[Coco] My CoCo 3 freezes when you tap on it.

[Harry Hurst]

> You still have video when it freezes. Sometimes you have a random
> character or two onscreen and some very slight "snow," others it's
> just a "clean" freeze,
>
> Looks like a bad solder somewhere, but how do I look for it?

Does it have trouble when you plug a cartridge/multipak in, but not
without anything plugged in? If so, look at the connections in the
cartridge port. If those look good then check the solder connections to
the cartridge connector.

If there is no difference in the symptoms w/ or w/o something connected to
the cart port it gets more difficult. I would start trying to isolate the
problem's location by tapping very lightly on the circuit board with a
pencil eraser. When you find you're in the general vicinity of the bad
connection you can perhaps visually locate it, or just touch up all the
solder connections in that area. That's all I can come up with right now.

>
> Maybe the 512K expansion is the culprit? Will it function if I plug in
> 4 of the DRAMs on the motherboard sockets, without C65 and C66? If
> not,what are these capacitors' values?
>

C65=82pF   C66=27pF

> Some of the DRAMs are marked 8802, and others 8806. Is there a
> difference? I only noticed that after I took them off.
>

Got nothin', but if it's been working up to now that doesn't seem likely.
Have you just re-seated the DRAMs and memory board?


HH