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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: jrkenn on February 17, 2008, 07:53:17 PM

Title: Blown Circuit
Post by: jrkenn on February 17, 2008, 07:53:17 PM

Anyone know what this circuit is? It is under the battery and the battery had some corrosion on it. As I examined the board I found this blown circuit. I was having problems with the mouse and got a new one and still had the same problem. Mouse would click but would not move.

(http://i67.photobucket.com/albums/h305/jrkenn/Amiga%204000/BlownPart.jpg)

Title: Re: Blown Circuit
Post by: AJCopland on February 17, 2008, 07:58:44 PM

What machine is it? A500? one of the big box amigas?

Title: Re: Blown Circuit
Post by: AMC258 on February 17, 2008, 08:30:39 PM

I doubt the two are related.  More likely a blown fuse.

Title: Re: Blown Circuit
Post by: SamOS39 on February 17, 2008, 08:33:41 PM

It looks like a blown capacitor.
You can replace it  but youll have to find the right type etc ..

Title: Re: Blown Circuit
Post by: Amiga4k on February 17, 2008, 09:04:12 PM

MOUSE OR JOYSTICK PROBLEMS

A known good mouse and joystick should be used to eliminate them as the source of the problem. If it is determined that the mouse and joystick are okay, the most likely causes are:
Mouse does not move, left and right mouse buttons okay, joystick okay:


EMI 1401 5.1 ohm resistor (supplies 5 volt to mouse). A2000 Rev.6 and up: F1 4 amp pico fuse.
8362 U4 (U201 A2000)
74LS157 U15 (U202 A2000)



http://home.arcor.de/kickstart/TKA/Tutorials/troubleshooter/a5kts2.gif :-D

Title: Re: Blown Circuit
Post by: banzai on February 17, 2008, 09:37:36 PM

That's the underside of the A4000 rev B mobo (the clock and battery are on the other side). In fact, I'd be willing to bet that the battery corrosion got underneath and either ate through or caused capacitor C177 (as shown here (http://amiga.resource.cx/photos/a4000,A4000revB-back), center right-ish area below mouse ports) to blow.

It looks like you may also have some trace damage, and since this is a multi-layer board, there's no telling what kind of damage has been done that we can't see.

The mouse is routed through the HCT166 chip on the top side (next to the HCT174 that typically gets damaged by the battery), so you can do a continuity check to it.

Hate to say it, but this one may take a while to fix...

banzai

Title: Re: Blown Circuit
Post by: jrkenn on February 18, 2008, 10:01:18 PM

It is the A4000 and I will check those HCT circuits and see if they are damaged. Here is a pic of the front side by the battery after I cleaned it up a bit.
(http://i67.photobucket.com/albums/h305/jrkenn/Amiga%204000/CleanedUp.jpg)