AMI Continental 2 selector assembly wiring and resistors

Hello everyone, I have a problem with an AMI Continental 2 , it blows the 1 amp fuse in the power supply after 5-10 minutes of power being on. I have narrowed it down to a problem in the electrical selector {keyboard} area. Mine has the keyboard backlights installed with 4 # 47 lamps. I have 3 resistors installed, one 75 ohm for the latch solenoid, one 150 ohm for the credit lights, and I have one 65 ohm one installed which goes to the keyboard backlights. I believe that the 65 ohm resistor should not be there., but Im not sure as the schematic does not show the keyboard lighting curcuit. There is evidence of burning and I can tell someone did some work in this area in the past. Can anyone tell me the proper way to wire this area up? And does the power for the keyboard lights come off the 150 ohm resistor also? Thanks for any help! Jim

Hello Jim

This model has an inverse function of the latch solenoid. If no credit is available, it is activated. If credit is available, it drops off. This means that the solenoid is switched on most of the time and would become very hot after hours of operation. In order to prevent this  the 75 Ohm resistor is connected in series to the coil to reduce the power. The coil with the series resistor is too weak to attract, but it is enough to keep the coil core in the attracted position. Therefore, there is a contact (called latch switch), which bridges the resistor until the solenoid has attracted. If this contact does not open, the current is high enough to blow the fuse after a few minutes. I think this might be your problem.

Best regards - charly49

Thanks Charley, but what about the extra resistor I have in mine. Couldnt it be causing too much current and blowing the fuse? I have checked the latch solenoid and it reads @ 10 ohms. The latch relay coil reads @ 40 ohms. Not sure what they should read though. Jim

Hello Jim

I think that the additional lighting works with AC, as well as the credit lamps. Therefore, it can not cause the blown DC fuse.

Have you checked whether the latch switch opens when the latch solenoid has attracted? Anyway, the 75 ohm resistor should become hot, but not the coil. You should also check if the fuse also blows when credit is available and when thze additional lamps are removed. This allows you to exclude some possible errors.

Best regards - charly49

Charly 49, I was back working on it today, still blowing fuses. I disconnected all the lights by snipping the resistor leads. So it is not the lights causing problems.The latch switch does open when the solenoid is attracted. The latch solenoid reads @10 ohms. The latch relay reads @ 40 ohms. This is really stumping me. Im almost tempted to to replace the latch solenoid and latch relay coil , but I wish I knew for sure if they bad first. Jim

Hello Jim

Have you checked if the fuse also blows when credit is available? If not, then it can not be at the latch solenoid because it is turned off. It is difficult to help if you do not answer the questions.

Best regards - charly49

Yes, Charly , the fuse also blows when credits are on the machine. It is on free-play . I have disconnected the resistors for the credit lights and the keyboard lights, and the fuse still blows. The latch solenoid reads about 10 ohms. I wish I knew what the correct resistance is supposed to be. The latch solenoid doesnt seem burnt or anything, but Ive seen a few where the coil wires weaken and resistance changes. Jim

Hello Jim

The latch solenoid so can not be the cause because it is de-energized.

There is yet another relay which is always attracted, whether with or without credit. It is the Pulse Conrol Relay R2. It is the right one of the two relays in the selector. You should check if it looks burned. If you're not sure, you should disable it (unsolder or push a piece of paper between the corresponding contacts on the Sprag Relay) and see if the fuse blows again. Unfortunately I have not the exact resistance values of the coils and also no device in the area, to measure the values.

If credit is available, is also attracted the latch relay. You can disable it by resetting the credit unit.

A word about the fuses. I hope you are using "SLO-BLO" fuses. Fast acting fuses are not suitable. Slo-blo fuses can withstand an overcurrent for a few minutes. Only massive overcurrent (> ten times the rated current) leads to immediate blowing. This property is used for protecting coils which may attract only momentarily. The current consumption is higher than the rated current of the fuse, but the fuse will blow only if the coil is powered for too long. Coils that are attracted for a long time (such as the three mentioned), must have a current consumption significantly lower than the nominal current of the fuse. You can measure the current consumption of each coil in order to assess whether the coil is good or not.

Best regards - charly49

Charly, I am using slo-blo fuses. One thing I should verify with you: When I put the switch on the control box in the "off" position, the latch solenoid stays energised all the time. I assume this is normal, so you cant make a selection when the switch is off. The latch solenoid is always energised also in the "scan" position. I assume this is normal also, so you cant make a selection while in this position. The 1 amp fuse blows most of the time when in these 2 positions. When in the "play" position it blows also, mostly after making a few selections.

Hello Jim

It must be stated, under which exact conditions the fuse blows. In your first entry you wrote that the fuse blows 5-10 minutes after powering. I have understood to such an extent that it happens, even if no selection is made. If so, the error should be found in the circuits already mentioned. When selecting only additional circuits are activated.

I would suggest that you first measure the current draw of each of the three coils. Then we can assess whether a coil is defective.

Best regards - charly49