Hoping to get some help from the very knowledgeable community here; looking for suggestions on replacing the lamp in a moviscop 16mm film viewer. It currently uses an Osram 8203 25v 1a 25w, but I’d like to gut it and replace with an LED.
Can someone walk me through this process?
I have done a bit of soldering, but am largely unfamiliar with even basic electronics, like how to read schematics, and where to begin with things like powering the bulb (it’d be nice to have adjustable brightness!)
Projector is a bit different in requirements. I’ve converted an 8mm viewer. At first I tried just using an LED bulb in the existing socket, but didn’t get enough light output from it. This is what I ended up doing:
Parts:
3W LED module
Separate small heat sink
current limiting LED driver (700mA)
power supply
female coax connector to match the power supply
Gutted all the existing electrics: clunky transformer, bulb holder, wires.
I thought about using a digispark and a poti to regulate the power output via PWM. I got a prototype working, but I decided it was overkill. My current solution is to use a universal power supply with adjustable voltage. I had one lying around which provided enough current for the driver. Since there’s zero input to the PWM pin of the driver now, it will always deliver 700mA to the LED. That means the voltage (up to the LED max. forward voltage) will determine the light output.
First I soldered all my parts together and did a test to make sure it worked and delivered the desired light output: Female coax power connector to driver input (watch polarity!). LED driver output pins to the LED power input (again, watch polarity). I used long enough wires so I would have enough flexibility to place the components inside the viewer where it was convenient. I could have used the existing power switch in the circuit to the driver, but was too lazy to do that. Unplugging the coax power connector to switch off the viewer is enough for me.
Next I installed the coax connector in my viewer where the power cord used to enter the case.
I found a good standoff out of the optical path to attach my driver PCB to.
Last I routed the wires to the LED to the area where the bulb used to be.
The final step needed a bit of fiddling and creativity: I needed to fix my LED with its heat sink in place of the bulb and direct the light output towards the prism. It took a bit of trial and error to find the best way to mount the LED and adjust the beam. You may need a reflector / lens to get the best light beam. Depends on what LED you end up with. My LED with star PCB heat sink already had a lens preinstalled. It may not be optimal, but is a lot better than the previous bulb.
The whole thing didn’t take quite as long as it sounds. I completed the whole modification including the trials in one evening. What took longest for me was the delivery of all the components from China. I bought all the parts off ebay and payed less than $10 for everything combined.