Fender Bassman 5F6A Repair

[misterc57]

You put a 5ar4 out of a HP test equipment in there (expensive tube) , most likely a Mullard. I would be using a Sovtek or JJ until you have figured out there is no excessive current draw. How many watts draw at idle?

Only other 5AR4 I could find. I always bring up slow on the variac. The entire amp is drawing around 0.6 A at idle. I will be ordering a JJ replacement.

[mozz]

72 watts I figure is about normal for a 50w amp. Others will correct me if I'm wrong. Using a variac is not going to show a sudden surge which may pop the fuse or make the tube arc. I'd still be checking the output tubes and their bias, and filter caps for leakage. Are you running 5881s?

[misterc57]

72 watts I figure is about normal for a 50w amp. Others will correct me if I'm wrong. Using a variac is not going to show a sudden surge which may pop the fuse or make the tube arc. I'd still be checking the output tubes and their bias, and filter caps for leakage. Are you running 5881s?

Yes 5881

I will report tube bias when I get the new 5AR4. Just ordered.

Thank you

[Helmholtz]

When you multiply mains current and voltage you get apparent (VA) power which is always larger than real (W) power.
The difference is due to the phase shift between voltage and current with a partly inductive load like a transformer.

E.g., my Vibrolux Rev. measures:

- Standby: 67VA/49W
- Idle: 110VA/95W
- Full 35W power: 165VA/147W

[mozz]

Yes, but much easier to compare amperage draw with other users. 72W does not seem excessive.

[Helmholtz]

Yes, but much easier to compare amperage draw with other users. .

Sure, but not with different mains voltage (230V here).
That's why I posted the VA numbers.
For current anybody can divide by his actual voltage.

72W does not seem excessive.

Should be obvious from my measurements.

[misterc57]

New GZ34 installed.

Total amp current on my meter about 0.63A

Seeing 37mA current at the 5881 tube with 449 VDC at the plate.

Still seeing noise at V2 when tapping the new tube or any of the pin wires at the socket, but not at the board components.

[The Dude]

Don't recall earlier posts, but have you tried cleaning the V2 socket pins. It sounds like maybe socket connection problems.

[misterc57]

Don't recall earlier posts, but have you tried cleaning the V2 socket pins. It sounds like maybe socket connection problems.

I did. And time ran out on this one. Owner needs it as it now sits...

Thank you everyone!

[Chuck H]

FWIW restensioning hasn't been mentioned. And newer tube sockets (as in less than a decade old if that correlates?) don't have the same resiliance to the spring tension needed for good contact and retensioning as the older sockets did. Nothing is like it used to be. Contact cleaners and retensioning and cleaning. Less than ideal alloys used on contacts is the new world for tube amps. It will get worse too. I'm hopeful a basic understanding of some fundamental rules will carry us. But hopeful is not the same as optimistic. Digital will overtake analog and there will be few sages to help any afficianodos that appreciate the real thing. I belive this forum is going to be the last bastion of tube amp service. And I'm sad for all true belivers involved.

[misterc57]

I sprayed, retentioned, reflowed, retubed (all the words spell checker does not like).

And yes I love this forum!!!

Thank you all.