8mm Forum: Muray transformer

This is topic Muray transformer in forum 16mm films for sale/trade/wanted at 8mm Forum.

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Posted by Terry Sills (Member # 3309) on April 28, 2019, 06:40 AM:

Long shot I suppose, but can anyone help me with a transformer for a Muray editor? I don't think it matters whether it is from an 8mm or 16mm model as I'm sure they are the same.

Posted by Steve Klare (Member # 12) on April 28, 2019, 08:36 AM:

Hi Terry,

With a little luck, this could be a standard part that you can buy brand new today, but you need to understand the specs.

You know your line voltage already, it's the output voltage and VA that are a question. Is this a motorised editor, or is the transformer just powering the lamp?

If it's just the lamp, then the transformer output voltage is the rated lamp voltage. The tranformer VA is at least the wattage of the bulb.

Other question: why do you believe you need a new transformer?

Posted by Terry Sills (Member # 3309) on April 28, 2019, 12:24 PM:

Thanks for your help Steve. Input is 240v - output is 25v which just powers the lamp (25w).
The reason I suspect the tranny is that it blows a fuse when switched on and all the wiring looks to be in excellent condition. Having said that so does the tranny, but I cannot see what else it could be.

Posted by Steve Klare (Member # 12) on April 28, 2019, 06:07 PM:

A transformer is a pretty respectable candidate for something like that. They have a pretty interesting characteristic: one might have several hundred windings, and if any one of them develops a short circuit, ALL of them will act like they are shorted!

-but: if there is a short across the secondary side it will be reflected to the primary and pop a fuse.

It would be nice if you can remove some wires and isolate sections of the thing and see where the trouble starts.

Oh, another transformer funny: never look for short circuits around tranformers with an Ohmeter. A transformer is an AC device and will look like a short to a DC Ohmeter seven days a week!

Here's a 240V to 24V, 50VA tranformer. (What's a volt among friends?). I doubled the power so it runs cool.
Does it look like what's in there now?

50VA Transformer

(Naturally, when we get close you'll want a vendor closer to home.)

Posted by Terry Sills (Member # 3309) on April 29, 2019, 02:10 AM:

Thanks again Steve. You're definitely the man when it comes to anything electric. Such an asset to this forum.
Yes that does look as though it would do the job, but shipping costs would be prohibitive. What I am hoping for is someone having a redundant or damaged editor that they will let go at a reasonable price.
Standard/Regular 8 models are by far the least desirable, so I think that my best option is to find one and just hope that the transformer is good.

Posted by Paul Browning (Member # 2715) on April 29, 2019, 03:55 AM:

A capacitor or transistor in the power supply could also cause the fuse to fail, I had a norisound projector that had such a problem.

Posted by Maurice Leakey (Member # 916) on April 29, 2019, 05:36 AM:

Here's a transformer on eBay.
230volts to 24volts at 25VA for £18.99 post free. (25VA is 25 watts.)
Steve's suggestion is a transformer at 50VA (50 watts), this is available at a slightly higher price of £21.99.

https://www.eb ay.co.uk/itm/CNC-Machine-Tool-Transformer-voltage-input-240-415-output-12-24-48-110-230/232479492148?hash=item3620db8834:m:mCD6iNsNx3X_206AefJCMwA

Posted by Terry Sills (Member # 3309) on April 29, 2019, 07:12 AM:

Paul
No transistors or capacitors in these Editors. Very simple circuits that just power the lamp, so only the transformer to go wrong really.
Maurice
Thanks for the link. Seems Steve was correct, they are readily available so that's a possible solution.

Posted by Steve Klare (Member # 12) on April 29, 2019, 10:01 AM:

Yes, if nothing else it's always good to have Plan "B".

It's pretty simple when it's a single secondary transformer and a common voltage. Where you start to have problems is when there are multiple different secondaries and all the windings have to make the right voltages, and then you throw on top of that it has to be the exact shape and mounting and connection style. This is why replacing the main transformer on a projector can be such a headache.

Posted by Terry Sills (Member # 3309) on April 29, 2019, 12:25 PM:

Paul
No transistors or capacitors in these Editors. Very simple circuits that just power the lamp, so only the transformer to go wrong really.
Maurice
Thanks for the link. Seems Steve was correct, they are readily available so that's a possible solution.

Posted by Terry Sills (Member # 3309) on April 30, 2019, 12:40 AM:

Paul
No transistors or capacitors in these Editors. Very simple circuits that just power the lamp, so only the transformer to go wrong really.
Maurice
Thanks for the link. Seems Steve was correct, they are readily available so that's a possible solution.

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