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Gentlemen -
I have on my bench a PCB version of a Vox AC30 with a blown fuse (500mA) between rectifier and choke. The grid (series) resistors on two of the EL84s are cooked, but read 1K instead of the expected 1k5.
I get solid connections from the cut circuit to the respective grid resistors.
Solid Cathode connections the bias circuit, which reads 50R0 to GND.
Good screen connections, good plate connections.
No unexpectedly low ohmic readings to GND from anywhere in the power amp.
The only oddness I find with power off and a DVM (20M scale, tubes in place) is about 2M across each PI coupling cap - but they read the same.
Apart from a suddenly bad tube, what could cook that Rg like that? There's a charred ring around both middles.
I have to source a fuse - looks like 4x20mm glass - but want to keep the new tubes and replacement components safe.
Thanks!
I have on my bench a PCB version of a Vox AC30 with a blown fuse (500mA) between rectifier and choke. The grid (series) resistors on two of the EL84s are cooked, but read 1K instead of the expected 1k5.
I get solid connections from the cut circuit to the respective grid resistors.
Solid Cathode connections the bias circuit, which reads 50R0 to GND.
Good screen connections, good plate connections.
No unexpectedly low ohmic readings to GND from anywhere in the power amp.
The only oddness I find with power off and a DVM (20M scale, tubes in place) is about 2M across each PI coupling cap - but they read the same.
Apart from a suddenly bad tube, what could cook that Rg like that? There's a charred ring around both middles.
I have to source a fuse - looks like 4x20mm glass - but want to keep the new tubes and replacement components safe.
Thanks!