[Wes S]

Not a fan of the RCA, and excited to read that they need lots of warmth, have the right pairing in mind for them. Will try that over coffee this morning.

The RCA grey glass is the most syrupy/lush 6SN7 around. I had a bright pair of cans back in the day, that I like to pair with the Grey Glass, and they sounded killer.

 

[JKDJedi]

The RCA grey glass is the most syrupy/lush 6SN7 around. I had a bright pair of cans back in the day, that I like to pair with the Grey Glass, and they sounded killer.

Maybe you can help me date mine, the date is rubbed off , this has to be a mid to late 40's when did they change the logo?

 

[Wes S]

Maybe you can help me date mine, the date is rubbed off , this has to be a mid to late 40's when did they change the logo?

That does look like the "meatball" logo, which is an early version. I can't remember when they made the change. Is there a letter followed by a number stamped on the base?

 

[JKDJedi]

That does look like the "meatball" logo, which is an early version. I can't remember when they made the change. Is there a letter followed by a number stamped on the base?

Looks like G5 or G8 (THAT OR 65) hard to tell. I just found date codes for RCA and there's no G , looks like manufacturing was from 36 to 82, so who knows, I ordered that Tube Lure book that @Paladin79 suggested a while back, maybe it will have some history on the logo. (and you were spot on about that warm tube.. Mullard and this is nice)
http://pax-comm.com/rcadates.pdf

 

[Wes S]

Looks like G5 or G8 (THAT OR 65) hard to tell. I just found date codes for RCA and there's no G , looks like manufacturing was from 36 to 82, so who knows, I ordered that Tube Lure book that @Paladin79 suggested a while back, maybe it will have some history on the logo. (and you were spot on about that warm tube.. Mullard and this is nice)
http://pax-comm.com/rcadates.pdf

That's exactly what I found.

 

[JKDJedi]

That's exactly what I found.

I DON'T SEE A g ANYWHERE.. Where's Waldo!

 

[Wes S]

I DON'T SEE A g ANYWHERE.. Where's Waldo!

My guess is 63 or 65.

 

[bcowen]

LOL...all the tung sol talks...you guys just successfully pushed up the bgrp price (look at the $500/pair just sold). Keep it silent so that I can possibly score one.

https://www.ebay.com/itm/2-Tung-Sol...lack-round-plates-matching-pair-/224036094872


That aside I have noticed the seller igolioto for long time. His 6SN7 testing values always seem way too high, normally in 3300 - 3500 micromhos range. And he calls his TV-3 tester calibrated - I highly doubt it. Remember a 100% NOS 6SN7 has Gm = 2600 micromhos.

Another seller I've noticed for long time is brhines2012. His 6SN7 testing values with some Mercury tester is suspiciously way too high either, in 3300 - 3500 micromhos range.

Beware and verify their testing values if you buy tubes from them.

I have a TV-3 in the closet. It still sits high atop the throne of PITA testers to work on. The TV-3's were made (primarily) for the Navy, and they sprayed some kind of anti-fungal, anti-corrosive goop all over the inside of them. Made sense I guess given the intended application. Perhaps that stuff used to remain in some semi-liquid state, but at this point it has hardened into something akin to a very thick coat of lacquer. EVERY test point is a pain to get to already, and then you have to somehow scrape this crusted gook off before you can get a meter reading on a cap or wire junction. Anybody that can fully and properly calibrate one of these things has my total respect. Then you get a tiny little meter to try and read GM readings on, and arrgghhh! I was so delighted when I got it because I had read that they are very good testers, and probably were when they were new(er) and functioning at 100%. I never could get mine to calibrate properly after expending Herculean efforts to do so and finally gave up on it. It's been a good organ donor though. Perhaps 'igolioto' has one that is properly calibrated, but like you I very (very) highly doubt it.

 

[cddc]

The measurements from igolioto and brhines2012 look so fake, compared to the measurements we normally see. So just beware.

 

[Ralf Hutter]

This:

Perhaps 'igolioto' has one that is properly calibrated, but like you I very (very) highly doubt it.

and this:

The measurements from igolioto and brhines2012 look so fake, compared to the measurements we normally see. So just beware.

Since the values are similar between the two of them, would you think that they're setting some testing parameters incorrectly (I know nothing about testing tubes) or are they just picking numbers out of the air and perhaps not testing them at all?

I have a set of brhines Sylvania GTB's that I'll send to somebody to test, if you want to compare his results with yours.

 

[JKDJedi]

This:



and this:



Since the values are similar between the two of them, would you think that they're setting some testing parameters incorrectly (I know nothing about testing tubes) or are they just picking numbers out of the air and perhaps not testing them at all?

I have a set of brhines Sylvania GTB's that I'll send to somebody to test, if you want to compare his results with yours.

Everyone's testers are calibrated differently, so you'll never get the same tests results across the board between different testers. So I'm told.

 

[bcowen]

This:



and this:



Since the values are similar between the two of them, would you think that they're setting some testing parameters incorrectly (I know nothing about testing tubes) or are they just picking numbers out of the air and perhaps not testing them at all?

I have a set of brhines Sylvania GTB's that I'll send to somebody to test, if you want to compare his results with yours.

IME with two different and truly calibrated testers (a Hickok and a Weston), tubes like 6080's and 6AS7's can show some really high values -- higher than NOS values in many cases. But 6SN7's are pretty consistent across the board as far as measuring right at average NOS values if they are truly NOS. I've had an odd one here or there that would measure higher, but like 2800 or 2900, NOT 3k+ like these guys are reporting. My guess would be they're just making the numbers up, or have testers that haven't been touched for a rebuild or voltage check since they were manufactured 50+ years ago.

 

[bcowen]

Everyone's testers are calibrated differently, so you'll never get the same tests results across the board between different testers. So I'm told.

That's quite true. But the readings should be reasonably close once converted to micromho values (depending on how the tester provides the GM reading).

 

[cddc]

This:



and this:



Since the values are similar between the two of them, would you think that they're setting some testing parameters incorrectly (I know nothing about testing tubes) or are they just picking numbers out of the air and perhaps not testing them at all?

I have a set of brhines Sylvania GTB's that I'll send to somebody to test, if you want to compare his results with yours.

You don't need a tester to find out they are lying. If you often check 6SN7 tubes (and of course their measurements) on fleabay, you'll find measurements from igolioto and brhines2012 are outrageously high, way above reasonable ranges. They either make up the numbers or their testers are garbage, in either case they are dishonest.

Dan Nelson calibrated TV-7 testers have reliable measurements. And lots of sellers use TV-7. Convert these TV-7 measurements to % quality, and you will have an idea where 6SN7 tubes should be tested at, and how ridiculous igolioto and brhines2012 's numbers are.

 

[bcowen]

You don't need a tester to find out they are lying. If you often check 6SN7 tubes (and of course their measurements) on fleabay, you'll find measurements from igolioto and brhines2012 are outrageously high, way above reasonable ranges. They either make up the numbers or their testers are garbage, in either case they are dishonest.

Dan Nelson calibrated TV-7 testers have reliable measurements. And lots of sellers use TV-7. Convert these TV-7 measurements to % quality, and you will have an idea where 6SN7 tubes should be tested at. Attention here, TV-7 measurements can be deceiving, you need to correctly convert them to percent quality. Read my write-up on TV-7 readings some pages earlier (https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/post-15691779).

IMO, Dan Nelson is probably as close to an expert on TV-7's as you'll find these days. While TV-7's aren't quite at the PITA level of a TV-3, they are rather complex to fully and correctly restore and calibrate, and I've never heard anything but rave reviews on the work he does. I'll make no claim to be an expert on vintage tester restoration and calibration (TV-7's or otherwise) as I do it mostly as a hobby, but I *do* know enough to know there's a lot to learn on these things and I'm most happy to refer anyone wanting a TV-7 restored straight to Dan. Problem with most of these questionable EBay sellers is that they don't want to spend the money to have the tester gone through and restored and calibrated. Using an uncalibrated tester is no better (and maybe even worse) than not even testing the tube to begin with.