Distortion sound when switched on..

jcw · Post by **jcw** » Fri Jun 22, 2012 7:56 am

Hi,
I have a pa80 returned to me. However it has a problem.

When it is switched on, a awful buzzing/hissing sound is heard. Th sound goes away when volume is 0. I tried switching speakers off which stopped the sound(obviously), but is still heard with headphones.

Program changes doesn't affect the sound or changing the pan.

It is impossible to play!!

Has anyone had a similar problem? Or any suggestions?

Thanks
John

Thoraldus · Post by **Thoraldus** » Fri Jun 22, 2012 1:17 pm

Ground loop? Do you have any other AC powered equipment plugged into the keyboard?

Open ground on audio input? Ground connection came loose in transit.

Loose internal connector in the audio chain? Same as above.

Power supply filtering gone bad?

If the noise is coming out of both channels equally I'd look for open ground on power amplifier board.

Could possibly be in the DtoA section and the board is converting garbage data into audio.

Did you just have the keyboard serviced? Shipped? Knocked about?

jcw · Post by **jcw** » Fri Jun 22, 2012 9:08 pm

Thanks for your response.

It was being used by friends and would have had lots of transport.

I will try and investigate your suggestions.

Do you know if there are any diagrams of internals available on thr web?

Thanks again
John

Thoraldus · Post by **Thoraldus** » Fri Jun 22, 2012 11:35 pm

John,

Check your private messages.

jcw · Post by **jcw** » Sat Jun 23, 2012 9:38 am

Well, I have opened up and cannot see any obvious loose connections with power amp or supply. I am not game to pull apart much more....

This is what happens when I switch it on...

1. Switch on with volume at 0
2. Turn up volume and a 'hissing' sound is heard
3. Play a key, the sound is widely distorted, but seems to ok in pitch

John