Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on March 29, 2017, 05:31:47 pm

Title: Standby Switch
Post by: TIMBO on March 29, 2017, 05:31:47 pm

Hi guys, Got a valve rectified amp that uses a DPDT standby switch. Half the switch is connected to the CT of the PT, this I know is not good.
The other half has an indicator lamp connected using the 6.3v heater supply.

As per the valvewizard http://www.valvewizard.co.uk/standby.html (http://www.valvewizard.co.uk/standby.html)
The best bad way is to put the standby switch after the reservoir filter cap with a bleed resistor across the switch.

Should I be concern that the DPDT switch will now have approx. 600vdc on one side and 6.3vac on the other.
The amp was built in the 80's and is the original switch.
 

Title: Re: Standby Switch
Post by: kagliostro on March 30, 2017, 02:36:29 am

Quote

The best bad way is to put the standby switch after the reservoir filter cap with a bleed resistor across the switch.

I think you mean The Least Bad Way is to put the standby switch after the reservoir filter cap with a bleed resistor across the switch

(http://www.valvewizard.co.uk/standby3.jpg)

The Standby switch on the CT result in 1/2 the AC voltage on the switch (considering voltage at the extremities)

Franco

Title: Re: Standby Switch
Post by: TIMBO on March 30, 2017, 03:25:12 am

Thanks K, That's what I meant.
After rectification the voltage on the switch is approx. 600v.
I'm concern that the switch is not capable of handling that sort of voltage and it may arc to the 6.3v side.

Title: Re: Standby Switch
Post by: kagliostro on March 30, 2017, 05:21:58 am

As you say, also I think that is a reasonable possibility

if the amp is so from the '80, may be it will be better to leave it as is

but wait for the opinion of someone that is more skilled than I

Franco

Title: Re: Standby Switch
Post by: dbishopbliss on March 30, 2017, 07:43:47 am

Valve Wizard makes a case to NOT have a standby switch at all. Could you just remove it?

Title: Re: Standby Switch
Post by: kagliostro on March 30, 2017, 08:54:10 am

You can "move" it to a mute switch, but I don't know if the 6.3v AC can give problems if you move to the switch the signal of the volume pot

Franco

Title: Re: Standby Switch
Post by: pompeiisneaks on March 30, 2017, 01:45:13 pm

You could create a mute switch really easily by shunting the input jacks to ground :)  (or just after the first input stage, either way, it's easier/better than a standby :P)

~Phil

Title: Re: Standby Switch
Post by: DummyLoad on March 30, 2017, 08:00:46 pm

hoo needs a nassy 'ol standby switch anyhow...


--pete

Title: Re: Standby Switch
Post by: TIMBO on April 07, 2017, 11:22:56 pm

Hi guys, Your thoughts on this setup for a standby. Thanks
http://www.londonpower.com/standby-switch (http://www.londonpower.com/standby-switch)