amiga 4000 paula audio issues

[therail]

hi recently i have been having issues with the paula audio. it all started when i set my a4000 up which contained additional hardware such as csmk3, picasso 4 and the 3.5 hd and cd rom drive. when i first set this up i had no trouble whatsoever with paula audio - i can conforim this as i tried octamed out when i first got it. but a day later i returned to octamed to discover that i was getting really low volume audio output (but not fuzzy). on advice, i was told it could be a psu unit power problem. so i unplugged the cd rom drive and hd, but not the accelerator and picasso iv and tried the octamed again. this time i got perfect paula audio output. i thought then that it was indeed a psu power problem. but today i decided try the above without the hd and cd rom and also without the picasso. instead of the picasso i used my flickermagic and bmon adaptor. i tried octamed out once again and to my horror i now only get paula audio output on the L (left side), absolutely none on the R (right side). i also tried other apps that produced paula audio output and get the exact same result as before. now i have taken out the flickermagic and bmon and reinstalled the picasso - and as if by magic i get perfect audio again! so my question is, is my paula audio buggered or is this the act of strange psu power behavior?! anyhelp guys?

[amiga4001]

Check for leakage around the paula area.
These capacitators are known too leak and destroy traces off the mobo.

[trilobyte]

I second that.  There are pictures on amiga.org of this.  I found it happened on both of my A4000s.

[Castellen]

I've covered everything you need to know here.
There's some audio test software there as well to help find and fix the problems.  You need to be able to SMD solder to repair it correctly yourself.

If you get stuck, I can do international motherboard repairs no problem.  Amiga repairs are about 5-6 days turnaround at the moment.

[therail]

thankd for the replies. i think that program may be a little bit pointless as i have music apps to test all channels of the paula audio. i never thought about paula leakage. can anyone link any pics of typical paula leakage to know what i am looking at. cheers

[Vlabguy1]

Just to clairfy..the Paula chip does not leak..but the capacitors around her..and
otherplaces on the MoBo..do leak..just take a look @ some of the photos that
I have posted...

Good luck!!
Im also in the process of fixing a few caps on my MotherBoard..

[Wol]

Also check the +12volts and -12volts from the
power supply.

The Op/Amp that amplifies the output from Paula is
on the +/- 12 volt lines, if one of these fail the
Audio will be badly clpped and sound {bleep}ty.



Wol..

[Castellen]

As the others have correctly mentioned, it's the electrolytic capacitors leaking.  It's not a fault with the design, more of a problem with the long term stability of the liquid electrolyte inside the capacitor.  It doesn't just happen with Amigas.

My audio test utility is not pointless as it creates a fixed frequency, fixed amplitude signal in both channels, which is ideal for level comparison between amplifier stages and between left and right channels.
Listening to music output can give you an idea if things are working correctly, but you can't easily see or measure the distortion or do a level comparison between the channels.

Depending what components have been affected, one of the audio stages can self oscillate which will introduce signal distortion which can be difficult to pin point if you're just using music as a source.

And lastly, all my notes and measurements in the article mentioned previously are all based around the output of that program.  So that provides many fixed point references which would be impossible to do otherwise.

I must have repaired more A4000 audio stages than I've had hot dinners, so you can say there's a bit of experience in there as well.

[therail]

hi i just contacted the guy from amiga repair france who repaired my mobo a few days ago. he said he couldn't find anything wrong with paula nor any leakages. plus he also said that if paula can work at all, then there is nothing wrong with the paula zone. as paula seems to work fine with the picasso iv installed (but with no cd rom and hard drive installed), it cannot be a paula related problem. what else could it be? is it a power psu related problem?

[Castellen]

If the -12V supply is missing, you'll get distorted audio in both channels.  Doesn't sound like this is the problem.

You sure it's not something as simple as dirty/poor contact RCA connectors?  Or possibly your RCA cable?
Have you tried a different audio destination, e.g. a different monitor or a home stereo system?

[therail]

i dont think the connector is dirty. it maybe broken though.

[therail]

hi I tried the A4000 out again. I worked out some of the problem. The RC/Phono cable i used for the R and L Paula output was broken so it caused one of the output to be not working. So Paula is indeed working ok. But this leads me back onto my original problem. If i connect evrything up including the picasso, cyberstorm and the hardware devices i get low volume sound or on just L or R, but if i just connect the picasso and cyberstorm i get perfect sound again. Is this due to lack of power in my psu?