8mm Forum: 1200HD Question.

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Posted by Tom Photiou (Member # 130) on July 23, 2004, 11:47 AM:

I need to change the IC number TA7139 to fix an optical sound problem, (or rather this going to be done for me). I am told that a capacitor is usually in need of a change as well. Can anyone tell me which one this would be.
The fault is lose of Volume only on Optical with very high Hiss. [Confused]

Posted by Kevin Faulkner (Member # 6) on July 24, 2004, 04:40 AM:

This is a new one on me. Tom I have never heard of this problem before. Its very difficult to get the TA7139P IC so best of luck on that one. Is the hiss present when you turn up the vol with no film running through or when playing optical film? Could be the optical cell out of position or covered with debris. The lens should be cleaned as well. If anything cuts the light down you end up having to turn up the Vol more and then introduce more hiss. A change of lamp sometimes helps as the output drops with age.

Kev

Posted by Tom Photiou (Member # 130) on July 24, 2004, 05:55 AM:

Hi Kev,
Iv'e managed to get a small supply of the last remaing IC's, i have two new ones here and hopefully another 3 on the way. The hiss is always there and increases with the volume to a level much higher than the film itself. I'm assuming it to be the second hand ic i had replaced two years ago, i wasn't too keen on the idea of a second hand ic but at that time i thought new ones were NLA. Another collector put me onto a company in the north who had stock.
The great Mr Parsons is the gent who is going to recieve my machine and he kindly informed me that when this problem occurs if one of these ic's go down he usually replaced a capacitor at the same time. I wonder if it was because this wasn't done by the previous repair that the ic has gone down again. The lamp is new and the optics appear to be clean [Confused]

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