Butler Tubedriver with distortion in one channel

[robertleo]

My butler tubedriver 475 has very bad distortion in one channel.The other channels are fine.Switching the RCAs made no differance.It is a fairly new amp. I have it fired up and ready to troubleshoot with your help.Meter on standby.......thanks Robert

[807tubenut]

Are the tube cards removable?

try swapping them and see if the noise moves to a new channel, could be a bad tube!

[robertleo]

A bad tube does sound like a possibilty.The tube cards are souldered in,no way to change them easily.......Robert

[Perry Babin]

Have you tried moving all of the pots and switches through their entire range to see if it makes a difference in the distorted channel?

Does the channel ever play cleanly?

[robertleo]

There are no switches,there are only two gain control pots(one for each channel) and there is no change when turning them up and down.The distorsion is always present.........Robert

[Perry Babin]

Do you have a scope?

[lumanauw]

I found that tube's heater often dead in this amp. Look at the tubes from the top, see if there is orange points glowing. If not, then the heather is dead.

[robertleo]

I have a Tech 465,but I dont have many scope skills,can you tell how to hook it up and what buttons to push?All the tubes have two glowing dots on the top side.Thanks for the responces...... Robert

[Perry Babin]

What probe are you using?

Do you see a trace when the beam finder button is pressed?

Set the trigger mode to auto. Does the scope produce a trace?

If not, turn the intensity up a bit until you have a visible but not overly bright trace.

[robertleo]

Thanks perry,here is a pic. of the trace and one of the two probes.I also have BNC to RCA adapters for hooking up with RCA patch cords....Robert