Re: IIe sound problem

[rubywand@aol.com (RUBYWAND)]

In article <326BE459.2936@ix.netcom.com>, JB <jbcole@ix.netcom.com>
writes:

>
>I have a IIe that works fine but is not making any sound.  It's plugged
>into the logic board OK.  Anyone know why it wouldn't make any noise? 

     If it does not BEEP (e.g. for a RESET), then, you have some kind of
hardware problem. Disconnect the Speaker cable from the motherboard and
check Speaker resistance through the plug and cable with an Ohm meter. It
should be a few Ohms. If you are using a multi-meter with a real meter,
there should be an audible CLICK on the RX10 or RX1 range. If R is very
high you have a messed-up cable or Speaker. If it is close to Zero and
there is no CLICK, you have a shorted cable or Speaker.

     If your Speaker and cable are okay, try scootching up and reseating
the 40-pin IOU chip. Pin 8 of this IC is the sound output signal which
goes to a transistor amplifier which drives the Speaker.

     If the above tries get you nowhere, the problem may be a blown
component in the transistor amplier circuit. Suspects include Q5 (an
MPSA13 darlington transistor)  and SA1. SA1 appears to be an Op Amp which
is supposed to supply negative feedback.

     You can zero-in on the place where things go bad using an audio cable
connected to a hi-fi amp. (Be a bit careful with the setting of the hi-fi
amp's volume. You do not want to blow your hi-fi speakers.)  Clip audio
cable GND to Apple II GND and touch a clip connected to cable center pin
to IOU pin 8. Do a RESET. If you hear a BEEP through speakers connected to
the hi-fi amp, you know the IOU audio output is working okay.

     The same procedure works for the motherboard pins which go to the IIe
Speaker. (Try both pins; one is GND and one is supposed to be output from
the IIe's transistor amplifier SPKR output.)  The sound level from the
motherboard 'hot' SPKR pin should be a good deal higher (louder) than from
IOU pin 8.

     If there is no audio signal from the SPKR pin or if it is no louder
than from IOU pin 8, you have a problem in the transistor amplifier. No
signal can mean a broken trace, bad connection, blown C79, blown R39,
shorted CR4, or blown Q5.

     For Low signal, a decent fix try is to cut the trace running from SA1
to the SPKR pin. If SA1's Input/Output is shorted, cutting the trace
should enable the darlington transistor to amplify the signal and your
BEEP will be back. (I do not know how much SA1 contributes to sound
quality. Eventually, you may want to replace it. Either that, or take
steps to reduce the gain of the amplifier.)



Rubywand