Kalamazoo Model One Switched Input Jack

[misterc57]

I am getting a 60 cycle hum on my Model One unless I plug in a guitar. Then it goes away.

I thought that the switched input jack # 1 is suppose to ground the input. I cannot figure out why it does not. The switch blade and tip blade have good contact. The ground terminal has a good connection to ground. I sanded away the paint inside the chassis at the jack.


If I jump a wire from the input blade to ground there is no noise.

What am I missing or doing wrong?

Thank you, MC

[nosaj]

Remove the insulated washers from the input jacks. Theyre not shown in the schem. Nor is a switched jack .
nosaj

[Enzo]

J1 is drawn as a switched jack. I agree we do not want insulating washers on the jacks.

[nosaj]

J1 is drawn as a switched jack. I agree we do not want insulating washers on the jacks.

My mistake. I also could be wrong about the washers they look like insulated washers but I guess patina on a toothed washer could look similar. OP will have to tell us.
nosaj

[misterc57]

No insulated washers, those are metal washers with teeth. I removed it from jack # 1 and I still do not have continuity from the positive blade to ground.

[Jon Snell]

I would fit a 3 core mains lead and place the earth on the spare solder tag then connect a wire from the bare flex shown between the two input sockets and the same tag as shown.

Then remove this thing with an orange line on it we call a death cap.

Then fit a switched socket in the right hand jack, the switched contact is missing!

Keep safe.

[misterc57]

Are those switched jacks suppose to have 3 lugs? I only have 2 lugs.

[misterc57]

I would fit a 3 core mains lead and place the earth on the spare solder tag then connect a wire from the bare flex shown between the two input sockets and the same tag as shown.

Then remove this thing with an orange line on it we call a death cap.

Then fit a switched socket in the right hand jack, the switched contact is missing!

Keep safe.

Will do. Thank you

[Helmholtz]

It's the correct shorting/switching jack but the middle lug seems to be broken off and missing. Should be connecting to chassis ground.

[Jon Snell]

Switched lug is missing.

[misterc57]

Another curiosity to me, input jack # 2 ground lug has a white wire connected to pin 9 of the 12AX7. This is the heater center tap. I do not see in the schematic where it should be connected to ground.

However I think I see this wire in a picture of another Kalamazoo. Looks like in that one a wire runs from jack # 2 ground through jack # 1 blade lug to jack # 1 ground lug to 12AX7 pin 9.

Thank you

[misterc57]

All working now. Thank you all for the advice. Picture shows what I ended up doing with the 3 prong and the corrected input jack. MC