RE: Converting PAL P500 to NTSC

RE: Converting PAL P500 to NTSC

From: Bil Herd <>
Date: Sun, 5 Jul 2009 17:23:59 -0400
Message-ID: <>
Some parts can run too hot to touch (comfortably) and still have junction temperatures within max spec.  It might be they run that way, it might be you have a load somewhere on an output causing the extra current draw (I suspect not if two are involved).  If it's load related you can troubleshoot by watching the noise on VCC and GND for coincidence with output switching. Looking at the spec you might be able to tweak the rails down for less Pd.

What brand/model parts are they?

For the life of me I cant remember what we did to switch PAL modes, I know there was a register in the VIC as we troubleshot what happens to dram cycles when you flip it in the middle of an active screen, but I don't remember why you really would have had to swap VIC's on top of that.

-----Original Message-----
From: [] On Behalf Of B Degnan
Sent: Sunday, July 05, 2009 5:09 PM
Subject: Re: Converting PAL P500 to NTSC

Ullrich von Bassewitz wrote:
> On Sun, Jul 05, 2009 at 09:47:13PM +0200, Ullrich von Bassewitz wrote:
>> I've done the opposite quite some time ago and yes, it's the same as in the
>> C64. As far as I remember, you have to replace VIC and crystal, and change a
>> jumper.
> Looking at the schematics, I see no such jumper, so it's probably just the
> first two.
> Regards
>         Uz

I swapped the VIC-II chip for the NTSC version, but not the crystal, and
now I can at least view a black and white screen on a 1701 monitor.
There is adequate heat-sink compound on the VIC -II.

All things considered, I do have a PAL-compatible TV with composite
video input, and I will probably return the original PAL VIC-II chip to
the computer and use the PAL TV.

On a related note...
The FPLA's are 906114-02 and 906114-03.  They run very hot.  Not quite
too hot to touch, but hot enough that I should have a fan on them while
powered on.  I am somewhat concerned about long-term use.   I am running
a step up/down power unit to power the computer.  The voltages to the
motherboard coming from the power supply are correct (+12V, -12V, 5V,
2.5V), the TIP29 transistor appears to be sending the correct
voltages.   I don't believe the power source is causing the FPLA's to
run so hot, but I could be wrong.  The computer appears to function just
fine other than the wrong crystal for display output.  My reason for
using this computer is to experiment with it, but I don't want to ruin
it either.  I have newer 906114's (-04 and -05) that I could try to see
if it makes a difference.  The version of the BASIC ROMs are -02.



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Received on 2009-07-05 23:34:45

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