5e3 Neil Young sound - destroying tubes? Which output transformer

if i remember correctly, NY's 5E3 was converted by his tech to run 6L6 tubes, and I believe the PT was swapped out for a more powerful one as well. runs at 18W instead of the standard 15

you could try installing some screen resistors on your power tube sockets, they could help prolong your tube life. the original 5E3s didn't have them so they are rarely present on most of the 5E3 kits out there, but as far as i understand it they became a fairly standard industry practice towards the end of the 50s. i have 3W 470R resistors between pins 1 + 4 on V3 and V4 of my 5E3 and have had no issues with power tube failure thus far despite constantly playing with a very similar tone to yours

 

Good idea. On the voltage question, what’s your bias in percent dissipation, and what measured resistance do you get on that 250R cathode resistor? And what’s your heater voltage pin-to-pin?

 

Neil Young's longtime Excellent amp/ gtr tech Larry Cragg,

Look him, and if he has a website or whatever you may be able to contact him.

I just found this on his venerable Fender tweed from Guitar Player magazine in the 90s interview with Larry.
Larry's always been free to do lots of very good interviews thru the years so you should be able to find the info just on interviews alone and features:


"I have fans pumping a lot of air into the back of the Deluxe, since we rebiased the amp to use 6L6s."

.

 

I read somewhere he prefers cheap Chinese tubes...have no idea if that's true or not.

 

I really wonder if that isn't just a mechanical failure of the tube and nothing to do with being overdriven. Old tubes sometimes lose vacuum, turn white and break all on their own in a stock situation. That one didn't seem to turn white or lose vacuum, but.... hmmm...

I would be tempted to be very careful about using old Output Tubes if you want to protect your OT. They can test and seem fine but fail and take it out. A set of NOS RCA 6V6's took out the original OT in my 65 BFDR shortly after installing and biasing them. A big flash and a destroyed OT.
I went to JJ's in all my 6V6 amps and never looked back.

 

Sorry, didn't mean to make this confusing. You're right to use Rob's calculator, and your calculations are OK. TLDR: if we choose to think of the 6V6 as a 12W tube (you want to be conservative to save your tubes), and if I read your voltages right, then your plate-to-cathode voltage on your hotter tube is 328–17 = 311V, and if your resistor is actually 342ohms, you're right in thinking your tube is dissipating nicely less than 100% (which is plenty safe for cathode bias) -- I get 86% at worst.

So you're not burning up your tubes by excessively hot plate voltage or bias (lots of 5E3s run up to 110–115% very safely -- they're self-biasing).

Which brings us to the heater voltage. Any voltage above 6.3VAC is putting unneeded strain on tubes -- the heater is basically a light bulb filament, and running it over spec will burn it out sooner. To measure pin to pin, you set your MM to VAC and put the red probe on one heater lug, the black probe on the other. This is often done on the lamp, where access may be easier than on tube sockets.

 

rob robinette on this topic in another thread:

"I feel that 5W is preferred but a 2 watt 470 ohm in a 6V6 amp is good enough. With your choices I'd go with the 470 ohm 2 watt grids."

http://www.tdpri.com/threads/robrob-5e3-screen-resistor-value-rating-question.741115/

sounds like 2W might work if you've got them! i'd check rob's site for a diagram on how to wire them up properly, can hunt down the diagram i used if you need

 

How many hours were on the Visseaux 6v6's? Do you run the amp wide open fairly often? Using a loadbox or attenuator to run the amp wide open will increase the wear on the power tubes and it's not uncommon to have a failure while doing so. Adding screen resistors will offer a bit of extra protection to the tubes. Lower wattage resistors (2 watt) serve double duty and act as a fuse if the screen pulls to much current. Higher wattage resistors (5 watt) will hold up to a bit more abuse before burning out. This is nice if your in the middle of a gig and don't want your amp to go down because of a blown resistor. If protecting your vintage transformers is top priority, the lower wattage resistor will fail sooner in the event of another tube failure.

 

Cool. I love it when we can save the 'jacket' on the old caps, and those look super nicely done.

I don’t really think you have a voltage problem, so I’m not trying to push this. Just trying to answer your concern if your amp was hard on tubes in some way. Of course you have single-strand heaters, I didn’t think of that. In that case you can measure heater VAC from the heater lug across the tube to its ground lug, or from the lamp lug to the chassis. Amp on, tubes in, it should be more than 'nothing', maybe around 6-7 VAC, or your tubes wouldn’t heat up.

 

I was gonna mention above that your plate to cathode voltage looked a bit low for a Deluxe. I was thinking that it may be normal for the older, 5D3 transformer but your posted heater voltage also seems a bit low. Are you plugged straight into the wall or are you using a variac to lower the voltage? Either way, I doubt that it has anything to do with the tube going bad.

 

I am no amp or tube guru but I've been able to get a good Neil Young tone with my PRRI and a 5F6 pedal. I previously had a Lovepedal High Powered Twin but the 5F6 did just as well. Also my Tone King Gremlin "lead" input has that Tweed sound it gets crunchy really quick.

 

Good for you. Probably not too low for the heaters; if you allow +/- 10% (but take away the +), -10% gets down to 5.67. But the questions about wall voltage from @dan40 are smart. Is Berlin 240V mains?

All in all, I think you’re right, your amp's voltages are probably not killing your tubes.