Squeeling Vibro Champ

dlovsnurb
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« on: September 16, 2008, 04:26:44 AM »

Hey out there,
I'm new to this forum.
I built a Ceriatone Vibro Champ kit a while back. I've had some recent issues. I usually run it into a Dr. Z Airbrake and then into a 1x12 cab, so I can crank it up in my apartment. I've been really liking the clean sounds recently, so I took the attenuator out, and noticed that it squeels when I have the volume set from 0 to about 1/3 of the way up. Past that it goes away. It's actually more like a high pitch tone. I was wondering if anyone out there had ideas about what's happening and how I might fix this. This was my first build and I built it exactly to the Ceriatone layout, as well as the chassis photos on the site.

Thanks,
-Corey


« Last Edit: September 16, 2008, 04:29:49 AM by dlovsnurb »	Logged

winston_smith
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Re: Squeeling Vibro Champ

« Reply #1 on: September 16, 2008, 10:35:23 PM »

Hi Corey,

While I have no idea what exactly causes your squealing problem, could you post some voltage readings? Does you amp squeal without your instrument plugged? Could you take a few photos of your build and post them in here?

WS


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dlovsnurb
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Re: Squeeling Vibro Champ

« Reply #2 on: September 17, 2008, 04:53:40 AM »

I will post some photos soon. I'm not very experienced with taking voltage readings so I don't really know where to take readings that might be relevant. I assumed that if I built it exactly like the layout and photos on the Ceriatone site that it would work fine. Shortsighted....I know. I'm very eager to learn, as I'm currently building a JTM 50 kit, for a friend. Any tips on where to take voltage readings would be greatly appreciated.

Yes, the amp makes the high pitched tone whether I have an instrument plugged in or not.

Thank you very much for replying!
-Corey


« Last Edit: September 17, 2008, 04:57:08 AM by dlovsnurb »	Logged

winston_smith
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Re: Squeeling Vibro Champ

« Reply #3 on: September 17, 2008, 07:23:10 AM »

Hi Corey,

The photos may prove very useful. As for voltage readings, here is what you should do. First, I cannot emphasize enough the dangers of working in a tube amp that is turned on. Please take care and read the available materials on the internet. Preferably, you should use a probe with an alligator clip attached to the chassis and you should handle the other probe with only one hand. With you digital multimeter set on highest DC voltage, measure the following: the voltage from the first filter cap to ground, second filter cap to ground, third filter cap to ground, then from pin 3 of the power tube to ground (that's the plate voltage), pin 8 to ground (this is cathode voltage, which is quite low, you should set your mm to to the nearest point higher than 20VDC). Next go to the preamp tube (V1). Measure the DC from pin 1 to ground (high voltage), pin 3 to ground (very low voltage), pin 6 to ground (high voltage). Same for V2.

Please take care.

WS


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