8mm Forum: EIKI (Elf) Projector Amp Hum

This is topic EIKI (Elf) Projector Amp Hum in forum 16mm Forum at 8mm Forum.

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Posted by Phil Clarke (Member # 4299) on October 01, 2018, 04:11 PM:

Hello all

I'm currently fixing up an EIKI/Elf ST projector I was recently given, and I have one task left: the whopping amp hum that starts up whenever the lamp and/or motor are running.

The hum goes away when you plug in a mic to the amp, and you get normal sound. So I'm figuring this is probably dodgy shielding or capacitor/s.

Just wondered if anyone here has seen this issue before and can advise where to look. I have a second donor machine available for parts if needed.

cheers
phil

Posted by Maurice Leakey (Member # 916) on October 05, 2018, 06:05 AM:

Phil

I'm no mechanic so my knowledge is somewhat limited.

That said, it sounds that extraneous light is somehow reaching the solar cell, perhaps the light shield is not in its correct position.

However, this might occur when the lamp is on, but you say that this also occurs when the lamp is off.

I assume that part of the circuit is by-passed when you plug in the microphone, so it seems that the problem might be in the early stage of the amplifier.

You can download a service manual of the Eiki ST/M on this website, perhaps it may assist you.

http://www.film-tech.com/warehouse/index.php?category=2#16mm Projectors

Posted by Jonathan Wood (Member # 6641) on October 06, 2018, 01:53 AM:

Hi Phil,

If it’s a very loud humming as opposed to the usual hum you get when you just crank up the volume without a film playing and if you only hear it once you either start the motor or switch the lamp on , then it sounds like a grounding issue to me ? Have you checked all the relevant wiring to make sure the insulation is ok and not touching something it shouldn’t be ?
Cheers , Jon

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