Tube Amp Archive

Ahh, yes

Do you think it's possible that's caused by one of the 22uF Filter caps?

I had a problem before that with one of the 70uF, it was completely closed (as a wire) after to put a failing 12AT7 in V3

Ok, I will check it.

What do you mean by (term off) ?

Ok, I will open the amp and check the voltage at this place.

Do you think is probably caused by one of the three ceramic disc ?

Yes I already replaced the V5, I will try a spare tube in V4.

Hi Guys,

The vibrato of my Vibroverb take a long time to be active (30 -40 seconds) sometimes more ,when the amp is cold (first start of the day). After that it works properly.

Does anyone have an idea?

Thanks.
Marc

Hi Guy,
Does anyone have a good grounding schematic of Plexi 18w?

I just finish this amp for the first time, but there's a hum on the vibrato channel, the normal channel is ok.

Thanks.
Marc

Ok Guys, the problem is resolved!

I changed the two main 100uF caps of the Filter board and the amp work perfectly.

Thanks for all!

Marc

The ground of the filter caps is ok. I will replace the two 100uF and see what's happen.

This is the pics, I don't know if you can see it. [img:2048:1536]http://nsm08.casimages.com/img/2013/09/08//13090810323113106011535110.jpg[/img] [img:2048:1536]http://nsm08.casimages.com/img/2013/09/08//13090810332013106011535115.jpg[/img] The wiring is exactly like this: http://www.tubeampdoctor.co...

Yes I'm sure about the OT phase.

Do you know how I can check the Filter caps without a scope?

Today i checked the wiring and trace it on the layout, i can say that' s ok. Now I suspect a bad Filter cap, I really don't see anything else. Thus, I re-explain the problem, the amp work and the Voltage and current value of the 6L6GC is ok without the choke (wire instead). But with the choke in pla...

Yes I talking about the filter caps, ok I don't do that But i don't have another set for the moment.

I'm sure about the phasing OT, because i was working like this before.

For the lift you talking about the 470R resistor on the socket?

I have no scope.
What can cause the ultrasonic oscillation ?

Do you think it's a good idea if I disconnect the ground wires of the filter caps board? I want to be sure the filter caps isn't the problem.

I will retrace the layout with multimeter.
Thanks for your help

Marc

Yes, out of circuit it's around 100R and it's the value noted by Mercury.

Both lead and chassis is infinite resistance.