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

 

[Perry Babin]

Push the Ch2 button in. All others in that column should be out.

The trig. view should be out.

Center the trace.

Set the ch2 vertical amp to 5v/div (one click clockwise).

Set the probe to 10x.

Clip the probe connected to the ch2 input to the calibration bar on the front of the scope.

Set the red knob in the middle of the ch2 vertical amp control to the fully clockwise position.

Adjust the trigger level until you get a locked waveform displayed.

Post a photo of this setup.

 

[robertleo]

465 display

 

[Perry Babin]

You need to clip the tip of the probe to that point.

Set the coupling switch (under the vertical amp control) to DC.

 

[robertleo]

The tip is now clipped to the calabration bar and the slide switch is set to dc.Thanks Robert

 

[Perry Babin]

Photo?

I want to confirm that the scope is working properly before we begin troubleshooting.

Do you have a test tone CD or a sine wave generator?

 

[robertleo]

I may have a CD that has test tones.But I cant find it,will have to search.My laptop is the only cd player I have.....Robert

 

[Perry Babin]

Photo?

 

[robertleo]

465 photo

 

[Perry Babin]

If that alligator clip is connected to the probe, it's shorting the cal signal to ground. Only connect the tip of the probe.

That's 50v/div. You don't have probes with the pin that tells the scope that you have 10x probes. You'll use the other scale.

If you're going to use the lighted scale, set it to 0.5v/div.

 

[robertleo]

Volt/div set to .5,probe set to x1.