TUNG-SOL KT-66's

[M Fowler]

Another amp forum noted

It has been brought to attention from Igor Boros, that the new TS KT-66 aren't really KT-66's at all and the metal base like a 6550 will short the bias voltage if the tube clamp touches them.

Pin 1 is tied to the metal base. Real KT-66 do not have a metal base.
This tube looks like a combination of a KT-88 inners, and the outer design of a 6550.

[Voodoo_Man]

Another amp forum noted

It has been brought to attention from Igor Boros, that the new TS KT-66 aren't really KT-66's at all and the metal base like a 6550 will short the bias voltage if the tube clamp touches them.

Pin 1 is tied to the metal base. Real KT-66 do not have a metal base.
This tube looks like a combination of a KT-88 inners, and the outer design of a 6550.

That's good to know, but who's Igor Boros? I bought a set of those for my JCM800, but never put them in.

EDIT: You said KT66, but I read KT88. Time for bed.

God Bless,
John

[Andy Le Blanc]

Someone might have found an old pile of tubes that tested like cramp as one
type, but looked pretty good in another light, exactly like the mortgage meltdown.
High gloss turd polish.

[Alexo]

Another amp forum noted

It has been brought to attention from Igor Boros, that the new TS KT-66 aren't really KT-66's at all and the metal base like a 6550 will short the bias voltage if the tube clamp touches them.

Pin 1 is tied to the metal base. Real KT-66 do not have a metal base.
This tube looks like a combination of a KT-88 inners, and the outer design of a 6550.

This sounds like a JJ KT66 too - at least the external description.

More on KT66's - I bought a pair of Shuguangs and a pair of Gold Lion "Re-issues" a while back, one tube out of either pair exhibited red-plating (more subtle in the GL's) biased to 17.5 watts with 440 volts on the plates. That GL is still (very subtley) red-plating, biased kind of cold in triode mode at 360 volts.

Anybody else have problems like these with the new KT's? I returned them to the supplier, who tested and confirmed, and told me he couldn't find a pair of either type that did not do this. Somehow, I took his word for it, though in retrospect, this sounds absurd. He suggested either cooling the bias or to just put them in there and "rock and roll."

But I digress... Is there a quality, reliable new issue KT-66 out there?

[Zippy]

I returned them to the supplier, who tested and confirmed, and told me he couldn't find a pair of either type that did not do this. Somehow, I took his word for it, though in retrospect, this sounds absurd. He suggested either cooling the bias or to just put them in there and "rock and roll."

But I digress... Is there a quality, reliable new issue KT-66 out there?

+1 on "absurd" - seems like if you take one from each of two pairs, you could have two good ones. Yes, they may not match but still...

The Shuguangs were recommended to me a few years ago by Bruce Collins (Mission Amps) as best value in KT66s. Maybe its more a matter of who you get them from regarding testing and matching?

[MARK1]

Hi folks,

I'm new to reply but have visited this site allmost every day last year.

I've used the TS-KT66 in my Mesa Mark 1 reisue without problems, bought them from TAD in Germany, btw I'm from Holland. Currently using EH-6CA7 now.

André

[gearhead]

Get the Penta KT-66s; work great for me. Believe they are "select" Shuguang's.

[M Fowler]

No it isn't that there is a problem with the tube, well in away yes. Pin 1 on the power tubes socket is used as an extra soldering lug rather than being left unused then there is a problem as the pin 1 would then be tied to the metal base.

Many amps use the extra pins of the socket for tying components to rather than leaving them empty this can then cause problems.

Mark

[M Fowler]

JJ KT66 Note:

The large flat base is just like a 6550 including the metal base ring that is internally connected to pin one. This is a red flag for Fender owners. A 6L6 doesn’t use pin one and Fender usually ties the input grid resistors from pin 1 to 5 for easy mounting. If this tube is inserted into a Fender or other amp using pin one as a tie off point problems will result. In this particular case shorting the input grid signal and bias voltage to ground if you have the standard retaining clip. A tech can work around this quite easily, but check before you buy.