RE: LOW VOLUME SOUND C64c

I am honored to have my question answered by you Bil.
I don't have an oscilloscope. What kind of SID does the Plus/4 have in it. I
have a Plus/4 in storage. 


Best regards,
Ed Johnson
 

-----Original Message-----
From: owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Bil Herd
Sent: Monday, January 30, 2012 10:17 PM
To: cbm-hackers@musoftware.de
Subject: RE: LOW VOLUME SOUND C64c

Typically we did not have a revision of a chip number make it incompatible
with other chips, so,me slight exceptions where constants needed tweaking.
If you have one it is worth a swap out I would think as even if it isn’t
100% compatible it should still be loud if the pcb is working.  If you have
a scope there are some places you could test voltage and signal, even a low
bandwidth scope due to it being audio.

Bil Herd

-----Original Message-----
From: owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Ed Johnson
Sent: Monday, January 30, 2012 10:12 PM
To: cbm-hackers@musoftware.de
Subject: RE: LOW VOLUME SOUND C64c

I see the 6581 uses a 12 volt supply - the 8580, a nine volt supply But does
the revision on the 8580 SID matter?

Best regards,
Ed Johnson


-----Original Message-----
From: owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Marko Mäkelä
Sent: Monday, January 30, 2012 2:02 AM
To: cbm-hackers@musoftware.de
Subject: Re: LOW VOLUME SOUND C64c

On Sun, Jan 29, 2012 at 04:43:51PM -0500, Ed Johnson wrote:
>I checked the fuse inside. It was good.
>The board is a PCB ASSY #252311 REV 3
>
>I has a very sharp clear video picture. Better than the older bread box 
>version I tested the power supply with.
>
>Any other ideas?

Could the SID chip be damaged? Over 20 years ago, I damaged a SID chip in an
old-style C64 (+12V VIC and SID) by hot-plugging the audio output to a
stereo receiver that was also hooked to an antenna amplifier that may have
been powered from a different mains voltage phase. This could have caused a
ground current.  I cannot remember clearly, but I think that the audio was
very quiet after the incident. Replacing the SID chip cured it.

	Marko

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