Red Plate Special

[@jimsalman7257]

Lyle, the world is a better place because of guys like you and Brad.

[@Mark70609]

Who is Brad?

[@alecalfaras5936]

The Guitologist

[@MichaelSmith-rn1qw]

I recently had a pair of red plating 6L6GC's in my 1968 Fender Bassman after re-building the bias supply. Yep, I had the diode installed in the wrong direction. I should have looked at one of my other amps to be sure, or even a video online, but I caught the problem within about 90 seconds when measuring voltages and saved the tubes.

[@jimsalman7257]

That might have damaged the bias filter cap, unless it was installed backwards also. You might want to measure it.

[@MichaelSmith-rn1qw]

@@jimsalman7257 My multimeter can only measure caps up to 20uF. After installing a bias trim pot in addition to the bias balance pot, my bias voltage is stable and in the correct range. I have the 6L6GC's biased to around 62% idle plate dissipation.

[@glenturrell4485]

Big thanks from South Africa for another great clip. I'm really grateful for the wisdom and experience that you so readily share.

[@maxvockner]

The valiant tale of a small but mighty Vishay to defend the king Princeton against the coked up Tubes!

[@PsionicAudio]

Well, it was the Victoria saved by the valiant Vishay but your point is vicariously valid.

[@CellZealot]

@@PsionicAudio One can never vitiate the value of a Vishay...

[@rhs1856]

Not Coke nor Pepsi - RC! 😉 Thanks for serving up the specials

[@ourlifeinwyoming4654]

I've had two, new-production tubes fail lately. Wonder if the current supply of newer production tubes are lesser quality.

[@JoshRoberts-fo5gq]

Just a service call for lyle....nice man

[@jnh73]

"It wasn't Pepsi" 😆

[@paulwatson8809]

Coke...the bane of many a musician.

[@rectangularcuboid]

Especially when spilled.

[@Laz_RS]

I have a Matchless 30/15 which tubes red plate depending on the brand of tube installed. I suspect it's biased really hot, as it also works as a space heater. I've stopped using it outside the studio.

[@ItchyBrother]

Hey, I've been chasing the red-plate tube issue too! Two different sets of, guess who, APEX matched pairs. Both sets were 6v6 Tung-Sol labeled (whatever they really are). I think these came from Antique Electronics Supply. I remember you mentioning APEX matched tubes were a problem, or was it the vendor that you purchased the matched pairs from that you feel is the problem? I've bought a lot of stuff from Antique Electronics.

[@jesseyasaitis9036]

The screen grid resistor now has its place in Valhalla.

[@richclayton5785]

It’s my understanding that slightly mismatched output tubes actually improve 2nd order harmonics. No?

[@jeffcotton2235]

Lyle, do you own a tube tester? Just curious.

[@Mark70609]

Good question, and what brands and models of valve tester does he like. I have an emission tester and I don’t have a lot of faith in it.

[@fugamantew]

I built one of the StewMac Deluxes kits and I haven’t been able to use it yet because I had mistakenly installed an 820ohms (instead of the corrext 820k) at the coupling stage of the output phase inverter and something popped, smelled, tube red-plated and then the fuse went out. Fixes the error and still got the red plate; the grids of the 6v6 are reading 30volts in one and -30volts in the other-could it be that I have leakage in one of the caps?

[@PsionicAudio]

Power it on without output tubes and measure the grids again. If you have a leaking cap you’ll measure it without tubes. If the grids are off (both should be the same amount negative) only with tubes installed you have a bad tube.

[@sassycat]

I saw "red plate special" and my first thought was 'Fender Bassbreaker'? 😅

[@nonemlinus]

Lyle sometimes I feel like I’m watching a Southern-American version of a Hercule Poirot show. (My wife grew up outside of the states and turned me onto the series…entertaining, and highly recommended…you might not learn about amps though.)

[@PsionicAudio]

Ze leetel grey cells, n’est pas?

[@nonemlinus]

@@PsionicAudio Use’em or lose’em! (Or keep trying and they may grow back, some say…)

[@j.d.saccociates3313]

Hey, you mentioned you knew of some good amp techs in British Colombia? Can you share some names? I've got a Garnet Session Man that could use some love.

[@j.d.saccociates3313]

I've tried myself, but quickly ran out of talent. Didnt take long.

[@PsionicAudio]

Dan Tramble, Dr Dan amps. If he can’t take it he’ll know someone else good in the area.

[@Bigfoot_Murray]

Gary of Economy Amps in Vancouver.

[@peterstephen1562]

I don't know enough to understand why most guitar amps run the screens at nearly the same potential as the plates. I have an amp with KT 88's at 660 volts and screens at 330 volts that gives 82 watts clean and has the original tubes since 1971. I would have thought that running screens at almost plate potential was negating the benefits of a beam tetrode ?

[@Funkybassuk]

Your comment sounds like a line from Star Trek to my ignorant ears!

[@PsionicAudio]

Most amps are designed as simply as possible and in the case of amps designed in the ‘60s and early ‘70s, often cheated datasheets because the tubes then were very rugged. Your amp probably taps off a half supply node in the middle of a series cap pair, like many Ampegs did. That takes real estate and more cost so most companies didn’t do that (most companies didn’t design with 660V B+ either). When needed I’ll bring down a screen node using zeners.

[@peterstephen1562]

Thanks for your reply Lyle.Yes the screens come off the centre of the smoothing cap chain. It is a Holden wasp made by Ron Holden in Christchurch New Zealand. My only trouble with the amp , besides the weight , is a buzz that's audible when playing quietly. I think it is diode switching spikes picked up by the preamp heater winding in the transformer. I've sorted it with DC heaters but am afraid of blowing the transformer. Maybe a separate filament transformer?

[@peterstephen1562]

Would little caps across the diodes in the bridge solve the buzz ?

[@U_ever]

Isn't Pepsi a New Bern, North Carolina based company ? ? ?

[@PsionicAudio]

Invented there, but that second rate invention is headquartered in NY.

[@tomfoolery2082]

What are the best 6v6/el84s tht last more than 6 to 8 months ? Thx

[@BradsGuitarGarage]

Nobody knows! That's the problem!

[@Mark70609]

They are aren’t that big a problem. What amp are you putting them into? I typically use the military Russian valves. They have a 14 watt plate dissipation instead of the standard 12 watt plate dissipation.

[@Mark70609]

@@BradsGuitarGarage the TAD valves are very good.

[@BenState]

Nice vid man!

[@williamknell864]

In the South? Mr. Pibb, perhaps?

[@YTPartyTonight]

My guess would be Coke or Dr. Pepper.

[@Mark70609]

Electroharmonix are not my valves of choice. My Mesa Boogie SOB would kill a set of EH 6L6’s in 18 months. I don’t have a problem with other brands of valves.

[@Funkybassuk]

Dumb question: are you plugged into a speaker or other load when powering up? You did the second time you powered it on but not the first. Was that because the tubes weren’t inside the first time you powered it on? Trying to learn from an expert.

[@PsionicAudio]

No need for a load without power tubes in place.

[@peterstephen1562]

Also if there is no signal on the amp there is no danger without a load. Keep a load on the OT when there is a signal to prevent the plate voltage swing going too high causing an arc in the output tube or output transformer primary.

[@PsionicAudio]

Also, technically there is a load in each of these amps with no speaker connected as the output jacks shunt to ground. The most common danger from having no load is a Marshall or similar that doesn’t shunt the output jacks or if you plug/unplug a speaker cable with signal. Or the drummer trips over your speaker cable and disconnects the speaker cab…

[@victorbeebe8372]

Mahalo Lyle!

[@sgt.grinch3299]

Nice

[@retread1083]

Depending upon where you go, a blue plate special might be tasty. A red plate special never is.

[@TwangThang57]

Probably ‘bacca juice on that speaker.

[@ditchgator1]

😎👍

[@briansilcox5720]

Yeah…sticky fingers.

[@sgt.grinch3299]

Modern tubes are no longer reliable.

[@Mark70609]

You have to be particular about the valves you buy. I like Tube Amp Doctor valves. I have bought quite a few of their branded valves and have been happy with them. TAD doesn’t make valves, they test them and match them.

[@Asshat237]

Algo help

[@jimilee459]

It wasn’t Pepsi 😂

[@jaycareaga9929]

It was new Coke 🤣🤣😂😂

[@martinreid1740]

Thanks for this Lyle, are we live chatting this week? Uncle Doug in his latest video went into in deep detail on how to wire the mains into an an amp. Please watch it and give us your opion.Thanks in advance. PS. I've just replaced the element in my cooker and the circuit breaker did the trick.

[@PsionicAudio]

Yes, but I don’t know that I’ll have time to watch Doug’s video. I hope he got it right, as I’ve shown it a lot on the channel.

[@BenState]

@@martinreid1740 Ive never seen him wire the safety ground correctly. You?

[@martinreid1740]

@@BenState If you watch his video he made a very convicing choice. He is a great teacher and I've watched him for years and hold him in the highest regard.