Johnson ranger 2 el34 idle current

[N2DTS]

Some rigs may have used high voltage octal sockets.
Those have ceramic around the pins, sort of like a box and the pin resides inside the box.

I have a set of those, they may have come out of one of the old rigs.

I have a pair of KT88's in my 32V3 that have 700 volts or more on the plates, with no arc over problems.
I always use ceramic sockets in anything that has high voltage on the pins (over 500 volts).

[WD5JKO]

Hi I purchased a used Johnson ranger 2 off the internet it has a lot of the timtron mods in it and some unknown mods  the modulators seem to have been replaced with jj el34 tubes..

SNIP

I was modulating it into a dummy load I was getting a ringing from the tubes or transformer and some high frequency feedback then a nice arc and smoke seems pin 2 and 3 on one of the el34 sockets arced over

    Fred, I wonder if you have made a schematic of the changes made, as compared to that Timtron series of mods on AM Connection? I ask because you say, "I was getting a ringing from the tubes or transformer and some high frequency feedback then a nice arc and smoke."  Perhaps the crux of this problem is power oscillation in the 10 Khz area, or perhaps there is an RF parasitic occurring?  With these thoughts in mind, I'd be inclined to remove any negative feedback loops as a temporary measure, and install some grid current stopping resistors going to the EL-34 grids. Since this modulator is class Ab1, no grid current should be flowing, so adding a series 10K carbon (or film) resistor at each EL-34 grid would discourage any RF parasitic activity, and also limit grid current from a momentary DC pulse, such as when you bang the microphone on the table.

I once used a JJ version of the 7591, and although they worked, the power was down about 20% from a well used pair that was 50 years old. Maybe the JJ EL-34 is a good tube, don't know.

Didn't the Heathkit Apache use the 6CA7? This is the RCA version of the EU version which had the EL-34/KT-77 labels.

I have played with several EL-34's which included some original KT-77 (Genelax - $$), and some of the Russian versions of the EL-34. The Russian versions all seemed fragile, where a momentary overload made them gassy. The one I settled upon was the Penta (Teslovak) E34LS. These have bigger ratings, and what appears to be the 6L6GC tri-metal plate. The 6L6GC with that plate would not get hot spots...instead with an extreme overload, the whole plate turns a dull red. I had an accident with my E34LS, and a single tube on 20 meters RF use, put out 100 watts key down carrier! I had a power supply failure such that the screen voltage went from 300V to 400 something. I had 750 or so on the plate. The DC idle current went sky high..The whole tube turned red before I realized what happened.    Oddly, no damage was done as that tube was unharmed.

http://www.pentalabs.com/Product.aspx?dept_id=1516&pf_id=e34ls
data sheet:
http://www.pentalabs.com/pdfs/EL34S.pdf

Jim
Wd5JKO

[W3GMS]

The American RETMA tube designation number for the EL-34 is 6CA7. 

Here is a scan of the Heathkit spec sheet calling out 6CA7/EL-34

Joe, GMS

[WD5JKO]

The American RETMA tube designation number for the EL-34 is 6CA7. 

Here is a scan of the Heathkit spec sheet calling out 6CA7/EL-34

Joe, GMS

Yes, but it looks like there are many inconsistencies:

http://www.thegearpage.net/board/archive/index.php/t-1239164.html

"Technically, Bluesky is correct. They were originally Euro ("EL34") and N. American ("6CA7") designations for the same (true pentode) tubes.It's only later, after appearance of beam tube U.S. EL34/6CA7 versions approximately two decades after initial design appearance of first EL34 by Philips in 1949, that the bigger bottled beam versions started to be considered "true 6CA7s" and the original pentode EL34s to be considered "true EL34s", to the point that those separate designations were held to actually specify beam vs. suppressor grid pentode types. And especially on the internet, where this conventional wisdom is repeated endlessly, by almost everyone. However, "6CA7" was registered by RETMA by 1955, and millions of Phillips and other EL34 pentodes were sold in N. America (U.S. and Canada) with no other designation on the tube or the box than "6CA7" in the '50s and '60s, starting with the original metal based Dutch versions, years before there were any other "true 6CA7s". So it actually was just like "12AX7" vs. "ECC83". Ironically, most beam 6CA7s seem to be labelled "EL34" as well, at least the original U.S. ones!-Jeff"

Looks like the RCA 6CA7 (Actually Sylvania made) was a Beam Power tube whereas the EL-34 is usually a Pentode.

I have several 7591's (Fisher Branded) that are called Power Pentodes in the RCA book, and yet I can clearly see the beam forming plates in the holes in the plate.

I am not sure what the Penta (Teslovak) E34LS is, but it certainly is a brute with power reserve.

Jim
Wd5JKO

[W3GMS]

The American RETMA tube designation number for the EL-34 is 6CA7. 

Here is a scan of the Heathkit spec sheet calling out 6CA7/EL-34

Joe, GMS

Yes, but it looks like there are many inconsistencies:

http://www.thegearpage.net/board/archive/index.php/t-1239164.html

"Technically, Bluesky is correct. They were originally Euro ("EL34") and N. American ("6CA7") designations for the same (true pentode) tubes.It's only later, after appearance of beam tube U.S. EL34/6CA7 versions approximately two decades after initial design appearance of first EL34 by Philips in 1949, that the bigger bottled beam versions started to be considered "true 6CA7s" and the original pentode EL34s to be considered "true EL34s", to the point that those separate designations were held to actually specify beam vs. suppressor grid pentode types. And especially on the internet, where this conventional wisdom is repeated endlessly, by almost everyone. However, "6CA7" was registered by RETMA by 1955, and millions of Phillips and other EL34 pentodes were sold in N. America (U.S. and Canada) with no other designation on the tube or the box than "6CA7" in the '50s and '60s, starting with the original metal based Dutch versions, years before there were any other "true 6CA7s". So it actually was just like "12AX7" vs. "ECC83". Ironically, most beam 6CA7s seem to be labelled "EL34" as well, at least the original U.S. ones!-Jeff"

Looks like the RCA 6CA7 (Actually Sylvania made) was a Beam Power tube whereas the EL-34 is usually a Pentode.

I have several 7591's (Fisher Branded) that are called Power Pentodes in the RCA book, and yet I can clearly see the beam forming plates in the holes in the plate.

I am not sure what the Penta (Teslovak) E34LS is, but it certainly is a brute with power reserve.

Jim
Wd5JKO

Hi Jim,
Its not an easy picture to paint is it!  Many variants for sure.  I do know that I have used tubes marked 6CA7 and tubes marked EL-34 in my Apache and they both worked well.   

I personal do not believe Fred's problem is with the tubes unless they are flat out bad.   

If I had his rig, I would first trace out the design.  You have to know what you have.  After that I would start to isolate the problem.  I still would like him to do my suggested test on the modulation transformer.  I do know that many folks that have installed new audio designs in the Ranger have had problems with the original negative feedback scheme.  I would disconnect the negative feedback loop and get it working without that first and then reconnect it along with making sure no RF was being fed back through that loop to the insertion point within the audio chain.  If you open up the FB winding don't forget to ground the correct side of the grid resistor! 

Anyway with a methodical approach, I am sure Fred will locate the problem.

73,
Joe, GMS