8mm Forum: Seperate 150 watt transformer, what do I need.

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Posted by Mark Todd (Member # 96) on May 16, 2005, 01:39 PM:

Hi, I`m hoping to soup up my really nice 100 watt machine, and wondered what I should look for in a transformer.
Can I buy one anywhere as is, or do I need to get one made up.
What are the amps etc I should ask for for the 150 watt 15 volt lamp please.
Do you think its worth it doing a heath robinson upgrade as it were.
Thanks Mark.
Ps its an elmo well fanned job, so no worries on heat etc.

Posted by Rick Skowronek (Member # 385) on May 16, 2005, 02:49 PM:

Hi Mark, Since this is a straight forward electronics question, I can provide the info.

To cover 15 volts at 150 watts you'll need a transformer that puts out that 15 volts at a minimum of 12.5 amps. 10 amps for the bulb and and a 25% safety margin. Obviously with your mains voltage in (240 VAC I believe, or so).

Rick

Posted by Tony Milman (Member # 7) on May 16, 2005, 03:10 PM:

Mark,

I know this one! I always remember it from school...... Ivy Watts.

(That's Amps x Volts = Watts) (If not then the sparks will look good)

Posted by Rick Skowronek (Member # 385) on May 16, 2005, 03:38 PM:

Just did some perusing of available transformers on the web.

Several companies make these things. What you probably want to look for to save money is a dual primary 115/230 VAC, dual secondary 28 VAC 6 amp which when hooked in parallel create 14 volts at 12+ amps. It looks like there isn't one that is specifically 30 volts w/ dual secondary or a single secondary at 15 volts in that amperage range. At least not one I've come across yet. Maybe the other folks know a source/type for that.

Oops, meant to add. These are going to be rather large. Certainly won't cram into the projector housing I suspect. Here's the size of the one I found:
3.12" - 79.4mm length
2.87" - 73.0mm width
3.75" - 95.3mm height
5.5lbs - 2.49kg weight

Rick

Posted by Mark Todd (Member # 96) on May 17, 2005, 09:40 AM:

Thanks Rick, and Big T, I`ll see if I can find one online in the UK, the size doesn`t sound too bd s I will put a fitting on the back of the mchne to plug in externally if you will.
Best Mark.

Posted by Kevin Clark (Member # 211) on May 17, 2005, 10:03 AM:

Hello Mark
It might be useful to speak to someone at a disco lighting supply shop as many disco lighting units use the A1/232 15v 150w lamp you are considering for your projector. As you don't need the electronics that make the disco lights flash they should be able to supply a basic suitable on / off type transformer to do the dropdown from your 240v supply.

Posted by Mark Norton (Member # 165) on May 17, 2005, 02:23 PM:

Just wondering why only 150w, if you are going to the trouble then wouldn't it be better to go for 200w and use the GS1200 bulb? I've got an ST180 that I have modified to take 800ft spools and have also been thinking about a brighter lamp.

Posted by Mark Todd (Member # 96) on May 17, 2005, 05:41 PM:

Is the 200 gs bulb the same shape etc, I know the 132 is, they are cheaper as well.

Worth a think though, thanks for the nod on the disco jobbies Kevin, sounds like its going to be worth having a crack at it.
Best Mark.

Posted by Mark Norton (Member # 165) on May 18, 2005, 01:29 PM:

Yes the GS1200 bulb is the same shape & size as the 100w. I remember a few years back a the Tadley convention 'Classic Home Cinema' had a Black ST180 for sale that had a 200w conversion, so it has been done before.
Price wise (the non ESC) Bulb is about £12.

Posted by John Whittle (Member # 22) on May 18, 2005, 03:35 PM:

You may find it from more economical to buy a "parts machine" such as an Eiki SL or Elmo CL and take the transformer out if it. They are 24 volt auto-transformers that can handle 250 watt lamps and you can use the EJL lamp.

The auto-transformer is a diffent design than those listed earlier in the thread that have issolation windings for the mains and secondary. In an autotransformer this is one winding and the lamp take off is lower down in the turns giving the lower voltage. It is an economical means of getting these lamp voltages at such high amperage and uses less copper and thus less weight. That's what those are the items you usually find in the OEM projectors.

Just a suggestion.

John

Posted by Lawrence Alan Fabbri (Member # 370) on May 18, 2005, 08:02 PM:

John
Would you know if the B&H series 1500 (EMM/EKS 24V 250 Watt) projectors would have a useable transformer. I have one with a cracked worm gear that I could use the transformer from to soup up my ST1200. Thanks Larry

Posted by John Whittle (Member # 22) on May 19, 2005, 09:30 PM:

Haven't taken one apart for years, but it would easy enought to find. Just open up the projectors and trace the wires back from the lamp socket thru the switch to whatever is feeding them. Usually the transformer will have multiple taps with the lamp having the auto-transformer winding and secondary windings for the amp and usually another one for the exciter lamp supply.

Old "dead" 16mm projectors with low voltage lamps should be a good source of parts for converting 8mm projetors. If the lamp socket and holder are in good shape they may be fitted to the 8mm rig. Remember there will be some light loss since the EJL and other 16mm pre-focused reflector lamps have the cone of light set for the .286 x .380 16mm aperture and there will thus be spill when putting the light thru the 8mm aperture.

John

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