Planetarium Star Projectors

[dar303]

Wow, thank you for taking the time to write such a detailed guide for disassembling the projector!
I have a date set for collecting it now, I'm going to take a day off work next Friday the 15:th, wish me luck!

I am reading the thread over on OC now, great pics!

EDIT: the other thread you are refering to, is it this one?
http://www.observatorycentral.com/in...showtopic=1625

[SpitzSTP]

Best of luck !! This A3P was from Brigham Young University Idaho which was disassembled and re-assembled. A few of these pictures show the analog control modules in the control cabinet, look for these and grab them if they are still sitting around. The photo that shows the colors reversed indicate the ropes that I use to position the machine while I am attaching the back half and starball to the core when there is nobody to help me do it.

[dar303]

Thanks for all the pictures! Sadly the beautiful control console is gone from my unit.
If anyone of you have a wiring diagram or any mechanical drawings in digital form I would be very greatful! I got an email today saying they found some documentation and possibly the software for the control computer but it is always nice to have a complete picture of the unit so to speak. my email is camp303 (at) gmail.com

I am toying with the idea of building a miniature control console, I build analog modular synthesizers for a living and as a hobby and have my own CNC-machine so the practical stuff is take care of!
It looks like mostly wirewound resitors/rheostats, shouldn't be to hard to make something functionally equivalent if the current isn't to high through them.
That square thing in the top in the pic looks like some kind of worm drive to gear down a potentiometer for precision, correct?

[m2b]

Thanks for all the pictures! Sadly the beautiful control console is gone from my unit.
If anyone of you have a wiring diagram or any mechanical drawings in digital form I would be very greatful! I got an email today saying they found some documentation and possibly the software for the control computer but it is always nice to have a complete picture of the unit so to speak. my email is camp303 (at) gmail.com

I am toying with the idea of building a miniature control console, I build analog modular synthesizers for a living and as a hobby and have my own CNC-machine so the practical stuff is take care of!
It looks like mostly wirewound resitors/rheostats, shouldn't be to hard to make something functionally equivalent if the current isn't to high through them.
That square thing in the top in the pic looks like some kind of worm drive to gear down a potentiometer for precision, correct?

The square thing (third from the right on the top row) is actually a readout for annular (yearly) motion. It will indicate seven years forward or backward from a given date. This allows the operator to get back to the current year after demonstrating the movement of the planets over a period of several years.

Most of the control panel consists of wire-wound rheostats to dim or brighten many of the projectors on the machine. These are brute force units (most are 25 watts) that vary from 2 to 50 ohms. Most lamps are basically 6.3 volt flashlight type bulbs.

[dar303]

Thanks! I just have to wait and see what the computer interface can do, maybe it has more modern drivers that one can hook up controls to.

Do the bulbs go out a lot? Has anybody tried to replace the bulbs with leds, that should be possible since there are those with quite nice color temperature now?

[m2b]

Thanks! I just have to wait and see what the computer interface can do, maybe it has more modern drivers that one can hook up controls to.

Do the bulbs go out a lot? Has anybody tried to replace the bulbs with leds, that should be possible since there are those with quite nice color temperature now?

The basic bulb used on the A3P is a PR12 lamp with a rated life of 15 hours. They are quite cheap at around sixty cents each. I have not done much experimenting with replacing bulbs on the A3P as I am spending most of my time rebuilding my Minolta as it is the first one I will put back in service. (see) http://www.observatorycentral.com/in...showtopic=5118

I would say that you could replace all of the tungsten lamps with LED's on virtually all projectors. The exception to this is the star ball lamp.

I agree with you that waiting to see exactly what you get will help you decide which direction you want to go.

[dar303]

Thanks for the info!
How many watts is the starball lamp on the A3P? I guess it is an expensive unit to replace

[SpitzSTP]

Thanks for the info!
How many watts is the starball lamp on the A3P? I guess it is an expensive unit to replace

The A3P uses a 20 watt xenon arc lamp as standard, and yes they can be expensive to replace. The A3P can also be field-upgradeable to a 75 watt xenon arc lamp (pictured). The arc lamp mounts in a starcup that has a fisheye lens above the lamp, in the case of a 20W bulb. The 75W bulb does not have the lens. The starcup mounts on top of the ballast which is suspended inside the starball on a hanger. For lamp replacements, contact Steve Pielock in the USA, he usually has spare lamps, xenon ballasts and other parts for sale. His prices are not cheap, but there are few other choices when it comes to these rare vintage components. ---> www.pielock.com

[m2b]

The A3P uses a 20 watt xenon arc lamp as standard, and yes they can be expensive to replace. The A3P can also be field-upgradeable to a 75 watt xenon arc lamp (pictured). The arc lamp mounts in a starcup that has a fisheye lens above the lamp, in the case of a 20W bulb. The 75W bulb does not have the lens. The starcup mounts on top of the ballast which is suspended inside the starball on a hanger. For lamp replacements, contact Steve Pielock in the USA, he usually has spare lamps, xenon ballasts and other parts for sale. His prices are not cheap, but there are few other choices when it comes to these rare vintage components. ---> www.pielock.com

Very expensive in my book. A new one goes for something like $800-$1000. That do have a life of about 1000 hours, so in the big picture you are talking about $1 an hour lamp operating cost.

Looking at the pictures, my understanding is the the first one shows the 20 watt bulbs as they are bent at 90 degrees, and the second picture shows the 75 watt ones as they are bent at 120 degrees. That is my understanding at least and I have been know to be wrong.

For every day playing around you might want to build an alternate lamp holder. We have found that a Stinger flashlight lamp has a small enough filament to produce good stars, however not as bright as the arc lamp. They have a 30 hour average life and cost around $6 each. That's about twenty cents an hour bulb operating cost. Building a conversion bulb holder can be found here: http://www.observatorycentral.com/in...ndpost&p=17092

[dar303]

Wow, you guys really know this machine!!!