Half power switch - How is it wired?

[Normster]

I'm planning out my next build and thought I'd try an ODS 100. How exactly does Dumble cut out two tubes for 50 watt mode? It looks like a mini switch on the back so I'm guessing it has to be a low voltage thing. I thought he might lift the grids, but that would remove bias voltage. Any ideas?

[ampdoc1]

He probably just inserted a double pole switch that opens the ground leg of the cathode resistors on one pair of tubes. Very low voltage and current here!

[toneman]

10 K across the poles of the switch. It works fine.

[v00d00blues79]

Would there be enough voltage there to power the LED then? or is that wired some other way?


Thanks,

Andy

[ampdoc1]

Don't know what you mean about the LED, but as this is in the audio chain, you wouldn't want to connect any indicator LEDs (or any other for that matter).

[tonelab2]

I would think it was more likely a multi-pole(forgotten what they're called- darn old age creeping in) type switch, one section switching the the cathodes while the other switches the power for leds.
Hope that makes sense. You've just have to find the right switch for the job.

[ayan]

I would think it was more likely a multi-pole(forgotten what they're called- darn old age creeping in) type switch, one section switching the the cathodes while the other switches the power for leds.
Hope that makes sense. You've just have to find the right switch for the job.

If I recall correctly, Dumble did indeed put the LED in series with the tubes' cathodes, with a 10K resistor in the path too. Short the resistor and LED and you get your 100 W mode, but flip the switch and two tubes barely pass a couple of mA's, but that's enough to juice the LED.

In my amps, I chose to lift he ground of two of the tubes on one side of the switch, while tapping off the 6.3 VAC supply with a diode + 390 ohm resistor + LED. In my case, LED on = 100W mode.

Cheers,

Gil

[v00d00blues79]

Gil,

might you have a layout drawing or something to help me/us visualize what you are talking about?

Thanks,

Andy

[ayan]

Gil,

might you have a layout drawing or something to help me/us visualize what you are talking about?

Thanks,

Andy

Andy, as I mentioned on another thread, I will be cleaning up my files and posting them here in the (very) near future. So if you can hang in there a little longer, you will see what I mean.

Cheers,

Gil

[tonelab2]

In my amps, I chose to lift he ground of two of the tubes on one side of the switch, while tapping off the 6.3 VAC supply with a diode + 390 ohm resistor + LED. In my case, LED on = 100W mode.

That's how I pictured it but couldn't quite explain it.
Thanks Gil for putting it in plain english for all to understand.
Is it a DPDT switch?

[ayan]

Is it a DPDT switch?

Yep, from Mouser Electronics. The P/N is 10TC260.

Gil

[Normster]

Thanks for all the replies! I think I'll try it Dumble style but I'll use a DPDT switch so I can just rewire if I don't like it.