The AM Forum

Some misc. tube questions..
 
Can 6L6GC be substituted for 6L6GB?
 
Are Chinese tubes worth the cost savings they generally bring?  I need to replace a pair of 6L6GB's and a 6146B.
 
Thanks

- JT

Hi!
For the first part of your question i got that from Google:

''The 6L6GB is similar to the more common 6L6GC, but has lower ratings (maximum plate and screen voltages 360V and 270V vs. 500V and 450V, and maximum plate and screen dissipations 19W and 2.5W vs. 30W and 5W). All of the curves for the 6L6GB are applicable to the 6L6GC''.

73'S john

I can't speak for the Chinese 6L6's, BUT, I found out the hard way that the quality control on the new chinese 6146B Shuguang tubes is TERRIBLE!

Tried to use them in a couple of rigs over a period of several months and ALL of them developed internal shorts (flash, crack, bang) when HV was applied.

It was a TOTAL waste of money. Ended up buying a pair of Phillips/Sylvania 6146B's from RF Parts and have had no problems at all. Live n' learn!

Bill
w0ng

a 6L6 is a 6L6 is a 6L6. use whatever you have and don't worry about it. other than using metal cased 6L6's in certain RF applications any US made gennie 6L6 should be fine in your application. but please use the real thing. a few years ago i eperimented with some of those aftermarket "Groove Tubes" 6L6's made for guitar amps with lackluster (or horrendous) results. to add insult to injury the pins were out of spec (too small diameter). Phllips/ECG, Sovetek, and Electro-Harmonix were not much better. GE and RCA, even used never fail for this guitar slinger. i have 6L6's from the 30's that my father used and they are actually some of the best. these are the ones in the big 807 size bottle.

I have the metal 6L6's in stock if you need any.
Keith

I think 'shuguang' is Cantonese for 'screw the round-eyes'.

But for some reason the audiophool community insists on glass 6L6's, and have driven up the price of 6L6G's, the ones with the 807 size and shape envelope.  For audio applications metal and glass should work exactly the same. 

I was always under the impression that the metal 6L6's was to provide shielding when it was used as an oscillator.

Thanks Keith but I was under the impression that metal 6L6's had a different pin-out than 6L6GB's?  My modulator in this rig is designed for 6L6GB's so I'm not sue if metal 6L6's would work.

- JT

 
 
Again
 
 
"6L6 Substitutes
Close or identical 6L6G, 6L6GT, CV1286, CV1947, CV1948, VT115, VT115A
Different rating or performance 6L6GA, 6L6GB, 6L6GC, 6L6WGA, 6L6WGB, 6L6WGC, CV2796, CV2817, CV3618, CV586, EL37, STR387, STR415, SV6L6GC
Different pinout 5B245M, 6BG6, 6BG6G, 6BG6GA, 807, 807W, ATS25, ATS25A, CV1060, CV124, CV1364, CV1374, CV1572, CV3809, CV428, QV0525, VT100, VT100A, VT60(RAF), VT60A(RAF)
Different filament voltage 19BG6G, 19BG6GA"
 
regards
FG5FC

SOVETEK Russian made tubess are of very food quality. Antique Electronic Supply is a good source for pubes..............THEN E-pay can come to the rescue too. I bought a pair of 6B4's for $50 NOS SOVETEK.

Fred

Well, the dude who sold me the radio and didn't pack it properly resulting in the broken 6L6GB's has agreed to replace the tubes.  I found some NOS RCA's I'm going to go with.  Thanks for the replies.
 
Unfortunately, the seller is not a ham and didn't realize how fragile this stuff can be.  He's selling off his fathers estate.

- JT

       good luck with the rig! as to the audiophools and those 807 size 6L6 bottles- i'm not an audiophool- you guys all know that, but for some reason the 30's and 40's vintage beer bottle 6L6's just seem to work the best, followed by the later smaller bottles from the 50's. metal ones are fine too, but if you go back and read the very first construction articles using them in QST- mid thirties you will find info on how they often do not work well as oscillators compared to the glass versions. more feedback was needed to to  get them to start and key reliably. i found this to be true on my novice 6L6 rig, which i still use with BC610 crystals, and modualted, on 75 AM.

      i have yet to have good luck with repro/knockoffs in any application- audio or RF. the worst was Groove Tubes. they had undersize pins and fell right out of the sockets of my Fender Super Reverb (a profoundly terrible amp but it's loud). good thing i was playing a big Gibson Arch Top jazz box that night. i was able to finish the song sans amp. i got them back in the sockets and finished the gig with the amp upside down on the stage. sure looked funny but it worked.

Would Sovetek 6L6WXT+ priced at $24 for a match pair be a good replacement for 6L6GB's?  They are supposed to be modelled after the vintage RCA 6L6GC "blackplate," the Sovtek 6L6WXT+ features larger plate dimensions and improved grid structure for increased power handling capabilities. The 6L6WXT+ also features mica spacers with metal springs to eliminate tube rattle and microphonics.
 
- JT

Oh, I also found a matched pair of Sovetek 6L6GB's for $19.  Maybe I should just go with those to be safe and save a couple bucks.
 
- JT

The original 6L6's were the metal version.  The glass, or "G" version came later.  To me, the more modern ones with the smaller bulbs and all the oddball suffixes added to the type number, are more akin to sweep tubes.

FWIW, the only real difference between a metal 6L6 and sn "ST" shaped one is that pin 1 of the metal one is tied to the metal shell for shielding, and on the glass one it is floating and attached to nothing.

If you are substituting a metal 6L6 for a glass one, be sure tha piece of equipment is NOT using pin 1 of the socket for a tie point. If so, what ever is tied to pin 1 in now also tied to the metal bulb. If pin 1 on the socket is either unused or grounded you are good to go and can use either one.

"GBs" and "GCs" carry a little higher dissapation and power handling ratings and are designet to have a little more oomph at higher operating voltages. And also more designed for audio than RF service. An 807 is absolutely nothing more than a 6L6 with a 5 pin base, a plate cap and little bit shorter internal leads. The grid and plate curves are identical.

"So there ya go!!"  ::)

                                                                  The Slab Bacon

But if a modulator is designed for "GBs", I shouldn't downsize to regular "6L6", correct?  But, I could upgrade to the "GCs"?
 
- JT

going from GBs to GCs should work fine since the GCs were designed to to replace anything lesser. As far as going bact to the plain Gs or metals, it depends on the amount of powa you need and what the plate voltage on the modders is.

Thanks for all the replies guys, think I will play and safe and go with GBs or GCs.. maybe these Sovtek 6L6WXT+'s even.
 
- JT