MW.E.c. and E.U. a2 for operation

[17thairborne]

1

[Funksammler]

The collectors could definately do with a clean. You need some contact spray, emery boards (the type used for polishing nails). Alternatively emery paper (very fine grit) and half of an old clotches peg will do the same job. Also get some cotton buds.

Before you start, lift the brushes. Spray a bit of contact spray on the collector and gently hold the emery paper while turning the rotor with your fingers in the normal direction of rotation. Make sure you do not scour the collector. Go around the whole circumference of the collector until the worst of the deposit is removed. Do the same at the other collector. Clean again with some contact spray and a cotton buds and let the collector dry.

Before putting the brushes back in place, measure the capactors mounted on the motor generator (one terminal on earth and the other on the contact of the capacitor). On the highest Ohm setting, the resistance should slowly rise until infinitive. If they measure a very low Ohm value or short circuit, they are defective (They look OK so I expect them to be fine).

Put the brushes back in place.

The cleaning process can be be repeated with a running motor by lightly pressing the emery board against the running collector.

Allow the motor to run as the brushes need to build up a new patina. There may be some sparking, but this will disappear as the brushes bed in. A good collector should look a bit blueish.

You should now hopefully get a more stable high voltage.

regards,

Funksammler

[17thairborne]

Collectors cleaned with contact spray, cotton swabs and very fine emery paper. Lots of carbon build up was removed.

I tested the 3 capacitors and two of them show a "0" reading on the ohm meter, and one shows right at 70Ω. I connected the wire coming out of the resistor with one end of the test meter and the other end with a set screw on the case to complete the circuit for the measurement.

I suspect the two capacitors have failed.

Are these available somewhere?

[Funksammler]

Just to be sure test the resistance on some of the other settings of your multimeter and see if it remains zero. Also, short out the capacitor for a few moments before measuring. There could be a residual charge in the capacitor.

regards,

Funksammler

[Yuri D.]

Also makes sense to take apart the motor, clean the ball bearings and re-lubricate them. The old grease can get quite hard.

[17thairborne]

The two capacitors which don't register resistance are mounted on the same side of the motor. The connection from one leads to one of the screws on the bakelite plate labeled "130v" and the other capacitor has a wire that leads directly to the other screw.

The other capacitor on the 12v side has a large wire leading to the coil.

The image shows the two capacitors which connect, via a thin wire, to the screw posts on the small bakelite plate (see arrows)

With the cleaning, the small volt meter on the Mw.E.c. registers correctly at 130 v, whereas before it was significantly less than that. Perhaps I do not know how to use a multimeter

BUt still, the power switch on the radio does not activate the Umformer, it is always running when connected to the battery.

[17thairborne]

Also makes sense to take apart the motor, clean the ball bearings and re-lubricate them. The old grease can get quite hard.

I will do so, thanks Yuri!

I must say one thing, my hobby room has that semi-sweet smell of ancient electronics.

[17thairborne]

Just to confirm I am checking the resistance properly, I am using the resistance portion of the meter, using different setting (200,2000, 20K) and connecting the points on the capacitor and the case as shown on the red arrow heads.

I am an A-10 pilot, not an engineer Is this correct?

[Quatsch]

The good news is if the thing is producing the voltages specced, the caps aren't shorted. If all the voltages are good I think it's time to do some radio listening.

[Funksammler]

I think it is best to uncouple the capacitors on the HV side for now, in the long term you need to replace the two capacitors. The original types are no longer available so you will have to repair them using modern components. Try to find capacitors with a similar value (22000 pf 250V) with a smaller diameter than the originals. This allows you to drill out the original componenent and place the new capacitor inside the old housing.

It is ok to run the motor generator without caps for a while, but it will introduce some static noise on the radio and will cause the collector to spark more and foul up quicker.

I assume that the Umformer runs with the the jumper between pins 1 and 3 so the relay in the Umformer is working OK. So there is a problem with the on off switch.

Does the on-off switch have an audible click between on and off? If it does the basic mechanics of the switch are OK and the contacts are dirty.

First try to clean the switch by moving it from the off to the on position and back repeatedly. You can do this with the Umformer connected. If you are lucky, the switch will clean up and your Umformer will react.

regards,

Funksammler

[17thairborne]

I think it is best to uncouple the capacitors on the HV side for now, in the long term you need to replace the two capacitors. The original types are no longer available so you will have to repair them using modern components. Try to find capacitors with a similar value (22000 pf 250V) with a smaller diameter than the originals. This allows you to drill out the original componenent and place the new capacitor inside the old housing.

It is ok to run the motor generator without caps for a while, but it will introduce some static noise on the radio and will cause the collector to spark more and foul up quicker.

I assume that the Umformer runs with the the jumper between pins 1 and 3 so the relay in the Umformer is working OK. So there is a problem with the on off switch.

Does the on-off switch have an audible click between on and off? If it does the basic mechanics of the switch are OK and the contacts are dirty.

First try to clean the switch by moving it from the off to the on position and back repeatedly. You can do this with the Umformer connected. If you are lucky, the switch will clean up and your Umformer will react.

regards,

Funksammler

Thank you for the repeated assistance. The switch does have an audible "click". I ran it connected and stitched on/off perhaps 100 times with no affect. Is this indicative of a short int he switch?

I will begin looking for some suitable capacitors.

[17thairborne]

I removed the two 130v capacitors and re-installed the screws on their posts. Using a caliper, the diameter of the ceramic portion of the capacitor is .25" or 6.35mm

I assume I remove the entire ceramic portion as well. Is that correct?

I have a vertical milling drill with precision clamp bed and should be able to carefully do that, but I will await confirmation.

I am finding many matching capacitors (22000pf, 250V) but still looking for a close diameter.

[17thairborne]

Here is a match in F/V, but not in diameter.

One end is routed to the post and screw, and does the other end get soldered to the end of the case as shown in the red arrow?

[17thairborne]

I suppose an easier way would be to make a tube with bracket out of brass that will house the new capacitor. It would be a slightly larger diameter (10mm), but would look fine.

[17thairborne]

Funksammler,

Would this type work in the application? I could easily make a new tube.


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