A4000 audio problems

Hi folks:
I'm having this strange problem on my A4000d. At boot time i get a disturbing, loud and strange noise.

After that when i run a game or demo the sound is saturated and with low volume. Any ideas?
I don't have Ahi installed or any sound card, is just the paula audio. Is there any software to test hardware integrity?

Best Regards

R

[lauri_t]

Booting a game from floppy should give a hint if it is a software or hardware problem.

[ant512]

Sounds like a PSU problem.

Hi:
booting from floppy gives the same result, bad sound.
Regarding PSU problems, any idea how could i check this.
Regards

Rod

[ant512]

One of my 1200s had a bad PSU and that caused the sound to go crazy. You could get a multimeter and check that the lines are all delivering the correct voltage. The only other solution is to get another PSU and test the Amiga with that.

[manicx]

Known issue. Leaking capacitors. The A4k 16V 22μF are el cheapos and after a period of time they leak to death. I had my A4k fully refurbished with all 16V 22μF capacitors in both the A4k mobo and CPU board (3640) replaced. You can check Anthony Hoffman's Amiga Technical Resource (currently having problems to access it) and this.

[Calgor]

Damn, just got my A4000D a week ago, and after booting up like on the 2nd week i now have distorted audio. Everything else seems fine. Will take out everything bar the cpu card and floppy to see if power supply problem (it was very hot today too...)

Also, would a cyberstorm ppc + cybervision ppc combo cause a strain on the standard A4000 power supply?

@Rod_cl

What turned out to be the problem? Was it the capacitors leaking?

[AMIGAZ]

Got the same prob on one of my A4000 here so you guys are not alone with the problem
Haven't seen any leakage from any capacitor..maybe it's just busted paula circuits

[Calgor]

ok so now i only have a4000 mb + df0 floppy + a4000 p/s + cyberstorm ppc and it still has fuzzy sound next to try another cpu card and p/s but that is for tomorrow so early in morning here now. how can it go so bad from one day to the next and i didnt even do anything

I read on the supplied link that paula chip itself is last resort and unlikely tho. board looks clean too. have a multimeter so might try that if cpu card and other power supply dont work.... need to grab voltage while it is running and resistance while it is off right????

Cant live without sounds!!!!!

[Calgor]

ok, just an update: I used a different power supply (same type but from other a4000D) and cpu a3640 card in the A4000D, but it still has distorted sound Looks like a motherboard problem :'(

Meanwhile, have transferred everything to the other A4000D, and sound works perfectly.... even tho that A4000 motherboard does not look as good and is buster9. The cybervision ppc gets so hot tho, thinking of getting rid of it to use picasso iv instead.

Would like to get the motherboard fixed, as it has a socketed buster11. If anyone has any advice, would be very grateful! I would like to do multimeter tests as suggested in the links above, but not sure how to do it properly. I should run the voltage checks while the computer is running right? Thanks in advance!

[adolescent]

Send it to Amiga Center France (www.amigacenter.com). They'll fix it up better than new.

[Calgor]

Thanks adolescent, but unfortunately I live in australia, so i imagine the postage up and back would be $$$. Anyone know of a place or person in australia? Melbourne or sydney?

I would like to do some tests beforehand too.

[manicx]

Send it to New Zealand. Check here. I sent my A4000D motherboard to Anthony and it fixed it. He is DA MAN to do such repairs. Just make sure you pack your amoga mobo in the best possible way (antistatic bag -get one from a PC board), those bubble things etc). You will have your board tested up to the last bit.

[Calgor]

Thanks manicx, NZ is next door, and he seems to know what he is talking about. Will be sure to contact him to get it fixed when I get the time.

[Psygore]

Thanks manicx for the links
It helps me to repair an audio problem on an a1200 board.

I recently get another a1200 and tested it some days ago.
Unfornutately, the sound was distorted (specially saturated in low frequency).
First, I've looked the capacitors and connectors if they are damaged, they seems to be OK.
Then, I checked DC voltages on LF347 chip as described on the website, there were only -12V, +12V but not 2.5V (where it should be).
The problem was the VREF (audio voltage reference) supply, a resistance is missing (R303). It seems there had never this resistance, the connectors are clean (no traces of solder).
I've just soldered one (1K), all voltages are OK and the sound is fine now.

[Calgor]

Ok so one of my A4000 has distorted audio, yet the board looks clean. The other A4000 has a discoloured solder next to the capacitor as mentioned on the website manicx linked too, but the audio works, but the audio input connector from the CD does not work!

Will the standard CD rom sound connector (as with PCs) work? This has 4 pin slots, with only 3 connected ones (1 sound, 1 ground, 1 disconnected, 1 sound). The A4000 input connector requires (1 sound, 1 ground, 1 sound). Connecting the cable to the board, only gives (1 sound, 1 ground, 1 disconnected).

My question is: Will connecting it this way cause any problems or not work at all? Will connecting it the wrong way (cd rom ground -> amiga sound, amiga ground disconnected) damage the amiga?

@psygore

Wish I was as electrically sound as yourself, but I am just a software engineer with a poor man's knowledge of electronics/physics

[Calgor]

To answer my own question, the audio connector when used with 4 pin standard pc cdrom connector only give mono sound output (right channel).

And to fix the no sound issue from the audio input connector, I just reinstalled OS3.9! (Needed to do it anyway, but the CDROM drivers were reinstalled in the process and must have fixed it). See this thread for more info on the CDROM audio: http://eab.abime.net/showthread.php?t=22280

Now to have a go at the hardware issue with the other A4000D....