Re: 85xx <------> 65xx Mutually replaceable?

From: Scott McDonnell (
Date: 2003-07-05 21:04:01

I had a 64 with what sounds like the exact same problem and it turned out
that the PLA was bad. If you can unsolder just the VCC and GND pins from the
(suspected) bad chip and piggyback it with a good chip to test (connecting
the VCC and GND to it temporarily), it might make your life a bit easier.

If you have chips (the 85xx and 65xx series) that are pin compatible, but
use a different voltage...perhaps you can carefully chop the trace to VCC
and tap the needed voltage from another point on the board. I would prefer
this over relying on heatsinks and such to protect the chip.
If going from 12v to 9v, you could use a zener diode to drop the voltage, a
voltage divider with a ratio of 4/3, or a  7809 Voltage regulator. If going
from 9V to 12V, the easiest way would be to get the 12v from the power
supply section.

Just some thoughts,


----- Original Message ----- 
From: <>
To: <>; <>
Sent: Saturday, July 05, 2003 9:20 AM
Subject: RE: 85xx <------> 65xx Mutually replaceable?

> Hello Ruud,
> thanks a lot, really helpful! But let me clarify something, and I will
> my original post: "[..] the C-64 only displays colored squares instead
>  of characters AND instead of sprites [..]" I never said this happens on
> startup - there you don't have sprites. This happens when I pop in a
> game cart. Otherwise, at startup I only see light blue squares on a dark
>  blue background. NOw I don't mean to say that you aren't correct in
> dismissing my assumption, I just want to provide all the data. BTW, the
> game is actually somewhat playable, except that sprites are bigger squares
> while there are 4 stripes/areas filled with colorful squares. When there
is no
> cart, at startup the light bue squares are located in those same 4
> Anyway, thanks a lot for a very informative post.
> mario
> -----Original Message-----
> From: ext Baltissen, R (Ruud) []
> Sent: 05 July 2003 15:00
> To: ''
> Subject: RE: 85xx <------> 65xx Mutually replaceable?
> Hallo Mario,
> > The 8500 has same pinout as the 6510, is it safe to replace a
> > 8500 with a 6510?
> No Problem.
> > And what about the 8580
> The 6581 needs 12V instead of the 9V for the 8580. The 9V won't harm the
> but i cannot guarrantee that it will work properly.
> > and 8565?
> No problem AFAIK.
> > can I assume with 95% certainty, ... that the 225 is bust?
> No. In fact I never encounterd a brooken CHARROM in my life. If the
CHARROM is brooken I expect allkind of garbage on the screen but in the
standard sturt-up colors. Certainly NOT all kind of colored squares.
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