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Title: Hopper chassis - common ground? Post by: frenchmarky on March 30, 2011, 03:50:43 PM Should I be reading continuity between the coin counter reset coil and the chassis of the hopper itself?
I've noticed a significant dimming of the lamps when the reset coil fires. They stay dim if I prevent the counter from resetting so this coil being fired sure seems to be the source of the load. Didn't seem to be doing this before so wondering if I now have something shorting somewhere. It even blew a non-SB 50v fuse I had in there. I don't see any dimming at all when the coil in the feature unit fires so seems like either the reset coil circuit is shorting or the coil itself is partially shorted, though reset occurs fine nonetheless with a SB fuse in there. I read 16 ohms on the coil with the hopper pulled, but I also am seeing zero / 16 ohms on the lugs when testing against the hopper chassis. Is this normal, i.e. reading continuity between the chassis and the counter reset coil? Or should the chassis be totally isolated from the coil circuit with the hopper removed from the case? Other than that I can't really see the coil's lugs shorting on anything, but also not positive if 16 ohms is correct for a coil like that either. I usually fix up EM pinball machines and that 16 ohms doesn't sound unusual. Thanks! Title: Re: Hopper chassis - common ground? Post by: Jim on March 31, 2011, 02:44:30 PM that does not seem normal for the chassis ground to read on the coil wire. the transformer in the machine steps down the 115vac to two operating ac voltages. one is 50vac for the coils, and 6.3vac for all the lighting. the 115vac is used for the fluorescents lamps, the hopper motor and the safety timer.
the output of the transformer is center tapped ,and the common wire (yellow) is used for both voltages. blue wire is 6.3vac, orange wire is 50vac. every coil should have a orange wire on one side of the coil,and the return side on the other. it usually goes thru a few switches etc. to get back to the common wire (yellow). a good way to test the coils is to find a yellow wire connection, use a wire and touch the wire from the yellow connection point to the opposite side of the coil (NOT THE ORANGE WIRE). if the coils fires and doesn't blow the fuse then the coil is usually good. NOTE; MOST MACHINES I HAVE WORKED ON HAVE FAST ACTING FUSES, 10 AMP FOR THE 6.3VAC, 8AMP FOR THE 50VAC, AND 5AMP FOR THE 115VAC. to help eliminate where the chassis ground is getting on the yellow wire would be to pull the feature unit, reel mech etc. to see if the short goes away. the feature unit reset coil should be the same as the payout reset for resistance comparison. according to the schematics, the payout reset coil is reset by the "B" switch which is located on the reel mech, left side around the middle. coil should have a orange wire on one side , a black/white wire on the other, it goes from the hopper to the reel mech "B" switch, thru the switch back to the yellow wire. Hope this helps Jim Title: Re: Hopper chassis - common ground? Post by: frenchmarky on April 02, 2011, 05:56:41 PM Thanks, that coil reading as grounded to the frame sounded odd to me too, and since otherwise the coil still worked and ohms were ok and ohms did match the one in the feature unit - I looked at the only switch on the counter that controls the coil, the zero stop, since that ground reading was with the counter pulled completely out of the hopper.
Turned out the insulator tubing on the inner lug had dropped down off the lug, and the lug appeared to be barely touching the switch mount. Maybe wasn't actually contacting the mount, but the vibration of the unit would cause it to short or arc there. Yayyy put the insulator back and that fixed it. The iffyness of the short explains why it started up outta the blue and didn't blow that first fuse immediately. Thanks for reminding me about the slo-blo also, I'll put a regular fuse back in it. As far as the insulator thingees, I'll be checking them from now on as I noticed some others in there had wiggled or were knocked loose as well. I'm more accustomed to dealing with pinballs... most of old ones I've restored usually have bare lugs on the relays and mechs. Although the mech board from an old 60s Bally pin (that I took some parts out of for use in this slot!) does have insulators all over the place. Thanks again! Mark |