A4000 motherboard

[doctorq]

Hi,

I have a problem with my A4000 motherboard. First of all, my serial ports isn't working at all. Is this a fixable problem?

The worst problem is that my audio ports can't play loud. Even if I have turned up the volume on my speakers on max, the music is barely listenable.

I put the computer in a tower, can this be the problem?

[amiga1260]

I think your CIA 8520 chips has been broken. Or your battery is leaking. When your battery is leaking, remove the battery as soon as possible or you motherbord will die.

[Quixote]

:pint: First, welcome to Amiga.org!  Have one on me.

;-) As for that audio on your 'miggy, are you using powered speakers?

The serial port is controlled by one of your CIA chips, if i recall correctly.  Fixing it may just be a matter of replacing the chip in question.  Also check for burned resistors, etc. on the motherboard.

Good luck.

[Framiga]

Check the -12 volts.

This power line, is used by serial and audio chips.

Check the ground also (near audio RCA output and the case/PSU)).

Ciao

PS- have you used a PowerTower or a PC modified case?

[doctorq]

My battery isn't leaking, because the clock still works, but I am aware of it. Thank you for reminding me.

The speakers I use is integrated in my monitor. I used the speakers with my A1200 without any problems.

Anybody knows how much the CIA cost? Could I use a chip from one of my other Amigas?

I bought a Mirage 4000 Pro Tower with Mediator, but I don't know if there are any problems with this type of towers. They use a different PSU than the old desktop.

[amigamad]

Mirage 4000 Pro Tower with Mediator

This should not make any difrence cia chips in the 4000 are difrent to ones in the other amigas difrent pin and size layout.I myself have a 4000 desktop wich is slightly dodgy but works altjough there are 2 resistors burnt out which i will replace. :-o

[Doobrey]

doctorq wrote:
My battery isn't leaking, because the clock still works, but I am aware of it. Thank you for reminding me.

Anybody knows how much the CIA cost? Could I use a chip from one of my other Amigas?

Just cos the clock works doesn`t mean the battery aint leaking...
 Someone on the amiga hacks yahoo group gave a warning about leaking capacitors the other day, so it might be a good idea to strip it down to the bare motherboard so you can give it a proper all over inspection.
But as for the CIA chips, the 1200 and 4000 use suface mount components. Spares shouldn`t be that hard to find, I hope you`ve got a steady hand to do that intricate solder work !

[Castellen]

I mentioned about leaking electrolytic capacitors a while back.
Look for black residue or discolouration around or near the aluminium surface mount electrolytics.  There are a number of these in the audio output stage, and around the serial port areas.

Checking the -12V supply is a good idea, as that is common to both the serial port and audio amplifier.

Check for +12V at U403 pin 8 and -12V at U403 pin 4.


If the problems only started after you put the board into a tower case, you may have shorted the -12V line to ground or something??


Failing that, and the CIA looks like it might be faulty, you can use either of the CIAs from an A600 or A1200 as they are the same part.
Get someone with good SMD soldering skills to do this if you're not fully comfortable with doing it yourself.