Vintage Solid State - Strange Wave Form

[dubulup]

I have a vintage amp on my bench and will no signal I get the first image...however my DVM detects 0Vrms and 0Vdc at the output. This amp has no audible hum/hiss or anything that would suggest this type of signal on the output.

When I run a 1kHz signal through the amp, I can see it riding on this strange waveform.

The amp sounds 100% normal and seems to make great power...can't get a power read with this behavior. My scope works just fine with tube amps, and I don't have another SS amp to test against.

Transistors 2sd388a/2sb541a

Any insight is appreciated!

[Jon Snell]

Possibly your probe is not a x10 probe ... that will cause it to go unstable due to capacitive loading.
Check the Zobel network is intact.

[dubulup]

Its a 10X, however I checked on a different probe and its solid. Thanks for the knowledge!!

[Helmholtz]

What amp (schematic)?
Where did you scope?
Was the ground clip connected to amp ground?
Looks like a higher frequency oscillation on top of a 60Hz hum, but not connecting the probe's ground clip may add a lot of 60Hz ground hum to the displayed signal and the "oscillation" might be your actual 1kHz signal.

Your display settings don't make much sense.
The Siglent is a great scope, but you really need to study the manual to learn how to best customize and operate it.
Don't rely on autoset mode!