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Discussion Starter · #1 ·
Again,


I'd like to have any suggestion.


I've found out that, after replacing all the output capacitors on the low voltage power supply, some 70% of the small lines (image noises) disappeard... but there are still some noises (some barely visible small "waves" on the image, running up and down) that are clearly related to the presence of the ACON BOARD.


If I pull it out, the problem completely disappears, and I've tried with 3 different boards.... always the same result.


I think that it's some pulsing voltage, re-entering the power supply line (probably the "pulsed" power supply for the step motors, produced by the NE555 and the power transistors...)



does anyone have any hint, to solve the problem, using the ACON?



thanks


Romano
 

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Yes, Romano,


Don't use the ACON! I think you'll have to re-engineer that board to make it totally clean. Otherwise, you might be dealing with one of the older backplanes that had lousy grounding with regard to the foil trace layout - they changed that design around the 4100 2nd year or so.
 

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Mike- it seems unlikely, but is there a chance the power supply is causing problems becase Romano is running 220V 50Hz (through a stepdown transformer) with the projector.


Romano, what current rating is the transformer?


Curt
 

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Well, rule number one.. is always work at the source, if at all possible. So, have you addressed the idea of replacing power supply components right at the acon board? This has potential to cure the problem. Yes, I noticed the gorunding problem too. My old 4100 had to be completely pulled aprt and put back toghether every now and then to keep the noise problems down. This is after all the mods. Sometimes i would loose the remote function! I had to pull the remote and all cards..and then it would come back fine.
 

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Discussion Starter · #5 ·
Thanks guys!


Curt,

no, I'm not using a power strasformer to provide 110V to the pj. The ECPs can accept 220V without problems, the only thing that is required is to change the connection between the small accepting board (the one where is located the AC socket) and the internal main power supply... after have "reversed" the small AC voltage changer located close to the AC socket (the ECP4500 doesn't require anything. It's fully 110/220 50/60 hz compatible without any adjustment).


Ken,


yes, I did it. I replaced the electrolytic caps on the power supply line of the Acon board, but it didn't change anything... (the fact is that I just replaced the caps with similar ones, without to increase their value in Mfd...). I think that it's the NE555 oscillator that works, providing a "pulse" voltage to be amplified, in order to drive the step motors. If any kind of oscillation (peaks) re-enters the supply line of the pj (on the "bus")... some other boards may suffer it (specially the video board and the cathode amplifiers)...


Mike,


yes, I tought that you knew the problem... the fact is that I don't know how to act...


probably the best way is to connect the scope to che power supply line of the bus (using the extender board) and to check it out if any kind of noise appears on the direct voltages (a "pulse" component...), connecting the ACON board. In that case, I will follow the supply line of the ACON board, just to see if there is any cap placed to filter the noises... in this case, it could be an idea to replace those caps with bigger ones (as Ken is suggesting)...



I'll let you know.


thanks again


Romano
 

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Hi Romano,


I'd suggest looking at any PLL circuits for beat frequencies that are escaping into the video circuits through the + & - 12V rails. I believe there are PLL circuits on that ACON Bd, and if I remember correctly they're on row C, pins 20 - 22 on the edge connector. The rails are row A, pins 27 (-12v), 28 (+12v), and 29/30 (+5v). Go for it, pal, you're a lot more ambitious than I am....;)
 
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