6CH6 find

[richwalters]

Surprise, surprise; over weekend pulled down a false partition in attic and uncovered crate of 200 x 6CH6 from the dust. On boxes where mice haven't been, is stamped 1957, made by Brimar UK and some have verdigris/ corroded pins. Not one tube is white inside.
Looking at the data sheet, this tube falls in line with the high gm flighty video types with quite low Vg, and some sites mention this tube as a substitute to an EL84, but is this really a proposition. Who's used it ?

richy

[mashaffer]

I have no experience but it looks like an interesting tube so I will be watching this thread. I also note that they go for about $20 at thetubestore.com so you have a pretty valuable find there if they are all good.

[aardvarkash10]

I have four... not quite the sizeable collection you have!

Tried them as a spud SE but got sidetracked and didn't develop it too far. Sounded ok, but needed a lot more drive than I was giving it.

Pete M or another of the "senior members" waxed lyrical about this tube when I posted about it. Perhaps they can give you more info.

[thevoice]

I came across a few of these in a miscellaneous box, so I did a bit of research a while ago.

Have a look at this page, they reckon it is equivalent to KT61, not EL84.

For a good data sheet look here.

As far as I recall they are not at all rare or expensive if you shop in the UK.

I wish I had random boxes of valves in the attic.

[aardvarkash10]

then her indoors wouldn't complain all the time about my "wire and bits..." I could put it in the attic.

Her indoors that is. I need easy access to the wire and bits.

[Eli Duttman]

Rich,

You are a LUCKY man. That is 1 VERY nice find. The 6CH6 = EL821. I've got a quad of Mullards in my stash waiting for money to build with. The EL821 data sheet is here. Yes, the type works with O/P "iron" usually associated with EL84s and 6V6s. Pay attention to screen grid fragility. Also, the type is (sic) even more sensitive than the EL84 and g3 is brought out externally.

Clean those pins. Get to work.

[richwalters]

Thanks for all comments. Like alot of these video tubes they like a lower side of Vg and driven hard for best results. WHen set up in a Williamson diff config as a triode, the distortion isn't quite as neat as the 12BY7A which I still rate as a first class runner.
25dB gain in triode config is mighty useful so I set up screen drive, which gave roughly 12dB gain and lo behold this tube runs with beautiful clean single 2nd harmonic. More work due.
I've cleaned up several, tested and all remarkably consistent.

A contender for my 7W amp; now thinking for a 50 yr refurbish and replace the ECL82 pentode section with 6CH6's; the o/p tranny at 9Ka-a is a perfect match. What I'm not sure if this tube prefers fixed or autobias. Vg will be lower, around 6V instead to the 14V for the ECL82.
Interesting time ahead.

richy

[richwalters]

the voice:: thanks for detailed datasheet link. This is far more detailed than Brimar one. By coincidence thro weekend I did a quick botch-plot and lo behold quite sim results.

richy