Are you sure it's energized?

When you turn the game off, does the flipper immediately drop?

If it doesn't, It could be as simple as a magnetized coil stop, or a damaged plunger. Important to determine if it's mechanical or electrical and you haven't provided enough information to narrow it down to either.

Shorted transistor on the flipper board?

Anything is possible. I just had an intermittent display problem on my Flight 2000, that turned out to be a shorted transistor.

Check the flipper diode. If it's bad or broken it will energize like that.

you need to disconnect one Side of diode to get accurate test,I would just replace it and eliminate that as a possible problem.

Just replace the diode. There are no caps as the EOS and flipper switch is low voltage in conjunction with a single wound coil. All high power and low power switching is done on the flipper board.

Have you tried to disconnect the EOS switch? Frankenstein doesn't need it because it uses an internal timer. I once had trouble when trying the EOS switch (as you do on other machines) and had to disconnect it.

Since you already changed the flipperboard, you could try to switch the wiring of the left to the right flipper (mark them well to restore correctly afterwards). If the problem moves to the left, you need to follow the signal to the mainboard and check the signals. A bad transistor is possible, but maybe the problem is in the logic control. If the problem remains, check the contact AND wiring of the flipperbutton. Have you tried to disconnect the connector of the button when the coil is energized?

Just thinking if you swap the coil conenction, and/or the buttons you can determine if the problem is in the backbox or not. Best to find the fault before changing parts. Where you swich it is up to you to find the easiest way

After the initial flipping, the flipper falls back to a hold voltage just to keep them up for as long as you push the button (most of the older pins use the eos for this) This is enough to hold the flipper up, but it doesn't take much effort to push it back down. According to pinwikki is should be 50V and 8V, so yours should be ok, you can find this article and others here :
http://www.pinwiki.com/wiki/index.php?title=General#Flippers

(I still think it's an electronics problem)

I never used a NTE261 but looking at the datasheet, it looks quit the same.
Does it get hot after just switching on or after you pushed a flipperbutton? In the first case maybe you made a short on the board with the replacement or perhaps a connector is positioned wrong?

Great you got it working again, i hope you enjoy the game as much as i do.

I have developed what appears to be the same problem with my frankenstein pinball. haven't measured the voltage of what is holding the flipper up but it is up strong enough to stop the ball coming out of the geneva scoop. my lower left flipper is sticking up occasionally maybe 1 time out of 30 or 40 activations. if I press the flipper once or twice it drops. I have already rebuilt all the flippers since I thought that might have been the problem because I knew for sure that the upper right flipper degraded enough so that the flipper was getting caught up on the way down and needed new bushings. I have ordered some new tip122 and 2n4401 transistors but was wondering if you could confirm that the transistors I would have to replace would be q35 and q43 for the lower left flipper? yes the flipper drops instantly when denergized so it is not getting stuck mechanically.

locked on coil is being supplied 4 volts.

I replaced 35 and q43. the occurence of stuck flipper was reduced but is still occuring. if I go to a switch test with the coin door open and the interlock off the flipper button registers and then turns off while I am holding it but if I wait awhile the flipper moves up slowly like it is using the holding voltage. does anyone know where to look for this problem on the left flipper?

When it goes down try pinching the EOS briefly with your fingers. I had this problem in the past with data east games and it turned out on one that the EOS needed cleaning and another that one of the contacts was loose on the leaf. Also seen cracked leafs exhibit this behavior.

the question is why is it going up with the high voltage interlock open. the right side which doesn't stick doesn't move the left when I hold it will move. I had this problem a moth ago then rebuilt the flippers with new eos sleeves , plungers and bushings. it sticks up occasionaly in game play which is the problem and is held with 4 volts.

If you lift the right flipper up with your finger and hold the button in does it stay up with the coin door open? This might tell you if the symptom is a red herring.

Have you checked to make sure the leaf switch is disengaging?

yes the right flipper will stay up if you move the flipper while holding the button in switch test mode. i removed the ball when the flipper got stuck up. the machine goes into a ball search mode. if I press and hold the button while it was stuck and doing ball search mode it stops the search mode proving its not the button. after I let the button go after a stuck flipper the flipper drops normally.

the leaf switch disengages

Finally got a chance today to really dig into the game. checked input on cn1-12 and it grounds when I hit the button and the l2 flashes and goes out when held, looking good so far. I pulled the board off the wall and layed it on a towel in the bottom of the game so that I would have easier access to it for probing some of the components. started a game and pulled the ball out. started playing with the left flipper only (the one that sticks up) hitting points occasionally to make sure the game does not go into seeking mode. 10 minutes later still no sticking. going to test it later with holding the flipper up for longer period of times. my plan was to see if I was getting voltage on r32 if the flipper is stuck but so far I have not been able to make it stick. My fall back position if I can't get it stuck again is that maybe moving the board shifted a connection to make it more reliable or maybe the board flexed while removing and made a better connection to a bad solder joint. If I can't get it to stick again maybe I will inspect the solder joints better and reflow. and also clean the connectors. other ideas to run down or am I barking up the wrong tree. I know the flipper switch is good because if it was bad and staying connected the game would never go into search mode if it was reading a stuck switch

this is very frustrating. played 20 games no problem then upper right flipper was delayed a second from lower right or a ball or so. i had reflowed the connectors but no sticking. mounted board back on wall and played a few games and the left flipper sticks up again. then to annoy me my plasma bumper controller for my green pop bumper stops working. its definetly the controller because moving around the connectors makes only that controllers bumper not light. i am now worse off then before

finally got to check on r32 with the flipper locked in upper position. I got a reading of 8 volts on it. this feeds the gate of sr2. from what I can see the gate should only be getting 5 volts max if I was supposedly holding the flipper button. does this mean that the sr2 might be bad and leaking voltage through to the gate? Would hitting the flipper button cause the 50 volt surge to shut off a defective scr? also thinking that the upper flipper problem might be the flipper getting out of time with the lower one since it has no eos on the upper and the delay might be 8 volt power trying to raise the flipper. this almost never happens so next time it does I will see if letting the right flipper drop enough to get eos to reset good will fix this. please someone who understands this circuit for the sr2 please let me know should I change it?