I am installing a Tsunami 750 in a Proto 2000 S-3. Today I disassembled the loco and put the capacitor (Keep Alive) in the cab. I painted the capacitor the color of the cab interior and reassembled the cab, the hood and railings. I then realized that I didn’t take note which was the + and - . I don’t necessarily want to disassemble the cab again. Is it possible to identify the + and - with a Ohmmeter? If so, how should I proceed?
I would certainly hate to have to disassemble the cad again and strip the paint off the capacitor.
Guy
Modeling CNR in the 50's
can't measure capacitance with an ohm-meter
???
greg - Philadelphia & Reading / Reading
if it's an electrolitic capacitor, the longer leg is positive ....
if it a supercap bank, the blue is positive ..
from what you said it's hard to determine what it is ?
Is the capacitor a TCS Keep Alive (or a Soundtraxx Current Keeper)? And are there not 2 wires from it (and what colors)? If so, the wire colors should indicate which is the one to hook up to the decoder positive (blue) wire, and the other one goes to the appropriate DC negative wire (or spot on the decoder).
The following shows how to hook up a Soundtraxx Current Keeper to a TSU-750. The blue Current Keeper is the positive one.
https://www.soundtraxx.com/documents/appnotes/currentkeeper_tsu750.pdf
If a TCS Keep Alive, the attached shows the positive wire as blue and the negative is black/white striped.
https://tonystrains.com/product/tcs-2000-ka3-keep-alive-capacitor
Paul
Modeling HO with a transition era UP bent
Sounds like the OP is using his own capacitor, not a commercial stay alive circuit. Often the only marking on a cap is printed on the side, marking the negative side. Once painted over, you are pretty much out of luck. Capacitors are cheap - easiest thing to do is get another one, and before painting it solder at least one wire too it, and write down which side you soldered the wire to.
If you used acrylic paints, isopropyl alcohol should remove the paint, and not harm the capacitor. Careful sanding may also work, stop as soon as the markings start to appear and don't keep sanding in one spot.
Paul Carlson (Mr. Carlson's Lab on YouTube) has a low voltage capacitor tester he designed (only available to peoople who contribute via his Patreon page, unfortunately) that can tell the proper polarity of the capacitor - a low enough voltage coonnected backwards woon;t make the capacitor go boom, and even a good electrolytic will have high leakage in the reverse direction. And I also found this, but you will need another capacitor witht he polarity known in order to try this test:
Connect the negative terminal of a cap of known polarity in series with a cap of uncertain polarity. Apply voltage and measure the voltage across each cap. If they're wired negative to negative, the cap of known polarity will get the full voltage. If they're wired negative to positive, they'll split the voltage.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thank you everyone.
The capacitor came with the Tsunami and the two wires are the same color and length. I understand I have no option but taking the shell apart one more time, trying to remove the capacitor which is glued to the floor of the cab and strip the paint off.
thanks again for replying.
Yes, the positive wire is longer than the negative lead. But alas, I can see it from here,: You have already trimmed the leads when you soldered wires to it.
Best I can say is live and learn.
I can not tell you how many times I have built and rebuilt things before I learned to look at them first.
In the computer world the black lead is negative, in the construction world you would be holding on to 110 volts.
So take it apart again and rebuild it, that will be the fastest and best way to solve this issue, and it will give you practice with servicing your locomotives.
LION pays no attention to color of wires, him uses what him has. These cables were from a 1920 pipe organ installation. Guy who bought the organ just snipped off the cables, and the LION took them to the train room.
Here is cable before the LION opened it up. It contains six groups of 11 wires each.
LION had to put a voltage on one end and use a tester at the other end until him discovered which strand had to be connected where. More fun than ditzing with capacitors!
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
If you can remove the paint from the cap parallel to one of the leads you will see a white stripe (negitave side) NO white stripe- that is the positive side .
The black cap has a whiteish stripe
The Green Cap has a black stripe.
When looked at from the connection end said stripe continues over the top for abut 1/16 inch, you can then see which lead is marked as negative.
Thanks again guys. Just to be clear, the capacitor which came from Soundtrax had wires of exactly the same length. As it was well hidden in the cab and painted, I had to disassemble the shell. It was not so difficult as I had done it the first time. As I had used acrylic paint, it was easy to remove the paint and read the negative sign. I put everything back after chopping a little bit off the negative wire.
Lion,
You are right. The more you do it, the more proficient you become.
BroadwayLionLION pays no attention to color of wires, him uses what him has. These cables were from a 1920 pipe organ installation. Guy who bought the organ just snipped off the cables, and the LION took them to the train room. Here is cable before the LION opened it up. It contains six groups of 11 wires each. LION had to put a voltage on one end and use a tester at the other end until him discovered which strand had to be connected where. More fun than ditzing with capacitors!
Very cool ... did you install a 32' stop or a Tuba Mirabilis to model the noise of operating on elevated structure?
All kidding aside: something here that I think deserves its own post is the extraordinary common sense of those "wiring diagrams" that show the wiring pinout ... complete with test pins at every point in the paper diagram. This could easily be expanded to include sockets or terminal strip where the relays at the bottom would be attached (to give modularity for troubleshooting away from the installation, or quick and positive replacement). Very cheap, very positive, very effective.
I am now kicking myself for not having wired a number of projects this way, and am already working on some 'best-practices' conventions for how and where to implement them ... probably not as well as this already is.