Amiga 4000 repair part 1/2 - Audio problem, leaky caps & much much more

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• published: 08 Feb 2013
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This Amiga 4000 turned up to be much more work than I could ever expect. It was claimed to not put out any audio on one of the stereo channels, which it indeed didn't do. But I never expected that this machine would turn out to have multiple issues with the motherboard to this extent. Fixing it was really a lot of work. In this documented repair, you can follow me on my troubleshooting journey, and watch me attack the motherboard with scope probes, multimeter probes, soldering irons and a bit of logical thinking in order to get everything up and running again. This is the first time I ever work on an Amiga 4000. If I was to work on an Amiga of the same model with the same problem again, I would most probably be able to troubleshoot it and find the problems much faster than I did in this video. During this repair, I am being misled by some of the readings I got. I first suspected components that were actually not at fault, which you can see in this video. Towards the end of the video (in part 2), I start working on the power supply in an attempt to lower the speed of the fan a bit, in order to make it just a little bit more quiet. Will I succeed with that little modification, or will I fail miserably at it? :) Please note that this video is a documented repair, and is not intended to strictly act as a tutorial. The explanations in the video are there to give you an idea of how I approach a certain fault, and to show you my way of analyzing and fixing it. Having that said, I will of course still be happy if you feel that you have learned something new from watching this video. :) And sorry for the puns in the video by the way. Sometimes I just can't help myself. :) Part1 -------- 0:00:00 - Introduction & What is clamed to be wrong 0:01:19 - First visual inspection 0:04:45 - Talking about the audio filter circuit & Initial boot up test 0:09:17 - Initial testing & troubleshooting begins 0:10:06 - First look at the schematic 0:14:45 - Performing tests & measurements in ProTracker 0:25:56 - Second look at the schematic & test results summary 0:29:04 - And the testing continues... 0:31:30 - Third look at the schematic & futher test results 0:33:03 - Disassembling the Amiga 4000 0:35:01 - A quick overview of the motherboard 0:37:02 - An interesting and rather amusing discovery 0:39:09 - First problem fixed & analysis of what went wrong 0:41:57 - Forth look at the schematic 0:44:20 - Soldering the first new component into place 0:50:42 - Talking about suspected bad capacitors & more testing 0:53:14 - Is this capacitor shorted? 0:53:37 - Fifth look at the schematic with more test results 0:57:42 - Back at the workbench 1:01:02 - Back at the schematic again for more analasis 1:03:50 - Testing a temporary fix & experimenting around that A very good webpage with info regarding audio problems on the A4000 (not my site): http://pink.myshoesaretootight.com/mirrors/amiga.serveftp.net/audio_repair.html