I have had quite a bit of problems with my Elmo 16CL. The exciter lamp is mostly not on. Sometimes, for no obvious reason it lights, and then it is off again. I have used a multi meter and checked the fuse, the socket and the lamp. All seems fine.

In the end I had it and thought I would just hard wire it on no matter if the switch was on or not. The lamp says 4V 0.75A. I measured 4.4V at the fuse marked exciter. Stupid me thought that might be the same. I hard wired and POOF. Bright light, ptich dark.

When I got to think about it, it hardly lights when it is normally on, and I suspect the lamp can be much brighter. So I have two possible explanations:
1. It should have a lower voltage, and I hard wired at the wrong place.
2. I should have had a resistor too,

Have any of you any clue? I tried to read the schematics on the repair manual, but I am not good at this:
https://issuu.com/filmmaker8.com/docs/el...-service-manual

Any help would be appreciated!

I'd have to see the electrical schematic to be certain to know what you've done here Eivind but either way, clearly some important circuitry has been bypassed.

There cannot be too much in this circuit to make your exciter lamp intermittent so the good news is once the problem joint or component is found, all should be fine again, including the switch circuit.

Thanks for the reply Andrew. I don't expect you you to dig into the schematics, but if you are curious you can find it here:
http://www.acofs.org.au/part_5_files/Elmo/Tech%2016%20CL.pdf

The circuit is mention on page 72 in the PDF (says page 67 from the scanned page number). There are more than one resistor there, I can see. But I am not very good at this. If it had been one resistor after the power source, I would have understood it :-) I have given up on the switch, and my plan is to hard wire it on all the time. But I obviously gave it too much :-( From what I read from the schematics, I had expected to measure 10V at the fuse, but I only got 4.4V. Oh well.. I better watch old Chaplins etc until I find out what i did wrong...

Oh, my, oh my... Am I stupid! I measured with a DC setting om the multimeter. Switched to AC and got 10V. I realized my error as the power came directly from the transformer. So I gave 10V to a 4V lamp. No wonder it blew...

Doh!!!

Oh well Eivind, we live and learn, even if it sometimes is the very hard way!

Much is gained from our own inevitable mistakes at times.
The main thing is we learn each time one is made and we never make the same mistake a second time!

At that point we begin getting good at such ventures!😊

You say the exciter lamp goes on and off. I suspect a dry joint somewhere in the supply to it, or even a dirty contact to the lamp.
The transformer, of course, does emit 10 volts AC, but the supply then goes thorough a full wave rectifier, the supply is now DC. Thereafter there are capacitors and a resistor, these presumably further reduce the voltage. Any of these components could have a dry joint.

The capacitor won't be there to reduce voltage supplied at the circuit finish, but a series resistor will do this work. The capacitor may be used just to smooth out the rectified voltage.
If it begins as 10v a.c. at the transformer secondary windings, then by the time it has been through the Bridge Rectifier, will then be down to 5 volts D.C. before the resistor and switch.(quite possibly single pole), then terminating at the lamp holder.
That's how I'd expect it be anyhow based Maurice's description of parts above.

The resister may account for the further 20% voltage drop after the rectifier.

All sections of the circuit can of course be checked for consistent voltage before fitting the lamp, however it is also worth remembering that if a circuit has dry joints etc, these may only appear very often when there is a load placed onto the circuit. I.e. once the lamp is fitted and draws actual current from the circuit.

There is a good chance I'd have thought, that if the machine has been well used now, the switch itself may have either dirty or worn out contacts.
This would be my starting point as the exciter lamp base connections are generally very reliable from the limited use I have witnessed from my machines with these fitted.

Obviously for a 16mm machine, these are in constant use so of course it is still worth checking first and being absolutely certain before sourcing any replacement components, if this proves necessary.

Thank you both for the input! I have learned my lesson on the voltage measurement. I will look more into this the next few days.

Back at the cabin where my spare lamps were, I tried to make a direct connection from the 10V output of the transformer through 3 big resistors and to the lamp. The resistors got really hot, and I got a 50Hz hum in the amp, so this was not the way to go. I just soldered the cut off cable back together and tried to find a loose connection somewhere. I didn't find any bad connection, but once I heard some noise in the loudspeaker, and I saw the lamp blink, but then it came back on and I couldn't get the lamp to drop out again. I looked at the backside of the circuit board and I found no loose connection. But I did find some corrosion there:




It is quite possible that this could affect a lot of things. I tried to brush things off, but I don't have much hope of fixing this issue. But for now the lamp is lighting again :-)

Hopefully Andrew or someone else can help you; it's not something I have any knowledge of.

Eivind, you've done the exact correct thing cleaning all of that corrosion away from the circuit board but in doing so, now we can see for certain at least one broken joint. (+11v)

If you have a soldering iron, some braid/ wick and flux, I would remove all the old solder from the obvious bad joint(s) using wick/braid so you can clearly see the hole and tracks again and then make sure the component(s) on the other side of the board are properly inserted into the hole before resoldering again using some flux on the joint to attract the solder.
Some solder has self contained flux in its core but a little extra carefully painted using a small artist brush just on the hole area and component leg tip cannot and will not do any harm at all to give you a nice clean joint(s) once again.

After this carry out tests using your multimeter to assess whether or not you have 4v or thereabouts at the lamp terminals and then see if the switch is now working again.
You can check any resistors and the switch in your circuit (before powering the circuit) using your omega scale but the capacitor is a little harder to check in circuit but hopefully will still be ok.

What is your next line of approach then Eivind, we never heard back from you on this one?