Marshall Standby switch deletion and bias tap design

[ViperDoc]

Any recommendations on proper values? The inrush calculators I’ve found don’t seem to apply to tube amps. The PT has a 345-0-345 VAC secondary rated at 150 mA.

[pdf64]

I’d look at an Amphenol CL80 or CL90.

[ViperDoc]

Super, sounds like a no brainer. Thanks.

[ViperDoc]

I'm building this Marshall now. Where would you recommend putting the thermistor? In the AC main or neutral line after the switch? Or in the secondary?

[sluckey]

Neutral goes straight to the PT primary. The fuse, switch, and thermistor all go in the Line (hot) side.

[ViperDoc]

Neutral goes straight to the PT primary. The fuse, switch, and thermistor all go in the Line (hot) side.

Thank you, sir.

[martin manning]

I don't think it matters. Fender puts it on the neutral.

[pompeiisneaks]

I thought it mattered a LOT... at least for the fuse and switch... if there is some kind of dead short in the amp on the hot side, then the fuse on the neutral will never short out, as it will see 0 current while the amp lights on fire. If the switch is on the neutral side and something shorts, it will continue to flow current until the fuse blows or the amp is on fire.

both are bad potential situations that using the neutral side can cause.

OTOH many crappy clubs have neutral and hot swapped... BUT that's an entirely different problem

Dual Pole Dual Throw (DPDT) switches with hot and neutral on both sides are very smart to handle bad wiring in a crappy club... for the switching, but not fuse... some people fuse both hot and neutral to protect against this type of fault, but... that's a bit excessive imo...

~Phil

[ViperDoc]

I put it in the 120VAC hot line between the AC mains switch and the PT primary.

[martin manning]

I thought it mattered a LOT... at least for the fuse and switch... if there is some kind of dead short in the amp on the hot side, then the fuse on the neutral will never short out, as it will see 0 current while the amp lights on fire. If the switch is on the neutral side and something shorts, it will continue to flow current until the fuse blows or the amp is on fire.

I'm talking about where the thermistor is located.

[pompeiisneaks]

ahh gotcha... but for similar reasons, wouldn't you want the thermistor on the hot side or it is more for simple current limiting and so long as the circuit is 'intact' it's doing its job?

~Phil