8mm Forum: Specto 500 8mm projector

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Posted by Michael Wright (Member # 1387) on July 10, 2014, 06:09 AM:

Hi all, I've just acquired this machine of Ebay. It's in good cosmetic condition and the motor runs, at least it does for about 10 seconds before tripping out the electricity. the original lead has the old rubber insulation, so I tried it with another lead with more modern wiring. Same result! What do you think I should try next? All help appreciated. Cheers MIKE

Posted by David Ollerearnshaw (Member # 3296) on July 10, 2014, 09:24 AM:

My experience of the old rubber insulated cable, and this is quite a while ago when I rewired my house it had some still in use ITS DANGEROUS. If you move it it will break and show bare wires.

If the leads is made of rubber it is more than likely used in side the projector. Take the cover off and check.

You could also use a meter to test for any short circuits on the mains input. Check all three wires to be sure.

Posted by Maurice Leakey (Member # 916) on July 10, 2014, 10:53 AM:

I think the problem lies with the motor which has brushes and a commutator, the armature has many coils, one of which may have gone down.

Did the eBay seller say it was in working condition?

Posted by Michael Wright (Member # 1387) on July 11, 2014, 01:58 AM:

Hi David/Maurice, thanks for your replies. I'll try replacing the internal wiring and see if that sorts it out. If it's the motor I'll have to get some help with that one! Cheers MIKE

Posted by Paul Mason (Member # 4015) on July 11, 2014, 03:37 AM:

Michael,
The fact that it runs for about 10 seconds suggests the fault occurs once the motor has warmed up. It's a good idea to replace the internal wiring anyway.

Posted by Rob Watson (Member # 382) on July 17, 2014, 06:46 AM:

Its curious that the projector runs for a few seconds then trips the electricity. I wonder whether its that big mains interference suppression capacitor in the base of the projector going open circuit when it builds up a charge. Its easy to test simply by disconnecting it.

Posted by Martin Jones (Member # 1163) on July 17, 2014, 07:11 AM:

Does it "trip" the MCB (fuse) in the Fuse Box, or does it "trip" the RCCB (main contact breaker)?
That determines what kind of fault you actually have.

Posted by David Ollerearnshaw (Member # 3296) on July 17, 2014, 10:55 AM:

Maurice says "I think the problem lies with the motor which has brushes and a commutator, the armature has many coils, one of which may have gone down."

Now this brought back memories of my first job. Motor Rewinder, one of the jobs was to make sure that each segment of the commutator didn't have have a build-up of carbon which caused a short circuit.

Could be another thing to look at.

Posted by Michael Wright (Member # 1387) on July 17, 2014, 12:15 PM:

It doesn't trip the mains circuit breakers. I was using one of the plug in ones you use for power tools etc. Does it make a difference? Cheers MIKE

Posted by Martin Jones (Member # 1163) on July 17, 2014, 02:03 PM:

Yes, it does.
Too much current being drawn will trip an MCB (or fuse) but NOT an RCCB (Earth Leakage Breaker).

A leakage of current to earth (ground)will trip an RCCB, but NOT an MCB (or fuse).

You are using an RCCB, therefore your fault is a leakage of current within the device.

An RCCB measures the DIFFERENCE between the current entering the device (Live wire) and that leaving it (Neutral wire). If there is a difference ABOVE a certain level, it will "trip", removing the supply. So, if the current leaving is less than that entering it must be going somewhere; that somewhere is some of it "leaking" from the live circuitry to the frame (or earth) of the machine, leaving the machine via the earth connection, NOT via the measuring part of the RCCB.

Tracing such a leakage, especially if it is not "instant", is more difficult than tracing overloads, which usually occur in well documented manners. It is usually achieved by a logical progression through the circuitry by someone with a clear understanding both of the circuitry and the manner in which leakage occurs. It is a "trial and error" process .. but it must be informed trial and error, not "stabs in the dark".

Posted by Maurice Leakey (Member # 916) on July 17, 2014, 02:51 PM:

Worn down brushes could cause the problem.
The carbon is worn off the brushes and distributed about the commutator end of the motor and as it builds up it forms a conductive path to the frame.

Posted by Michael Wright (Member # 1387) on July 18, 2014, 02:08 AM:

Martin and Maurice thanks again for your invaluable advice. I'll try the motor brushes first. I seem to remember from another thread that it can be tricky to remove the brushes, that the bakalite can easily break. What's the best way to tackle this? Cheers MIKE

Posted by Maurice Leakey (Member # 916) on July 18, 2014, 02:41 AM:

The brushes are held by large screws (bakelite?) which should easily unscrew. The brushes are square with a round end which contains a spring, It is very important to very accurately note how each brush is fitted as it is removed.

When first fitted the continual rotation will make a mating fit to the commutator ring therefore it is necessary when being re-fitted that the brushes go back exactly as they were removed.

In ideal conditions the commutator should have a bright copper like colour, old and well used projectors will have a ring of black carbon deposit around it. Try to remove this carbon deposit, perhaps isopropyl alcohol will do this.

Do not use the plug-in trip.

The interference capacitor should not be a problem, but it might be a good idea to unsolder one end to take it out of the equation.

Posted by Michael O'Regan (Member # 938) on July 19, 2014, 01:08 PM:

Can anyone point me in the direction of a photo of this machine?

Posted by Douglas Meltzer (Member # 28) on July 19, 2014, 01:40 PM:

Michael,

Here's a YouTube video that features the Specto 500.

Doug

Posted by Maurice Leakey (Member # 916) on July 19, 2014, 02:01 PM:

Another thought about the trouble. The Specto just loves oil. Perhaps all the gearing has dried up, forcing the motor to draw extra current.

Try turning the mech over by hand using the inching knob at the rear. It should turn quite easily.

Here is a link to Specto details including the instructions and also how to lubricate.

http://www.cinerdistan.co.uk/Specto.htm

Posted by Michael Wright (Member # 1387) on July 20, 2014, 05:38 AM:

It gets worse! I took off the back to check on the lubrication of the gears and drive train and found out that the big resistance that works the lamp is broken in several places. I just presumed the lamp had blown. Does anyone have a circuit diagram? Is it worth trying to replace it or would it be better to bypass it and use a lamp the works off 230 volts?

Posted by Maurice Leakey (Member # 916) on July 20, 2014, 10:00 AM:

The rotary switch is coupled to the resistance to give preheating of the lamp for longer life. The lamp is a standard pre-focus A1/7 which is also available for mains voltage direct, although it probably would not give as much output as the 115 volt lamp.

Unless you are very adept at wiring I would suggest you sell it on for spares and perhaps consider buying a Eumig P8 of which there are always plenty on eBay.

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