EL84 Free Pins As Tie Points?

[sluckey]

EL84 Free Pins As Tie Points? I recently came across this topic in another forum.

Are there really any free pins inside my EL84 tube? Maybe. Maybe not. Datasheets from different manufacturers show conflicting info. Take pin 1 for example. JJ says nothing about this pin. Ei says NC (no connection), and RCA says IC (internal connection).

I like to mount screen resistors and/or grid stoppers directly on the tube socket when possible. This is very easy and convenient for 6V6s, 6L6s, etc. But the EL84 is a crap shoot. I've seen people mount the grid stopper between pins 1 and 2. In fact, our host does that on his EL84 based amps. But is pin 1 really available to be used as a convenient tie point? That depends on the brand tube you use.

I have four brands of EL84s... RCA (USA), Ei (Yugoslavia), JJ (Slovak Republic), and Golden Dragon (China). The JJ tube has nothing connected to pin 1. But RCA, Ei, and Golden Dragon all connect pin 1 directly to pin 2. Now if I were to mount my grid stopper between pins 1 and 2, only my JJ branded tube would work as expected. The RCA, Ei, and Golden Dragon would all put a short circuit across my grid stopper. Not a big deal. The circuit would still work just like a circuit with no grid stopper.

But suppose I mounted a screen resistor between pin 1 and pin 9. That would be a disaster when using my RCA, Ei, or Golden Dragon tubes.

There doesn't seem to be a consensus between manufacturers as to a standard use for pins 1, 6, and 8 inside an EL84. I've never seen pin 8 used for anything. Pin 6 looks to be used just as an alignment pin to position the bottom mica wafer properly (just a guess). Pin 1, just flip a coin. Better yet, look closely at the tube and/or use your ohm meter.

These inconsistencies are enough reason for me to not use any "free" pins on an EL84 socket as convenient tie points. I've included a pic of my RCA 6BQ5 that clearly shows a connection between pin 1 and pin 2.

[g-man]

Deleted

[sluckey]

Here's a quote from that website...

"There are several modern EL84 amplifiers which have wiring violations on pin 1 of one or more EL84 sockets. NOS EL84s have internal connections between pins 1 and 2 where modern EL84s do not. Sometimes designers of EL84 amps assume that pin one is a safe location for a "tie point", a place to connect a grid resistor and the signal wire from the phase inverter. This will result in a NOS tube placed in such a socket furiously "red plating" and the amp humming. If run this way for long enough, damage to the EL84 tube and/or the component connected to this socket will result."

Whoever wrote that doesn't know what they're talking about. It's not a difference between NOS and modern tubes. I just showed two modern EL84s that have pin 1 connected to pin 2. As for furiously "red plating", no way. This is an example of a grid stopper resistor being mounted between pins 1 and 2 of the socket. The grid stopper would be shorted out and non functional, but this has zero effect on tube bias so there will be no furious red plating going on. And no damage to the resistor is possible because it is shorted out.

[jojokeo]

Thanks for the info and reminder sluckey. It goes to show that you just can't blindly believe everything you see, read, and hear. I've also had this issue with preamp pentodes for pins 2 & 7 on an EF86 for example, whether to use them as tie points or just tie them to ground.

[DummyLoad]

use them as tie points or just tie them to ground.

expanding your words...

use them as tie points to ground. 

although, i sometimes tie them both the cathode; when i'm feeling lethargic.

--pete

[PRR]

> look closely at the tube and/or use your ohm meter.

It's a rainy night in Lodi NJ. I get to a Very Important Gig an hour early, and discover a dead/sick EL84. No problem, there's a Banjo-World nearby (and I have the $36 inflated-retail price in my pocket).

Will B-W put-up with me opening all their EL84 boxes and poking some mystery-meter at them? (Do I even have an ohm-meter with me? _I_ would, but most don't.) What if none of the bottles in stock have the connections my amp expects/needs?

> not use any "free" pins on an EL84

Agree fully.

[Willabe]

It's a rainy night in Lodi NJ.

The hit from CCR, 'Oh Lord, Stuck in Lodi Again' came from being on the road in the US, because, believe it or not,  there's more cities named Lodi in the US then any other city.           

[msaudiotech]

Here's a quote from that website...

"There are several modern EL84 amplifiers which have wiring violations on pin 1 of one or more EL84 sockets. NOS EL84s have internal connections between pins 1 and 2 where modern EL84s do not. Sometimes designers of EL84 amps assume that pin one is a safe location for a "tie point", a place to connect a grid resistor and the signal wire from the phase inverter. This will result in a NOS tube placed in such a socket furiously "red plating" and the amp humming. If run this way for long enough, damage to the EL84 tube and/or the component connected to this socket will result."

Whoever wrote that doesn't know what they're talking about. It's not a difference between NOS and modern tubes. I just showed two modern EL84s that have pin 1 connected to pin 2. As for furiously "red plating", no way. This is an example of a grid stopper resistor being mounted between pins 1 and 2 of the socket. The grid stopper would be shorted out and non functional, but this has zero effect on tube bias so there will be no furious red plating going on. And no damage to the resistor is possible because it is shorted out.

I know this post is from months ago, so apologies if it gets needlessly pushed to the top of the feed. 

On my bench today is a Lexicon Signature 284.  Twin single-ended EL84 in stereo.  Pin 1 on these amps was used as a tie point for the screen grid resistor (going from pin 1 to pin 9), not the grid stopper.  With an internally connected 6BQ5 you'd be putting high voltage right on the control grid.  So yeah, red-plating is a distinct possibility with this amp.

[drgonzonm]

It's a rainy night in Lodi NJ.

The hit from CCR, 'Oh Lord, Stuck in Lodi Again' came from being on the road in the US, because, believe it or not,  there's more cities named Lodi in the US then any other city.         

And I thought the common city name was springfield, and found out that the web says its washington I guess I've been watching too much "The Simpsons"

[jeff]

Oh, man
My whole life I thought he was sayin, "Oh, Lord, stuck in a LOW DIVE, again" as in a crummy dive bar.
Welp, learned my "somethin' new" fer today!

[JPK]

Wow I did not know about this. Based on your post #1, I would agree to not use them as tie points. Now it makes me wonder about other tubes. JJ 6V6S pins 1 and 6? Or is this one where they are all consistent?

[jeff]

You could test with a multi-meter before popping them in to be sure.
I tested my EL84, some had i.c. some didn't.
Not sure about other tubes/brands/relabeled "close enoughs"

[sluckey]

Now it makes me wonder about other tubes. JJ 6V6S pins 1 and 6?

JJ 6V6 S does not even have a pin 1 or pin 6...

[JPK]

Now it makes me wonder about other tubes. JJ 6V6S pins 1 and 6?

JJ 6V6 S does not even have a pin 1 or pin 6...

I guess we're safe on that one. 

[bmccowan]

The Lodi in the song is Lodi California according to this Lodi News-Sentinel interview with CCR drummer Doug Clifford.
Q: Since you're appearing in Lodi, tell us the tale of the song, "Lodi"?

A: It was a long time ago, there wasn't much out there. We played in this bar and we played four sets and there were some big dudes and they kept telling us to turn down the music. They were all drunk, there was nine of them ... . We went up to get paid, and they said, "We're not paying you." They stood up and said, "You better leave now." We hurriedly got out of there. Stu (Cook) had a brand new bass amp and we were passing this stuff along to each other to get out of there as fast as we could. (John) Fogerty was backing out his brand new station wagon and ran over Stu's brand new amp.

Lodi is a great place to visit BTW. It is the center of red Zinfandel wine making. There is also a sadly fascinating village named Locke. It is National Heritage center now and was home to Chinese immigrants who built the levees that allowed the Sacramento river delta to be tamed as farmland for grapes and vegetables. Sad because they were treated so poorly, but fascinating as they developed a unique culture in the village.

[PRR]

It's a rainy night in Lodi....

When I was "on the road", it was Lodi New Jersey. Through WWII, a good factory and trucking town. The good times peaked in 1960, population waffled +/-24,000 for decades. Which really meant the place went downhill. In the 1970s the older mill-men and truckers still lived and drank in Lodi. Ken and I had a couple off-night gigs in Lodi. Maybe intuiting what Fogerty went through in California, I wasn't using good amps or a nice car; wanted quick getaway at the end of the night.

"What is Lodi NJ famous for?  Lodi is home to the transmitter and towers for New York radio station WABC. In the HBO crime drama The Sopranos, the Satin Dolls go-go bar in Lodi was used as the filming location for the fictional Bada Bing bar."

Apologies to today's Lodi NJ which seems to have perked-up considerably since my lost years.

Or maybe not?