3M Thermofax Bulb Conversion... attempt.

[3mconverter]

I haven't tried wiring a different bulb to it, i've only chcked to see if there was the 121v there for the bulb whenI do get it installed. The 121v is there for it. I will post pictures once I get the bulb installed. I didn't want to clutter this thread with pictures until I get it wired up correctly. Then i'll post some pics with good views of the modified wiring. Hopefully the bulb shows up tomorrow so I can. Button this up.

 

[gary350]

Hi All! Electronics hobbyist here. I've been at the hobby for about 4 years, and have primarily worked with older audio circuits (tube radios, instrument amplifiers, phonographs, etc). I've mostly done troubleshooting and repair - only a few scratch builds under my belt, so I'm still pretty green when it comes to theory and circuit design. I'm hoping you can help me learn!!

A friend of mine recently picked up a 15 amp 3M Thermofax transparency maker for next to nothing, and asked me to give it a once over. It's cleaned up nicely, and I've got it working, but I've found that the bulbs for this particular model are almost impossible to find and change hands for about $275. He wants to use this professionally, so not having replacement bulbs on hand isn't an option... and at that price, he would be better off buying a different 40 year-old Thermofax every time he needed a new bulb.

Long story short, I'd like to convert this unit to use the more common 1350watt bulbs from a 12 amp machine, but don't really know where to start to drop the current sufficiently to keep from exploding bulbs or burning his place down.

I have not been able to get my hands on a circuit diagram for this model yet, but I'm still looking. My questions are:
1) What characteristics of the circuit do I need to know to understand what modifications to make?
2) Is this truly as simple as wiring some high-wattage resistors in series with the bulb, or am I fooling myself?
3) Does anybody have a schematic for this laying around? It's not a complex circuit, but I'd still like diagram to stare at.

Thanks in advance for the help. I really want to learn as I go here!
-Mike, St Paul MN

I had 3 of those replacement bulbs laying around for 20 years finally put them on Ebay and sold them all. Last 1 sold 2 weeks ago. Sold them all in about 1 month. People are still looking for those bulbs other wise I would have never sold mine. But maybe someone had a science project to build.

 

[3mconverter]

I had 3 of those replacement bulbs laying around for 20 years finally put them on Ebay and sold them all. Last 1 sold 2 weeks ago. Sold them all in about 1 month. People are still looking for those bulbs other wise I would have never sold mine. But maybe someone had a science project to build.

The old 3m secratary transparency maker is still 100% releveant in the tattoo industry. It's still the most preffered machine by far. They could open the production line back up and be supported for a long time to come. Sure there are other newer options out there, but I would not expect any of the newer options out there to last 20-30yrs the way these work horses do. I would not be surprised if you got $300 per bulb if they were the orginal 15amp lamps.

 

[3mconverter]

I got everything buttoned up. The light turns on and everything seems to work, but it does not make a stencil. I don't beleive these are correct instructions to convert this bulb over. Maybe using a different bulb might work, but the bulb listed in this thread is not powerful enough to make a transparency.

 

[Diver300]

I'm sorry to hear it doesn't work.

If the light is turning on and off at the right times, the relay has to be working. Relays can't really fail in subtle ways and they are incapable of letting the wrong amount of power through.

The assumption behind making this conversion is that the 120 V bulb is much the same dimensions and power as the 300 V bulb. If that's not the case, the transparency maker can't work.

Have you got any way of measuring the current or power taken by the bulb?

 

[Jinked92]

Thanks, Diver. Awesome write up, and very helpful.

The parts are en route, so I will report back once I have everything wired up and can pull the voltage readings across the relay coil. Stay tuned!
Mike

sent you a private message and if you can help me that will be great please.

 

[Mad86mike]

Can anyone send me a up close picture of the beefy terminal block , so I can see how it is original wired , 15 amp thermofax