A4000 Rev B Audio Low One Channel

[Loedown]

Another obscure fault and a solution.

Fault: Left channel is far quieter and mildly distorted

Solution: Audio output is fine through each stage of the LF347 but distorted on the final stage of the LM833, found resistance to ground from C443 pin 2 at 800R, should be close to 2K. R443 is the closest resistor to the 22uF capacitor C443 on top side. Leakage from C443 had caused R443 to read much lower and once removed and cleaned area and verified that R443 was indeed 1K replaced and audio is now clear.

[roy bates]

so you was expereincing a clipping effect.

[Loedown]

Quieter and distorted, a synthetic sine wave ( generated out of Paula ) looked almost like a sawtooth with some impurities. I tend to use the Vangelis Demo for audio testing and you could hear it but one channel was far louder. The audio faults in Amigas tend to be just one channel not working or low and distorted audio on both sides, this was a more rare and interesting instance.

[roy bates]

i normally use samples played through a med player or other so i can have one channel or both(i think a few peaple do it this way?)
these sort of effects can clearly been seen with a scope.
do you find you have to be very careful with hot air stations in that area,with some parts being more prone to damage due to localised heat from not pre heating the motherbaord?

[Loedown]

Originally Posted by roy bates

i normally use samples played through a med player or other so i can have one channel or both(i think a few peaple do it this way?)
these sort of effects can clearly been seen with a scope.
do you find you have to be very careful with hot air stations in that area,with some parts being more prone to damage due to localised heat from not pre heating the motherbaord?

The only part(s) I generally use hot air for in the audio area is LF347 and LM833 removal and I've got a Bosch paint stripper that does a great job on low setting. I've got a Metcal iron with half a dozen tips that makes soldering an utter breeze. I also use HxC Floppy controller for the disk images and winUAE to make any disk images I need, anything specialized.

I found this link http://pink.myshoesaretootight.com/m...io_repair.html which has the sine wave generator on it

I think it's Anthony Hoffman's webpage.