Hi,
I’m refurbishing an old Maas Rowe cathedral chime system. It consists of 18 small chime bars that are struck by solenoids. The bars each have small pickup coils that feed a preamp. I’ve looked for a schematic but no luck.

There is a transformer that powers the solenoids and there is a mystery capacitor across the transformer output. The voltage measures 27.4 volts across the output.

The problem is that it’s an old wax cap that I’m sure should be replaced and I’m not sure of the value. I’m think it reads 25uf 200VDC, but if could be .25uf as there is a scratch over the front part of the first digit. The two might be a three, but I’m pretty sure it’s a two. I’m sure it’s not 2.5uf. The cap is about 2.5” long and 5/8” diameter. It measures 2.0uf on my multimeter. There are a bunch of .1uf 200v caps in this unit that are about 2.5” long and .5” diameter and most measure anywhere from 550-1000uf with a couple as high as 1.5uf. There are three 15uf caps used in the amp power supply that all read about twice their listed rating.

One side of the power out goes to one side of all the solenoids which are only a foot or so away from the power supply. The other side of the power goes down a six foot cable to the keyboard used to switch on each note. These return through a multiwire cable and a jones plug back to the other sides of each corresponding solenoid. Each solenoid has a .1uf and large “domino” 400ohm resistor in parallel. I’ve seen snubbers that have a series resistor and cap in parallel with solenoids, but these solenoids are wired with the cap and resistor both in parallel.

So, my questions are, what is the purpose of the mystery capacitor by the transformer output, and what is the most likely value - .25uf or 25uf?

Thanks!

 

Please take a picture of the cap with 800x600 .jpg file.

 

Photos attached

 

Photos attached

@Swaine1615
Your photos show excellent detail of the background and rule, but little detail of the caps. Please try to focus on the writing on the caps and not the background. Since you have the caps out-of-circuit, perhaps a heat gun (low setting, not too close) would smooth the wax for easier reading? Perhaps you could also experiment on some innocuous area of the label (or another cap) by rubbing off some of the heated wax to see if that improves readability without removing the ink along with the wax? I believe that wax caps of 25uF @ 200V would be huge. If the cap now reads 2uF, why do you say you are sure that the label does not say 2.5uF? This sentence does not make sense: "There are a bunch of .1uf 200v caps...most measure anywhere from 550-1000uf with a couple as high as 1.5uf." You describe the output of the transformer not having any means of rectification; is that correct? The mystery cap is directly across the AC output of the transformer? What is the DC resistance of each solenoid?

 

a mystery capacitor across the transformer output.

Does it has any diode between the transformer and cap ?
If no diode then it could be 0.25uF, otherwise it is 25uF.

Does it only the cap over there or have other caps?
If there is no other caps then it is 25uF.

As you measured it as 2.0uF then it could be a 25uF, because almost the capacitance is reducing, it can't be increasing.

Edit : from the labels position then it is looks like .25uF/200V, like this one, maybe you can draw the circuit.

 

If you need to improve visual of markings, pass a flame briefly and the wax will melt/drip leaving a smooth clear film.

Compare the time an analog pointer ohmmeter deflects with another known capacity to discern a near magnitude value.

 

Thanks to all. Someone mailed me a copy of the schematic and it turns out to indeed be .25uf. Appreciate all the support!

 

A capacitor connected directly across a transformer winding is generally intended to protect against voltage spikes. If you can post the circuit probably an explanation of the actual function can be discovered. But if the capacitor is not leaky or shorted, why replace it. And is this post about the same project as needed the old selenium rectifiers replaced?

 

Hard to read.

Looks like .39μF 200VDC

Try removing the wax.

 

Thanks, now that I have the schematic and can confirm the value at .25uf I think I’m good. I do appreciate learning the purpose.

For the record the pictures I included *are* in focus on the cap writing - it’s just that the writing is blurred by the wax. I think the place I can’t read is actually a rub on the paper and not just covered by wax, but I’m going to try the flame idea just for fun.

Yup, same system as the selenium rectifier post, but I started a new thread because this is unrelated. The 15uf caps I mentioned are associated with the amp power supply and not this part of the circuit, which does not have any rectification. I only mentioned them because it was interesting to me that they read significantly higher capacitance than their rating. I know that capacitance is supposed to reduce with aging, but I have also read that the original capacitance can be much higher than their rating. So I couldnt be sure that the mystery cap reading would mean anything.

I said I was sure it wasn’t 2.5uf because the scuff only masks the first part of the number and if there was a decimal between the digits I think it would be legible.

The resistance of the solenoids is 100ohms.

I think that covers everything and all my questions are answered. Thanks!

 

Thanks, now that I have the schematic and can confirm the value at .25uf I think I’m good. I do appreciate learning the purpose.

For the record the pictures I included *are* in focus on the cap writing - it’s just that the writing is blurred by the wax. I think the place I can’t read is actually a rub on the paper and not just covered by wax, but I’m going to try the flame idea just for fun.

Yup, same system as the selenium rectifier post, but I started a new thread because this is unrelated. The 15uf caps I mentioned are associated with the amp power supply and not this part of the circuit, which does not have any rectification. I only mentioned them because it was interesting to me that they read significantly higher capacitance than their rating. I know that capacitance is supposed to reduce with aging, but I have also read that the original capacitance can be much higher than their rating. So I couldnt be sure that the mystery cap reading would mean anything.

I said I was sure it wasn’t 2.5uf because the scuff only masks the first part of the number and if there was a decimal between the digits I think it would be legible.

The resistance of the solenoids is 100ohms.

I think that covers everything and all my questions are answered. Thanks!

@Swaine1615
Thank you for bringing us up to date on your efforts and letting us know your questions are answered. Good luck on your project.

 

For good pictures take advantage of daylight, not under the sun light, and not in the interior of out home. The shining patch would not happen and the reading of the marking would be much easier.