I recently acquired a 785 coaler and after a little tweaking and resoldering got it working really nice except for the clamshell. It closes properly but when the up button is released to clamshell does not release as it should. A slight tap and it opens.
The clamshell closes when current is applied to a solenoid drawing the core up and closing the clamshell. I lightly lubed all moving parts and ensured no binding. When manually working the unit up into the coil of the solenoid it does not catch, only when current is applied and then maybe 7 out of 10 evolutions.
Could the coil be retaining enough magnitism to keep the core in the coil? If so any ideas to correct?
If when I resoldered to power leads to the solenoid If I reversed them would that cause a problem?
Here is a pic
This is a really nice coaler and I want to get the bugs worked out before I put it on the layout.
Might not be the coil but the plunger that goes in the coil. Could of gotten magnitized. Happens with E-units. Not sure of how to demagnitize them. Some remedies I heard of with the E-units is putting a spring around the plunger not one with too much tension maybe just a couple of coils of the spring just to give it a little shove open.
The polarity of an alternating voltage does not matter at all to a solenoid. Reversing the wires is equivalent to applying the same voltage 1/120 of a second earlier or later.
You usually demagnetize something by putting it in a strong alternating magnetic field, then gradually reducing the field strength. Since this is what the magnetic circuit of an e-unit sees in normal operation, it should remain thoroughly demagnetized. I believe that the “magnetized” e-unit is a myth. Every sticking e-unit that I have examined had small notches worn into the crotches of the drum teeth. Evening these out, with a small chisel, for example, invariably fixed the thing.
