Yamaha THR - DC in jack switching, what's what?

[Guitarist]

Anyone know which is switching on this DC jack, the +'ve or is it the -'ve?? The jack is completely busted so... just want to boot the unit up for now.
Here is the replacement part but I doubt the amp will work anyways and shipping out here will take ages.

https://www.google.com/url?q=https:/...xMlIUMT6iMzZpQ

thanks

[The Dude]

Caveat: Making some assumptions, so with a grain of salt......

Check it with a meter.

Assuming chassis is ground, does the chassis have continuity with battery negative? If not, they are probably switching the ground side.

Also/Or, I'd think there's likely a filter cap off the adapter + input. Does one of the jack pins show continuity to an input filter cap?

This shouldn't be too hard to figure out with a couple minutes of circuit analysis.

[dmeek]

I don't understand the question but maybe this will help.

https://music-electronics-forum.com/...1&d=1568346508

[The Dude]

From the schematic it appears tip is positive and ground is switched. So, one of the solder pads that went to the jack will go to battery positive. The other two will need to be connected together for battery power to function.

[dmeek]

From the schematic it appears tip is negative and ground is switched.

Maybe that's a typo. The schematic not laid out very well but if you follow the tip it goes to the battery connector +, switch goes to - . Tip is Positive

[J M Fahey]

Agree with above suggestions, and as I see it, in general with hollow plugs center pin is fixed contact and barrel is switching, for mechanical and practical reasons, it´s way more complex to do otherwise.

Notice I´m not talking polarity, only that it´s mechanically easier to fit a switching contact to barrel, which is both larger and external, than to center pin which is the opposite.

}EDIT: in this case I agree with center pin / plug tip positive; barrel/body negative.

And since it´s a Negative ground circuit, yes, ground is switched.

Sounds counterintuitive but it´s the simpler/practical way to do it.

[The Dude]

Maybe that's a typo. The schematic not laid out very well but if you follow the tip it goes to the battery connector +, switch goes to - . Tip is Positive

Yes, typo. Thanks for the catch. I'll try to correct the post.

[Guitarist]

Yes, ground is switched. With the jack out, there is no path from the battery Negative to a circuit ground, as per suggestion. With Positive, yes.
The replacement jack has a non-pedal size barrel. But the amp doesn't power up, so it looks toasted, fall-jarred and fertig. Sad, because it's only a year old and it was costly for that lovely couple.

[The Dude]

Did you install the new jack? If not and you're trying to run off battery, you'll have to bridge the two traces where the jack switches them together.

[J M Fahey]

Yes, ground is switched. With the jack out, there is no path from the battery Negative to a circuit ground, as per suggestion. With Positive, yes.

Well, it MUST.
So follow the path from Battery "-" to JK501 Switching pin to JK501 Ground pin (and there is where I suspect a failure) to R57 which apparently is a zero ohm resistor a.k.a. a wire link to PCB ground, such as C504 or C505 Ground (negative) terminal.

The replacement jack has a non-pedal size barrel.

Powwr supply plug and amp jack MUST match.

But the amp doesn't power up,

Make certain those 15V reach the PCB .

[Guitarist]

OK, I jumpered the ground to the switched ground and now it still doesn't power up. So I'll try and follow the +15 voltage downstream and see where it is interrupted...