Elmo SC-18M with dead motor - service manual needed

[Nantawat Kittiwarakul]

Hi there,

Recently got a call from my friend saying that his Elmo SC-18M projector is acting up. Everything is fine except its main drive motor is dead silent - assuming faulty/sticky microswitches on the main control he said. Asking me if I can help changing it out?
Not a big deal I thought. In the worst case I should be able to replace those switches - probably a standard off-the-shelf parts. So I brought it back home.



Wrong - turns out that it was NOT the switch. No voltage even reached the switch.

Traced back to the transformer - seems OK. (The lamp&amplifier power up just fine also.)



For now the only suspect would be the middle man - the speed control board, especially what that looks like regulator transistor (is it?). I definitely can measure the voltage going in, but absolutely nothig comming out. Googling from its label leads to nothing useful.
(Its number D525 says amplifier, but it should be voltage regulator isn't it?)





The most probable solution would be the service manual to refer to. Is it available somewhere for download?
Or if anybody does have any info/recommendation about this it would be more than thankful. Cheers.

[Xander van der Merwe]

I have a similar machine with a potentially similar problem. I’ve had it for about 10 years or so but never used it. A few months ago I took it out and discovered all the belts have turned to goo and replaced all of those, but then realised that the main motor does not turn on when flicking the rotating switch forward. It put it away again to look further into on another day, but will follow your thread as I may learn something.

[Nantawat Kittiwarakul]

My plan B is to forward this to some local electronics service shop. Hoping that there's still some old techs familiar with this old-style electronics, and willing to have a look at. But I won't set my expectation too high.

BTW just noticed something odd. Its main drive motor should run on around 28-30vdc, which means the ac input to this board should be about the same at least. But the measurement shows less than 14vac. Things might get more complicated than I thought...

[Lindsay Morris]

If it is a variable speed control projector then the device will be a transistor and NOT a voltage regulator as all they do is provide a stable voltage OUT irrespective of the load within the device's power handling capacity.
Data sheets turn up a 2SD525 being a bipolar PNP transistor and anything in that TO220 style that has a working voltage of 100V and can carry 5A would be a suitable replacement. Try a BD650 or a TIP42C both are PNP types with similar ratings to the 2SD525.
However IF that motor really does need 28-30V DC then there is something wrong back towards the DC power supply section IF you are only seeing 13.6v DC and on the input only 14V AC. Where has the other at least 14V AC gone to??? Dirty fuse or connector or cooked transformer winding.

I would expect to see a DC supply of at least 30V to feed that speed control board. A service manual is needed for sure.

Lindsay

Edit... just had a quick look at the old forum and there is a ref on there to a member in Greece wanting a Service Manual but no luck. He has a PDF copy of the User Manual which he was looking at posting it to the FT site. A Google search for a Service Manual turned up nothing but one was for sale on Ebay some weeks ago and was sold. Looks like the manuals are rather rare beasties !!! A manual would be invaluable in your case as trying to reverse engineer printed circuit boards to be able to draw out the actual circuit is a pain in the butt. Good luck.

[Nantawat Kittiwarakul]

Upon a second REAL CLOSE look I found that the output to the motor board was labeled as 0-28, and what appears to be a pair of rectifier diodes at the top of the transformer board, before the output tab (behind those capacitors - not visible in the pic). So the output is supposed to be a rectified AC around 28-30 volts correct?
If that's the case, is it possible that just one of the rectifier went poof - effectively halving the output? I may try having it really checked, for the last time.

BTW I had already talked with the owner, admitted that this would be way beyond my capability to have it correctly resolved. He's now convinced to forward this to other electronics expert instead.

Would be quite a disappoint ending but that might be the best move for everyone.