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-   -   Marantz 9 output power switch (http://www.diyaudio.com/forums/tubes-valves/135145-marantz-9-output-power-switch.html)

Tubesin 20th December 2008 12:28 AM

Marantz 9 output power switch
 
When I switch the power from 70W to 35W, suddenly the switch appears smoke and the amp makes loud noises, I power off immediately. So, what's the reason? Is the switch malfunctioned? Where can I find a replacement switch of this old vintage kind? I'm grateful for some help, thank you

HollowState 20th December 2008 01:11 AM

Switching from partial triode (ultra-linear) to full triode is something you should never do when the amplifier is running. Because you're switching high voltage from an inductive source causes the switch to arc and burn. Especially and old switch in an amp of that vintage. The switch appears to be a simple double pole-double throw type. I don't remember if it is a rotary type or a toggle. Either way it is a pretty standard type that you should be able to find locally or on line.

Tubesin 20th December 2008 01:36 AM

Thank you HollowState, I switch before power on as usual, but, this time when power up, it start immediate smoking, maybe are contacts problems from the failing switch. Its a toggle one. Now to get a toggle switch for high voltage is a problem here, only has 250V 5 or 10Amp, and its something in the 450volts that it switches....

HollowState 20th December 2008 02:08 AM

I think if you buy a new brand name quality toggle switch (not Chinese) it will probably work ok. Even though it is only rated for 250V it will withstand more when new. 250 volts is a conservative rating. And you will be no where near its maxium current rating. If you remove and examine the old switch, you may see a similar rating on it. The original switch has arced internally and is permanently damaged. If you are still concerned about it, perhaps you could mount it with insulating washers. But this would require enlarging the hole. Something you may not want to do to a classic amp.


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