A4000 Audio Problem

[da9000]

Hi Len,

without much thinking about it (the mouse troubles complicate the matter), but my first guess is that you've got to do this anyways, since it'll save your A4000 in the future, but primarily because of the broken sound:

http://amiga.serveftp.net/audio_repair.html

Smell the SMD caps to see if there's a nasty odor. That'll be a good indicator.

And while you're at it, perhaps this could be a possible job for you too:

http://amiga.serveftp.net/A3640_capacitor.html

Both should be easy for you, given your background with surface mount repairs on SNES systems. Of course you might be 70 years old by now and have shaky hands (I hope not!) in which case get some helping hands as some areas are tight and lifting pads is common. I've done both jobs on many Amigas, so I can always help if need be (I'm in the US though, don't know how far).

Good luck

[da9000]

Hey Len,

I would not recommend using a heat-gun for the SMD caps. It's not very hard to do it with a decent soldering iron, and less chance of screwing something else up. Plus there's a decent number of them (if you want to do them all), so it'll be much quicker with the soldering iron, than having to cover all the areas needed to blast with the heat-gun.

As for Paula, what Anthony means in his site is that if there are signs of battery leakage or whatnot, then remove/replace. If you don't have such a problem I would do 4 things:

1) remove and re-seat Paula and see what happens

2) if no improvement, get another Paula, try it

3) if no improvement, perhaps add solder to the pins/holes of the Paula socket, from the back-side of the motherboard, and see what happens

4) if no improvement, start with the audio-circuitry SMD caps. I use tantalums for replacement because I don't want to bother with SMDs when I'm your age :-)

Good luck!

[da9000]

Ah. Well, skip to the SMD caps then :-)

Like Anthony says, these chips don't damage so easily.

Has the battery leaked at all?


EDIT:
I've not tried this with any custom chips, but it works for DRAMs: you can piggy back another chip on top of the faulty one, so you can temporarily test to see if the new one makes a difference and thus isolate the problem. It'll be tricky with Paula or anything such, with so many pins and everything on it. DRAMs with 10-20 pins are much easier.

[da9000]

Len, you can try some of Kin's suggestions, because as I recall last time I had this same problem with the right mouse button, it turned out to be the cable of my mouse.

Still, the audio is almost definitely SMD caps. And as far as battery clean up, water with just a drop of non-polar detergent should do the job. For an in-depth discussion: http://68kmla.net/forums/viewtopic.php?t=2381&start=25

EDIT:
As for battery leakage, you can look around the board and see if you spot any corrosion on the copper tracks or any thin green tint on various component legs. If you do, those are signs of it happening. Obviously the worse signs will probably be where the battery was (unless this machine had a Lithium coin-cell, in which case no leakage)

[da9000]

BTW, and again, excuse me if I'm reiterating stuff you probably already know, what I do sometimes to test things (while waiting for the parts to come) is I rip off some broken hardware some axial/radial capacitors with equivalent ratings, and use those temporarily to see if the problem is fixed. Then I remove them and put the finalized components (in my case the tantalum 'tear drop' ones, which I got from jameco.com, in case you're looking for a source - if you need parts numbers, let me know as well)

Good luck with the project!

[da9000]

spaceman88 wrote:
I tried cooling Paula and some audio parts with freeze spray, but no effect.

You obviously know your stuff ;-)

It's weird, how it behaves, but the time-factor seems indicative of something to do with caps and/or inductors, but then again...

Anyways, I agree with Countzero on the full replacement of all SMDs, so here's what I got from jameco.com for replacing *all* A4000 (desktop models) SMD caps (please double-check in case I typed something wrong):

Code: [Select]


Description              Jameco#      Item#  Quantity
Cap,Tantalum,100uf,6.3V  TM100-VP-R   33702  1
Cap,Tantalum,47uf,16V    TM47/16-VP   94124  10
Cap,Tantalum,22uf,16V    TM22/16-VP   94095  5
Cap,Tantalum,10uf,35V    TM10-VP-R    33691  1
Cap,Tantalum,4.7uf,35V   TM4.7-VP     33807  1
Cap,Tantalum,4.7uf,25V   TM4.7/25-VP  94044  1


[da9000]

@Tension:

read the entire thread, it might not be a CIA problem...

[da9000]

@Tension:

my point was that we've not entirely sure of the exact cause - all these things we've talked about are theories so far. It could be the CIAs, it could be a custom chip, it could be the leaking/dying SMD caps, dry solder joints or a combination thereof. Thus, I'd wait for the OPs results before jumping to conclusions.

[da9000]

@spaceman88:

No prob. Good luck with the project. BTW, if you're going to order from jameco.com or similar you might want to look at their catalogue, since they have so many goodies :-)  I've no personally tried to, but you might want to see if you can locate a plug similar to that used by the A4000 PSU, so that you can create your own PC PSU -> A4000 PSU hack, just in case the problem is with the power supply or for having a 2nd PSU for the future. Just a thought. I also picked up some Schotcky  diodes and coin-holder for doing the lithium battery hack.


QuikSanz: post a link, not sure which ones they are, but won't hurt to have'em around.