RE: PET 50Hz editor ROMS

From: Martin Hoffmann-Vetter <>
Date: Thu, 7 May 2015 14:18:38 +0200
Message-ID: <008001d088bf$f3bfd1b0$>
>> Yes, it think too, this 970150-07 must be near to 901474-03 with
>> changed crtc registers. But it's possible, they changed anything
>> else, too.
> I think it more likely a 901447-29 with crtc initialization added.

Yes, you are right. The 901474-03 is a 80 column rom. On a 9" screen a 40
column is better. So the 970150-07 must be a 40 columns version, too.

>>> This could also be used with an adapter to drive external
>>> monitors. The 50Hz PAL is probably for an external monitor,
>>> otherwise there is no reason to make it PAL compatible. In which
>>> case, monitor size doesn't matter.
>> Isn't it? This 901474-04_ can be for an european system board
>> replacement with 50 Hz. This must be working with a 9" crt. The
>> changes about 970150-07 and 901774-04_ must be the 50 / 60 Hz
>> difference. So 901774-04_ looks to 970150-07 as 901774-04 to
>> 901774-03!
> Was there a different system board for the European thin 40 or was
> there just a different video board?

On the normal thin 40 the video board is on the system board. I think, the
old boards without crtc runs in europe with 60 Hz, too. So no different roms
exists for basic 1.

> The system board would not need to be different

Yes, i think, too.

> and the power transformer could be wired to be either
> 220 or 110 V.

That's an other question. Many first PET have an additional transformer for
the 220 to 110 V transfoming!

> The ramp generator for the horzontal sync would have to
> be different.

Why? The crt is the same and the system board to drive the crt are also the
same. For minimal interferences only the vertical sync is defined to the
frequency of the main power.

> However, this could be accomplished by changing the
> capacitor in the horizontal ramp generator.

Okay, so you can change the specification of a crt. But is this needed?


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Received on 2015-05-07 13:00:06

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