Sunn 200s running on 6L6 tubes?!

[Pacafeliz]

I'm back here in Mexico and happened to pick up an old 200s, and it's working. But i did realize it has a pair of 6L6 tubes instead of KT88s - that can't be right, right? Rectifier is an 5U4 tube.
Original owner says he's been running it like that for the last 20-30 years!
The outputs on the back are not marked what impedance they take, so i guess it's 8 and 4, right?
So my brother has a big Fender Dual Showman cab here, which should be 4 ohms, so I connected that one.
No nasty noises, good sound, but one of the power tubes was massively redplating, so i shut it off.
Will take it back to Germany with me and get some KT88 first, then have my tech guy check it out.

Any thoughts?







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[s_mcsleazy]

do i see a virtual boy in the background?

[Pacafeliz]

do i see a virtual boy in the background?

What is a virtual boy...?

Edit: i asked my bro, yes it is! Never knew of its existence.

[jthomas]

The KT88 and the 6L6 have the same pinouts so you could stick a KT88 in an amp designed for 6L6s and put a 6L6 in an amp designed for KT88s. That said they are different tubes. For example, the 6L6 has a heater current of 0.9 amperes, while the KT88 heater draws 1.6 amperes. The power transformer would need to be able to handle that and the other differences. Maybe the amp has a really robust original power transformer or maybe someone took the time to put a PT in, appropriate for a KT88? dk.

Pls report back when your tech has a chance to open it up.

[Pacafeliz]

The KT88 and the 6L6 have the same pinouts so you could stick a KT88 in an amp designed for 6L6s. That said they are different tubes. For example, the 6L6 has a heater current of 0.9 amperes, while the KT88 heater draws 1.6 amperes. The power transformer would need to be able to handle that and the other differences. Maybe the amp has a really robust original power transformer or maybe someone took the time to put a PT in, appropriate for a KT88? dk.

Pls report back when your tech has a chance to open it up.

Thnx man, yeah I'll order some KT88s and see how they behave. The left 6L6 does massively redplate (haven't turned it on again) but i was surprised there was no excessive noise, hiss or hum.
What about the rectifier tube?

Thnx

[jthomas]

A quick look online (I have never messed around with one of these amps) seemed to say that they ran with a GZ34 rectifier. I can't say without a bunch of research what a 5U4 rectifier would be expected to do in that circuit.

[Pacafeliz]

Alright, no prob thanks. Will also get one of those.
Though I've seen some people replacing them with solid state options...