Vox AC30 Breaking up Too Soon

[Masco]

I'm sure God doesn't care...

[pdf64]

Maybe I should stick a 12AY7 and two of those Russian tubes in it and see what happens

Best to keep all the output tubes reasonably matched / balanced. They're all sharing the same cathode resistor so one hot running tube will force the other 3 to run a bit colder.

If the requirement is to increase the available sound pressure level then by far the most effective way (assuming that the amp is functioning correctly) is to increase speaker efficiency; more speakers of the same efficiency or replace the speakers with a more efficient type.
Pete.

[selloutrr]

do you have the amp to work on yet?

how does it sound stock? can you hear what they hear or is it possible just a figment they have created to compensate for being uncomfortable in some other way while playing?

I get what i call Gremlins on the bench all the time. usually turns out to be a user error related to not knowing what to listen for. things like it doesn't sound the same as it does in my house. and idk during a show it's just not the same.

it comes down to a volume battle.. hello mr. guitarist .. meet mr. drummer.. and if you are lucky... smoking hot big titty girl bassist. now everybody play nicely.

[The New Steve H]

I have it, but I have not had time to do anything but remove the rear panel. I am going to pull the rectifier tube out and see if it's shorted. After that, I'll see what else I have to do.

[selloutrr]

in my experience the Rec tube shorting usually trips a fuse.

[The New Steve H]

Right, well there is a fuse blown.

[selloutrr]

I've only had 2 rec tubes short in almost 1500 amps it's rare.
Look for a leaky filter cap. It's also possible the fuse just gave up dud to a power surge.
Put a new fuse in and bring it up to voltage on a variac and watch the amperage. If the amperage goes up you have a problem shut it down and find out why.

[The New Steve H]

No Variac, unfortunately. All I have is a current limiter.

Thanks for the help.

[The New Steve H]

I'm wondering if miswired electrical outlets could cause problems. When I took my Bassman to church, the standby light worked backwards. I think I'll check their outlets.

[tubeswell]

Are 41N007 diodes a good choice for the rectifier? ... I read somewhere that they were a little small for the job, so I should use two, but then I realized that voltage was the big issue. I don't think reducing the current through each diode by paralleling them is going to have any effect on what high voltages do to them.

You want them in series to overcome higher PIV. Take a look at the BF amps where they use 3 x 1N4007 in series on each side.

[Zippy]

I'm wondering if miswired electrical outlets could cause problems. When I took my Bassman to church, the standby light worked backwards.

It sucked the light out of the room???

[kevster]

I'm wondering if miswired electrical outlets could cause problems. When I took my Bassman to church, the standby light worked backwards.

It sucked the light out of the room???

Man, that clever comment struck me as really funny.. It was clever, and I'm over tired on top of it... Wow, I'm glad I didn't shoot coffee out my nose!

[The New Steve H]

When the bass player plugged the amp in, the light came on. Then he turned it on, and the light went off. At home, it works fine.

It didn't actually suck the light out of the room, but for little while, time went backwards, so we all got home early and had breakfast all over again.

Now I have to figure out a sturdy way to put diodes in series. I don't quite see how that divides up the voltage, but I will take it on faith until Google saves me.

[tubeswell]

Now I have to figure out a sturdy way to put diodes in series. I don't quite see how that divides up the voltage, but I will take it on faith until Google saves me.

4th para on this page

http://www.freewebs.com/valvewizard/fullwave.html

[The New Steve H]

Thanks.

I still don't see how this works out to be a thousand-volt voltage divider, but then I have never understood everything about diodes. When I learned about them in college, the prof drew layers and little Ps and Ns on the board, and he told us diodes break down when you apply too much voltage in the wrong direction, but that's about all I learned. Studying up on it now.

Ordering some tougher diodes now, so I don't have to go through all that mess with the capacitors. It's not worth it to save sixty cents.