Nigel Goodwin wrote: > > In message <008d01c02697$6bb4c4a0$ecc8a7cb@joe>, Jinx > writes > >I've rescued a couple of good 12" colour monitors due to be > >biffed out because the focus can't be adjusted anymore. The > >pot on the transformer is at the C/W limit. Is there a reason why > >I can't add a resistor in series with the lead that goes to the tube > >PCB or will this just make the focus even more O/S. Is the > >problem that there's too much resistance already ? > > The focus control is a potentiometer fed via a high value resistor at > the top with another high value resistor down to ground from the bottom. > Assuming the bottom resistor has gone high, you could perhaps add a > resistor from the focus output down to ground to compensate, but it's > more usual that the top resistor goes high and you get too little > voltage. > -- > > Nigel. I suggest getting a Philips tv focus pot assembly from an old KT3 or KL9A chassis set (old wooden cabinet). These are about 22M ohm and strippable for cleaning and made to handle the high voltages. Maybe you could use a philips K11, K12 type but these are not as big and not strippable. Old philips tvs like these are all over the world and common. Should be able to get them for a few dollars (or free) from a friendly tv repair guy. Just be straight with him about what you are doing, not setting up in competition to him or anything! :o) The focus pots on the LOPT that go bad like yours either go high or low, so you may need to melt the plastic near the orig pot and disconnect, then run a wire to the new philips pot. Seal it with about 1" thick silicone (non acetic) after you are done. It's about 6kv so be careful. You must seal it well from the air. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics