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RE: Blown 6CA4?

Posted by 6bq5 (A) on January 18, 2024 at 12:47:32

In Reply to: Blown 6CA4? posted by Ozzie on January 18, 2024 at 11:02:31:

Ozzie,
You describe: " It just blew the AC input fuse. I put in a 3 amp fuse as I could not immediately source a 2 amp fuse. Poof! Blue flame, open fuse."

2X input fuse blew, I would look at P/S Caps to make sure that there is no short to Ground-

However you then say: "I got creative and disconnected the umbilical from the power supply to the pre amp itself. I'm not sure if this is valid as the power supply may require a load for the PS to come up. Poof! The new fuse blew. Same blue puff in the tube." - Did the 6CA4 have a blue spark earlier?
Per the data sheet on the 6CA4 it is fairly robust, and having a reverse voltage could definitely cause the blue flash-

The issue is that there is a short somewhere-
Yes, the tube could be bad (how many hours on it?, how is the getter flash?, still opaque?
I am not sure that the rectifier is the issue- I am more concerned that there is a bad input cap / filter cap that is dooming the system.

You should be able to power the Power supply w/o the PreAmp connected - and you might think about bringing it up on a variac to check voltages -
But based on what you have said so far - my money is on a bad Electrolytic cap.
Yes, there could be a basd resistor or other component, but...

Tube data at Linky
Happy Listening

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