I'm adding a few turnouts to my 20-year-old-layout. I use twin-coil switch machines and push buttons on control panels wired through the auxiliary contacts on the switch machines to throw the switch and cut off the power when it is thrown. This is all old technology, but it works most of the time.
have have some switch machines I picked up at a white elephant sale, Kemtron, NJ International, and Hallmark. I installed, and eventually removed, the Hallmark switch machines. They just weren't throwing. On the work bench I tried cleaning the contacts with spray contact cleaner and filing the contacts. It appears that the Hallmark contacts fail to work over 20% of attempts.
I am tuning up the Kemtron and NJ switch machines. But I wonder if anyone has had similar problems with Hallmark and has a solution.
Wow, you are really pulling on my memory banks here. I have not used twin coil switch machines since the 1980s.
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I never had problems with the contacts. I would be willing to bet that your problem is from age and deterioration.
Are you wiring the coils through the contacts? I have never heard of this done when using push buttons for control. I wired some of mine through the contacts so I could use a standard toggle to control the switches. I stopped doing it this way and wnet back to momentary toggles due to fear of contacts sticking and burning a coil.
How old are the switch machines?
-Kevin
Living the dream.
I wire through the contacts with an LED and resistor in series. The LED shows how the turnout is thrown and the rersistor limits the current. The push button is across both LED and resistor; when pressed the switch throws. I used to use an incandescent bulb before LEDs.
I have one Hallmark switch machine in a box, unused, with an M.B.Kleain price tag for $6.25. That might help guessing its age.
I found that the contacts on the Kemtron switch machines continue to work very well, so I've swapped them to the Hallmarks from Kemtrons with burnt-out coils. That seems to work. I just was looking for an alternative solution.
MyHallmark as removed from layout. There's no insulator between the contacts at A, just an insulator on the arm that opens the contacts. As you can see, I have bent the arms to increase the pressure on the contacts. This is my standard procedure and works very well. At the work bench when I apply power to the coils directly, they snap smartly. But when I apply power through the contacts, the solenoid is sluggish if it operates at all. I conclude that the contacts are high resistance. I haven't been able to decrease that resistance.
P.S. I have a picture, but can't figure out how to insert it. I tried the insert image icon but it doesn't seem to upload.
Old.Professor, I do believe that you need a photo hosting site (like flicker-photo bucket or what ever the other ones are called) to add a photo here. I'd be curious as to what the voltage is going in to one leg of the point and what is coming out the other end with the point closed/make.
The Hallmark comes with 2 SPST auxiliary contacts and 1 SPDT power routing contact set. I'm using each of the SPST contacts to throw the switch machine to the opposite position, opening the circuit when the movement is near complete. This is more-or-less what you wrote.
At the control panel I have a LED and current-limiting resistor in series with every wire to every switch machine. One of the two LEDS for each switch machine is always on. The LEDs are inserted in the control panel to show the position where the turnout is currently thrown. There is a push button bridging the LED and resistor; when that push button is closed, the switch machine goes to the opposite position and the other LED is illuminated.
I power the switch machines with filament transformers (remember that term?). I think they nominally put out 6.3 volts. I have seperate transformers for each leg of the layout.
I guess that the Kemtrons burned out when the push buttons failed in the closed position.
Sorry that I haven't figured out how to load pictures to this forum yet. I'll try again.
I used an ohm meter to measure resistance across the contacts. It was difficult to get steady readings on the slippery metal that would have been soldered. However, what I did get confirms my guess that the Hallmarks have high resistance contacts. The Hallmarks measured a low of 0.6 K ohms to a high of 0.87 M ohkms. The Kemtrons measured a high of 3.9 ohms to a low of 0.4 ohms.
I think I'll just continue switching contacts.
Old.Professor I used an ohm meter to measure resistance across the contacts. It was difficult to get steady readings on the slippery metal that would have been soldered. However, what I did get confirms my guess that the Hallmarks have high resistance contacts. The Hallmarks measured a low of 0.6 K ohms to a high of 0.87 M ohkms. The Kemtrons measured a high of 3.9 ohms to a low of 0.4 ohms. I think I'll just continue switching contacts.