68kMLA Classic Interface

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Colour Classic blows fuse when turned on.

Posted by: Jon183 on 2018-02-02 21:05:23 Hi everyone, decided to ask for help with repairing the colour classic analog board instead of using it for parts. The details: Fuse was blown on stock CC analog board. Board has been recapped, some new resistors and zener diodes replaced, blew new fuse when switched on. Logic board has been recapped and works inside of my LC575. DF2 is still original and hasn't been checked yet. Any ideas for what to look at?

Posted by: bibilit on 2018-02-03 01:49:20 Obviously something is shorted. Have a look at the Mosfet, or everything shorted in the neighborhood (bridge diode) for instance.

Posted by: Jon183 on 2018-03-01 04:25:12 Got a replacement board and recapped most of it including the largest cap. It now has a chirp-like noise on loop when turned on, does that without the logicboard inside as well. View attachment 20180301_222245.mp4

Posted by: Jon183 on 2018-03-01 17:49:46 It works now but screen is fuzzy and has tint.

Posted by: techknight on 2018-03-03 10:01:44 This is fixed easily.  On the back of the CRT is a shielded neck PCB, there is an adjustment on the back of that PCB called the H-STAT or Horizontal Static Convergence adjustment, if you tweak this with an insulated tool, the "fuzzyness" or convergence will pull right in.  the tint issue is the pots in the back of the analog board need cleaned, or very minimum worked around a bit.

Posted by: Jon183 on 2018-03-03 18:27:24 Thanks, adjusted using a tool made from a piece of plastic. Display is set to a thousand colours. Ill work on the other trimpots once I find the right tool.

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