WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
Dear friends I have three VT4B Westinghouse tubes but two of those have yellow spot (something like paint) on top.Please tell me if you know what this mean and his value.Thank you and best regards