5F11 startup - power supply issue/cold 6v6

[sluckey]

Sluckey,
V2 pin 3: 1.43k
V2 pin 8: 59.4k

Do you still have zero volts on pins 3 and 8? Are the filaments lit up?

[6G3Victory]

Still no voltage..

V2 filament is not glowing. I dismissed this possibility since I was getting 6.3ish onto the filament pins.

Looking at the empty tube socket, tube pin receptical #1 looks to be damaged - it’s not got that football shaped opening that the others do. Gonna guess this may be keeping the tube from sitting properly in the socket.

I guess I’ll be replacing that socket!

[sluckey]

Can you post some hi rez gut shots of this amp?

[6G3Victory]

Here you go,

[Stevem]

If that green wire you are using for the filaments is solid core then I would ohm check it for continuity, and a dead on zero ohm reading.

Your tight winding process may have snapped it open and it’s only then making enough contact to read voltage to a meter, where as passing large current flow as it needed to power tube filaments will not take place.
BTDT!

Also some of your soldering does not look the greatest, like your iron just can’t get hot enough to flow the solder well on the tube pins with a lot of wire mass on them to heat up.
When I do this type of soldering my station is up at 700 degrees with a nice wide tip on the end to hold and transfer a lot of heat fast.

The typical 40 watt iron will not get things like this done the way they need to be!

Also are you sure you have the filament wires feeding pins 2 and 7 on those output tube sockets?

[6G3Victory]

Hello Stevem,

Points taken on the filament wire and soldering. I do believe I’m getting voltage on all the filament pins, but I had not considered that the tight winding (perhaps I will go back and redo the wire between output tubes, I was never happy with it) could be causing issues.

I agree I need to work on my soldering, and indeed I am using a 40w iron. Maybe some YouTube instructional videos and a bigger iron are in order..

Was pretty sure I’m hitting the right pins for my output tube filaments (they light up, and heat up), but I’ll check the things you mentioned. Might not be until the weekend though.

Thanks for your feedback!

[6G3Victory]

Hello again guys,

My buddy and I just finished another session, and got V2 running, after replacing the socket. We measured the appropriate 50V off the phase inverter cathode. We also measured 20v going into the phase inverter grid, but based on something we read on valve wizard, we think we should be seeing a volt or 2 higher than our cathode voltage.

On top of that, we heard faint guitar signal through the speaker only briefly, before getting nonstop high pitched oscillation.

So, happy to have V2 running, but we don’t have any ideas about our new problem. We will learning about oscillation next.

As always, any feedback appreciated!

[martin manning]

We measured the appropriate 50V off the phase inverter cathode. We also measured 20v going into the phase inverter grid, but based on something we read on valve wizard, we think we should be seeing a volt or 2 higher than our cathode voltage.

No worries. Your meter is loading the circuit and upsetting the bias point. You can measure at the bottom of the 1k5 bias resistor.

[sluckey]

There is a yellow wire that connects the speaker jack to a 56K resistor on the board. Disconnect that wire. Does the nonstop high pitched oscillation stop?

If so, swap the OT primary leads on pin 3 of the output tubes.

[6G3Victory]

Is that what that might be? I knew I might have to swap the OT wires but thought I’d be hearing more of a howly feedback. I got the wires right the first time with my 6G3 so I’ve never heard the oscillation before.

I’ll disconnect the NFL tomorrow and report back.

[6G3Victory]

Ok, so I swapped the OT leads and…
She works! Sounds great! Lively, rich cleans, an impressive amount of overdrive, I’m happy!

This has been a great experience building the amp, and troubleshooting. I can safely say I have a better idea of what goes on in an amp after getting this vibrolux operational.

Thanks again for the help, guys!

Kris

[bepone]

to cut short all the problems in startup of PP amps, always start without feedback.. after all is running and verified, then apply the feedback to see if is positive or negative. enjoy the amp !