Those Magnificent Television Tubes

[TonyTecson]

do not scoff at mere tv tubes, they have very strong cathodes, stronger than any kt88, 6550 out there..
just that screen grids do not like higher voltages as they are quick to die....

 

[efm7]

Oh I adore the TV tubes as they really scratch my itch for glassy clear highs that they seem to excel at.

 

[TonyTecson]

engineer's tube amp...lot's to learn here.....http://www.pmillett.com/DCPP.htm

 

[kodabmx]

Hi, I recently scored a few dozen TV tubes with 150v screen grids… (6/12/17DQ6, 6/17GE5, 6BQ6, 6JN6, 6CD6, etc…) And I would like to use them as my everyday listening tubes and save the nicer KT88s and 6L6GCs for when I have guests haha.

Would it be possible to maintain the UL and Triode modes ?

Are there “minimum” screen voltages that need to be respected? If so imagine any sort of modulating voltage feeding into the screen needs some sort of scaling and positive offset to ensure operation within an acceptable window…

Sorry if this has been asked a bunch of times before, I am unable to find a “satisfying” answer. Yes I did see the “UNSET” thread but it really has me scratching my head…

Am I naively asking for the holy grail?

I use those tubes at 320V in triode mode (tie screen to plate through 240R/2W) with no issues for years. One of my Modular Amplifier 1 configurations uses them. The screen is always a slightly lower voltage than the plate so it doesn't draw much current. I wouldn't try it with UL though.

 

[efm7]

I use those tubes at 320V in triode mode (tie screen to plate through 240R/2W) with no issues for years. One of my Modular Amplifier 1 configurations uses them. The screen is always a slightly lower voltage than the plate so it doesn't draw much current. I wouldn't try it with UL though.

Do you use cathode bias or fixed bias?

not sure that matters…

With the 6DQ6B at 300v, just tried 1k screen resistor in my fixed bias unit and it hasn’t gone into runaway yet so that’s encouraging… i’ll try stepping it down to 470R and 220R (i have screen resistors on a dial)

 

[kodabmx]

I've used both, but normally I use automatic fixed bias like the AB-4 or the AB-Q from Pavel at audioamp.eu
You get more power since there's an extra 60V of B+ to play with

 

[kodabmx]

If you size the screen resistor just right, it'll open in a failure instead of the screen

 

[Triodenklaus]

With the 6DQ6B at 300v, just tried 1k screen resistor in my fixed bias unit and it hasn’t gone into runaway yet so that’s encouraging… i’ll try stepping it down to 470R and 220R (i have screen resistors on a dial)

6DQ6B in triode mode a 100 Ohm screen resistor is enough.

Best regards!

 

[rongon]

Does EL86 count as a Magnificent Television Tube?

 

[kodabmx]

I think so - at least the 6P43P Low mu (triode) and high peak current means 10W from a trioded push pull pair

 

[Kay Pirinha]

No, not really, as it was designed by Philips especially for OTL amplifiers in tube radios. Anyway, it's sibling PL84 matches this term .

Best regards!

 

[OldHector]

No, not really, as it was designed by Philips especially for OTL amplifiers in tube radios. Anyway, it's sibling PL84 matches this term .

Best regards!

I wonder whether it is.. I built a PL84 version of the Tubelab SPP, and in finding the right operating point to respect the screen limits I discovered there are a lot of different specs out there for EL86/PL84/UL84. Going by maximum limits of each type, the EL86 is just a bit beefier than the others.

 

[Kay Pirinha]

As far as I'm informed, these three tube types only differ by their heaters. The first one in chronological order was UL84, derived from EL84 but optimized for supply voltages as low as just 100 Vdc, followed by EL86, where Philips put EL84 heaters into UL84 cathodes for more convenient PSU designs in their OTL radios. Tha last to be introduced was PL84 for TV service (AF output) in 1955.

Best regards!

 

[Mercury99]

Using Curve Captor I captured (manually traced) the data from Curve Set #4 in post #25 (triode mode) which produced the following model from the attached fitted curves (I added the 26W Pa line based on the datasheet):

* 6cb5a macro model
.subckt 6cb5a P G K
koren8(0.01338107979,-0.06422320865,0.1403707944,69.59565876,-27.12750462,38.45402696,-9.115093614,1.596498127)
.ends 6cb5a



JM

I want to use this model. However, I don't have the code for koren8. Can someone share the model with me?

 

[stenak]

Bought some El 36 tubes and I want to build me a single ended amp with these tubes..Maybe 6sl7 as the driver tube? Are there anybody out there who can help me with a schematic?

 

[TonyTecson]

Bought some El 36 tubes and I want to build me a single ended amp with these tubes..Maybe 6sl7 as the driver tube? Are there anybody out there who can help me with a schematic?

el36 is said to be the poor man's 300b...https://www.diyaudio.com/community/threads/pl36-triode-se.276028/page-4

 

[kodabmx]

6P36S is the real poor man's tube IMHO since it's less money...

 

[Parafeed813]

The EL36 is one of my favourites.
To compare it in triode to a 300B is a bit ambitious considering it's 15W rating (a+g2) compared to the 40W of the 300B.
Treat it like a 2a3 and it'll do fine.
6SL7 driver should work.
It also works well in PP pentode. One of my amps runs them with regulated g2 and kathode feedback.
The daily amp of the past months here is Tubelab's unSET beta board running the incarnation without topcap.

 

[Kay Pirinha]

...the E235L, I suppose?

Best regards!

 

[stenak]

Any schematic of a SE amp. Am I right that the plate (anode) are connected from the to cap?