voltage readings

[djroge1]

A friend has the first 2 stroke I built and he lives on the other side of the country. I decided that I want to build another one but I’m not getting any sound.

In the process of trouble shooting I took voltage readings for the power tube grid and plates. They both read around 50v higher than what Dave says in the book.

The 12ax7 is spot on for voltage.

Any one else have that happen? What readings are you getting? Also, at the first filter cap (40uF) I have around 393volts. Does that sound right?

[Andy]

I have some notes from a build that seem to indicate that I was up to around 395V on the 40uF. I will have to measure to see if I corrected that or if my notes are from troubleshooting a problem.

I can take some measurements perhaps on Monday am or later tomorrow afternoon for the power supply.

Can you trace the input signal at all, or insert a sine wave?

[M Fowler]

Not sure what is going on with the amp but remember the voltage in the US and EU are higher and some places way over 120v.

My house is 118 to 119.8v but many people say they have 125v. This will raise your HV to the plates so you have to drop voltage with a zener diode for HT to plates and larger value dropping resistors to get the preamp voltage lower.

But 395v to plates of a 6V6 sounds good.

Mark

[Andy]

My Power Supply voltages are:

393 at the 40uF
359 at the 16uF
250 at the 8uF

So it looks like you are in range. Are you able to trace an AC signal?

[Robin]

Different rectifier tubes can produce a 40-50v change in the power section. You stated you are not getting any sound, is there at least a slight hum or hiss from the circuit/transformers, or is there no noise at all from the speaker? Forgive me for mentioning the obvious, but double checking the speaker and OT connections is a good place to start (at least, for me), if there is no noise at all. If you are using the original build instructions, be sure that your not sending the input signal to ground at V1. That has been an issue for some.

[Andy]

Hey all,

Added a new topic and moved this thread over there about the pop supression as it is a pretty common topic and it will be good to have it isolated.

[djroge1]

It’s ALIVE! The voltage readings are still a wee bit on the high side and I am using a NOS International Electronics Co (IEC) 5Y3.

[Author]

Posts