3M Thermofax Bulb Conversion... attempt.

I assume you checked the pot on all three legs? Pin 1 to pin 3 should measure the full value of the pot, pin 2 to any other should vary linearly. Other than that, hard to say without seeing the control circuit. I would start by tracing the wires from the pot to the control board (check for continuity). Then map out the circuit the best you can.

Electrolytic caps will typically bulge at the tops when bad. If it's like the other models I've seen, there is also a white ceramic resistor on the board, check that too.

Can you post a pic of the board and tell me which wires come from the pot, and which wires go to the motor?

Thanks much, Robb. Yes, I measured the pot as you described. It checks out.

I don't have the unit here anymore so will get pics ASAP. Can you describe how the motor control circuit on these work?

I changed the e-caps in the can for good measure since I was already in there. The wax cap on the board looked like it had led a rough life, so I swapped that one as well.

Pics to come.
Mike

I haven't had to troubleshoot the motor circuits on these yet, so I'm not really sure what's all involved. I've only replaced a pot that was dirty. I also don't have one here to look at. Motor control circuits typically consist of a pot, diac/triac/diodes or SCR/transistors, as well as a handful of caps and resistors. There may even be an IC in there somewhere.

Everything but caps can be easily checked in circuit with a DMM (depending on parallel connections). The caps would need to be removed, or use an in circuit tester such as an ESR meter.

FIXED. Check the simple stuff first... all the spade terminal connectors on this unit are sheathed in thick rubber sleeves, and one of the connections had come apart, but wasn't obvious because of the thick sleeve. I found it by mistake, reconnected it, and the motor speed control works great once again.

Thanks again to all for chiming in!
Mike

I Got the Relay and The Resistor Wired them in and Bulb Lights up and Works Motor Speed Will Increase and Decrease when Turned From Light to Dark. But will Not Make a transparency. (stencil) Even Turned all the way Dark, and It will travel Thru Slow on Dark and fast on Light Like it is Suppose to. Anyone else have this Problem ?

It Act's Like the Bulb is not Intense Enough, Any Idea's ????

None... mine works fine with line voltage. Do you have a DMM to figure out if the bulb is getting enough voltage?

Mike

Hi Rave0035 i saw you did the bulb convertion on a thermofax, is there any way you could do that to my thermofax, I m in minneapolis, thank you.

Hello, I was wondering if anyone can help clarify some of the things in this thread. The 2 pictures shown are of very poor quality and it makes it difficult to see where the wires are going and comming from. There is aguy on ebay (rouben) that is charging tattoo artists an extra $70 for this information and I refuse to pay him for the information that you techs here have graciously donated to us for free. If you ask him for a 15 amp bulb he will tell you that he can get you a 15amp bulb. Then he tells you to buy his $72 bulb and he will adjust the invoice for $142 for the bulb. What he doesn't tell you unless you press him is he is going to send you the same $72 bulb with instructions on how to convert your machine. You still have to order the parts to convert it yourself at an extra charge. He doesn't even provide the parts for the extra $70. He's kind of sheisty, so i'd like to help everyone convert this machine for the cost of reading this post.

Sooo..
I'm converting a model Thermofax 45 CG from 15 to 12amps. I've purchased the parts in this thread and mounted them, but the wiring is where i'm gettng confused because the 2 pictures do not clearly define where the wires are going.

The relay has 4 posts on it and i'd like to define what each post is connected to.

This is the relay.
https://www.digikey.com/product-detail/en/HE1AN-AC240V/255-1639-ND/570776

Is this correct?
Posts
#1. To bulb?
#4 120v?
#5 to reistor, then to 300V
#6. 120V?

Any help would be greatly appreciated. Thank you in advance.

You have two 300 V connections, that go to the old 300 Volt lamp. It does not matter which is which, but just call them "A" and "B".

"A" connects to the resistor.
The other end of the the resistor connects to #5 on the relay
#6 on the relay connects to "B"

On the bulb, when you have the 120 V bulb, you have the correct connections. What isn't mentioned is the other end of the bulb. That must connect to the neutral of the 120 V supply, where the line of the supply goes to #4 of the relay.

I hope that help. Please tell us if it works.

Thanks Diver300!

So here is what i'm thinking should be right and makes sense.

There is 300V currently going accross the bulb when activated. Basically we pull those 2 wires off of each end. One wire goes through the resistor then to either Post #5 or #6 and the other wire goes to the other post either #5 or #6.

Whats left are Posts #1 and #4. Those 2 posts then connect to each end of the new 12amp bulb.

Thats the only way I can see this working.

Sound about right? If so, i'll try it and give a more detailed description for everyone if it works. The new bulb should be here today.

Thanks for you r help.

So my last post was incorrect. I connected both sides of the 300v source to posts #5 and #6, one side via the resistor. Then I checked the voltage at posts #1 and #4 when the light should have been activated, but the voltage is in the millivolts range, not at 110-120volts where it would need to be to power the lamp. Maybe putting the lamp in line might trigger something, but it doesn't seem as if it will. I guess I need to study a little more about how this relay works.

When the lamp should be on, you should get around 240 V between #5 and #6. If you aren't getting that, you need to investigate why.

The connections #1 and #4 of the relay act like a switch. You need to add power.

Firstly, find a power source at 120 V. The power inlet, preferably after the mains switch and a fuse, is what you want.

On the power you have line and neutral.

Connect line to #1.
Connect #4 to one end of the 120 V lamp.
Connect the other end of the lamp to neutral.

I guess the part that is confusing me is the 300 volt source. In order to get the 300v to the relay, you must disconnect both sides of the light bulb. So the moment you disconnect both sides of the light bulb and connect them to #5 and #6 of the relay, the light bulb is not connected to anything, including the 120v source that keeps being mentioned. It's just sitting there with no power or wires connected at either end.

So the 300v is now going between #5 and #6 on the relay. I assume the resisitor is what is breaking down the voltage to 240? Correct?

It seems like a wire needs to be spliced in to somewhere for the other half of the 300v source and the bulb needs to stay connected at the left side. Then a 120v source needs to be added to the relay.

Should the resistor be connected between #5 and #6? Or in series with the 300v input? I'm rereading your original posts and trying to get this right.

OK, I think I get it after rereading everything on this thread.

Take the original 2 wires that are the 300v connections from the bulb.
Connect 1 side to post #5 with the resistor in series.
Connect the other side to Post #6

Then find a 120v source in the unit, preferably the first connection leading in from the wall outlet. Add a pair of wires (White and black) to extend that power source to both the bulb and the relay.

Connect 1 wire (black)of the 120v circuit directly to the relay post #1.
Connect the other wire (white) to 1 side of the new lightbulb.
Then take the wire from the other side of the light bulb and connect it to post #4 on the relay.

I hope that sounds right, because it makes sense to me.

3mconverter said:

OK, I think I get it after rereading everything on this thread.

Take the original 2 wires that are the 300v connections from the bulb.
Connect 1 side to post #5 with the resistor in series.
Connect the other side to Post #6

Then find a 120v source in the unit, preferably the first connection leading in from the wall outlet. Add a pair of wires (White and black) to extend that power source to both the bulb and the relay.

Connect 1 wire (black)of the 120v circuit directly to the relay post #1.
Connect the other wire (white) to 1 side of the new lightbulb.
Then take the wire from the other side of the light bulb and connect it to post #4 on the relay.

I hope that sounds right, because it makes sense to me.

Click to expand...

That's all correct.
Also the resistor is to reduce the voltage on the relay to around 240V. 300V relays are rare, so a 240V relay plus resistor is far easier to find.

Done. Got 121 across the bulb. Gotta get the new bulb installed to see if it works.

Gonna make an art project out of this burnt out bulb after all this...

Thank you!

As far as I can tell from the relay's data sheet, it's rated at 200 to 240 V on the coil, with a tolerance of -30% to +10%. If that's correct, the voltage can be anywhere between 140 V and 264 V and the relay will be fine. It's a good idea to check the voltage when it's on (usual dangerous voltage warnings) and if the voltage is too large or too small, you can change the resistor value up or down.

Since I still doint have the bulb yet, I ran a few voltage tests this morning. I rechecked the 300Vac source. The dmm showed 297Vac. I place the resisitor back in series and checked it, 297Vac. It doesn't seem like the resisitor is doing anything at that point. When the 300v source is connected to post #5 and #6 resisitor in series, the voltage accross post #5 and #6 is 184Vac and the voltage accross #1 and #4 is 121Vac.

I'm not sure what the volatges will be with the lamp/load connected.

The resistor will only reduce the voltage when the current that the relay takes is flowing though the resistor, so I wouldn't expect any drop in voltage if relay isnt' connected.

184 V between #5 and #6 looks fine.

However, if you haven't got a bulb, getting 121 V between #1 and #4 seems strange.

For testing you could use any 120 V bulb as the load. I suggest an ordinary incandescent one.

When the 300 V is off, I would expect:-
0 V between #5 and #6
120 V between #1 and #4
the lamp is off with 0 V across it.

When the 300 V is on, I would expect:-
around 200 V between #5 and #6
0 V between #1 and #4
the lamp is on with 120 V across it.

Have you got any photos?