[noskipallwd]

Hello, I've had the Cornet2 up and running for about 3 weeks. The other day I turned it on, began listening and one channel is very low with a kind of white noise sound. I re-flowed solder joints, switched tubes except the 2 12ax7, I have 2 on their way. Checked voltages and are all okay, I am at a loss now. Any suggestions? Thanks in advance for any help.

Cheers,
Shawn P.

[el34]

Relax and wait for your 12ax7 subs to arrive, that's a likely cause anyway.  You did try swapping your input cables between channels, right?

[noskipallwd]

Thanks el34, yeah switched cables to each channel, also tried a different pair of ICs. Instead of twiddling my thumbs i finished building my Castanet. What a fantastic sounding amp, too bad it's discontinued. Can't wait to hear it being fed by the C2

Cheers,
Shawn P.

[el34]

Yeah, I like my Cornet, and Ripper too... Good luck with the debugging

[poty]

If voltages are OK tubes are OK too or it should be very strange behaviour. Are you shure you checked all marked voltages (on plates, grids, cathodes...), not only power supply voltages?

[el34]

Another debugging trick is to get a test lead with alligator clips on both ends, ground the grid of the first, and then the second 12ax7 tube, and listen for the noise to go away, that will isolate the problem to a section of the circuit that way.  Unplug, let the voltage drain from the caps, check that with your voltmeter, install jumper, remove hands, then power up and listen.  Don't do this on the 12au7 tube, its grids are direct coupled and not at ground voltage.

[noskipallwd]

Just thought I would update, it was a bad tube. Installed the JJ 12ax7s and problem solved!

Cheers,
Shawn P.

[poty]

Then the initial voltage measurings were wrong.

[noskipallwd]

Hello poty,
It's funny but I think there is a short in the bad tube, after I subbed the 12ax7s I decided to find which tube was bad. So I put them all in different configurations and they all worked, I thought damn there is something other than a tube, but the tube showed itself shortly. When I put the amp on it's side as I do when I am measuring voltage it seems it is not shorting out. All's well that ends well though, I have the amp back. Thanks for the help.

Cheers,
Shawn P.