68kMLA Classic Interface
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| Color Classic picture distorted | |
| Posted by: mrpippy on 2015-06-17 00:35:08 I picked up a Color Classic off eBay last week, had to bypass a via and now it boots! The picture doesn't look very good though, just isn't that sharp and there's some serious pincushion distortion:  As usual that picture looks worse than real life (that line across the middle and the rainbow effects are just from the camera) but the distortion is accurate. I haven't done any recapping yet (on logic board or analog board), obviously there was some leakage on the logic board but not too bad. I haven't pulled the analog board out yet, but from the top I don't see any capacitors that have leaked or are bulging. I assume the bad picture is caused by bad analog board caps, are there any I should try replacing first? CF8 next to the Zeners is a common one I guess Also is there any list online of the analog board caps, including the diameter/length? | |
| Posted by: uniserver on 2015-06-17 01:42:16 i would change the caps first. clean up the cap goo, then install some fresh caps. both AB and MB. | |
| Posted by: 360alaska on 2015-06-17 08:46:52 And...after new capacitors:  | |
| Posted by: techknight on 2015-06-17 16:05:01 This hopefully is a rather simple repair, caps or adjustments. But in some cases, the pincussion amplifier transistor shorts, and will do that. There is a separate circuit that generates the pincussion drive signal, and it gets mixed/injected onto the horizontal drive waveform to the horiz output, it gets amplified by the horizontal output transistor which drives the yoke and flyback. So, if the pin amp is bad, you wont get any pincussion drive for the H out. I have only seen this happen 1 time, and that was with an Apple multiplescan 15", when its pin-amp shorts, it causes only a half-raster with a single bright wiggly line from the center down. and it flashes/pulsates. The pin-amp is a separate board bolted just behind the flyback. But I digress.... | |
| Posted by: mraroid on 2015-06-21 07:01:41 360alaska.... I found your alignment photo extremely helpful. I also have a color classic. I am saving that photo in case I need it in the future. You do not happen to know what head and size alignment tool is needed for the color classic do you? I have a set of alignment tools coming in mail from Amazon, but I have no idea what size I am looking for.... jack | |
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