• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Douk EL34 Amp kit

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Avo111

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Joined 2015
here is how it looks inside
 

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M Gregg

M Gregg

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Joined 2010
Avo111 said:
both dead at the moment, imbalance was what prompted valve change
Click to expand...

Measure with DC volts one side of the meter to ground what voltage do you have on pins 3 and 4 of the EL34's show left and right side measurements.
I know your probably tempted to wiz off and try lots of other things but please be slow and meticulous..:)

Regards
M. Gregg
 
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M Gregg

M Gregg

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Joined 2010
Avo111 said:
left pin 3 423 vdc
right pin 3 426

left pin 4 359vdc
rightpin 4 358 vdc
Click to expand...

Now here is the interesting bit..look at pin 4 measurements!
Looking at the drawing pin 4 should be 225V..

So the input tubes might not be conducting..

What voltage do you have on pin 2 and 5 of the input tube?
Shown as 120V on the diagram

Regards
M. Gregg
 
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A

Avo111

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Joined 2015
No signal through either side left was humming and crackling but isn't since EL34s swapped.

originally both sides worked with one very low, swapping input valves swapped low channel. it stopped working altogether when i changed to 5h9c and still didn't work when 6n9p were put back
 
M Gregg

M Gregg

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Joined 2010
OK change of idea,

Do you have some cheap speakers you can attach to the amp?

Put one lead in the meter and touch the probe on the pin 5 of each EL34 do you get a pop buzz or anything out of the speakers on each side?

It could be that you "may" have a faulty input tube and a faulty output tube very strange but possible..

We need to get an EL34 that buzzes when you touch the pin 5. Keep that one in and put the other out of reach for a moment.
Then check both input valves with the working EL34.

Regards
M. Gregg
 
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M Gregg

M Gregg

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Joined 2010
Just a quick check while I think about it,

You do have the wire from Pin4 EL34 to the 10K on the PSU?

A quick safety mod put a 2Watt 470K 500V resistor across (same positon in circuit) the 330uF to discharge. (solder in permanent) keep it away from the cap and anything else it will get warm!
Do the tests in post 54#..

I must admit its a bit daft there seems to be a lot of variables so if you do the tests in post 54# and at least we will know if the EL34's and output circuit are any good :D

Regards
M. Gregg
 
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