• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Those Magnificent Television Tubes

There are a lot of these tubes out there. I don´t mean the picture tube, but all the other ones. F. ex. the well known audio tubes 6CG7, 12BH7 and 6CW7 etc. are actually designated for TV-sets.

There are a lot of other quality tubes in Europe & US, costing almost nothing, like PL84, ECF82, PC86, PF86 ECF83, PL81 etc (P stands for 300mA heater current & E for 6,3V voltage)

F.ex. the EC/PC86 triode will outperform ther popular ECC88/6922 types with lower noise and higher gain & linearity.

In US there are 450 & 600mA heater current tubes I think.....(due to 115V mains & series connected heaters)

When a manufacturer sold a tv-set with 20-30 tubes and guarantee, the incorparated tubes have to be of very high quality.

If you have made an amp or other things with these tubes, please give a hint or schematic diagram in this thread.

Regards, Johan
 
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F.ex. the EC/PC86 triode will outperform th popular EC88 types with lower noise and higher gain & linearity.

That's an interesting triode. Data sheet here. It would seem the same sort of extraordinary precautions against parasitic oscillation employed with the 6С45П (6s45p) and the 5842 are in order, when the EC86/PC86 is wired common cathode.
 
That's an interesting triode. Data sheet here. It would seem the same sort of extraordinary precautions against parasitic oscillation employed with the 6С45П (6s45p) and the 5842 are in order, when the EC86/PC86 is wired common cathode.

The EC/PC86 were originally made for the UHF input/mixer/oscillator so better put a few hundred Ohms resistor close to the grid input to keep it calm.
Not extra ordinary, but the same precautions as recommended for the ECC88/6922.

Johan
 
It's a grounded grid amplifier type, with high gm and multiple grid connections. That kind of tube comes damned close to oscillating in the cardboard box. :( Wire 3X 3.3 KOhm carbon comp. stoppers in a "cone" to the 3 grid connections. Put ferrite beads on the heater supply wires. Finally, put a 100 Ω carbon film stopper on the plate. When wiring up "in box oscillators" common cathode, take no prisoners!
 
It's a grounded grid amplifier type, with high gm and multiple grid connections. That kind of tube comes damned close to oscillating in the cardboard box. :( Wire 3X 3.3 KOhm carbon comp. stoppers in a "cone" to the 3 grid connections. Put ferrite beads on the heater supply wires. Finally, put a 100 Ω carbon film stopper on the plate. When wiring up "in box oscillators" common cathode, take no prisoners!

Oscillating in the box....HeHe...A little overkill with the ferrite beads....

Another very interesting tube for compressor/expanders is the very low noise vario-mu EC/PC900 Originally made for regulated TV VHF input amplifier
Square root caracteristic over more than four decades.......Makes very low distorsion in a push-pull configuration.

Johan
 
If you have made an amp or other things with these tubes, please give a hint or schematic diagram in this thread.

Regards, Johan

Been there; done that: Le Renard

The 6BQ6s, especially, make great audio finals, even though there is no mention of such use mentioned anywhere in the spec sheet. These sound as good as the 6V6, but can handle a lot more power, and some spec busting doesn't hurt at all, but improves the sonic performance.

The 6BQ7s also make excellent cascoded LTPs. This is another type that doesn't mention audio applications, and it does have some squirrelly plate characteristics (undocumented variable-u feature?) that makes it a bit more difficult to find a good audio load line. However, for this particular application, it works quite good.
 

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Rod Coleman

Member
Paid Member
2004-07-25 6:55 pm
UK
It's a grounded grid amplifier type, with high gm and multiple grid connections. That kind of tube comes damned close to oscillating in the cardboard box. :( Wire 3X 3.3 KOhm carbon comp. stoppers in a "cone" to the 3 grid connections. Put ferrite beads on the heater supply wires. Finally, put a 100 Ω carbon film stopper on the plate. When wiring up "in box oscillators" common cathode, take no prisoners!

Eli, I agree, this is the right approach.

When I use PC86s, I remove the socket-contacts for the two grid terminals located next to the two anode terminals, and one of the anode terminals also.
Use pin 1 for anode & pin 6 for grid, and remove the unnecessary metal connected to the other terminals! If you are not working at UHF, multiple terminals are a weakness, not a benefit - they present transmitting (anode) and receiving (grid) 'antennas' - undesirable feedback paths that cause oscillation.

I also used ferrite chip-beads in the anode (Murata BLM21A121S), and high values of carbon-comp grid stoppers.

The PC86, and other tuner triodes are designed for cascode operation, and this is where they give their best. e.g. Shunt-Cascode, Single-stage: B+ = 200V, gain = ~280, highly linear swing all the way from 0V to 160V, output Z = 20K.....

Some very nice Russian near alternatives are available, too - e.g. 6С3П with a normal 6,3V heater.
 
Nice thread.

I have a couple of new telefunken PC86, will they sound as the ECC types?

Ronny

A well built premium brand PC/EC86 or the special quality type E86C (with gold pins) has more gain, lower noise and is a more linear triode than ½ E88CC types. Should then preferbly be run with over 5mA anode current and at least 100-120VDC to avoid grid current.

http://frank.pocnet.net/sheets/062/e/E86C.pdf

In order to run a PC86 (3,8V, 300mA) on a 6,3V heater voltage you just need a 8,2 Ohm, 1-2W resistor in series with the heater.

Johan
 
Most readers here know that I have been playing with TV tubes since the 60's when they were free for the taking at the local trash dump. I have been going through my tube collection sorting out the stuff to keep, and the stuff that must find a new home. In the process I have found a few oddities that even I didn't know existed.

Ever seen an EL84 with a plate cap????? Yeah I didn't think so until I had it in my hand. This one is made in the USA by Sylvania and has a 1980 date code. It is an EL804. The specs reveal that it is really a 6CW5/EL86 with a plate cap.

Most of us here know by now that the venerable 6L6GA was repurposed as a transmitting tube, the 807, and a sweep tube, the 6BG6GA. Do you know that it was also stuffed into a 6V6GT sized envelope and sold as a sweep tube for smaller TV sets? Would you want to find some NOS black plate RCA 6L6GA's in a tiny bottle with a different pinout for $3 each?
 

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