A1200 graphics breakup when playing sound

[mjnurney]

I have a 1d1 motherboard that has graphic issues when playing sound. It works perfectly until sound is accessed , mods or whatever.

The screen gets horizontal lines that slowly work down the screen and then reboots or guru's.

The sound is played but so faint it can hardly be heard on full volume.

Caps were replaced a couple of months ago.

I have resoldered Paula and local ic's , I will replace the audio caps again.

Any other ideas?

Mike.

 

[roy_bates]

what hardware have you got in this system mike?

 

[mjnurney]

I tested it with my accelerator / my hdd but I will try the bare board tonight Roy.

---------- Post added at 12:39 ---------- Previous post was at 12:38 ----------

It has worked perfectly as my main system a couple of months ago, with my accelerator / hdd and so on.

Odd it's playing up now

 

[thgill]

Hmmmm....possible power supply issue?

I have seen similar (though not exact) symptoms with a duff psu.

Have a spare one to test it with?

 

[mjnurney]

No the psu is a 400watt pc supply , running my 68060..

It's fine I suspect

 

[roy_bates]

is this your project a1000 with an indi installed?

 

[hooverphonique]

with audio, +12V/-12V comes into play, so saying there's no problem because it's a 400W psu running your 5V accelerator doesn't really count ;-)

that being said, I don't think this is a power issue.. lines on the screen that aren't flickering suggests that somehow your bitplane data in chipram are being overwritten, which again could point to some sort of DMA issue (agnus/alice)..

 

[Tajmaster]

Could it be faulty RAM?

 

[Ed.D]

If you haven't done so already MJ, try reseating the ROMs perhaps?

If it occurs gradually could it be an overheating issue and therefore undervoltage on 5v or 12v rails?

 

[mjnurney]

No it's not my Indy motherboard, and it happens from cold or warm but only when sound is played , I'll pop a pic on later.

I haven't tested with out the accelerator in it yet but the hdd / acc / ram work perfectly on my other board and some one else has tested this board with a different psu / ram / accel so I have discounted them. This is a board fault not other hardware ( I think )

I'll try it without acceleration and just chip ram.

Roms have been changed 3.0 / 3.1 and other 3.0

Mike.

 

[hooverphonique]

do these artifacts disappear when you move a window past the area where they appear? (of course they will appear again shortly then)..

 

[imaga_050]

Just a wild guess but it's probably some bad chip ram since both paula and lisa use this RAM.
Oh, all the girls that's in the Amigas i don't need my lady anymore i have plenty right here

 

[mjnurney]

hello,

yes they disappear if you move over them but come back again.

small update.

i have recapped the whole board again and resoldered all the large IC's on the board, cup, ram, paula,lisa,cia's etc

and I've changed the sound amp too.

now i have sound that is loud but very bass and thick but at leasts its sound.

i will have to examine the whole sound circuit and replace bits as i go ...

i am still getting screen corruption but not as much and as i have sound now. I'm using polarised caps on the audio but this should not make any difference really. a short you tube vid showing the thick sound being produced.

sounds horrible but its a step up from having the volume on full on the TV and just being able to hear it.

test setup:

a1200 1D1
0 fast ram
2 mb chip
no accelerator
booting from floppy

test games : lemmings / turrican / cover disks

YOUTUBE VID:

http://www.youtube.com/watch?v=Iv6vG_ogTUc&feature=youtube_gdata_player


mike.

 

[roy_bates]

i cant really tell from the vid mike,but does it sound like someone has taken the treble away?or a channel.

 

[mjnurney]

yes thats about it roy , one channel is missing and possible its too bassy - more or less

 

[BLTCON0]

Mike, I had a similar problem with one channel going berserk (too weak, hissy-scratchy sound etc, when only the other channel was playing all was perfect).
It's discussed here, at first I naturally thought it was the caps but turned out to be a fractured R321 resistor, once replaced all was good.