Valve Itch phono

[merlin el mago]

Looks like a bad cap somewhere

Electrolytic?

 

[stajo]

Probably

 

[merlin el mago]

Only litycs in the PSU, I will check tomorrow, thanks stajo.

 

[Salas]

Its like -10mV then stays a little around zero then goes -10mV dances again then up to +10mV in the video, its not steady DC and it is not much DC. So the amp's detector won't react to perceived danger even if it is the same with 100k across the output after probing in the same way.

 

[Salas]

Is it on the output too or only on the rail?

 

[merlin el mago]

Rail, I didn't measured the outputs.

 

[Salas]

It can very well be the JFET thermal drift then

 

[merlin el mago]

SSHV2?

 

[merlin el mago]

Salas can't attach mp3 files I recorded using the headphones.

 

[stajo]

The dancing doesnt seem to be the problem to me, it should move at least some. The HF must be oscillating and that can be a cap or something feedbacing on the rails

 

[Salas]

SSHV2?

You use SSHV2 I think. Has some JFET thermal drift, the Vref cap is only 10uF to filter it. +/-10mV on 300V does not seem weird to find if it is that.

 

[Salas]

The dancing doesnt seem to be the problem to me, it should move at least some. The HF must be oscillating and that can be a cap or something feedbacing on the rails

If there is some excess hiss that would be a problem indeed, not some mV rail dancing

 

[Salas]

But Merlin did not say he saw some rail oscillation in the uS sweep range yet

 

[merlin el mago]

You use SSHV2 I think. Has some JFET thermal drift, the Vref cap is only 10uF to filter it. +/-10mV on 300V does not seem weird to find if it is that.

There is a way to check it?

 

[Salas]

Confirm with the DCV meter what you see on the scope I guess. Use min-max mode.

 

[merlin el mago]

The video dancing scope set to max time base.

 

[stajo]

I take it the scope is on AC coupling?

 

[merlin el mago]

Confirm with the DCV meter what you see on the scope I guess. Use min-max mode.

Ok I will set to AC and I'll measure the rail.

 

[Salas]

The video dancing scope set to max time base.

Max turning the time knob to the left or to the right?

 

[merlin el mago]

To the right.