Re: VIC 20 without audio tone

From: Francesco Messineo <francesco.messineo_at_gmail.com>
Date: Sun, 6 Jan 2019 20:29:00 +0100
Message-ID: <CAESs-_wLs+k1_yfxn=PHUDEVCMxRPSQi42f3UMvprGrMBr+n_w@mail.gmail.com>
On Sun, Jan 6, 2019 at 6:38 PM fabry891 <fabrizio.vita80@gmail.com> wrote:
>
> >9VAC can be measured only between the two AC pins, that supply is just
> >a floating (i.e. not connected to ground) transformer secondary.
>
> if I measure AC voltage between two AC pin the voltage is 10.5V.

that is correct for an old C64/VIC-20 power supply. In many countries
they were calculated for 220V input, but now all EU has 230V AC line
voltage, so about 9V goes to about 11V on the secondary.

>
> >6561 are very expensive and by the way, are you only trying via a RF
> >modulator to a TV? RF modulators easily go out of tune and can produce
> >a way off sound carrier or transmit out of frequency between two
> >channels too. Your TV might be trying to autotune (and might also fail
> >at correctly auto-tune) or might even not try to tune to the correct
> >channel.
> >You can't conclude anything without trying how the audio sound
> >directly at the A/V connector.
> >PS: 6561 don't need to be programmed.
>
> I tried to connect audio/video VIC20 to tv with either RF modulator either
> Scart cable that I made connect the pin 3 of VIC 20 audio to pin 6 of scart
> connector, with the same result.

Try to change C11 (I'm assuming you have a VIC-20CR, the one with 2 x
6116 SRAMs and 3 x 2114 SRAMs)
On the old VIC-20, the one with all 2114 SRAMs, it's labeled C16. If
this doesn't solve the problem, then try changing Q1 (new VIC-20CR) or
Q5 (old VIC-20). But you should first check that the transistor is
really bad or if it's just a failed connection or polarization
resistor etc... (most of the checks can be done with a simple
multimeter).

Frank IZ8DWF
Received on 2019-01-06 21:00:08

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