Sankyo Sound 500 Projector Problem

[Steven Downer]

Hello,

I took a risk and bought Sankyo 500 Sound projector.

It powers up ok, some internal light comes on and I can hear scratchy sound if I turn it up and down.

However, the motor doesn't appear to operate, also bulb seems burnt out.

I opened it up, and measured power on the terminals. It gets about 14V to the board. Power to the motor is about .4V with the leads attached or ~1.2V if they're unattached. I hooked a 9V battery up to the motor leads and it barely turned extremely slow, but maybe this is because it's a 9V battery.

I'm not sure if the motor is bad at this point or something on the board. It seems like there should be a higher voltage going to the motor?

thank you for your help

[Nantawat Kittiwarakul]

Most dc motor in this sort of projector operates at around 30V, roughly 24-36v range. That 0.4v when loaded definitely means some issues in its power supply section.

Could be anything - too soon to assume for something specific...

[Steven Downer]

Thank you Nantawat, any ideas where to start looking next? Also, is there any archive of schematics anywhere?

[Joerg Polzfusz]

Hi!

According to https://www.filmkorn.org/super8data/ your test with a battery was a good idea as the projector is supposed to have a DC motor. Unfortunately, this database isn’t always correct. So your projector might also have an AC motor. Please check this before continuing…

quote from the above link:
“motor: ellectronically controled DC magnetic motor
power source: 100-110-117-125-200-240 V AC, 50/60 Hz, 130 W“

…as you can also see in the quote: Your projector was sold internationally. Please check whether it’s set to the correct voltage (110V/60Hz - or is 117V/60Hz more appropriate as the USA is reported to have switched to 115V/60Hz?).

Unfortunately, I have only found user manuals for this projector on the internet, but no service manual. Sorry. But it looks like Janice has a service manual for the Sankyo 600 (that should be similar enough to your projector):
https://8mmforum.film-tech.com/vbb/f...2585#post82585

Good luck!

[Steven Downer]

Joerg, thank you for looking! Janice sent me the manual and it looks like it has some useful information. I'll let you know how it goes.

[Nantawat Kittiwarakul]

Since this projector definitely uses dc type motor therefore you can rule out ac line frequency issue. The rest of the possible cause lies in ANY of the following elements in its power train.

It would start from the transformer's secondary winding output (around 30-35 vac). Then bridge rectifiers with smoothing capacitors (still a "wavy" output voltage at this point). After that it should be at least a regulator transistor with two potentiometers for speed control (now smooth dc output). Finally it would reach the main control switch to turn the motor on/off, and changing its directions.

With some basic electronics skill and if you're comfortable with using multimeter it would be possible to trace it out. Wish you luck!