Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jammied on October 24, 2020, 06:28:14 pm

Title: Proper setup for 6p3s(6l6gc)
Post by: jammied on October 24, 2020, 06:28:14 pm: Well not sure what to make of these tubes? Getting blue electron glow. Using classic tone 18watt 8k primary transformer.

B+ 395

Pin 1 = 32.8mv

Pin 3= 384v

Pin 4 = 355

Pin 5= -33.5

No red plating but had the blue electron glow

So I swapped the the bias resistors and took these numbers

Pin 1= 7.8ma

Pin 3= 407v

Pin 4= 382

Pin 5= 46.4

Now no blue electrons but doesn't seem very good to me.
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: jammied on October 24, 2020, 07:02:46 pm: Well after some research these tubes have the fluorescent blue glow. And seems that's just the way they are? Some audiophiles are putting them on display because they have the blue glow.

Found a article at the tube store and from what I gathered the fluorescent blue glow is fine from what sylvania said?

They weren't red plating at all just some blue glow. Guess I will swap the bias resistors back . And give them a go
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: tubeswell on October 24, 2020, 07:14:19 pm: Are you using the 6P3s? or the 6P3sE?

Both are rated for 20.5W plate dissipation, but the 'E' version is a completely different tube and can handle a lot more power and voltage.

I wouldn't run the 6P3S version higher than about 350V
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: AmberB on October 24, 2020, 07:17:05 pm: Is the tube running single ended? If so, then it is usually biased at 90-95%, and the blue glow would be quite normal.
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: jammied on October 24, 2020, 07:35:08 pm: It is jtm45/blues breaker type of circuit .

They are the regular 6p3s version so 385v may be to high. But I was aware of the 20watt max for them

Running 385v on the plates and 35.2ma across the 1ohm cathode resistors. Biased about 13-14 watts per tube .
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: HotBluePlates on October 24, 2020, 09:38:57 pm: Quote from: jammied on October 24, 2020, 06:28:14 pm
... Getting blue electron glow. ...

If your blue glow looks like the tube below, it's fine. It is fluorescence when electrons strike the glass. The tube in the photo is in my own Vibro Champ.

(https://i.imgur.com/A4oHTJS.jpg?1)

If inside you see some kind of colored glow from within the plate structure, that's very bad as it's ionized gas particles in the tube (glowing like a neon bulb) and usually caused when some tube element is overheating (often seem like the screen causes this). Example below:

(https://jacmusic.com/techcorner/ARTICLES/English/blueglow/BLUE-ECC802S-2.jpg)
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: jammied on October 24, 2020, 09:51:00 pm: Definitely looks just like the vibro champ.

But one tube seems to have more than the other? But not so sure they were matched very good either.

Doesn't seem to be a very reliable source for these 6p3s tubes.
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: HotBluePlates on October 24, 2020, 10:04:13 pm: Quote from: jammied on October 24, 2020, 09:51:00 pm
... But one tube seems to have more than the other? ...

So what? :icon_biggrin:

The tube in my photo is an RCA 6V6GT. I've got maybe 40-50 old American 6V6s, and some of them have blue glow while others don't (and individual tubes that do glow vary in how much they glow).

It's a curiosity, but not something to devote time thinking about. You will find the blue glow normally flickers with the stuff you're playing.
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: imgumby001 on October 24, 2020, 11:05:52 pm: Quote from: jammied on October 24, 2020, 09:51:00 pm
Definitely looks just like the vibro champ.

But one tube seems to have more than the other? But not so sure they were matched very good either.

Doesn't seem to be a very reliable source for these 6p3s tubes.

It took me buying from two different sources the get two that ran close to one another. Just my luck that the key busted off the newest one. At least the vendor is sending another for free. Hopefully I’ll get one that matches one of my other two.
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: HotBluePlates on October 25, 2020, 12:13:49 am: Quote from: imgumby001 on October 24, 2020, 11:05:52 pm
... Just my luck that the key busted off the newest one. ...

Keyway Replacements (https://www.tubesandmore.com/products/keyway-replacement-piece-octal-tubes) work, and when the tube is no good anymore you can re-use it on another tube.

Just need to look closely to be sure you know where the original guide was to make it with the new one.
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: imgumby001 on October 25, 2020, 01:40:32 am: Quote from: HotBluePlates on October 25, 2020, 12:13:49 am
Quote from: imgumby001 on October 24, 2020, 11:05:52 pm
... Just my luck that the key busted off the newest one. ...

Keyway Replacements (https://www.tubesandmore.com/products/keyway-replacement-piece-octal-tubes) work, and when the tube is no good anymore you can re-use it on another tube.

Just need to look closely to be sure you know where the original guide was to make it with the new one.

HotPlate you are a master!!!
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: jammied on October 25, 2020, 09:40:28 am: So I did a quick internet search and typed in "6p3s blue glow" and jacmusic.com popped up and they have an entire article on the blue glow in tubes. And a pic of some 6p3s tubes glowing .
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: imgumby001 on October 29, 2020, 10:56:09 pm: Received my replacement 6n2p from viva today. It was to late to really do anything but throw it on and take a quick mA measurement-it’s literally double the other low current tube. Swapped sockets, same result. They just keep coming hotter, and hotter, and hotter!!!!
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: jammied on October 30, 2020, 04:39:59 pm: I assume you ment 6n3p English translation 6p3s?

Bought or shipped singly I can see a mismatch. Pairs or quads now that tells me they really are not matching them. The matched pair I received from viva tubes is spot on when first firing up the amp. Then after playing 10-15 minutes the one tube stays the same and the other drops about 3ma. I have verified that it is the tube.

They are not burning in and then matching. But 3ma is within my specs. Most tube places 2ma is the goal.

Good news is nesstone has matched quads for around $18 shipped to the door for $25. Might not really be a matched quad. But one could very well end up with 2 pairs
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: jammied on October 30, 2020, 04:48:31 pm: Just looked at the test results tagged on the tube boxes.

V1 has 15.1 then under that is 2050

V2 has 15.1 then under that is 2200

So they must have at least been warned up for testing and matching from Viva
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: imgumby001 on October 30, 2020, 05:31:06 pm: Quote from: jammied on October 30, 2020, 04:39:59 pm
I assume you ment 6n3p English translation 6p3s?

Bought or shipped singly I can see a mismatch. Pairs or quads now that tells me they really are not matching them. The matched pair I received from viva tubes is spot on when first firing up the amp. Then after playing 10-15 minutes the one tube stays the same and the other drops about 3ma. I have verified that it is the tube.

They are not burning in and then matching. But 3ma is within my specs. Most tube places 2ma is the goal.

Good news is nesstone has matched quads for around $18 shipped to the door for $25. Might not really be a matched quad. But one could very well end up with 2 pairs

Yes, I did mean that. My second, individual purchase, was from viva. I don’t remember the name of the first guys that sold me the mismatched set. It’s true though, out of four, I did end up with two pair that were close, one within 5mA, and one even tighter. There should actually be a nesstube order showing up at my house any minute!!
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: jammied on October 30, 2020, 05:44:05 pm: Oh ok

Out of curiosity what tubes did you order from Ness
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: imgumby001 on October 30, 2020, 06:17:32 pm: Two matched pair-6L6GC’s and EL34’s. I’m gonna run em all and choose which ones I like best in the little beast!! The others will be fodder for future builds.
Title: Re: Proper setup for 6p3s(6l6gc)
Post by: HotBluePlates on November 01, 2020, 01:25:32 pm: Quote from: jammied on October 30, 2020, 04:39:59 pm
Bought or shipped singly I can see a mismatch. Pairs or quads now that tells me they really are not matching them. ...

Or that they are not burned-in to allow the tubes to stabilize. Or that they don't stabilize the tubes then test for plate current (which amount to more time sitting in the test fixture).

Quote from: jammied on October 30, 2020, 04:48:31 pm
Just looked at the test results tagged on the tube boxes.

V1 has 15.1 then under that is 2050

V2 has 15.1 then under that is 2200

So they must have at least been warned up for testing and matching from Viva

Who knows what any one store's stickers/marking mean. However, I would guess the test results listed above for V1 mean "15.1mA idle current (at some arbitrary plate/screen/bias voltage), 2050 micromhos of transconductance (for some arbitrary test signal)."

The European way to say "2050 micromhos" is 2.05mA/volt, or "2.05mA plate current change per volt of change on G1." Which means V2 is 2.2mA/volt.

Transconductance is not constant in tubes, but you have one that's 2.05mA, another than 2.2mA. If your bias voltage is -30v, then there would be a 30v peak drive signal:

- the "2050 tube V1" has a plate current change of 2.05mA/v x 30v = 61.5mA
- the "2200 tube V2" has a plate current change of 2.2mA/v x 30v = 66mA

They apparently closely match at idle, but diverge further apart when driven. How much "divergence" matters? That's up to you; if you don't need every last clean milliwatt, then probably not much.