Hello,

What would be the specifications of the transformer?

Perhaps Mat Janssen from the dutch forum http://www.elektronicaforum.nl/ will know a solution.
I am moderator on that forum too.

Bertus

 

Hello,

Is here something for you?
http://www.ringkerntrafo.nl/shop/high-end-audio/voedingstrafo-s.html

Bertus

 

Are you sure about those resistor values? If the 238V was shorted to ground you would be drawing less than 1 watt.

Looks about right, only the output tube is going to draw much current. The drivers are often behind Very high resistances from B+. Look at the values for this old amp.

http://www.ampslab.com/vintage_dynaco_mkiii.htm

 

seems like a strange place for the switch.

I've seen this in a CRATE guitar amp that I'm working on for a friend. It's a "Standby" switch. The "Power" switch is in the primary. The Standby switch is turned on a while after the Power switch. With a single power transformer, this lets the heaters warm up before applying plate and bias voltages....as I've been told.

Not sure I trust audiophile design logic.

Ken

 

You have a thread for this already. The two threads have been merged.

 

I've seen this in a CRATE guitar amp that I'm working on for a friend. It's a "Standby" switch. The "Power" switch is in the primary. The Standby switch is turned on a while after the Power switch. With a single power transformer, this lets the heaters warm up before applying plate and bias voltages....as I've been told.

Not sure I trust audiophile design logic.

Ken

The standby switch seems to minimizes hum during the first few seconds of warm up. Mostly a Simply way to turn off the output when gear is moved around at a concert. My son just flips both at the same time for home/personal use. I don't quite see the point for a 5W practice amp in this case.

 

IIRC applying HV to the anode before the cathode has heated up will strip off electrons off the cathode and damage the coating on it.