Help in analysis of oscillogram

[Tonewood]

I'm learning to use my scope for debugging and hoping to find a book or site that shows what causes different looking distortions. Any suggestions?

My current specific problem looks like this:

About 800Hz. Starts deforming at 1 Volt pp in and 40 Vpp out. The slope of the deformation increases as freq. goes down. If I'm using Merlin's Load Line Plotter correctly, it looks like I should be able to get 2 Vpp in?? This is a Kalamazoo amp. The input sine wave is measured at V1A pin 2 to ground and the output is at pin 1 to ground. I have made some ckt changes and my anode voltages for V1B & V1A are about 145 & 150 not 183 & 210, and my R3=1.8k, R13 =2.2k & the trem ckt is lifted out, however the problem existed before my changes.
kalamazoo_m2s.pdf
As I'm writing this, I am realizing that I should have tried a new C3. The PS caps have all been changed.
Any ideas would be great.

Thanks

[nashvillebill]

You might try this thread http://music-electronics-forum.com/t23258/ and see if there is a book there called Oscilloscope Techniques by Alfred Haas.

Then look at the oscillogram on page 92, figure 528.

[Dave H]

The signal at pin 1 of V1a will be clipped at ~15V peak in the positive direction by the grid of the 6BQ5 (V2). The slope is caused by AC coupling to the 6BQ5 grid through C3.

Dave H.

[Tonewood]

Bill-Thanks for the great book tip, that's what I was looking for.
Dave-You were correct that's exactly what happened.
Thanks again!