Wednesday, August 19, 2020

Fixing the Video on my Amiga 600, after inadvertently breaking it


A good few months ago now I recapped one of my Amiga 600's.  The caps were really leaky and it needed immediate attention. However after I recapped it I noticed a horrible blue scan line that sat at the bottom of the floppy on the boot screen and slid upwards as the disk is inserted into the drive on screen.  This only appeared on the composite out and not the RGB.

After doing some reading I saw this blog entry ( amiga-600-video-encoder-upgrade ) with someone who had also recapped his Amiga with the same issue and he suggested the cleaning fluids went up into the 221 and 222 cans and broke them.  I did pour on a LOT of cleaning agents to clean off the acid.  He used a CXA1645M to replace the original chip and some Kapton tape to isolate the 221 and 222's. There seemed to be a lot of parts that you needed to solder on to the chip with that solution to get it working, it just looked way too fiddley.

Looking further I managed to find this blog entry with a solution that suited me a little better ( https://www.ikod.se/cxa2075m ). It used just a CXA2075M and one resistor.

So I ordered some CXA2075M 's from EBay and now here we go.

** Warning **  This was a little challenging so if you don't have the equipment or skills to do it, get someone experienced to do it for you.  When you remove the CXA1145M all display outputs stop working!!

Here is the board before I started with the Original CXA1145M and the 221 and 222 cans.  You can see the effects of the corrosion of the leaky Capacitors on the legs of the chip.


Here are the new parts as per the reference blog post ( https://www.ikod.se/cxa2075m ) 



The biggest issue I had was that the blog post was for an A1200 and not an A600.  So the removal of parts to disable the 221 and 222 parts wasn't valid for me.  As I have a desoldering gun I just removed the 221 and 222 parts instead which works just as well.  I also used a hot air rework station to remove the chip.
 
When removing the 221 and 222 parts you will likely need to add solder to the pins several times to help suck all of the old solder out.  Be patient and they will come out easily.

Taking the parts off was easy, putting the new parts on was a bit soldering of a challenge.  Oh I wish I had three hands sometimes. Here is the end result, all in all I am pretty happy with it.



The old parts removed from the motherboard

As you can see both the RGB and the composite out work a treat now and no more horrible blue line!!







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