constant hum

I will tell you a story that you all will think is a story but I know it is
true. I had a situation in a large church once where we were getting a low
level 60Hz hum even with the amps turned off. What we ultimately discovered
was that the 1/4" phone speaker connectors were just installed through metal
plates without isolating insulating washers. The stage was built on metal
studs which sat on concrete and was directly connected to the conduit to
which the metal speaker jack plates were bolted. There was enough AC leakage
at ground potiential between the earth ground of the amps and the ground on
the stage to activate the speakers enough to hear. I put in the insulating
washers and removed that ground path and the hum went away. I deal with
ground potiential voltage differences every day in my business. It does not
take very much AC to make a speaker hum.

Jim

"John Robertson" wrote in message
...
This is starting to sound like a filament shorted to a cathode and/or
grid of an output tube...that is the only way I can see a hum sneaking
into the speakers on a Seeburg amp with no B+...

John :-#)#

On Tue, 23 Nov 2004 09:41:10 -0600, "Crazy George"
wrote:

Rick:

Interesting. Be sure of that fact before proceeding further. DIsconnect
all speakers. If the hum goes away, then you
have some sneak path, sometimes incorrectly referred to as a ground loop
in the speaker wiring. Finding that will
require careful examination of the wiring of the speakers and the output
transformer and associated terminal strip(s).
I hope you have a correct and complete schematic. Good luck!

(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

Hi, not in this case as I just replaced the 4 6cz5's with 6973's...hum still there.


John Robertson wrote in message . ..
This is starting to sound like a filament shorted to a cathode and/or
grid of an output tube...that is the only way I can see a hum sneaking
into the speakers on a Seeburg amp with no B+...

John :-#)#

Jim:

No, that is an expected occurrence. It is similar to putting a microphone circuit in a mobile radio installation. DO
NOT ground the low side of the mike circuit at the dashboard, or you are guaranteed noise and alternator whine. And it
is surprising how few people know this.

The general case is that if you provide an electrical path, current will flow in it, and some of it will be AC. And if
you draw the equivalent circuit, you can see where the current flow produces a voltage drop across the victim item. If
I were a betting man, I would bet that Rick's amplifier is grounded to the box through one of the speaker wires.

--
Crazy George
Remove N O and S P A M imbedded in return address

"Jim Murphy" wrote in message ...
I will tell you a story that you all will think is a story but I know it is
true. I had a situation in a large church once where we were getting a low
level 60Hz hum even with the amps turned off. What we ultimately discovered
was that the 1/4" phone speaker connectors were just installed through metal
plates without isolating insulating washers. The stage was built on metal
studs which sat on concrete and was directly connected to the conduit to
which the metal speaker jack plates were bolted. There was enough AC leakage
at ground potiential between the earth ground of the amps and the ground on
the stage to activate the speakers enough to hear. I put in the insulating
washers and removed that ground path and the hum went away. I deal with
ground potiential voltage differences every day in my business. It does not
take very much AC to make a speaker hum.

Jim

"John Robertson" wrote in message
...
This is starting to sound like a filament shorted to a cathode and/or
grid of an output tube...that is the only way I can see a hum sneaking
into the speakers on a Seeburg amp with no B+...

John :-#)#

On Tue, 23 Nov 2004 09:41:10 -0600, "Crazy George"
wrote:

Rick:

Interesting. Be sure of that fact before proceeding further. DIsconnect
all speakers. If the hum goes away, then you
have some sneak path, sometimes incorrectly referred to as a ground loop
in the speaker wiring. Finding that will
require careful examination of the wiring of the speakers and the output
transformer and associated terminal strip(s).
I hope you have a correct and complete schematic. Good luck!

(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

Hi guys
OK. I tried I everything except for the sheet metal as I don't have
any laying around...will have to buy some. I disconnected all of the
lights...still hum. Removed the stepper fuse, no change...removed the
5u4 rectifier, no change...disconnected the molex type speaker plug
from the amp, no sound as expected. That leave what george mentioned
above about a possible speaker wire grounding the amp...all wires are
clear, so that would leave a possible bad speaker wire inside the amp/
plug or bad caps that were just replaced..or were they? I put the
original speakers back in and they sound pretty good...much better
bass punch and decent mids/ hi's, so I think i'll leave them in (now
the juke is back as it was designed (proper speakers and output
tubes). Now another couple of problems:
1. motor rumble thru the cartridge. Does anyone here have new flywheel
rubber mounts (don't know what they are actually called)?
2. After I exchanged the speakers, the mech. tries to play a
nonexistant record (stops and loads) at the next right position just
before V8 (the rightest most record).This is where the last plastic
blank filler record would be). What did I do to cause this? I had to
remove so cables to get the back door off to get at the ch1 speaker.
Everything looks connected right (I did pull some tight trying to
remove the door without disconnecting them). Thanks for all your help
and suggestions, Rick (who is getting this 222 to be almost right!)


"Crazy George" wrote in message ...
Jim:

No, that is an expected occurrence. It is similar to putting a microphone circuit in a mobile radio installation. DO
NOT ground the low side of the mike circuit at the dashboard, or you are guaranteed noise and alternator whine. And it
is surprising how few people know this.

The general case is that if you provide an electrical path, current will flow in it, and some of it will be AC. And if
you draw the equivalent circuit, you can see where the current flow produces a voltage drop across the victim item. If
I were a betting man, I would bet that Rick's amplifier is grounded to the box through one of the speaker wires.

--

Rick:

The speakers which hum: Take an ohmmeter and check for continuity (or just look) from the speaker terminals to the
speaker frame (basket). If there is a jumper from one of the terminals to the frame, that is the cause of the hum.

On the selection problem, I suggest you repost the question. No one in their right mind will be following this thread
and pick up that question. I am not familiar enough with the bigger carriages to hazard a guess as to the problem.

--
Crazy George
Remove N O and S P A M imbedded in return address

1. motor rumble thru the cartridge. Does anyone here have new flywheel
rubber mounts (don't know what they are actually called)?


Rick - not sure if this is the part you need, but check it out. Also
might be worth calling them. - Mark


84-002 Motor support plug, rubber, for under mechanism motor 1.50
84-003 Mechanism turntable drive grommets, Seeburg part # 245464, pair
4.00
84-004 Mechanism frame rubber bumper, Seeburg part # 245291, pair 4.00


http://www.jukeboxusa.com/catalog/Seeburg222.pdf

Thanks George. I tried to email you a thank you but have no idea how
to get thru...all replies bounce back. Thanks, Rick.


"Crazy George" wrote in message ...
Rick:

The speakers which hum: Take an ohmmeter and check for continuity (or just look) from the speaker terminals to the
speaker frame (basket). If there is a jumper from one of the terminals to the frame, that is the cause of the hum.

On the selection problem, I suggest you repost the question. No one in their right mind will be following this thread
and pick up that question. I am not familiar enough with the bigger carriages to hazard a guess as to the problem.

Thanks Ace and all who have tried to help, Rick.


(Ace) wrote in message . com...
1. motor rumble thru the cartridge. Does anyone here have new flywheel
rubber mounts (don't know what they are actually called)?


Rick - not sure if this is the part you need, but check it out. Also
might be worth calling them. - Mark


84-002 Motor support plug, rubber, for under mechanism motor 1.50
84-003 Mechanism turntable drive grommets, Seeburg part # 245464, pair
4.00
84-004 Mechanism frame rubber bumper, Seeburg part # 245291, pair 4.00


http://www.jukeboxusa.com/catalog/Seeburg222.pdf