8mm Forum: My first Elmo ST-600DM not work!

This is topic My first Elmo ST-600DM not work! in forum 8mm Forum at 8mm Forum.

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Posted by Dariusz Wysocki (Member # 4557) on November 27, 2014, 02:15 AM:

Hello Users!
Unfortunately, the engine does not work, the driver was not properly repaired.
Would the chance to get the circuit diagram of the controller?
I do not know whether it was appropriate parts are.
Sorry, my english is poor.
Thanks
Darek

Posted by Steve Klare (Member # 12) on November 27, 2014, 08:28 AM:

Hello Darek,

Welcome!

I've e-mailed you two circuit drawings. Someone else e-mailed them to me, so I am passing along a favor.

The question is this: Is the motor getting voltage, and if it isn't then why not?

There are a pair of switches activated by cams on the control knob which reverse the motor voltage and direction. If either of these is not connecting there will be no voltage on the motor.

There is a speed regulator circuit that controls how much current is fed through the motor with power transistors. The later ST-600 used an integrated circuit as a controller. Any of this could also be causing an open circuit.

Then there is wiring, connnections, solder joints and the rectifier circuit that gets the motor voltage from the transformer. (Maybe the transformer...probably not.)

Unless nothing else on the machine works, it shouldn't be the fuse. There's only one for everything.

Since you are an electronic technician, I think you will do OK here!

As I said: it's good to ask questions here. Many times you will find out someone has had a similar problem and they know exactly what to do.

Good Luck!

Posted by Dariusz Wysocki (Member # 4557) on November 27, 2014, 03:37 PM:

Thank you Steve!
Transistor D525 has break emitter - base
What's next for the moment I do not know, I'm waiting for the shipment of transistor 2SD525 (repl. D525)
Even two weeks!

Posted by Steve Klare (Member # 12) on November 27, 2014, 10:40 PM:

This Sounds Good!

Something you can try while the transistor is coming is measure the drive voltage from the regulator IC. When the motor is stopped I would think the drive will be high because the regulator will be trying as hard as it can to make the motor speed up.

Now if you solder a short circuit across the D525 Emitter-Collector, the motor should run, but it will run too fast, so the drive voltage should fall because the regulator wants the motor to slow down.

At least if this works, you know the regulator circuit is OK.

Posted by Dariusz Wysocki (Member # 4557) on November 28, 2014, 03:17 AM:

Thank you Steve , I have a technical question.
Between the heat sink
and the heat sink transistor is a piece of thick foil
( look at photo from priv).
Is this transistor is insulated from the heat sink?
or have to apply the conductive paste.
Thank you.

Posted by Steve Klare (Member # 12) on November 28, 2014, 08:05 AM:

Hi Darek,

Your photo looks like you have a sil-pad between the transistor and the heatsink. This is for a good thermal connection, but it is sometimes used for electrical insulation too.

If the transistor is meant to be electrically insulated from the heatsink, the washers between it and the screw can not be metal, they need to be plastic or some other insulator.

When the heatsink is installed, is it electrically connected to the projector chassis? Are there any other devices also on there that the transistor should not be connected to? (rectifiers maybe?)

(-if it is still installed, try an ohmmeter reading between collector and heatsink?)

If any of these is true, then thermal grease is not the right thing, the transistor has to remain insulated.

Just for thermal connection, the white thermal grease is better, but factories don't like to use it because it is messy, expensive and just a little bit toxic too!

It keeps the devices cooler, though.

When I worked on aircraft systems we used this stuff: we hated it, but there was no substitute.

Posted by Dariusz Wysocki (Member # 4557) on November 28, 2014, 11:59 AM:

Thank you Steve again.
You me confirm my guess,
I was not sure if anyone has not changed anything.
I'm sorry I'm writing something does not make sense, but I'm working on a translator. [Big Grin]

Posted by Steve Klare (Member # 12) on November 28, 2014, 05:43 PM:

You are doing fine!

I hope I am translating OK!

Posted by Dariusz Wysocki (Member # 4557) on November 30, 2014, 09:48 AM:

Fortunately, I know what you're writing, I have a good base of electronics,
I worked at construction IC testers.
Thanks

Posted by Steve Klare (Member # 12) on November 30, 2014, 07:31 PM:

Good, then you and I can both speak "op-amp"!

I used to work for companies that did the power systems for integrated circuit testers and fabricators (LTX, Applied Materials, Cymer, Schlumberger...)

One did the precision low voltage for the test heads, another did a high voltage pulser for laser lithography.

I liked working with the low voltage systems better: the pulser scared the crap out of me a couple of times!

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