Butler Tubedriver with distortion in one channel

[Perry Babin]

Set the trigger coupling to AC and the trigger source to normal or ch2.

Adjust the trigger level to display a locked waveform.

 

[robertleo]

Coupling set to ac,source set to normal.There are two steady fine lines with the probe touching the calibrator....Robert

 

[Perry Babin]

You should see a square wave, not two lines. If adjusting the trigger level didn't make it lock, turn the vertical amp control 2 clicks clockwise and try the trigger level again.

 

[robertleo]

Ok,I have a square wave now.

 

[Perry Babin]

Post a photo of the square wave. Your probe may need to be calibrated.

 

[robertleo]

The lines are thinner than the photo shows,the vert. lines are dimmer than the horiz.

 

[Perry Babin]

There is no photo attached.

 

[robertleo]

pic

 

[Perry Babin]

OK. Connect the probe to the distorted channel. Drive it so that the distortion is clearly visible. You may have to change the vertical amp setting. Set the timebase to 2mS. Use a test tone of 60-100HZ.

 

[robertleo]

I have a Nakamichi t-100 that I used to send a 100 hz tone into the tubedriver via RCA cables.I touched the probe on the speaker pos. and the probe ground to the neg.The first pic. is the good channel and the 2nd pic is the bad channel.....thanks Robert

 

[Perry Babin]

Connect the scope probe ground to one of the non-bridging speaker terminals. Touch the probe to the bridging terminal for the channel you're testing.

Set the vertical amp so that the signal doesn't go off of the top/bottom of the display or reduce the signal level.

 

[Dr Zeus]

Hey, I dont know much about your scope but if your signal is going off the screen like your first image of the good channel you can A - lower the gain or input signal voltage/amplitude or B - turn the Volts/Div dial to a higher number (counterclockwise).

On the second image, can you turn the Volts/Div to a lower number to try and 'widen' the signal displayed? It looks like the scope is tracking something more than just flat-line on that channel but its hard to see.

Wiggle the RCA of the bad channel.

Post images and what V/Div setting you used on the scope.

 

[807tubenut]

That looks like a bad tube, can you confirm all the filaments are lighting up?

also, whats the tube model number? might start with 12 or 6

 

[robertleo]

I made some adjustments on my scope(see pics.).The tube type is 6n9p, and the all look the same glowing.The first pic. are the three good channels.The 2nd pic. is the bad channel,probe touching the bridgeing channels...Thanks for the responses...Robert

 

[Perry Babin]

Can you post a photo of the preamp end of the board (between the tubes and the RCA jacks?

 

[robertleo]

TD. preamp

 

[Perry Babin]

There should be at least one more 4 channel (or two 2 channel) op-amp. Do you see any others (other than the two near the RCA jacks)?

 

[robertleo]

The only other ones I see are on the other end next to the power supply.....Robert

 

[Perry Babin]

Drive the same signal into the amp and check the signal on the output pins of the two op-amps near the RCA jacks. The output pins are pins 1 and 7.

 

[robertleo]

I probed the pins of both the o-amps,they both have identical readings,1 and 7 shown.