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Author
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Topic: Yelco P-111B and the Mystery Diode
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Steve Klare
Film Guy
Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003
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posted August 14, 2015 08:37 PM
Last year my son told me he wanted a projector of his own, so I revived a dead Yelco P-111B and gave it to him.
The machine runs fine, but the picture is beyond dim: whites are gray, it can't handle more than a TV sized screen without washing out. When he uses it at CineSea in daylight conditions he's down to an A sized sheet to be visible at all.
This uses a 50W lamp, so nobody expects it to burn holes through the screen, but it seems to me it should be a lot brighter than this. I've had other 50W machines that weren't like this.
-so I poked around...
Transformer output for the lamp: 8 Volts, fine! Lamp voltage? 3.9V! This is less than half what it should be, so the lamp power is less than a quarter what IT should be! This is under 12.5 Watts, about two editor bulbs...
I noticed something funny: the lamp circuit seems to have a diode inserted in it. Now this starts to make sense: you only let AC current flow one way, you lose the current when it doesn't flow the other.
-half the current, half the voltage, one quarter the power.
My guess is the former owner was using the machine on a small screen and cut back the brightness to stretch his lamp life. I knew the guy: he's a fellow electronics guy and doing this is definitely something he could pull off.
My question for any other owners of Yelco P-111Bs is when you look at the back of your machine near the base, do you see this hex nut on a stud passing through the chassis?
-I'm guessing: "No!".
This is something new here: we deal with machines that are worn out and damaged all the time. This may be the first sabotage!
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All I ask is a wide screen and a projector to light her by...
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Mathew James
Jedi Master Film Handler
Posts: 740
From: Hamilton, Ontario, Canada
Registered: Dec 2014
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posted August 15, 2015 09:22 AM
Hi Steve,
I tried looking for this one to see if I could find a rotated view of the projector to see if the nut was there, but I cannot find anything....
This looks to be your machine here?
http://www.youtube.com/watch?v=YkmnzasH7X0
Other Info:
marketed in 1969-70
standard 8 mm \ super 8 mm film
format change: auto, by lever
lens: Zoom f: 1.3 \ F: 15-25 mm
lamp: 50 W, 8 V, CXR
reel capacity: 120 m
projection: forward, reverse
projection speed: variable speed
variable speed control: by rheostat
film loading: fully automatic reel to reel threading
sound: no
motor: DC magnetic motor
power source: 93-100-110-125-160-230-240 V AC, 50/60 Hz
weight: ?
dimensions: ?
made in Japan by Yamawa
Your pic may be the only uploaded back view of this one. Sorry I cannot help further.
btw- this looks like it was also marketed as another machine here:
http://www.super8data.com/database/projectors_list/projectors_ifba/ifba_quartz.htm
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Cheers,
Matt 📽
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Steve Klare
Film Guy
Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003
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posted August 15, 2015 06:20 PM
That is indeed the machine: it's actually a nice simple little projector with continuously variable frame rate. A lot of people like them for telecine.
In my case I just wanted something user friendly to give to my 12 year old (now newly 13) so he could have his own.
-it's kind of neat how well a kid of the "app" generation adapted to changing sprockets and aperture, framing, focusing and rewinding!
I have a little more pondering and measuring to do, but my gut is telling me once I bypass that diode things will get a lot brighter.
-next step: go through it with an ohmmeter, pencil and paper, trace the circuit and make sure my gut knows what it's talking about.
I did find him a spare spaceman lamp: worked out to about a buck an hour for the rated life! By the same token at the rate he uses it showing 200 foot silents, the two bulbs should last him until college, or Eumig or Elmo (Whichever comes first!).
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All I ask is a wide screen and a projector to light her by...
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Steve Klare
Film Guy
Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003
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posted September 28, 2015 08:57 AM
Thanks Guys and Gal!
That's really interesting Graham. So it was a do it yourself Hi-Lo switch, but all we got was "Lo"! I wish he'd done the switch as well: I would gladly have left it alone.
I think this is actually good for Steven. Everything he deals with is software: Apps, Games, Uploads! This essential knowledge these days, but I think it's good to understand motors, gears, belts and pulleys too! Someday when there's steam pouring out of his radiator cap, a little mechanical horse-sense will serve him well!
(I'm grateful for it every time the garage door or the dishwasher goes into rebellion!)
This also says a lot for the people at CineSea. He walks around the place like one of the Veterans and the guys make a point of putting interesting stuff on screen for him. Besides, that picture only ever happened because Doug was willing to clear a spot on his table for him.
I'd love to know what he was watching here. I'm betting the title isn't "Homework"!
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All I ask is a wide screen and a projector to light her by...
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