VIC-20 -- no sound

From: Lawrence Walker <lwalker_at_mail.interlog.com>
Date: Tue Sep 8 11:43:29 1998

On 7 Sep 98 at 19:14, Tony Duell wrote:

> > It's been a while and my VICs are buried under a pile of other stuff but I
> > think the problem is that the box is a RF modulator that has to go directly
> > into your TV to split the signal into audio and video. I don't remember there
>
> Wait a second....
>
> According to the Tech manual, the output from the VIC20 is composite
> video and line level audio. There was an external RF modulator that
> plugged into that socket and connected via a switchbox to the aerial
> socket on a TV, but if you TV has composite video inputs, etc, then
> there's no need to use a modulator.
>
> It sounds like that's what the original poster was doing. The fact that
> they got perfect video implies that _something_ was right - mix up RF and
> composite video signals and you won't get anything.
>
> -tony
>
>
 I just checked my old VIC20 Programmers manual from C= and
VIC20 manual both showing the pinouts. They call the pin 4 video low
and pin 5 video hi. The pin 1 +5v has a note 10mA max. Is it possible the
difference between the video pins was the hi-lo tuning on older TVs
(CH 2-7 .8-13 ?). That would explain why there were 2 plugs
on the RF modulator box output. A C64 plug with the 4 (or 2) line split-out
would give him the composite and audio signals needed.
The Programmers manual is a great little book, C= also included the
schematics with it. I see that Q1 output is tied to both pin 4 and directly
to pin 5 but with the pin 4 fed thru R8 a 47ohm r and with another line thru a
75 ohm R8 to ground. The schematic also marks the 1pin as 6v . Why the
discrepancy between the +5v pin 1 p-o diagrams in both of my C+ books and the
schematic and your tech manuals' +6v ?

ciao larry

  
lwalker_at_interlog.com
Received on Tue Sep 08 1998 - 11:43:29 BST