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How to Revive the Flyback Transformer? Reviving the LC 575?

alvin777

Member
Hi. My LC 575 was working rigth before I dismantled everything, to clean its contacts and spray the analog board, all the internal parts with contact cleaner (contacts sandpapered as well). I'm cleaning it to sell it. When I assembled it although I've gotten the sound back and everything works ok, except that it doesn't have video. Before I cleaned it however, everything was ok including video but not the sound. The problem now has reversed. I have no way of buying a flyback transformer or analog board where I live if that is its problem but it could well be any part that is problematic.

Are there unorthodox methods of reviving its flyback transformer. Any suggestions how to revive this LC 575? If there's no way at all, how much is this LC 575 now without its video but with everything else working?

 

tomlee59

Well-known member
Your question presumes that the flyback is dead, but you don't seem to have done any testing at all to verify that this is in fact the case. So to ask about "reviving" it is a bit premature. Many things can cause loss of video. Maybe your flyback is dead, but do a little testing first before you flail about.

First, your video disappeared during or after you took things apart. In my experience, the most likely cause of a problem is the one doing the disassembly. Carefully check over your work. Common errors include things like cables left unconnected or cables connected improperly (e.g., off by one pin, or backwards, or a pin bent). Verify that the crt's connector is in place securely (it's easy to bump). And if you happened to have bumped it hard and heard the "hiss of death" then your problem is a bad crt.

If you have a small neon bulb handy (like the type often packaged in cheap "pen" type electrical testers sold for a dollar or two in grocery stores), you can check for the presence of high voltage (and therefore, test the flyback indirectly). Just hold it near the high voltage lead (do not disconnect the high voltage lead). The strong ac field in the vicinity of the wire is sufficient to excite the neon atoms if HV is present.

Needless to say, performing that test requires you to work on a powered-up, exposed-guts Mac, so use caution. We don't want to lose any Forum members!

 

alvin777

Member
Thanks for the reply. I'd also like to check the logicboard. Would you know where the video chip/gpu is on the 575's board? Is it one of the Texas Instrument chips?

 
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