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Hey, this Fonzarelli MV loads the PI outputs down as you turn the MV down. I don't think the Fonz would find this to be cool.

1/2 of the human-perceived volume of 150 watts is 15 watts. That's why volume knobs are log taper.

My 74 (Vibro) Champ was idling at 20watts on the 6v6 when I got it. Use an excellent 6v6 after changing the cathode cap. I guess a 6L6 would not need to be as excellent to take the voltage and/or current these amps run the output at.

In the OP's example, hotter bias (compared to anything close to "normal") will result in less output power. This is from the "earlier" clipping which is often a goal. The reduction in power is minimal especially in the audible world.

OT shunt method is not accurate depending on the internal resistance your meter adds in ma mode. This can be significant in this application, even in an excellent meter.

Old wax caps like that are often leaking DC. Interesting how they added a power tranny but kept the higher filament-voltage tubes by ground-tapping the secondary. Much safer yet still lower cost with only one secondary.

Keep in mind that the bright-cap/switch on a volume pot does nothing when the pot is cranked. And very little when almost cranked.

You could try testing with some "socket savers" for continuity. However, if the male pins on the SS are larger than "normal" it won't be a valid test and could make the sockets even looser. Or just leave them in and you shall be saved! Gently tilting the tubes around a little, with the amp...

Very similar to my 920 model. I see an issue. I don't see a 9pin socket (e.g. for 12ax7 type tubes or el84 or many others.) My 9pin socket was changed when I got it and I changed it again myself due to poor contacts. Mine is from 1947 IIRC. It did not have EL84 or 6V6 on its roller but I...

I jammed with a guy who brought his brand new Bassbreaker. Mediocre tone to me but maybe they sound great.

As mentioned, we don't know if you changed only the PI or also the trem to the EC scheme. The 5E9-A trem modulates the cathode of the PI so changing (only) the PI to cathodine is likely not kosher. You would now be modulating the thing that modulates only one of the output tubes.

Set the bias to something a little cold on an existing pair you already have. Change one tube on one side and measure the milli-voltage on that side via the probe port. Assign that number to that tube and take it out. Put in another and measure and assign that # to that tube. Keep changing...

I would be concerned with WHY the secondary opened. The standard suspect would be that it was driving a shorted load.

My '71 distorted above 3 until I changed out the original speaker. Have you tried a different speaker/cab?

The problem you are referring to is with the taper of the pot. Get a new pot with a more logarithmic taper. Maybe the stock ones are linear? Larmar is cool and I like mine on homebrews and my '71SFDR but that's really a separate topic from correcting a taper issue.

The amp and the parents will be happier at 8ohms.

Considering that plugging into a single jack can also switch other things, I don't know if one can universally predict the results of doing so on one end of a loop. Most newer bass distortion effects now use a "blend" approach which is sonically analogous to a parallel loop. If you have...

Never noticed that change. The 77-78 would cause a much larger sudden draw from the rectifier when switching into "play" mode from an initial power up. Probably not a problem for a 5u4gb but I like the earlier approach. I think some amps have the standby between those 2 caps, so to speak.

I would try a cap across the 470k that goes to the wiper of the reverb control. Maybe 1000pf to start for experimenting.

Ultrasonic parasitic oscillation? I would add small caps to ground on each el34 grid as a test. ~2000pf or so.

Epiphone valve jr. It is SE and less than $100 used. Just use a good voltmeter and measure the cathode dc once warm for a while. Tubes with the same cathode dc in there should be dc matched in a PP amp. If you use a PP amp for matching, you have to leave one tube in side A, changing out the...

I removed all the Brown couplers in my '71 since the internet said I should. I kept them and years later tested them. They are all in spec and do not leak dc. I'll test them for ESR when I get such a meter one day. I'll put them back in when the internet tells me they are cool since they...

Loosing highs while rolling the volume down is a common thing and depends on the pickups, pots, bypass caps (all in the guitar) and the load the amp's input places on the guitar. Amp wattage and amps tone controls and headroom and 98% of the circuit are not related to the specific phenomenon...

I was surprised the 1st time I saw an unused pin used like that. I choose to use wire nuts in my amps instead. I use a tie strap to ensure against strain and movement. Never has one come loose.

Could there be a Duct Tape solution here?