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Strange tube

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pilovis

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Joined 2012
#1
I found this strange "three tubes" on a Grundig Stereo Radio.

ECLL 800E, Tube ECLL800E; Röhre ECLL 800E ID31029, Triode+Do

It is not a fake, it was a commercial "tube".

ecll800e%2Ejpg


ecll800e%5Fschacht%2Ejpg


ecll800e%5Fseite%2Ejpg
 
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#2
Looks like a DIY compactron or some scheme to get around a tax per tube in radios. Maybe a repair workaround for a discontinued production tube for some radios. Any tube #'s on the tubes themselves? ELL80?
 
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#5
According to Oldeurope in a 2008 thread:
http://www.diyaudio.com/forums/tubes-valves/125099-pse-help-unity-u-triode-phase-inverter.html

The triode section in that ECLL800E (and presumeably the original ECLL800) had a Mu of just 1 for making a unity gain inverter stage. It would be very interesting to know what tube they used in the ECLL800E "E"mulation (picture with two tubes side by side, the right side one being the smaller triode apparently) for the triode function. Oldeurope would certainly be interested in knowing, since that was what he was searching for then. It's hard to imagine how one would even make a Mu=1 triode. Maybe the ECLL800E "E"mulation part used a higher Mu triode with some attenuation.

Ouch!, according to that radiomuseum link, 221 different radios used the original ECLL800 part.
 
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#6
The "real" ECLL800 in one envelope. The one shown is a substitute.

I have experimented with substitutes for the very expensive ECLL800´s that are to be found in the vintage Hagstrom guitaramps.

The best way today is to make a fake one by using two ECL82´s where one triode is left unused. No problem to go this route as the triode is for PI in paraphase.
 
#10
That looks pretty wild, almost as crazy as the 6550 replacement I wanted to make with a 6CB6 current mirrored to preserve curves and feeding a big transistor... I had my eyes out for a ECLL800 thinking it'd be fun to see how good of quality an amp could be made with one tube, but on looking closer I realized it would be so challenging. It has extra limitations with so many things tied together to get down to 9 pins. With only one cathode connection there'd be no hooking up feedback from the Com and 16 Ohm output taps with the 4 Ohm tap grounded. Even the inverter triode has the same cathode in common with the pentodes, the control grid tied to one also. The datasheet says mu=1.2 for the triode, which means that unity gain inverter uses no divider or external feedback beyond the influence of the plate signal on current. it looks like all three sections get -9V bias from a single 180 resistor. I suppose a Zener would be a minor upgrade to keep the triode from seeing variation. If biased a little hotter to get more gain, maybe the triode plate resistor could be trimmed for AC balance, maybe vary the bias on the second pentode some too? Maybe a 1N5302 current-source triode plate load then trim the following grid resistor for gain balance? Run the global feedback resistor with a lead compensation capacitor from the speaker to the input grid and and use a series input resistor for inverting mode? A series RLC across the transformer primary to kill the resonant peaking? Fire up those PC spectrum analyzers!
 
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#12
50uA/V ! Wow, now I've seen everything.

I've heard stories that the Russian MIG fighter jets used multi-section valves like this, and maybe still do. They're immune to the EMP of a nearby nuclear warhead (good luck to the pilot of course). Could even be true, dunno.

Thanks,
Chris
 
#13
If they could come up with a non-emitting sleeve to put between the heater and the cathode, tied that to the filament to act as an anode and made the cathode so the inside could emit too (or just added a diode section connected to those places), there could be a rectifier and still have just 9 pins. For some reason I'm visualizing a shaded-pole phonograph motor with added coils for the filament and plate supplies. If semiconductors had never developed on this planet, I wonder what tubes could have evolved into? I remember a time when rebuilding machines for c.r.t.s were being offered for t.v. repairmen to do their own simple electron gun replacements and thinking if would be fun to roll my own mutant tubes. I once wanted a crt a rebuilder didn't have and talked them into to installing a gun with a different type of base on mine. It worked well after wiring in a new socket. There's a video on Youtube of a guy making some primitive triodes.
 
#14
This is the Hagström amp I talked about. Straight from the IC amp Wavebourn showed. The real tube has the same envelope as an EL84 maybe somewhat longer.

Hag310%20schematic%201.jpg


As I said before, the best substitute IRL is two ECL82 with a resistive divider for the triode used to get 0dB gain.
 
#16
You guys want to see a really strange tube?

This one has had an extension job done on the end of it, the tube envelope is normally shorter but its had a job done to extend the tube length!

Either that or it has overheated..

the markings all but one a H inbetween two other markings are rubbed off.

sGZzn.jpg

PRsPt.jpg

50I1i.jpg
 
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#18
kevinkr said:
...Very 0dd.. Must have been a work around for a tube that was designed in and was not available at some point in the product life cycle.
Click to expand...

That is what I read on "AskJanFirst"'s homepage (he is selling some of these weird workarounds); these are 2x EL95 + 1x EC90. According to him this thing is an industrial production run possibly to fulfill delivery contracts at the end of production of the ECLL800. The ones he is selling are from Hoges/Hochohm GmbH.

Martin

Disclaimer: No affiliation whatsoever with FJZ/AJF
 
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