Jan Philips 6L6WGB

[EFK]

These are early 80s production short bottles and there seem to be an abundance of them at pretty reasonable prices lately. Supposedly, these have the same internals as the 35 watt 7581A beasts. So, all of the tube sellers are claiming that these are not true 5881/6L6WGB spec but can actually take up to mid 400s plate voltage and can be treated as a 30 watt tube or 6L6GC. I have seen some others say this is a bad move.

CAN ANYONE set this right? I want to use these in a 6L6 based *cathode bias* amp, plate pin 3 to ground is about 420 but working plate voltage (pin 3 to pin 8) is around mid 380s depending on cathode resistor. Should I scale the bias resistor as if these are 23 watt tubes? 25 watt? 30 watt? I'm quite confused here!

[Diablo]

I'm using those tubes in a 5F6A Tweed Bassman clone. I have them biased as if they are 23 watt tubes - 35 mA with 460 volts on the plates. These tubes break up earlier than 6L6GC tubes, so I doubt they are the same wattage.

[fyl]

These are early 80s production short bottles and there seem to be an abundance of them at pretty reasonable prices lately.

Abundance? Stocks are nearly depleted...

Supposedly, these have the same internals as the 35 watt 7581A beasts.

Only for late production models, earlier versions used standard 5881/6L6WGB parts.

7581A:



Pix: Wiwitubes

Large T12 bulb and top getter.

Late 6L6WGB:



Pix: Natubes

Compact T11 bulb, side O getter.

Bulb and getter aside, they use the same elements.

So, all of the tube sellers are claiming that these are not true 5881/6L6WGB spec but can actually take up to mid 400s plate voltage and can be treated as a 30 watt tube or 6L6GC.

They are correct. Max voltage is 500V plate/450 v screen (except in UL). Max dissipation is limited by the bulb size - less surface, worse thermal exchange - but 28 to 30 w is IMO a safe max rating (7581A's are rated at 35 w).

[fyl]

These tubes break up earlier than 6L6GC tubes, so I doubt they are the same wattage.

Breakup is linked to current drawn: less current drawn, early breakup; mo' current, late breakup.

[g1]

They have worked well for me (and others) at 540-545 plate volts in Ampeg V4 for many years. That being said, it is with stock bias circuit which I imagine biases them quite cold though I've never checked.

[stokes]

They are very hearty tubes,but they are not 7581A's as some dealers say.I have seen many stand up to the extra plate volts/current,but I've seen some fail.A supplier buys a big lot of them,tests them at extreme limits and says they are "7581A's".But how long did he test them? I once put a NOS pair of Tung-sol 5881's in a 60 watt Boogie and they lasted a couple of hours,and then a couple of hours later they failed.So if I pull them out after an hour or two does that mean they can take the punishment like a 6L6GC? Not at all.Sure many of these WGB's will take extra abuse,but they aint 7581A's.

[Casey4s]

The Jan/Sylvania 6L6WGB is not a true 5881 which is a 23 watt tube. The Sylvania and some GE 6L6WGBs were simply a 6L6GC in a short bottle to meet military size specifications. These tubes are 30 watters, not 23, but are great NOS tubes. Real Tung-Sol 5881s have a max plate voltage of 360V in PP AB.