which is the ground wire??

[Shark]

im working on Freddy doing a few things.. I read on the dedicated Freddy pinball forum, a way to cure the loud speaker humbing problem.. by running a wire from the ground on the psu to the ground on the speaker. looking at the speaker in the base of the cab, it has two wires.. a solid white one and a white one with a black stripe. which would usually be the ground wire? (i do have a volt meter, but no clue how it works or how to use it) thanks!

 

[cooldan]

just don't fall asleep while you're doing it ....... or Freddy will getcha!

:scared:eep::eeek::help:

 

[Shark]

Sorted: the plain white wire is ground.. Freddy was making a loud humming noise from the base speaker in the bottom of the cab. common gottleib problem I believe.

I disconnected the speaker ground spade and ran a wire from the ground on the psu module to the ground on the speaker.

now there is no humming! cured. he was a very noisy machine even when silent he sounded like a a guitar amplifier turned up full but with no input. hhmmmmmmmmmmmmmm

thankfully now I can leave him switched in between plays, silence is sweet!

 

[Calimori]

I would like to be able to explain the reason for the hum caused by an earth with interference but I can't. :wackoz:
Good to know that there is information on how to fix these issues and we have one more positive fix posted on the forum. Well done. :thumb:

 

[Moonraker]

I would like to be able to explain the reason for the hum caused by an earth with interference but I can't. :wackoz:

The two earths were seperate so they were slightly different values, which could be a few ohms difference but that was enough to cause interference (I guess on an amp circuit). The Gottlieb system 80's are a good example of differing earths if you don't do the grounding mods!