Use of multimeter

[Mann]

I'm about to start soldering the serious parts of a tube amp kit and would like to know what to use as the ground when measuring the voltages in different places with a multimeter - the chassis?

[aron]

Since you are building it, you must know where ground is. I know this sounds like a puzzle, but it isn't meant to be. If you are going to be poking inside your homebuilt amp, you really do need to know where ground is. If the chassis is not isolated, then yes, it can be used as ground. If it's a star-grounded system, then measure from the start ground point.

All I am saying is that an amp is really a dangerous place to be poking around if you are not sure where ground is.

[Garrett]

I agree with aron.  If you don't know where ground is or which ground in reference to what voltage then you should'nt be in a tube amp with the power on.  It could be deadly.  Also remember filter capacitors (the big tall ones) can still hold a deadly charge even after power is turned off or removed from the amp.  So remember, after the amp is unplugged from the wall always take a insolated handled screwdriver and short the two leads of the filter caps (to release any charge) before you start working on the tube amp.

                                           take care, Garrett

[Mann]

Sorry about the vague question - the amp is star grounded so that after star ground point (which is isolated from chassis) there is a resistor which is connected to the chassis.
There is also a "safety ground", which is the third wire of the AC mains (short wire to chassis).
I was just wondering which one would be the "right" ground when measuring voltages.

[H.Manback]

If there is a resistor between chassis and the ground point, then measure it at the ground point.

Why is there a resistor between chassis and ground by the way?

[vfr800fiman]

So remember, after the amp is unplugged from the wall always take a insolated handled screwdriver and short the two leads of the filter caps (to release any charge) before you start working on the tube amp.

A wirewound power resistor is much safer than a screwdriver (and less noisy).
Glenn

[H.Manback]

Yeah but what about the sparks! We want sparks!