10 Jul
2009
10 Jul
'09
10:31 a.m.
I just inherited a Commodore 64, 1541 disk drive, some joysticks and
various other related stuff. I've tried the C64 and 1541 by attempting
to boot a couple of games that came with the package and it seems that
the computer and drive work okay. The games come up and display their
start screen. My problem is that the sound doesn't seem to work. The
games came up silent when I suspect that they have some sort of music
associated with their start screens and a simple Basic program that I
typed in to test the sound also fails to produce any output. I know
that the SID chips in these machines are prone to failure but I was
wondering if there were any other likely causes of a lack of sound.
The main reason I was interested in this machine was to play around
with the SID so it will be very disappointing to find that it is bad.
Is there anything other than a dead SID that can cause sound problems
on a C64?
Thanks
David
10 Jul
10 Jul
10:37 a.m.
----- Original Message -----
From: "David Betz" <dbetz at xlisper.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Friday, July 10, 2009 11:31 AM
Subject: C64 sound problems
Is there anything other than a dead SID that can cause
sound problems on
a C64?
How are you outputting the audio and video? There is a built-in RF
modulator with an RCA connector that outputs VHF to a television, and there
is an 8-pin (5-pin on really old C64s) audio/video monitor connector that
converts the audio to an RCA plug that plugs into your monitor or an audio
system.
If you're using one, try the other.
If you're using a monitor cable, it's possible you have a bad cable or
forgot to plug in the audio connection.
The RF connection is designed to connect to an RCA male-to-male cable that
plugs into an RF switchbox, but you can use a piece of coax cable with an
RCA plug on one end and a standard coax cable connector on the other to plug
into most modern television sets.
Jim
10:46 a.m.
Is there
anything other than a dead SID that can cause sound
problems on a C64?
How are you outputting the audio and video? There is a built-in RF
modulator with an RCA connector that outputs VHF to a television,
and there is an 8-pin (5-pin on really old C64s) audio/video monitor
connector that converts the audio to an RCA plug that plugs into
your monitor or an audio system.
If you're using one, try the other.
I haven't tried that yet. Good idea.
If you're using a monitor cable, it's possible you have a bad cable
or forgot to plug in the audio connection.
I have a cable with a DIN connector on one end and four RCA plugs on
the other. I've used a multimeter to determine which RCA connector is
connected to which pin on the DIN and have used the RCA connector that
connects to DIN pin 3 for audio output and the one that connects to
DIN pin 4 for composite video output. Is that correct?
10:57 a.m.
----- Original Message -----
From: "David Betz" <dbetz at xlisper.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Friday, July 10, 2009 11:46 AM
Subject: Re: C64 sound problems
I have a cable with a DIN connector on one end and
four RCA plugs on the
other. I've used a multimeter to determine which RCA connector is
connected to which pin on the DIN and have used the RCA connector that
connects to DIN pin 3 for audio output and the one that connects to DIN
pin 4 for composite video output. Is that correct?
I can't recall, but I believe the audio RCA plug is either white or red, if
memory serves, if you're using a Commodore cable.
Jim
11:02 a.m.
I have a cable
with a DIN connector on one end and four RCA plugs
on the other. I've used a multimeter to determine which RCA
connector is connected to which pin on the DIN and have used the
RCA connector that connects to DIN pin 3 for audio output and the
one that connects to DIN pin 4 for composite video output. Is that
correct?
I can't recall, but I believe the audio RCA plug is either white or
red, if memory serves, if you're using a Commodore cable. 
10:38 a.m.
are you using the correct cable plugged into the correct place?
this is usually the biggest cause.
sound was mono, and you need the proper wiring, and your tv/etc may only accept
mono sound on a specific input
From: dbetz at xlisper.com
To: cctalk at classiccmp.org
Subject: C64 sound problems
Date: Fri, 10 Jul 2009 13:31:30 -0400
I just inherited a Commodore 64, 1541 disk drive, some joysticks and
various other related stuff. I've tried the C64 and 1541 by attempting
to boot a couple of games that came with the package and it seems that
the computer and drive work okay. The games come up and display their
start screen. My problem is that the sound doesn't seem to work. The
games came up silent when I suspect that they have some sort of music
associated with their start screens and a simple Basic program that I
typed in to test the sound also fails to produce any output. I know
that the SID chips in these machines are prone to failure but I was
wondering if there were any other likely causes of a lack of sound.
The main reason I was interested in this machine was to play around
with the SID so it will be very disappointing to find that it is bad.
Is there anything other than a dead SID that can cause sound problems
on a C64?
Thanks
David
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10:48 a.m.
are you using the correct cable plugged into the
correct place?
this is usually the biggest cause.
sound was mono, and you need the proper wiring, and your tv/etc may
only accept
mono sound on a specific input
I think I'm using the correct cable. The one I'm using for audio
connects to pin 3 of the A/V DIN connector. I'm plugging it into a TV
that only accepts a mono input and I've verified that the TV sound
works correctly by plugging it into an Atari 800xl.
11:43 a.m.
are you using the correct cable plugged into the
correct place?
this is usually the biggest cause.
sound was mono, and you need the proper wiring, and your tv/etc may
only accept
mono sound on a specific input
One thing I've been wondering about is if this could be caused by
problems with the 12v supply feeding the SID. Is there anything else
in the C64 that uses that voltage or is it just for the SID?
23 Jul
23 Jul
5 a.m.
On Jul 10, 2009, at 2:43 PM, David Betz wrote:
I finally got around to checking the 12v supply in my C64 and it seems
to be working. I also verified that 12v is getting to the VDD pin on
the SID chip so lack of 12v is not my problem. One thing I noticed
that I thought rather strange was that the VCC pin on the SID reads
5.27v but the output of the 5v regulator is correct. Is there a reason
why the VCC at the SID would be higher? Could this be causing a problem?
are you using
the correct cable plugged into the correct place?
this is usually the biggest cause.
sound was mono, and you need the proper wiring, and your tv/etc may
only accept
mono sound on a specific input
One thing I've been wondering about is if this could be caused by
problems with the 12v supply feeding the SID. Is there anything else
in the C64 that uses that voltage or is it just for the SID? 
9:57 a.m.
David Betz wrote:
I finally got around to checking the 12v supply in my
C64 and it seems
to be working. I also verified that 12v is getting to the VDD pin on
the SID chip so lack of 12v is not my problem. One thing I noticed
that I thought rather strange was that the VCC pin on the SID reads
5.27v but the output of the 5v regulator is correct. Is there a reason
why the VCC at the SID would be higher? Could this be causing a problem?
It would seem weird, wouldn't it - however, there are three 5V sources in the C64.
When you say 5V regulator do you mean the 7805 (VR2)? - that is not the supply
for the SID (pin 25), so one can expect a discrepancy.
(I know very little about C64's, just happen to have the SAM's photofact
schematic here.)
10:15 a.m.
David Betz wrote:
I finally got around to checking the 12v supply in my
C64 and it seems
to be working. I also verified that 12v is getting to the VDD pin on
the SID chip so lack of 12v is not my problem. One thing I noticed
that I thought rather strange was that the VCC pin on the SID reads
5.27v but the output of the 5v regulator is correct. Is there a reason
why the VCC at the SID would be higher? Could this be causing a problem?
Further, pin 27 is the audio output from the SID, it feeds a transistor (Q8) in
emitter follower cfg.
The emitter of Q8 feeds the RF modulator and pin 3 of the audio/video
connector. Might check or 'scope around those.
10 Jul
10 Jul
8:42 p.m.
David Betz wrote:
My problem is that the sound doesn't seem to work.
Open it up. You may find the SID completely missing. A lot of
electronic musicians are buying C64s just to get the SID to use with
their own music projects. The now-mute C64s are then given or thrown away.
11 Jul
11 Jul
4:12 a.m.
David Betz wrote:
The SID chip is there. It just isn't producing any output.
My problem is that the sound doesn't seem to
work.
Open it up. You may find the SID completely missing. A lot of
electronic musicians are buying C64s just to get the SID to use with
their own music projects. The now-mute C64s are then given or
thrown away.
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13 comments
5 participants
participants (5)
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dbetz＠xlisper.com -
dgahling＠hotmail.com -
hilpert＠cs.ubc.ca -
jim＠photojim.ca -
trixter＠oldskool.org