5E3 running with step up transformer, fidling with voltages.

[tweed]

I all, I hope that you are doing well.

Can you guys help me to clarify a couple issues with this tweed deluxe clone I built a couple years ago?

Have spent some time back and forth between EU and USA, because of that I installed a Mercury Magnetics to be able to use it with 220/230/240v primaries, it was perfect despite the fact that it has stock B+ 380-0-380 , a bit hot but singing very well.

A few months ago I came back to the USA, and didn't bother getting a new PT for 110V primary, instead I got a step up transformer to bring the voltages up to 220v as per my wiring.

So, I blowing up a NOS Sylvania 6V6 to later discover that the step up transformer kicks out 245V instead 220v as rated, my primary is not 110v but 126V... and B+ was above 400V with the plate dissipation on the 15w ball park :shock:

Please correct me if I am wrong, To tame this voltages I switch the primary tap from 220v to 240v and installed a "switchable" 25w 30 V Zener diode attached between chassis and B+ center tap.

As result I am having the following reading, how does it looks?

Mercury Magnetics FDTD 240M 380-0-380 and 270Ohm cathode resistor.

W5Y3GT (50's)
PIN2=388V(without zener), 359V(with zener)
PIN8=388V(without zener), 362V(with zener)

6V6GT (50's)
PIN3=378V(without zener), 347V(with zener)
PIN4=344V(without zener), 319V(with zener)
PIN8=21V(without zener), 19V(with zener)
PIN3TO8=353V(without zener), 330V(with zener)
Plate dissipation 13w/38Ma (without zener), 11w/33Ma(with zener)

Is this ok, am I getting the right 5e3 sound? Should I keep the Zener Diode?

thanks for your time reading,
ps: below is a picture, the zener is by the pt behind the wiring, is huge!

[deci belle]

Do you like the way it sounds better with the zener? Otherwise, the voltages are a bit high without it. I have that PT (120v), and I like it a lot, but my NOS 5y3 is putting out 380v and there are 370v on the 6V6s and 130+v on the AY7.

I don't do Blues, so higher voltages don't bother me; as long as your amp doesn't mind, let your ears decide whether you should keep the zener.

[tweed]

Do you like the way it sounds better with the zener? Otherwise, the voltages are a bit high without it. I have that PT (120v), and I like it a lot, but my NOS 5y3 is putting out 380v and there are 370v on the 6V6s and 130+v on the AY7.

I don't do Blues, so higher voltages don't bother me; as long as your amp doesn't mind, let your ears decide whether you should keep the zener.

Hi Deci Belle (cool nick),

It does sound good, is actually almost imperceptible without the voltmeter but the amp seems overall a bit smoother. The V-dump works very well.

Also, I took the opportunity to review my grounding scheme and simplify it a bit. There are a lot of different approaches to this matter but I decided to give use to the brass plate. So, I soldered the pre-amp cathode grounds directly to it with a very short solid wire, the power tubes cathode connected to one of the PT bolts, the filaments and B+ CT to another bolt, and everything else is self grounded to the chassis (pots, jacks, OT and a self dedicated ground point for the power cord).

Although, I think the amp wasn't noisy before, unless when cranked up. Surprisingly, I later found that separating the cathodes grounds actually improved the hum reduction.

Here is a few pics of my amp, I built it in 2009 and it came out really nice after some normal troubleshooting, it was my first build and I absolutely love it.

[deci belle]

Nice job— even with that fat wire going to the tube sockets, mate!! Old tubes too, yum!!