Need advice on power for Stromberg Master CClock

[BCR]

I finally completed my newly acquired 1939 Stromberg Master Clock. Gleaming clean and freshly lubricated movement, all bushings are perfect. Cleaned all electric contacts, etc. Here is what is happening. The clock runs perfectly for 4 to 10 hours and then stops. After watching it closely, I found that the contact point that is activated once each minute begins to fail, and so the spring is no longer getting wound, and the clock stops. This has happened twice in the last 2 days. I removed the contacts, cleaned them because the contact point actually sparks when the contacts touch...so I carefully remove the burnt spot with fine emery paper, and reinstall the contacts, and all is great until the sparking/charring ruins the contact surface. I am purely a mechanical clock guy, so not at all trained in electrics except to make sure all contact points are bare metal clean. I have cleaned all wiring contacts, etc. When I remove the 2 main wires and touch them together, the coil fires every single time, but when I allow the clock to run on its own, the sparking occurs. OK, so the clock came to me with a 24v DC transformer. Is it possible that this is simply too much power and is causing the sparking? Any help is most appreciated. Thank you.

 

[Wayne A]

Not familiar with this clock but it sounds like the 24vdc is powering the solenoid. Solenoid's are large inductive loads and when operated by a contact you need to provide a means to limit the solenoids collapsing magnetic field from generating enough voltage to bridge the contact with an arc. Use of diodes is common in industrial controls for this. Perhaps your clock is missing something to combat this?
https://www.azatrax.com/image/CoilDiode.png

 

[BCR]

Thank you but this is like reading Chinese to me. I guess I need to know what diode or resistor I should use. And even where to get such a thing. Thanks for the wiring diagram. I simply don't even know where to begin as far as contacting someone locally....an electrician? The other thing I noticed is that the 2 contact "legs" have steel pieces, similar to very small nail heads inserted in them and the steel is actually what should make contact. But on one of the "legs" the steel is gone, as if it has been burnt away over the years and now there is copper contacting steel....perhaps this is also a problem. I guess I should remove the old tiny steel pieces and replace them so that it is steel to steel.?

 

[Tim Orr]

Good evening, BCR!

It might be that you need arc suppression, and this looks for all the world like a works similar to the Self Winding Clock Company clocks, though not exactly the same. I am not familiar with Stromberg, but I would bet that Ken Reindel at kensclockclinic.com is.

In clocks of this vintage, arc suppression was often handled by special wire-wound resistors. Also, the contacts were generally not steel, but rather, platinum or platinum-iridium or palladium, which might look like steel, but of course, is very different, and designed to handle high heat of the kind you get when arcing occurs. A diode would probably work, but as Ken pointed out in a presentation he gave to Chapter 21 in Denver on Monday night, it's not historically correct, and it makes the clock polarity-dependent, which they were not originally. Perhaps a "purist" viewpoint, but correct nonetheless.

Meanwhile, more pictures from the sides would be interesting. Would like to see the spring that is wound each minute, for example.

You might also be correct that the 24v DC power supply is too much for the clock. If it's not regulated, the transformer might be putting out a good deal more than 24v. If the clock was designed for a lower voltage, it might be way too much power, even if regulated.

The analogy I might make is to mechanical clocks where, because of wear, congealed oil and age, people keep putting in stronger and stronger mainsprings to overcome the wear and gummed-up pivots, but by so doing, are creating even more and faster wear.

You might try a search on this forum for Stromberg clocks, for more ideas.

Good luck, and best regards!

Tim Orr

 

[BCR]

Thank you Tim. I appreciate your input and advice.

 

[Toughtool]

Stromberg Electric questions
This thread in posts # 12, 13, 14, 15 in particular talk about the voltages of the discussed Stromberg master. I agree with Tim, the voltage may be 10 volts and having 24 volts supplied would push more than twice the current through the contacts. A 9 volt battery may be enough to test the magnet to see if it will work on 10 volts. The poster said his 9 volt battery lasted four days.

 

[BCR]

Not familiar with this clock but it sounds like the 24vdc is powering the solenoid. Solenoid's are large inductive loads and when operated by a contact you need to provide a means to limit the solenoids collapsing magnetic field from generating enough voltage to bridge the contact with an arc. Use of diodes is common in industrial controls for this. Perhaps your clock is missing something to combat this?
https://www.azatrax.com/image/CoilDiode.png

Wayne, I have received several suggestions about how to resolve the overpowering and sparking of the contacts on my Stromberg clock. Your diagram is very helpful. I have been informed that this Stromberg clock actually should be powered by a 10V DC transformer, and also installing a diode across the coils will help. So, I now have an adjustable DC transformer, it goes from 9V to 24V DC, and I bought a pack of recommended diodes for just a few dollars on Amazon. I think, according to this diagram, that I can simply install the diode right across the 2 points where the wires connect to the coils. Does this sound correct to you for the diode connection point? It is a point after the switch, and the wires connect directly to the coils from these 2 terminals.

 

[Wayne A]

according to this diagram, that I can simply install the diode right across the 2 points where the wires connect to the coils. Does this sound correct to you for the diode connection point? It is a point after the switch, and the wires connect directly to the coils from these 2 terminals.

Yes that's all there is to it. Just mind the polarity so the stripe end of the diode is where the positive wire connects.

 

[BCR]

Thanks again Wayne,
Now to illustrate just how unfamiliar I am with electrics...How do I tell negative from positive? There is a WHITE wire, and a BLACK wire on the coil, but the wiring coming into the clock is all black, but one of the black wires coming from the transformer has a gray stripe. I assume that one is positive and should connect to the white wire on the coil.

 

[Wayne A]

BCR,
Don't think I would make any assumptions of wire color and polarity. It needs to be verified. Use a volt meter to verify the positive DC source from the power supply then trace the wiring to the coils.

 

[BCR]

OK, I got my voltmeter out and watched a video and figured out how to test the barrel plug on my new transformer. Now I know that the outside sleeve is positive and the inside is DC Ground. BUT, what about the coils? Must I be concerned to which terminal I connect the positive and DC Ground wire from the transformer. Is it now OK to assume that the black coil wire is DC Ground and the white is positive. If not, and there is no power connected to the coil, and the terminals are NOT marked, then how does one determine ground and positive? Sorry for so many beginner questions, and I certainly do appreciate everybody's help.

 

[Toughtool]

If you connect your power supply to the coils [without the diode] first, then measure the voltage across the two terminals of your coils with your meter, you can determine the polarity. If you are using a digital voltmeter, the display should read something like 10.0 volts. The positive terminal will be the red wire.

If the meter reads -10.0 volts, then either reverse the meter leads and remeasure or understand the red lead is connected to the negative terminal and the black lead is connected to the positive terminal.

Now that you have determined the polarity of your connection, you can connect the Cathode (the bar end (white band) of the diode) to the positive terminal and the Anode (arrow end of the diode) to the negative terminal of the coil.

As a training aid, measure the polarity of a common battery (A, AA, AAA, etc.). These are marked with a + for positive. Joe

 

[BCR]

Thank you Joe...Here is a picture of the diode that you suggested that I might buy. I bought them. A nifty pack of 50 for less than $7.00 I don't see a white band on the diode itself, but in the packaging, one end has red tape and one end has white tape....Is this the secret code. Maybe that one end has red tape and one end has white tape?? OMG...this is so foreign to me!!! UGH!!! But again, thank you....Deep breath....move ahead and learn new things.

 

[Wayne A]

BCR, the stripe is on the black barrel section of the diode and it actually looks more silver than white. Its on the right side of the picture.

 

[Toughtool]

I circled it here. Joe



click on the photo for a larger view

 

[Toughtool]

Thanks Wayne A.
The goal here is to get the clock to wind itself. At this point it probably does not matter what polarity you have connected the power supply wires to the clock since the coils do not care. However when you start connecting other things to your master (like a secondary (slave)), it will be important. If you have not destroyed the 24 volt connection yet, take photos and measure with your volt meter to determine which wire is positive. As Wayne A has suggested, trace the wires and make a drawing (schematic) of the original wiring. Your first wiring photo (post #1) looks correct to wind the clock.

 

[BCR]

Thank you to everybody who has offered help and advice to help me figure out how to properly wire my power supply to my clock. I do want to restore the contacts and may end up sending them off for that work. Looking forward to having this old clock running dependably. My only other Self Winding clock is an IBM, and it has run flawlessly for years with only routine maintenance, and it is a very accurate timekeeper. Guess I got lucky on that one.
One last note...I do still have all of the original electrical contacts in place, along with the original 24V power supply. I took readings with the volt meter and it actually read 30.28V, when what the clock should be running on is only 10V. I suppose it is no wonder that my contacts were sparking and burning. By the way, it is wired the same as the diagram in the first reply to my post, so that's a bit of good news! Again, thanks to all for your very kind help and encouragement.

 

[BCR]

The Stromberg Master Clock is finally completed. The clock still has all of its original components, but the old contacts, which were problematic, have been disconnected, Of course, they remain in the clock just in case a future owner might wish to restore them someday. The solution was provided to me by ken@kensclockclinic.com Just click on the following link to read about this perfect solution Model 1900W-UNV Modular Clock Winder - Ken's Clock Clinic . I also opted to get the plug in adapter and not use batteries. It is a very compact unit, installs neatly, and looks very professional. I like it so much that I bought a second 1900-UNV for my IBM Master Clock. What I really love about the 1900-UNV, is that it provides one electrical impulse per minute to activate the coils, and it also senses exactly how much voltage your particular clock needs, and adjusts the impulse accordingly.