Tube change help (99j)

[AcornHouse]

I need some help with my '60 99j. I decided to do a full tube swap (almost) since it had a mixed lot of tubes in it. I got EH12AX7s and Sovtek 6L6WXT+s. I haven't changed the rectifier, yet, although I have a JJ GZ34 of unknown usage waiting in the wings.
After installing the new tubes, and letting it warm up for a couple of minutes, I kicked the standby on. I immediately get a mishmash of static and hiss that ebbs and flows. But, the guitar also gives nice rich sounds at an expected volume.

So, what did I do wrong? (This is my first tube change.)

Are the 6L6WXTs not compatible, since the original specs call for 6L6GCs? Here's the write up from the Tube Depot, which is why I got them:

Modeled 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. The Sovtek 6L6WXT+ yields a 20% higher output than the Sovtek 5881WXT and offers superior tone and overall performance.

Any help? (missing the good Cap'n now )

What's my next step, before I blindly try swapping things?

 

[beinhard]

I would first try replacing preamp tubes, one at a time.
You still have old ones that worked, right?
Sometimes even brand new tubes are bad.

Another problem that sometimes shows up when swapping tubes is bad contact in the tube sockets.
Try moving each tube a little in its socket before switching the amp on and see if that changes anything.

beinhard

 

[Default]

Pop the old preamp tubes back in and see it that makes a difference. 6L6's are 6L6's. Some have better tone than others, but you're fine.

 

[AcornHouse]

Finally had a chance to get the tubes tested at my tech. There was one bad tube in the old tubes and one bad tube in the ANOS "new" tubes. No wonder I had trouble IDing the issue.

The good news, is the RCA long plate 12AX7 that came with the amp is good , so it went into the No.1 socket, with the two good EH 12AX7s in the other spots.

Also found out I had another probable RCA long plate that I had got in a mixed lot from TGP that also tested good. 8) Saving it as a backup for No.1.

Btw, the bad tube that came with the amp? A Groove Tube! :evil: There's a reason they're the cheapest. :lol:

 

[Default]

From what I've heard, Winged C Russian are the best of the new production 6L6's, should you want a backup set of tubes.

 

[SFIV1967]

And a bit of background on "Winged C": http://www.wingedc.com/
Ralf

 

[AcornHouse]

The 6L6s that I took out (and forget to bring with me to the tech, unfortunately) are branded Dumont. From what I've been able to find, they didn't make any tubes, but rebranded them.
The codes on the glass are:
ERP
80-22
———
171a

Anyone have any info on them? They're probably still good as a backup.

 

[AcornHouse]

Here's a couple of pics of the Dumont tubes.


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Maybe this will help with an ID of the maker. They're certainly vintage, anyways.

 

[Default]

Dumont made tv's and had one of the first television networks (also the first to go belly up ;-) ) and like you said rebranded tubes. A lot of manufacturers did that.

 

[SFIV1967]

Well, the "E.R.P." stands for "Emerson Radio and Phonograph", who purchased portions of Dumont's manufacturing and selected use of the name in 1958.

@Chris: Is there any grey (probably hard to read) painted number or code somewhere else on the tube? Not that I would know what it is, but maybe there is an original manufacturer code somewhere hidden on the glas near the bottom where the black plastic starts.
Ralf

 

[AcornHouse]

@Chris: Is there any grey (probably hard to read) painted number or code somewhere else on the tube? Not that I would know what it is, but maybe there is an original manufacturer code somewhere hidden on the glas near the bottom where the black plastic starts.
Ralf

On one of the tubes there is some remnants in white (could be grey) and I think I can make out "ao", but the rest is pretty much gone.

So that would mean these are probably the original tubes, given the 1960 date. Over on TGP, I asked the the same questions, and one post thinks that they are Russian, from the internals. That doesn't seem to line up with the codes that you interpreted, though. Would Dumont have been able to import Russian tubes in 1960? It seems unlikely.

 

[SFIV1967]

Chris: I am not a tube expert at all, and basically just used the info that "ERP" was only used starting 1958
"ao", that's tough. At least the presence of grey or white letters would indicate that the tube was re-stamped by Dumont I would say.
Look for instance at that old Philips codelist to understand the difficulty. And here one from Brimar.

The inner construction should be a clear indication who made the tube, but I can't find a good page that explains the differences of each manufacturer. The two plates on each side of the top are special. The below are Russian (Reflector Plant in Saratov) made tubes from 1988 and 1989, which show very similar plates and similar inner construction.

Ralf

 

[AcornHouse]

There's been a number chiming over on the TGP thread that they are Russian from around 1980. Since the US couldn't import them from CCCP, they said they probably got them from UK sources. Here's the thread, if you are a member there: http://www.thegearpage.net/board/showthread.php?t=1076653

Maybe the codes are apocraphyl, the internals are pretty much a perfect match with the Soviet tubes. Maybe to get around the import ban, they marked them as NOS, with the mystery 171A an internal code to show that that they weren't really NOS . :?

The world may never know (unless we can find someone who worked for Dumont at the time(s). :mrgreen:

 

[Default]

There's been a number chiming over on the TGP thread that they are Russian from around 1980. Since the US couldn't import them from CCCP, they said they probably got them from UK sources. Here's the thread, if you are a member there: http://www.thegearpage.net/board/showthread.php?t=1076653

Maybe the codes are apocraphyl, the internals are pretty much a perfect match with the Soviet tubes. Maybe to get around the import ban, they marked them as NOS, with the mystery 171A an internal code to show that that they weren't really NOS . :?

The world may never know (unless we can find someone who worked for Dumont at the time(s). :mrgreen:

They are counterfeit if they are russian. Dumont didn't exist in 1980. Google Dumont tvs.
en.m.wikipedia.org/wiki/DuMont_Laboratories#_

 

[AcornHouse]

OK, (ARGGHHHHHHH! :lol: )

So, maybe the Soviet tubes were modelled after the Dumont tubes (or whomever really made them?!?

"'Curiouser and curiouser', said Alice"
:|

 

[Default]

OK, (ARGGHHHHHHH! :lol: )

So, maybe the Soviet tubes were modelled after the Dumont tubes (or whomever really made them?!?

"'Curiouser and curiouser', said Alice"
:|

No, I think it's more a case of in 1980, "we can charge 7 bucks for Russian tubes or we can charge 14 bucks for "American" tubes. My 99J has Sylvanias in it. Not saying that the Russians are bad tubes, just that Occam's Razor might apply here...

 

[SFIV1967]

It's a fun topic nevertheless! I corrected/changed my earlier postings and deleted obviously wrong info that I had found on some other forums.
Ralf

 

[SFIV1967]

Chris: O.k. "ERP" was obviously used way later than 1960, as this example of another Dumont tube here is from 1974 and shows ERP as well.

Ralf

 

[AcornHouse]

I think they were made be elves, and imported from Middle Earth. "Elvish Research Product"!

 

[SFIV1967]

Well, we know that ERP is Emerson Radio and Phonograph, there is no doubt. Somebody else at TGP also said "The easiest way to spot Russian tubes is by their "flying saucer" shaped getters. No other tubes have this and every Russian tube I can think of does."
So I think we should take this as indication that they are Russian made. If the 80-22 is the date when they were relabeled as Dumont/ERP or if that was the original date of the Russian tube will be hard to find out. And they most probably made their way via Western Europe to the US.
I guess that's all you can find out.
Ralf