Tremolo not working AC 10 build

[fagus_sylvatica]

Dear all,

I finished my ac 10 build, but I can't get rid of that tremolo not working. Everything is fine on both channels excepted the tremolo not working no matters the trem switch position and speed / intensity pots positions. I have checked the circuit several time without finding an error. I have attached the schematic with some tension I measured, and a picture of the amp as a bonus.

Thank you for any idea !

RG

[tubeswell]

Check your wiring over again. Especially the socket pins for the trem stage.

[shooter]

After Tubeswell's suggestion, does the 150vdc you measured wiggle a lot?

[PRR]

You have the right DC voltages on the trem oscillator.

I'll assume the "150V" is rock-steady, not wobbly (as it should be). That "foot switch" is installed or jumpered.

To oscillate, the C18 C19 C20 string and associated resistors must be right value, wired right.

Given reasonable DC and right C-R-C-R-C-R network, the tube has no good excuse for not wobbling. Unless it is very sick, but it is unlikely to hit nominal DC values if it isn't healthy.

[fagus_sylvatica]

Dear All,

Thank you for helping !

After investigation I found :

• R40 to be 185k instead of 220k (-16 %)
• R 24, R26 and R43  being approx 250 k instead of 330 k (-25%) ; they came from same batch, so maybe an error from retailer ...

Do you see it as a plausible source of non oscillation ?

All best,

Romain

[tubeswell]

Check the C/R divider filter values in the LFO stage. (C17/R31+R32, C19/R35, C20/R38)

[fagus_sylvatica]

Hi,

The values you asked all lie within a 10% interval 

Cheers,

Romain

[tubeswell]

Are you positively sure? I can't confirm that from the picture you posted. I can't see the cap values - there is not enough resolution in the picture.


(0.01uF = 10nF, and is usually marked as '103'. Similarly, 0.0047uF = 4.7nF, marked as '472')

[fagus_sylvatica]

Hi,

Yes unfortunately checked it 5 times, that's well .01uF Mallory 150M

I'll try to change the 330 k to new ones closer to the right value. And if it doesn't work, I will do without tremolo 

Cheers,

Romain