Speakers humming / hissing

[zak]

What causes speakers to make a constant humming noise? (gets worse when turning the volume up).

Are the speakers just old and knackered? Anyone else had this problem?

[yosai]

What cab and doe it have an amplifier? Is the noise mains hum?

does the cab hum with no board attached?

[zak]

What cab and doe it have an amplifier? Is the noise mains hum?

does the cab hum with no board attached?

It's my Canary. I cannot see an amplifier in there.

I'll test with no PCB attached.

[zak]

does the cab hum with no board attached?

No hum when there is no PCB attached.

[zak]

Any ideas guys?

[cools]

Grounded properly?

[zak]

I am not sure. It's all the original wiring.

However, the ground prong on the power cable has been removed. So it's now 2 pin head.

Could that be it?

[cools]

Yes.

[zak]

Thanks Cools. Time to buy a new power cable then.

So the entire cabinet is not grounded at the moment.

Why would they snap the ground prong off?

Surprised I haven't been shocked by the cab yet.

[yosai]

There is probably a earth pin somewhere on the cab and definitely one on the step down. Wire those two together with some heavy wire.

Failing that I've got a load of 3 pin US IEC leads with the earth pin. You're welcome to have one of those and modify it.

[cools]

Why would they snap the ground prong off?

It's commonplace. They ground the cabs another way, as their wall sockets don't have an earth.

[zak]

There is probably a earth pin somewhere on the cab and definitely one on the step down. Wire those two together with some heavy wire.

Failing that I've got a load of 3 pin US IEC leads with the earth pin. You're welcome to have one of those and modify it.

Thanks mate greatly appreciated!

I already ordered one from Amazon I'm likely to screw that up, so expect a PM in a few days

[zak]

There are 3 wires in the cable. Black, white and grey.

I can see that grey is used for ground. Is the black one live and white neutral?

[geotrig]

If you multimeter the wires, powered up obviously you should get

V (earth-neutral) = 0 V
V (live-neutral) = 240 V
V (earth-live) = 240 V ..

With those results you can determine which wire colour is which.

[zak]

Sorry, I meant the Japanese cable is black, white and grey. already chopped it...

I can't find Japanese wiring colour standards

[zak]

This page says black is live:

https://www.leadsdirect.co.uk/knowledge ... ains-lead/

But the cable is pretty darn old...

[zak]

I guess the white is neutral:

https://en.wikipedia.org/wiki/IEC_60446 ... _and_Japan

[geotrig]

Don't worry about the "colour " measure as above right down your results and you'll then know what is live and neutral

[zak]

Thanks geo. All wired up now with the new cable.

The good news is that I didn't screw it up.

The bad news is that there is still a hum from the speakers with a PCB plugged in.

[cools]

At least you now have a chance of fixing it.

Is there continuity between the grounds on the JAMMA edge and the ground on your new cable?