Faulty EL84

[johnmarshmanagain]

Hi All,
While I wait for a substitute from Italy, this EL84 has me puzzled : the anode's on 300v, g2 on 255V, cathode at 6v (so it must be passing current), and g1 hovering around 0v, and yet no output when signal is then applied to g1 ! Is this a known failure mode for this valve ?
Thanks jm

[Techman]

Capacitor short circuit across the output transformer?

[Nuvistor]

Originally Posted by Techman

Capacitor short circuit across the output transformer?

Plus open circuit speaker or a fault in that part of the set.

[Techman]

Yes, that's right. Also, I should have made it clear that it was the transformer primary I was referring to regarding the shorted (tone correction) capacitor - a common fault, as is the above mentioned o/c speaker, or connection to it.

[Cruisin Marine]

Apart from the other suggestions, make sure with small probes you actually measure the voltages on the actual valve base pins, I have had B9A sockets go open circuit between valve and base before, or lose springiness.

[johnmarshmanagain]

Hi All. thankyou for those ideas. The cap' across the primary was cut out, and there is a faint hum in the speaker. I will try that last suggestion as to the valve base ofcourse. The hunt continues.....

[murphyv310]

Open circuit G1 on the valve or zero signal getting to the G1 pin on the valve.

[peterpiper]

Hi, remember that some EL84s have pins 1 and 2 internally connected. This caused me grief on some older Ferguson radios where pin 1 was used as a handy tag for other uses. Fine sets these Fergusons, sometimes! Peter