Chasing noise..

[playonit]

Looking for a good reference to chase down some noise in my DC30 clone..

Channel 1 is dead quiet.. but, channel 2 (EF86) has a persistent hum.. Don't know if the channel should be quiet or not, first of all. One interesting thing is when I turn the cut knob the hum gets louder?? I am not real versed on trouble shooting and was looking for any good references that would tell me to start...

I used the ceriatone Layout to build from....

Thanks

[selloutrr]

have to confirmed continuity to ground. Try metering the ohm load to ground and see if any meter higher and resolder them. You may have a cold solder joint. Tighten bolts and nuts to assume a snug ground.

if no luck.

try a new tube in second stage.

Ground Loop?

[M Fowler]

playonit

I inherited one of these amp kits recently havent got it all together yet.

Does it make a difference with the noise if the MV is switched off? Wondering about the wiring of the cut control and MV.

[ChrisM]

playonit

I inherited one of these amp kits recently havent got it all together yet.

Does it make a difference with the noise if the MV is switched off? Wondering about the wiring of the cut control and MV.

Cut and MV are common to both channels so if one channel is fine...

[Structo]

Not familiar with that amp but from what I've read, EF86 are very hit and miss unless you are running NOS tubes.

Very prone to noise and other anomalies.

Make sure lead dress around the tube is perfect and keep leads short and on point.

Pins 2 & 7 are the interior shield and must be grounded very close to the socket, like the socket screw.

[playonit]

playonit

I inherited one of these amp kits recently havent got it all together yet.

Does it make a difference with the noise if the MV is switched off? Wondering about the wiring of the cut control and MV.

Master volume is fine when on and does not add to the noise like using the cut does.. Master volume used with channel 1 is dead quiet.. I poked around with a chopstick and nothing changed the hum.... I do wonder if the ef86 is suspect. Don't know much about the tube.. It's a Mazda Belvue made in Holland?? The amp even with hum sounds great in channel 2 played through a 2/12 cab with Celestion blue and a G12H30 it's just annoying...

[Andy Le Blanc]

Pentodes are high gain and high impedance, there are some recommended
ways to reduce hum interference right on the data sheets for ef86.
Take a good look at how the socket is dressed and compare to the sheet
for the tube type. You can tweak the bias point (Rk), and the screen grid (Rg2),
You can also reference the screen grid bypass cap (Cg2) to the cathode,
instead of ground.

You'll have to get a small hand full, to swap around to find the quietest tube otherwise.

[Andy Le Blanc]

Pins 2 and 7 are internal shields, and there's a few recommendations
in the last few pages of this pdf.