Re: Apple IIGS Rom 3 - NO SOUND

[Roger Johnstone <roger@ihug.invalid>]

In <287c502d.0401190922.74f2a453@posting.google.com> Carlos Bragatto 
wrote:
> Hey mates
> 
> I just got hold of a Rom 3 Apple IIGS that works flawlessly except for
> there's absolutely no sound !!! I first thought it was something in
> the sound control panel, but no luck there.
> 
> Is it possible to the GS to boot, flawlessly load games and demos if
> the Ensonic sound processor is blown ??? I really don't think it's
> blown, because (as I read in the FAQ) the Apple II sound (from the
> MegaII) isn't routed to the Ensonic, and as such it should be audible,
> but no, no sound from both GS and II sides.
> 
> I even thought the internal speaker was broken, but I changed it (I
> have a spare GS case), and I even plugged an earphone to the plug on
> the back, but nada.
> 
> Any ideas ? Is there something like an internal amp on the motherboard
> ?
> 
> Thanks in Advance
> 
> Carlos Bragatto
> Brazil

If it was an original 256KB motherboard I would suggest checking the 
jumper header W1. If a link is installed across W1 it disables the DOC 
sound chip by shutting down the clock to it. I have no idea why this 
link exists, but I don't think it is present in the 1MB motherboard used 
in the ROM 3.

The IIGS uses an LM380 amplifier IC. My 256KB IIGS has the 8-pin DIP 
version of the IC in a socket located at the front of the main board 
near the DOC sound chip. This amplifier may have been replaced at some 
point as the socket does not look original.

The sound from the DOC also goes through several op-amps before being 
amplified. Unamplified audio is available from pin 3 of the 7-pin sound 
expansion connector. If it's present there than one of the op-amps or 
the power amplifier is likely faulty.

-- 
Roger Johnstone, Invercargill, New Zealand

PS/2 Mouse Adapter for vintage Apple II or Mac
order at http://vintageware.orcon.net.nz