8mm Forum: Chinon SP 330 motor stopped running

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Posted by John Pechulis (Member # 620) on September 21, 2017, 12:20 PM:

Anyone know why the drive motor would stop running on a Chinon 330 sound projector? Is there an actual service manual available?

Belt is fine, the actual motor does not run

Posted by Janice Glesser (Member # 2758) on September 21, 2017, 01:09 PM:

More information would be helpful. When was the last time you ran the projector and it was working? Did the motor stop while it was running? Have you had trouble with the motor slowing down or turning on and off prior to it stopping completely? Does the light go on even though the motor doesn't run? There are lots of reasons a motor stops running...and usually they have nothing to do with the motor itself. Could be a bad power cord... dirty or faulty main switch...a bad capacitor, transistor, bridge rectifier, or micro switch. If inclined you can pull out the power PCB ... and start testing components.

Posted by John Pechulis (Member # 620) on September 21, 2017, 02:44 PM:

Hi Janice, I use this projector on a regular basis to capture the sound track from sound films. I then marry the sound track with the digital transfer I capture on my dedicated machine in post.

The motor stopped running while film was being projected. Next thing I knew the frame burned through.

I checked all the obvious like switches, but I measure no voltage before the control switch from the motor supply.

It is most likely a component failure, but without a schematic, I would have to shotgun replace components until I get voltage at the motor circuit. This can be time consuming and a bit of a guessing game.

Not to mention the circuit board was a REAL pain getting it out of the chassis - you had to remove just about everything to slide it out and I still had to cut the record LED wires to allow the board to slide all the way out.

I purchased 2 other Chinons from ebay to finish a job I am in the middle of, but one of these is showing signs of impending motor stop. It slows, stumbles and then continues at normal speed. It is definately an electronic issue and not a mechanical one. The other has a broken rewind arm. So I am limping along trying to finish up this project.

If anyone knows where I can secure a schematic for these Chinon SP 330's I would greatly appreciate it

Posted by Maurice Leakey (Member # 916) on September 21, 2017, 02:58 PM:

John
I once had the same problem with my Chinon Sound 7500. Its motor stopped.
The problem was solved by replacing two capacitors which were blowing the motor's fuse.
I realise your model is different from mine, but it's possible the same circuitry is used in both models.

Posted by Janice Glesser (Member # 2758) on September 21, 2017, 03:56 PM:

Hi John...Thanks for the details. I agree without a schematic it's difficult to troubleshoot these types of problems...however I have never seen a schematic for the SP330. I have a SP330...nice projector...clean audio.

I haven't had to work on the sp330 power board...sounds like a bear to get out. However I have a Sankyo 800 that the motor stopped. I replaced the bridge rectifier and the large capacitor next to it to get the motor going again. I would start looking around the main power transistors and accompanying components.

Posted by John Pechulis (Member # 620) on September 21, 2017, 05:25 PM:

Thanks, I'll start with the power supply components. Although I can't find any info on the bridge rectifier. It is made by Toshiba and it has the number 491 on it.

I've tried all combinations to find out the specs of it, but have come up empty. It is a round case approximately 10 - 12 mm in diameter.

Any ideas?

Posted by Steve Klare (Member # 12) on September 21, 2017, 05:50 PM:

If you measure the voltage on that capacitor you can learn a lot.

Posted by John Pechulis (Member # 620) on September 21, 2017, 06:57 PM:

In doing a little testing on individual components, I find a TO-220 case trasistor on leads mounted to the chassis near the lens which plugs into the section of the board which controls the motor. It is probably used to regulate the motor speed settings.

It is giving me out of the ordinary readings (open juntions or high resistance junctions), so I have a feeling this may be part or all of the issue.

The bridge rectifier for the motor section reads as it should at the junctions .6 in forward and open in reverse.

The bridge rectifier for the amplifier section gives me weird readings as well (like the 220 case transitor) so it looks like I'll be replacing that as well as all the electrolytic capacitors. I had a 60hz hum in the audio when everyting was working, so likely many of the caps are dried out.

Posted by John Pechulis (Member # 620) on September 27, 2017, 05:59 PM:

An update on the SP 330: It lives again!

About $10.00 worth of electronic parts has me up and running again.

Replaced the following:

Bridge rectifiers for both motor and amplifier sections

Speed control transistor

And ALL electrolytic capacitors (probably could have just replaced the supply caps, but since the board was a pain to get out, I did all of them)

She runs good now

One suggestion, if you decide to get into the repair like I did, take lots of photos as you progress. I didn't and had to refer to another machine I purchased

Posted by Janice Glesser (Member # 2758) on September 27, 2017, 07:07 PM:

Nice work John. Congrats on getting it up and running again.

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