8mm Forum: Elmo ST-180E Short Circuit Problem

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Topic: Elmo ST-180E Short Circuit Problem

Milan Djuric
Junior
Posts: 3
From: Užice, Serbia
Registered: Dec 2018

posted December 12, 2018 08:52 PM

Greetings for everybody on this forum.

I made a dumb thing using a naked screwdriver to check the lamp connection inside the socket. There was a short circuit to the ground, through myself personally, that even blowing amplifier fuse could not stop. Now, whenever I plug my Elmo in the wall socket, fuse automatically blows.

Interestingly, film reproduction still works, but VU lamp and 18/24 fps switch doesn't (not sure about anything else).

Technically, I can see a diode bridge on the opposite side of the circuit board where the fuse is, which should power up two big capacitors, but I am not sure without the diagram.

I was wandering if anyone here has any diagram of ELMO ST-180E and is willing to share it? I would appreciate any help.

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Leon Norris
Jedi Master Film Handler

Posts: 958
From: Elkins Park, PA, USA
Registered: Jun 2012

posted December 13, 2018 09:30 AM

Milan, On your st180 projector. CHECK the Rectifiers on the machine! Usely that's the problem! I think you have two or three on the circuit board. I fixed these machines before and that's the problem. The first thing to remember is when it starts blowing fuses check the rectifiers. Good luck! Leon Norris.

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Milan Djuric
Junior
Posts: 3
From: Užice, Serbia
Registered: Dec 2018

posted December 14, 2018 12:41 PM

Thank you for your reply Leon.

You confirmed my suspicions so I did some soldering.
It was very difficult to reach PCB contacts as I needed to either remove transformer (and disassemble half of the machine) or to desolder lamp and PSU wires. So I did latter. There was no obvious evidence of the short circuit so I had to remove Graetz bridge (pointing red arrow on the photo). The ohm check showed that the half of the bridge was broken causing the short circuit and blowing my fuses (literary)! [Smile]

I couldn't find exact match locally as there are no other markings on it except manufacturer label, so I had to improvise finding one that matches fuse rating (aka 3A).

After assembling everything back and expecting it to snap again on socket plug, it simply... WORKED!

I hope someone finds this useful.
Thank you again Leon, this time for your help.

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Mathew James
Jedi Master Film Handler

Posts: 740
From: Hamilton, Ontario, Canada
Registered: Dec 2014

posted December 15, 2018 08:03 AM

I have this machine but no schematic. If you(anyone)do happen to source one, please share with us as we can save on this forum for the next person who also may need.

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Cheers,
Matt 📽

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