Tube Amp Archive

Yes, I agree, the caps are discharged. Zero volts on B+. No current flows.

And minus B+ on the open CT. Better instruments or sims would change nothing. There's nothing particularly sensitive about this measurement.

No offense... but I'm about to give up. Reality is as I've stated.

I cross checked my "thought experiment" in a real amp, and then in an LT SPice sim just for good measure. The sim and the reality bear me out. Why don't you try it yourself?

-Evan

Take a 9V battery and a capacitor. Ground one end of capacitor connect battery (+) to ungrounded end of capacitor. Leave battery (-) unconnected. Please explain how this can charge up the capacitor without ground return path to battery (-). What is relevant is what you've left out of your example. ...

Your latest example isn't relevant.

Maybe try a sim. You'll see.

Best regards,

Evan

Without the meter the CT is "floating in the air at undefined potential", meters internal resistance provides a current path to ground - that's why you get a reading. On the contrary -- the secondaries are not floating. The reference point is through the rectifier and bleed resistor and/or tubes th...

That was a really interesting read.

Do the same for ... I didn't know quite what you meant by this since it basically rehashes my arguments. Then I read the thread again and see that you claim there is no HV across the open standby switch on the CT. Well, heck with thought experiments, I tried it on a real amp. What I get is close to...

From what I've seen of the usual on/standby switch, it appears that the switch rating (AC-250V) is overtaxed, even if we are talking about DC rather than AC... Or have I got this all wrong and somebody out there can enlighten me as to the obviously safe and reasonable way to do a standby switch? In...

This is correct. By using a ground lift, there is no high voltage across the switch. -g I don't think that's correct. Thought experiment #1: If there's no potential across the open swich... then closing it will make no difference. Thought experiment #2: If I replace the switch with a resistor -- sa...

Cool.

Always worth doing on a small chassis.

-E.

Yes, you have it right on the headphone trick. No load is required on the PT. Obviously, be careful with those PT secondaries. Small wire nuts are handy for this. If you have multiple taps on the OT, use the 16 ohm output. On the orientation, yes, in general (there are occasional exceptions like the...

Hi Ken: Your tube layout looks okay to me. I would recommend checking your transformer layout with the "headphone trick" --- wire a socket on yout OT secondary for your phones and power up the PT primaries. I think you will find some 60 Hz hum present in the layout you have (based on my experience w...

Yeow. One seriously unusual beast.

Thanks for the confirmation.

-E.

Surely "4m7" should be 470k and "22m" should be 220k...?