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    Building, troubleshooting and testing of these amplifiers should only be
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Those Magnificent Television Tubes

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#881
Sylvania branded tube, actually made by Sylvania.

That tube no longer exists, however I have 44 more of them. The boxes are branded Sylvania ECG Electronic Tube, and are also labeled PhilipsECG (no space). The tubes are all branded Sylvania, no mention of Philips or ECG (Electronics Components Group). All have three getters, and the heater center tap on pin 7 (probably for mechanical strength). Some have the top mica loose or cocked at an angle.

I have two older Sylvania 35LR6. No mention of Philips or ECG and they are well made. One has 2 getters, the other has 3. Both have the heater tap on pin 7.

I have 1 GE branded and GE made 35LR6. It has 2 getters and no heater tap. Pin 7 is not connected.
 
#884
The picture in post 870 of the 35LR6 looks like a real Sylvania. They used a strange looking plate fin structure possibly meant to maximize the fin area near the glass for getting the heat out. The GE variety has the usual boxy plate with wide, straight fins. The marking on the Sylvania tubes also follows their usual convention. As far as I know, these are the only two companies that actually made the tube. If I remember correctly,I have a few RCA s that are re-marks.
 
#885
A few months ago I purchased 8 Sylvania 35LR6s from one of the Florida tube outlets and they did not have the filament center tap.

wrenchone said:
The picture in post 870 of the 35LR6 looks like a real Sylvania. They used a strange looking plate fin structure possibly meant to maximize the fin area near the glass for getting the heat out. The GE variety has the usual boxy plate with wide, straight fins. The marking on the Sylvania tubes also follows their usual convention. As far as I know, these are the only two companies that actually made the tube. If I remember correctly,I have a few RCA s that are re-marks.
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#886
If the filament tap is not a documented feature in the tube spec, I would not expect it to consistently be in place. Perhaps Sylvania used a convenient spare pin as a tie point on some production runs to enable them to use a couple of stock filament assemblies that added up to the right voltage drop (a couple of 17s, for instance).
 
#887
Try the 7094 by any chance?
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I have never seen a 7094, but it sure doesn't look like a cheap tube. Tubes like these that run in the kilovolt range also need a load impedance in the 10K ohm region which makes OPT design more difficult, and costly.

I already have the OPT's for my big amp and they are 1250 ohms, so that dictates the tube choice. The OPT's were originally intended for use with 8 X 6550's.

35LR6s from one of the Florida tube outlets and they did not have the filament center tap.

As wrenchone states the Sylvania data sheet only states "IC" for pin 7, which implies that pin 7 COULD BE internally connected to something inside the tube, but it could also be connected to nothing at all.

Look at the type number on your tubes. If it says 35LR6 with the letters USA ( without periods) under the number, it is a Sylvania made tube.

If there is a "dot pattern" under the 35LR6 it is a GE made tube. There can be a dot pattern AND the letters U.S.A. but there will be periods.....these are GE made tubes.
 
#891
My Biz Partner Tom had a Melos; a sweep tube amp with basically a solid-state front end. It runs like 800 volts to the plates from a massive toroid power xfmr; but on audition it was lackluster. Mr. 'Use a Transistor Go To Jail' here ripped out all that solid-state crap; put in a bunch of chokes and an extra transformer for the new 5-20 type front end (triple triode compactrons) and changed over to Sofia-Matched 6KN6's to make the amp an all-compactron unit. Fired it up; let it idle a while; dead quiet on the Concert Grands; then doused the lights and adjusted the bias to get just a hint of color. Turned up the volume and plunged into that phat rich sound. A. Lot. Of Power. I had it plugged into my custom power monitor; idle was around 200 watts; the bass riffs were pushing well over 500.
 
#893
That QE08-200 looks better than the 7094 for sure, but looks like there is only one left on the planet for $90. Looks like it is internally built from 3 tube sections in parallel.

Might as well buy 3 x 36LW6, ..MC6, ..LR6, or ... other sweep tubes for 1/3 to 1/2 total price.
 

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#894
Might as well buy 3 x 36LW6, ..MC6, ..LR6, or ... other sweep tubes for 1/3 to 1/2 total price.
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I paid an average of $6 for my 36LW6's about 10 years ago. I got the 35LR6's for $3.50 each 7 years ago.

If my efficiency enhancements work at the 500 WPC level (tested 10 years ago at 20 WPC) then I can get by with 4 X 36LW6's per channel. If they don't work out, then I will use 6 X 36LW6's per channel. So where else can you get 500 watts worth of tubes for $36?
 
#896
I was saying that one could get the equivalent of the 100 Watt QE08/200 for about $20 to $33 now using multiple (3 or 4) tubes in parallel. (4X 26DQ5, 6HJ5, 21LG6 $4 each, or 3X 36LW6 $11 each) (if any are around still)

18 Watt 21HB5's were $1 a few years back, so 500 Watts worth would be $28 if you have a box of them collecting dust and 28 sockets. Plates are same size as 6HJ5, so maybe a little less than 28 needed.

Umm, 6HB6 or 12HL7 ($1, 10 Watts) 50 of them for $50. With a 1,000,000 gm bonus! Then there's 24 Watt 26DQ5 for $3 if any are still around. There's still some 10 or 12 Watt combo tubes on the $1 list.
Oh yeah, 38HE7 for $1, good for about 15 Watts if only the pentode is powered up. (it's very close to a 21HB5)
 
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#898
I was saying that one could get the equivalent of the 100 Watt QE08/200 for about $20 to $33 now using multiple (3 or 4) tubes in parallel. (4X 26DQ5, 6HJ5, 21LG6 $4 each, or 3X 36LW6 $11 each) (if any are around still)
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indeed, i have a quad of those on hand and i have made an OPT for them, i will make an amp out of those in future....
just that having that kind of power in a single bottle and not so overly high voltages are simply too hard to ignore....
 
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