8mm Forum: Ampro XC projector

This is topic Ampro XC projector in forum 16mm Forum at 8mm Forum.

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Posted by Justin McInvale (Member # 1236) on July 31, 2008, 10:26 PM:

Does any one know anything about this projector? I got one about two years ago in bad shape. Judging by the board the projector was mounted on it may have had an external amp, but I'm not sure about that. As found the exciter lamp was missing and it is also missing the phototube. It has no other tubes either. The mechanics work great as well as the projector bulb. I would like at least to find a schematic of the projector so I can get the audio working. Also does anyone have a manual for this projector?

[ August 01, 2008, 01:49 PM: Message edited by: Justin McInvale ]

Posted by John Whittle (Member # 22) on August 01, 2008, 03:21 PM:

Start with a schematic for the oldest Ampro Premier you can find. I think this was the first Ampro sound projector and the basic head was used later on the Arc model. Remember that in dealing with a phototube pick up in a tube amp that there is a 90 volt DC bias applied across the phototube and that a coupling cap let's the ac audio signal through to the first stage. Also in the Ampros I've worked on, the exciter lamp circuit is part of the tube filament supply and at least the one I have had used DC on the first input stages to reduce hum (something you don't find on all tube amps in projectors of that vintage).

Finding an exciter lamp and phototube shouldn't be too hard, but getting the amp to work without them will require figuring a bit of loading to balance the circuit.

John

Posted by Justin McInvale (Member # 1236) on August 01, 2008, 10:05 PM:

That's the problem. I'm not sure what tubes are used in the amp. There are two octal sockets and one loctal socket on the metal chassis the head mounts to which also has the volume and tome controls on it as well as a transformer which I'm thinking may be the power transformer. The head runs like a dream. I may try and get into 16mm film provided I can find some good movies that don't cost too much $$$. I saw one about a year ago at a flea market, but I did not have an empty reel large enough and the person selling the film didn't either.

Posted by John Whittle (Member # 22) on August 02, 2008, 08:52 AM:

Well the easiest solution is to buy a "modern" parts machine like an Eiki SL and take out the amp, exciter lamp, transformer and solar cell and fit those to your projector. You'll have a modern well regulated exciter lamp supply, low noise solar pick up and a low distortion amp. You can also use the leads off the transformer for the 24 volt lamp and modify your lamp house to take the new style lamp (which will burn a lot less electricity as well as have better light output and you can get rid of those old condenser and reflector in the lamp house since the new lamps are prefocused for the 16mm frame and mount 2 inches back from the aperture).

As for the tubes, finding an early Ampro Premier projector manual will probably have the same circuit. These were licensed back then by Western Electric (usually) or RCA since they were sound film devices. But your machine is old enough that it pre-dates the "minature" tubes that came out in the late 40s.

The machine I worked on was a Stylist and made later and had the minature tubes. In that machine I had to replace every paper cap and a few resistors but got the sound back with the original tubes!

Once you look at an old circuit I think the tubes will fall into line, there is going to be a pre-amp tube, a rectifier (unless it's got some old device) and probably a couple of output tubes (if it isn't push pull then it's really low power) that should feed into a transformer that then leads to the speaker.

Just guesses, but you'll find these are much more alike than different once you get into a few and you'll see the cheap designs like the Revere S-16 compared to the better designs like the RCA and Ampro and Bell & Howell.

John

Posted by Justin McInvale (Member # 1236) on August 02, 2008, 11:56 PM:

I take it there wasn't an external amp then? There is a hole in the back of the projector that looks like it could have fit an octal socket or something. Where would the output transformer be as I only see one transformer in the amp.

Posted by John Whittle (Member # 22) on August 03, 2008, 12:28 PM:

It's possible that the projector used an electro-magnet speaker which was popular for a while. The DC from the amp supplied the coil current for the magnet and served as a dampner to the amp. Maybe they used other windings to handle this as well. There were Filmosounds with both PM and EM speakers and as a kid we had a Magnovox radio that had EM speakers.

Don't know except that there was a licensed EM speaker sound projector circuit and back then all these circuits were licensed by either ERPI or RCA.

Also the first Kodak 16mm sound projector had the phototube, exciter lamp and pre-amp in the projector and the amp was actually located in the speaker box so it might be like that as well. The Kodak has a multi-pin cinch-jones connector which connects the pre-amp to the amp and supplies all the voltages to the pre-amp and exciter lamp. The volume control is on the projector and then the ouput runs to the final stages of the amp. The machine is cir. 1938 and we discussed it here before. I've restored one projector and now have all the parts for the amp but haven't gotten to that project yet.
John

Posted by Justin McInvale (Member # 1236) on August 03, 2008, 11:07 PM:

I cannot seem to find any info on this projector on the internet. In its current state the electronics would take a lot of work to get operating again.

Posted by Justin McInvale (Member # 1236) on August 04, 2008, 12:06 PM:

Unless I find another similar projector with the same electronics I may wind up doing nothing with this one.

Posted by Michael O'Regan (Member # 938) on August 04, 2008, 02:15 PM:

Theres a lot of AMPRO stuff in the Film Tech manual area - maybe you can find what you need right there.

http://www.film-tech.com/

-Mike

Posted by Justin McInvale (Member # 1236) on August 04, 2008, 07:03 PM:

Unfortunately that didn't help. I'm going to try and sell this one and find one that works properly.

[ August 05, 2008, 09:23 AM: Message edited by: Justin McInvale ]

Posted by John Whittle (Member # 22) on August 07, 2008, 03:36 PM:

Justin,
If you're looking for a projector to actually use, then look at the Eiki SSL or SNT or the Elmo CL-16 (also branded as a Kodak CT1000). These were the last projectors made, have the most modern amps, best regulated exciter lamp supplies and parts that are 30 to 40 years newer than the last Ampro made.

The old projectors are fun, but you have motor governor circuits, tube circuits with assorted voltages and then old bearings, shafts, washers, phototubes, etc. It's a fun challenge to get them working again, but to run a film and get a good steady picture, the newer machines are by far an easier path.

I think you're missing the second part of your projector and while you could build up the necessary amp and power supply and put in an exciter lamp and solar cell, by the time you were done you still wouldn't have the image quality that you'd get from the Eiki or Elmo with it's fifty year newer projection lens, which is faster and sharper, etc etc.

John

Posted by Justin McInvale (Member # 1236) on August 07, 2008, 09:37 PM:

As I recall I had a Singer once which was solid state with two internal speakers and an 8 inch speaker and tweeter in the front cover that could be placed elsewheres in the room. I will try and look for a newer model.

Posted by John Whittle (Member # 22) on August 13, 2008, 10:56 AM:

Justin

Just saw this on ebay item 300248515046. I think it's your projector missing the film gate but with the amp and case. You probably could cobble together a working machine with this.

John

Posted by Justin McInvale (Member # 1236) on August 13, 2008, 09:20 PM:

Unfortunately that is a model N not a model XC. Thanks anyway.

On a side note I saw three Ampro speakers for sale on Ebay.

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