Not sure if you did already, but make sure all your screws are tight on all the boards in the backbox and replace if any are missing! loose or missing screws will cause a hum. I had this hum noise on my HS and check my boards and was missing several screws. I pulled one and headed to the hardware store to get more, installed screws and no more hum noise! If you already did this then proceded on grasshopper!

That's what it looks like to me.

I would put some heat shrink over the cap and resistor leads, as they could short out to other components pretty easily.

Don't know if it's your photo or my eyes but your C8 looks like it has a bit of bulge to it...

And yes, cut the trace with an xacto and shrink tube over the leads.

viperrwk

Yes. I had a service call for some very loud nasty hum on a Jokerz and replacing the bridge on the power supply removed most of the noise and doing the factory mod removed the rest. I did not remove any grounds, but I have seen that work in old Bally sound boads.

A few years ago I replaced EVERY thing on both power supply, and sound boards. I mean everything, amps, caps, transistors, you name it.I even replaced the volume control wire with a better shielded one. Hum is still there. The worse noise you get is the flashers send a buzz over the speakers. It's said to be a cross talk with-in the board it's self, and not necessarily repairable. I did the update on the rear of the board, and it did not help. Yes you sever the trace completely, but please ignore my oops, as I went a little too far, hence the white jumper wire to fix.

A few years ago I replaced EVERY thing on both power supply, and sound boards. I mean everything, amps, caps, transistors, you name it.I even replaced the volume control wire with a better shielded one. Hum is still there. The worse noise you get is the flashers send a buzz over the speakers. It's said to be a cross talk with-in the board it's self, and not necessarily repairable. I did the update on the rear of the board, and it did not help. Yes you sever the trace completely, but please ignore my oops, as I went a little too far, hence the white jumper wire to fix.

IMG_0563.JPG IMG_0564.JPG

I've been all over this topic with some of the best. I believe looking at the schematic, Jokerz is a kind of mock up stereo set up, Yes there are 2 separate audio channels, but there is no real left and right. it's the same signal split over the 2 channels. I added the Pinball pro speaker kit, and a parts express 100 sub amp to my game for that extra punch. Unfortunately it somewhat amplified the buzz, and hum. I think I even did new speaker wires from the sound output as well as new volume wire. I also did the bridge rectifier, and the main transistor as well.

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If you hook up the left speaker, but don't let it touch ANYTHING metal, does it still hum?

So if the speaker is connected, but the frame is sitting on a piece of styrofoam, does it hum?

So I too have a Jokerz with the BUZZ! just replace all the caps in P/S pcb, and no improvement. Is this a lost cause?

I remember talking to the guy at the Coin Op Cauldron, he felt that the hum is coming from cross talk on the board, built-in interference if you will...

Just a minor correction in terms, not likely RF (radio frequency) noise that you are experiencing but "inductive" noise. The motor and associated driving circuits create fields of magnetism that affect nearby circuits, propogating through wires in many cases, or even the traces on the boards. The problem is the noise gets in way early in the audio stream. Everything mixing and amplifying downstream is going to aggravate it, and it can be very difficult to remove the root cause.
I spent a lot of time on my DE Maverick, and what helped the most was floating the sound board. It's the only game I have had this actually reduce the noise on. Floating the ground is somewhat counter intuitive to my nature, but I work in pro audio stuff so I am familiar with ground loop problems so I gave it a try. This is part of the reason why our pro audio products are often designed with highly isolated digital and analog grounds.

For those who read this thread - I did this Mod it greatly reduced the hum I had, but did not eliminate it, good enough for my game room. The shown example is correct and its worth doing for sure.

I have "floated" sound boards a few times on SYSTEM 9/11 and DE pins to help determine the cause of the hum. So far I have found these causes of HUM (most common problems toward the top):

missing screws or missing GROUND (braided wire) connection in the backbox
bad connection on plugs
bad speaker
bad amplifier on sound board/MPU
bad caps on sound board/MPU
bad diodes/resistors on sound board
bad caps on power supply
bad potentiometer in cabinet or sound board
bad connector/open solder joints
low/high voltage on sound board
bad motor in the game somewhere
bad GI bulbs/sockets/feature lamp wiring (I know, a very strange one)

I use the "floating" trick but only after first checking all the above things.

I actually owned a Jokerz! long ago and my hum went away after I performed a playfield swap. I assumed that it was probably a bad connection on the playfield lamp matrix or GI somewhere.

As with another poster, MOST of my issue is shooting through the left speaker. If I duplicate the sound from the right side am I missing anything sound wise? Music or FX?

Since it is the left sound channel, what in the schematics if you trace them could be the culprit?

I can't believe in the 25 years of this machines existence that a fix for the BUZZ hasn't been found.

The hum is there too but it doesn't bother me so much. the BUZZ makes my machine very unplayable.

I am gonna poke around, re-seat things. But I am gonna redo my speaker also if this can't be permanently fixed.

Toyotaboy, did you ever replace the Bridge on the P/S pcb?

OK! So some progress.

The hum is like 90% gone, and the buzz is no more!

What did I do? I disconnected the motor that spins the card wheel. Thats it.

Loud buzz that made you not play the game. GONE!

Loud Hum that was almost as bad as the buzz, 90% GONE!

So, I think I will order a new motor? Maybe the quality will be better?

Jokerz is fun again!!

You may want to check the resistance of the motor to see if it's still within spec...

You may also want to try to ground the frame of the motor to see if the hum goes away before you just assume it's bad.

So here is where the learning curve happens, how do I check the resistance of the motor?

Grounding the frame I get...

I just recently owned a Jokerz! which had a constant hum as well and it sort of increased to a buzz when the cards spun. It is sold now and it never really bothered me too terribly much but it's interesting to know that it wasn't just my machine and that this is actually a factory issue.

So I have the same issue with my Jokerz, and when I unplug the motor, no issue. With it plugged in, the sound is very bad, and the machine occasionally resets when both flippers are pressed! Unplugged, plays fine. Any ideas?

Not a brushed motor. It's a stepper motor.