Re: CBM 3032 (PET 2001N-32), no video?

From: Francesco Messineo <francesco.messineo_at_gmail.com>
Date: Sun, 4 Mar 2018 22:34:39 +0100
Message-ID: <CAESs-_zb2EAD1oJDGheAea+TZK+kyjOgCvBE-7NOnPX5O30z_g@mail.gmail.com>
On Sun, Mar 4, 2018 at 10:10 PM, Sherry Haibara <v.castelli92@gmail.com> wrote:
> Good news, everybody! Thanks to your amazing suggestions, it seems like the
> problem is fixed!

good to know

> I'm not entirely sure about what was wrong in the first place, though: as I
> later determined, what I was measuring without the voltage regulator in
> place was not in fact a short, but the resistance of the tube - or something
> closely related to that. With the tube disconnected, the resistance between
> the output of the regulator and ground was indeed in the order of megohms.
> The diodes of the rectifier were fine, as were all the traces and the L701
> coil.

the heater filament of the tube has usually a very low resistance when cold.

> I just ended up replacing the voltage regulator and applying fresh solder on
> all the solder joints of the power supply circuit, like those of the diodes
> in the bridge rectifier and of the big 4700 uF capacitor, and amazingly
> enough, it works perfectly now. My best guess so far is that either the
> voltage regulator itself died after the first power-up due to old age, or
> that a combination of electrical, thermal and transportation stress may have
> weakened some of the solder joints.

good job!

> There is just an extremely minor vertical wobbling of the image which is
> very hard to notice, and which may suggest that the caps are in need for a
> replacement, but for now I'll probably leave them alone. The screen is
> crystal clear and pretty much on focus. The logic seems to be in working

yes, usually the wobbling can be cured by replacing some other electrolytics.

> order - to be fair, I did not perform an extensive test, limiting myself to
> printing a "hello world" message, but so far so good. It seems like it's
> running some sort of custom ROM, because the greeting message is "*** PET
> Club Scharinger ***", which seems to be referring to an Italian IT company
> founded in 1979 in Sudtirol, instead of the usual "*** COMMODORE BASIC ***".
> Is there an alternative easy way to determine which BASIC version it's
> running?

DLOAD (and many other commands) exists only on Basic 4.0
If DLOAD"*" gives a syntax error, it's probably Basic 2

You should try to dump the ROM contents and send them to this list,
custom ROMs are probably very rare by now.

Frank

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Received on 2018-03-04 23:02:37

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