ac-dc power converter

Hi Joe - Before we can talk components we need a plan and some more information.

Is size or weight a consideration?

How well do you need the 9 volts regulated?

My first thought is to bring the 70V AC down with a step down transformer. If you used a transformer that was intended for 120V primary and 24 V secondary and put the 70 volts on the primary the secondary would have 14 VAC. Then I would rectify and filter the 14 VAC. Then I would feed the DC output to a variable voltage regulator capable of handling the 4 amps that you require.

I am a little old fashion and tend to reach back a few years for my solutions to these questions so some of the younger guys may have a quicker simpler solution. You may also want to search around for a schematic that will give you some ideas on how to do it and what components will be required.

John

Hi Joe - Before we can talk components we need a plan and some more information.

Is size or weight a consideration?

How well do you need the 9 volts regulated?

My first thought is to bring the 70V AC down with a step down transformer. If you used a transformer that was intended for 120V primary and 24 V secondary and put the 70 volts on the primary the secondary would have 14 VAC. Then I would rectify and filter the 14 VAC. Then I would feed the DC output to a variable voltage regulator capable of handling the 4 amps that you require.

I am a little old fashion and tend to reach back a few years for my solutions to these questions so some of the younger guys may have a quicker simpler solution. You may also want to search around for a schematic that will give you some ideas on how to do it and what components will be required.

John

What I have is a video projector and the bulb is broken and I can not afford to spend $100.00 or more for a bulb so I have a 9volt dc 30 watt camcorder light I would like to use in place of the original bulb. the original bulb is 70 volt ac 130 watt and the camcorder light has to be connected to the original connector for the bulb or the projector will not work. so i just need a small board around 1.5 inches square that will convert the 70 volts ac to 9 volts dc if that is possible.

I know of no way to make the conversion from 70 volts AC to 9 volts DC at 4 Amps in such a small space. Even if we could do it, would 30 watts of light be enough to make your projector work? Have you given ebay a try to see if they might have a bulb that is cheaper? What is the code for the bulb that you need?

John

Yes the cheapest I have found is 199.99 on some sites here in the us and Canada but there are none on eBay the number is Hitachi c10h projector lamp the 30 watt will be fine for what i need. i could use an external power converter just run the ac from the projector out to a brick then from the brick with the 9 volts back to the bulb.

                                thanks Joe

How about taking the power converter outside the projector? Is there any reason that the 9 volt bulb has to be powered with DC. Is it incandescent? We could bring the 70 VAC out to a transformer and then take the 9 volts AC back inside to the 9 volt bulb. You mentioned that the projector would not work without the bulb. Do you mean that the bulb is part of another circuit in the projector? If the bulb isn't part of the circuit you could use a commercial 120 V power supply to give you 9 volts for the bulb. If the bulb is part of the circuit then we have an additional problem as the 9 volt bulb will not load the 70V circuit in the same way as the original bulb did. Sorry lots of questions.

John

The projector has to sense that the bulb is plugged into the projector and the bulb I have has a circuit board in it. I have not taken it apart so it may run off 9 volt dc then convert it to 9 volt ac for the bulb. I will take it apart and see if that is the case.

These two pieces of equipment do not appear to be compatible. If we attempt to jury rig the wrong bulb into the projector I feel there is a good chance you will damage one or both. Projectors that sense the pressence of the bulb and bulbs with internal circuit boards are too unique to be easily hacked. Procede at your own risk.

John

Yes I think I will dismiss the idea and see if i can find another solution seams to be to much trouble.

                                                                                                        thanks joe