The coils in this machine are DC and you'd expect to see ~40VDC present at the coil at all times when measured to ground (the ground strap in the cabinet is a good place to test too). The SDB completes a path to ground for the coils when they fire.

The AC voltage at this coil is concerning. Check the voltage at the rectifier board. With your DMM on VAC put the black lead on E8. This is one of the connection points for the transformer. Put the red lead on TP4. You should have ~7.3VAC. If this is right then test the other TPs with black on ground. If they are fine then test the diode on the coil in question with the machine off. If it is OK then maybe the 20VAC on the coil was a misreading due to the coil firing.

Here is a link to the manual if you don't have one https://www.ipdb.org/files/2406/Bally_1978_Strikes_and_Spares_Manual_w_Schematics.pdf

Post last edited 5 years ago: “added link to manual”

You're currently viewing posts by Pinsider Cheddar.
Click here to go back to viewing the entire thread.

Reply

Wanna join the discussion? Please sign in to reply to this topic.

Hey there! Welcome to Pinside!

Donate to Pinside

Great to see you're enjoying Pinside! Did you know Pinside is able to run without any 3rd-party banners or ads, thanks to the support from our visitors? Please consider a donation to Pinside and get anext to your username to show for it! Or better yet, subscribe to Pinside+!

This page was printed from https://pinside.com/pinball/forum/topic/should-alltek-driven-coil-line-be-reading-20-vac-always?tu=Cheddar and we tried optimising it for printing. Some page elements may have been deliberately hidden.

Scan the QR code on the left to jump to the URL this document was printed from.