clock speed switcher. Perhaps there's another wire that goes to a different clock source so that you can feed different speeds into one of the CPUs. I'm not sure why it's a double-pole switch though.

 

It looks like they cut a couple of traces near R27 too. Or maybe it's just coated in dust there?

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Without tracing where exactly the wires connect in relation to other components, I can make a guess: One wire connects to R47, which is part of the Z80 clock output. Another on that same pole from the switch goes down to the glue logic at the bottom. This looks like a clock speed switcher. Perhaps there's another wire that goes to a different clock source so that you can feed different speeds into one of the CPUs. I'm not sure why it's a double-pole switch though.

 

It looks like they cut a couple of traces near R27 too. Or maybe it's just coated in dust there?

All early 128 motherboards have the wire off the z80 from the factory. None of the switch wires connect to the z80 as far as I can tell.

 

I had the same thought though some kind of clock switch or an NTSC/PAL switch if such a mod existed.

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Yeah I assumed that the larger wires with the hot snot are bodge wires. I was looking at the fact that it pulls off of a clock circuit (maybe--depends on which side of the resistor it's connected to) and sends it somewhere into the 7400's. And with the apparent removal of a section of some traces, it's possible that the new wires are for changing the clock source for at least one of the big chips.

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