Vibrolux AA964 : serious lack of power

[Strat76]

Hi everybody,
I built a Vibrolux close to the original AA964, except that I added a hum balance pot.
Everything works well : vibrato is ok, reverb ok, no spectacular hum or hiss, the tone is good (although a bit too scooped in the mids and thin for me) and all the voltages sound good to me. All could be perfect in this perfect world...

But this amp is very weak.

I mean, when I crank the volume on ten, it is not louder than my 5e3. I even think that my 5e3 is louder.

I changed all the tubes several times of course, checked the bias, re soldered all the connections, and even changed the OT. FYI this OT is a Magnetic Components and I use the 8 ohms tap. The Speaker is Celestion Gold 12" 8 Ohms. I checked, re checked, thank about it since one week, and I need new tracks to explore. My brain is smoking ...

I have all the voltages so if somebody ask me I can give it asap.

Just FYI : Vplate : 424 V et IK : 42 and 51 ma. Bias Point : -46,62 V


Some ideas ?

Thanks in advance

[MWJB]

Plate dissipation is on the high side, there is a mismatch but not enough to neuter your amp.

How is the volume at 7 or 8? I ask because some pots turn down again near the end of their sweep.

Go on then, give us those voltages...plus pics of the circuit board, pots & tube sockets.

[Amp Kat]

Put one tube in at a time and see if it each individual tube is making sound. It will work with one tube. You can also do tube current and voltage to see how much power it is outputing individually

[Strat76]

Plate dissipation is on the high side, there is a mismatch but not enough to neuter your amp.

How is the volume at 7 or 8? I ask because some pots turn down again near the end of their sweep.

Go on then, give us those voltages...plus pics of the circuit board, pots & tube sockets.

The pots are from PEC. At 7 or 8 it is no so bad. But like my Princeton at 7 or 8.

Here are the voltages :

V1
1: 185V
3: 1,34V
6: 189V
8: 1,31V

V2
1: 182
3: 1,41
6: 196
8: 1,31

V4
6: 187
8: 1,43

PI
1: 187
3-8: 72
6: 184

B+ : 421
D : 280

Pics are following

[Strat76]

Put one tube in at a time and see if it each individual tube is making sound. It will work with one tube. You can also do tube current and voltage to see how much power it is outputing individually

Thanks for the info. But I did that before. I saw this way that I used one weak tube. I changed it of course.

[Strat76]

[Strat76]

[Strat76]

[Jazz P Bass]

Can you measure the Vac speaker voltage with the amp cranked?
With that tidbit of info you can see what wattage the amp is producing.
V squared divided by the speaker R = Wattage.

[Strat76]

Just a quick note : don't take care about the input jack wiring. It changed. Because I realized than the layout I used was for a different type of jacks than mine (switchcraft).

[Strat76]

Can you measure the Vac speaker voltage with the amp cranked?
With that tidbit of info you can see what wattage the amp is producing.
V squared divided by the speaker R = Wattage.

Well of course, I can try ... with no input ?

[Strat76]

Can you measure the Vac speaker voltage with the amp cranked?
With that tidbit of info you can see what wattage the amp is producing.
V squared divided by the speaker R = Wattage.

Well, with a shy low E played on the guitar : 1,4V ....

[Strat76]

I forgot to say : filament voltage 6,10 VAC

[MWJB]

Idle screen 6L6 plate voltages?

How did you change the wiring from the inputs? Your wires from the volume pots are very long, these & the wires from the input jacks should be shielded.

[MWJB]

Rebias the hottest power tube to ~35mA, pull V2, V3, V4, V5. What happens to the heater voltage? What happens to overall volume through the normal channel & AC voltage at speaker jack with vol, treb, bass set to 5.5?