8mm Forum: Motor Wattage or Current Draw of Sankyo 600

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Posted by Phil Mitchell (Member # 3876) on January 05, 2015, 01:37 AM:

Happy New Year all.

Any clever electronics etc types here know what the motor in a Sankyo 600 or similar unit, would draw, as in Wattage or Current Draw.

Thanks
Phil

Posted by Andrew Woodcock (Member # 3260) on January 05, 2015, 02:41 AM:

Not got a Scooby Doo Phil, but you could measure the current yourself using a Multimeter or Clip On Ammeter.This would also then allow you to calculate the input power to the motor if you so wished by also measuring the voltage at the motor terminals.

Posted by Steve Klare (Member # 12) on January 05, 2015, 04:51 AM:

We could come up with a rough estimate like this example for numbers I have here:

The ratings plate on the back of my Elmo ST-800 says 200W total. The lamp is 100W so we can subtract that out. The sound is 5W max, but you can double that and subtract it out too. Since the lamp, the motor and the sound are basically the whole show you can estimate the motor (plus motor regulator if it has one) at 90W. Since the 200W number is probably padded a little (for safety) you can call this 90W number "generous" too.

The current to the motor depends on where you want to see it. It's powered through a transformer so it's much higher at the motor than at the line cord. You'd just need to know what the voltage is where you are interested and divide the 90W by that voltage.

If you can tell me the wattage rating on the back of your machine, we can probably do this for you too.

Posted by Paul Mason (Member # 4015) on January 05, 2015, 07:21 AM:

Don't forget AC is affected by "power factor" so say 90W at 230V will draw 0.4 amps minimum when the power factor is 1 (one) and say 0.5 amps at 0.8 power factor.

Posted by Steve Klare (Member # 12) on January 05, 2015, 09:08 AM:

True, but we don't have an estimate for the PF.

As I said, the 90W probably has fat in it, so it can absorb the effect of power factor.

It depends on what you want to do with the number anyway: just for curiosity a rough guess is fine, trying to land an operational movie projector on Mars: now you need to sharpen it up quite a bit!

Posted by Phil Mitchell (Member # 3876) on January 05, 2015, 07:37 PM:

Hi Steve and Andrew, thanks for replies.

Back of Sankyo unit says 240V AC, ( I am in Australia so 240v is right) then symbol that looks like ~ 50hz, 160W( I am Australia so that is right) yes Lamp is 100W, but is these numbers on back plate that tells me the answer to my query.

AMP 2W (Ext4w)

Reason why I need it, friend of mine has helped me fix the speed controller PCB of the Sankyo, but it is only running at 24fps, slider switch I have Ohms tested and it is fine. Pots on board do not change anything. He tells me
"that we need to change to 1K resistor and the also the large 5 Watt resistor. This will need to increase as we do not have enough current reduction" I've uploaded a picture of circuit drawing he did of board and this may help others with similar units. On his drawing the resistors he is talking about are R2 R3 on it.

But not knowing how many Watts the Motor is drawing, he doesn't know what to tell me to replace those two Resistors with.

Cheers Phil

Posted by Phil Mitchell (Member # 3876) on January 06, 2015, 12:55 AM:

Hi guys,

I did a bit of learning today to use my Multimeter and work out how many amps Motor is drawing.

It is drawing 500.1ma DC

Does that seem low or high?

Voltage coming from speed board to motor is 49.7, VDC

Thanks
Phil

Posted by Andrew Woodcock (Member # 3260) on January 06, 2015, 03:31 AM:

The current (amps) / power (watts) figures will vary depending on what "work" the motor is doing Phil. Rewinding with a slight gentle hand resistance will probably give you the maximum load ever likely to be subjected to the motor using a full reel of film on the largest spool size the machine can take. This will therefore give you the peak current reading subjected to the motor and it's drive circuit, while freewheeling without film travelling through the machine will give you the least load subjected to the drive motor and therefore almost "no load" current.

Why would you ever need to change the design spec of components fitted to the motor control circuit board?

I guess I must be missing something here Phil? Surely the design specification components are "fit for purpose" assuming they are all healthy and fully functioning?

Posted by Steve Klare (Member # 12) on January 06, 2015, 08:43 AM:

I'm with Andrew here.

The values that were specified when the thing was built were correct. If some change has occurred that has made them "wrong" then the change is the problem, not the values.

Let's check out the circuit instead. (So nice to have a real schematic for a change!)

As I interpret this character, it is a selector switch choosing one of two variable resistors. When they are chosen, they provide a base current to that power transistor (over by the heatsink) and it shoots a current through the motor. The variability of the resistors means someone can fine tune that bias current to provide either 18 or 24 FPS motor speed.

The question is: When you apply a voltmeter across either of those variable resistors (with everything connected up and powered) and flip that switch, is there voltage in one position but none in the other? This is what I'd expect if everything is OK.

Posted by Phil Mitchell (Member # 3876) on January 08, 2015, 02:26 AM:

Hi, sorry for late reply guys.

Yes sorry I should of put what had happened to PCB originally, previous owner had been playing around with it, especially the Trim pots, I assume to adjust projectors speed, which they can do, but he used the wrong sized screws to attached the heat sink back to Unit and of course I was not aware of this and not as wise to things electronic as I have since learnt, that the heat sink which has the Transistor screwed onto it, came into contact with back of Speed PCB

Hence the change in two resistors and also the transistor on Heat Sink and the circuit drawing above.

So that is history of it.

Good point about running motor under load of film, 600foot reel, actually it didn't draw that much more, once I got the Amp reading from MM, with my friends help I now know the calculation to work out Wattage, which you guys probably know.

Which is Volts x A = Watts

With my original Amp draw test of 500ma, that gives us 12V x 0.5a = 6 Watts.
With film on reel MA increase was 10 or 15ma depending which way motor was running.
I guess then I have answered my on query.
What I am checking is the Ceramic 5W 1k resistor he replaced one with, is it going to take the load.
He feels it will, to quote him.
"The 5W White ceramic resistor will need to burn anywhere between 4 to 1.8 Watts. As such a 5W resistor is sufficient for the job.
Now using the formula V=IxR, we can calculate the R for 18fps should be around 18 ohms and for 24fps it should be around 15 ohms.
"Target a resistor of between 15 to 20 ohms and let the switching (frame rate slider switch) and the Trim pots do the rest."
I assume he means replace the 10k 5Watts to between 15 and 20.
I have emailed him back to double check this.
As one thing I have always wondered with this Sankyo 600 while trying to get it back working, is why doesn't it have the large axial 470ohms Ceramic resistor attached by a bracket to the screw above the board And then has two blue wires on each end of it and they go to the PCB and are soldered to PCB on the back of it just above the Terminal for negative and terminal for positive for motor wires.

Like my Titan does and its setup is the same

Also seen other posts here with Sankyo 600 and they also have the axial ceramic resistor the same.
I have check this with my friend and he doesn't think my one needs it, which sounds right as it ran okay for 3 months before board shorted.
Anyway sorry for a long reply. Hope it makes sense.
Hopefully what I have learnt will help others, I know Janice has had problems with her 600 stopping intermittently and then restarting which as I suggested to her, maybe could be dirt of something in the brushes for the motor. As I know when I checked my wires to motor there was a bit of fluff. I actually changed the brushes on mine
Cheers
Phil

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