Is JAN Sylvania 6L6WGB under rated the same as JAN Philips 6L6WGB?

[elipsey]

Folks seems to think the JAN Philips 6L6WGB is "really" a 25 or 30 watt tube:
http://music-electronics-forum.com/t20272/

In so far as this is actually true for the JAN Philips, is it also true for JAN Sylvania?

Anyone here have any experience running the Sylvania at higher idle, like 25+ watts implied max dissipation?

They plate structures look just like the Philips to me, and I'm wondering if I could mix and match them. I think the date code on the Sylvanias I was looking at is '80, and I've heard that the late 80's ones were different, but I'm not sure about this....

[g1]

If there are no visible differences aside from the name, it's possible they were even built at the same plant. Re-branding goes way back.

[elipsey]

If there are no visible differences aside from the name, it's possible they were even built at the same plant. Re-branding goes way back.

Yeah, that's what it looks like to me too. So what do you think about biasing them hotter than the usual 5881?

[Tone Meister]

According to the 6L6WGB Datasheet the 6L6WGB is a 26 watt tube, but Watford Valves claims they are able to dissipate 30 watts.

https://www.watfordvalves.com/produc...il.asp?id=1313

Also, Mike K at KCA NOS Tubes claims they "hold up well in amps with plate voltage up to 470 volts."

https://www.kcanostubes.com/content/...philips-6l6wgb

[elipsey]

According to the 6L6WGB Datasheet the 6L6WGB is a 26 watt tube, but Watford Valves claims they are able to dissipate 30 watts.

https://www.watfordvalves.com/produc...il.asp?id=1313

Also, Mike K at KCA NOS Tubes claims they "hold up well in amps with plate voltage up to 470 volts."

https://www.kcanostubes.com/content/...philips-6l6wgb

I meant to ask specifically about the JAN Sylvania, not the Philips.

However, I'm glad you reminded me to read the data sheet because I thought 6L6WGB/5881 were 23W max plate dissipation, but it looks like that's not categorically true....

[Tone Meister]

Read the Watford Valves link, it goes into some detail about these tubes and provides some clarity on the Sylvania and Philips relationship during this particular era.

From Watford Valves website
"Philips electronics components group was the name given to the products marketed in America after Philips bought the American valve manufacturer Sylvania in the early 1980’s. Sylvania was a major manufacturer of valves and Philips bought them to get the lucrative American Government and military contracts. These valves are of the highest military grade which offer outstanding performance and were all made in the USA."

[elipsey]

Read the Watford Valves link, it goes into some detail about these tubes and provides some clarity on the Sylvania and Philips relationship during this particular era.

From Watford Valves website
"Philips electronics components group was the name given to the products marketed in America after Philips bought the American valve manufacturer Sylvania in the early 1980’s. Sylvania was a major manufacturer of valves and Philips bought them to get the lucrative American Government and military contracts. These valves are of the highest military grade which offer outstanding performance and were all made in the USA."

Sorry, I see it now. Thanks.

[Tone Meister]

No problem, I hope the information helped answer your questions. More than a few of us have been confused by these tubes. It's a common misconception that they are 19 or 23 watt tubes when the datasheet indicates 26 watts. Further, more than a few very respected sources claim they can easily dissipate 30 watts and another states they hold up to at least 470 volts on the plates. That's a pretty robust tube that's on par with most any 6L6GC.

I have several matched quads of these so you can say I have a dog in the hunt, so to speak. I hope this helps.

[g1]

These are not the typical NOS 5881/6L6WGB. These are 6L6 in a small bottle, so they could be used in places that would only fit the physical size of the WGB in military applications.
If you could find them at a decent price anymore, I would not hesitate to use them in any 6L6 application (and have done so with no issues ever).

[stokes]

I have both the Phillips and Sylvania branded Jan 6L6 WGB's and they are certainly identical and produced in the same plant.It is very common to find tubes from the old days made by one manufacturer with another brands label.They made millions of tubes for the military and quite often it wasnt possible to meet a production deadline with your own machining so they often made tubes for a competitor to label as their own.As to using a 26 watt tube in a 30 watt application as described with these tubes,I have done it and never had a problem,but if I do it for a customer I always give the obvious warning

[elipsey]

For anyone who cares, or those out there in Internet land who found this thread because it was indexed, I got samples of each of these tubes and took a couple of pictures, which are posted. The envelope, base, and plate structures look really totally the same, however, for whatever it's worth, the ones I tried have very different idle currents with the same plate and bias voltage. At about 400Vp and -43Vg1 the Sylvania passes .031mA while the Philips allow 42mA and 44mA. Obviously a small sample size. Your mileage may vary.

[Enzo]

The trouble with that observation is that tubes are not precision parts. That is why we have matching, because we cannot count on tubes being the same even from one manufacturer in one production batch. When you compare two brands for specs, you will likely find a difference, but you will just as likely find a difference comparing two tubes from the same batch of one brand. In other words the variation in tube performance is not due to branding, it is due to natural variation tube to tube.

[J M Fahey]

.031mA

I hope you meant 31mA ; otherwise that would be a seriously worn tube.

As of plate dissipation, rather than reading 1000 old datasheets and imagine which one matches (if any at all), just_do_the_test [tm]

Place one in an amp in a semi darkened room, start rising current until you see a red spot on the plate, back down slowly until it just becomes invisible. Record dissipation.

Do it for all tubes involved.

Compare notes.

Post results.

FRWIW we often find great variations in gain or transconductance, because that is affected by tiny variations in grid to cathode distance, measured in thousandths of an inch, but raw infrared emission/dissipation is a far simpler parameter, directly depending on plate surface and shape, (and maybe thickness) and those are dimensions easy to get with precision.
Transconductance can vary up to 3:1 or 300% while plate surface must be within 1% at worst, after all it's a simple sheet metal punching and bending operation.

[km6xz]

The needs of a guitar amp user and the military are quite at odds. The tubes the military bought needed to be plug compatible and never ran even close to rated spec or even tube manual "typical application". Like test gear, most military equipment had the same set of tubes in them as new when they were sold to scrap 30-40 years later. The small bottle 5581 style used active cooling systems usually because they were spec'ed for circuits that were more compact. A few things can be expected from the actual military stock tubes was rugged heaters. Very little was sold to the military by 1980 but dealers used that term as if it meant higher performance when selling retail. The only equipment still using tubes in military use by the mid 1970s were RF systems and a couple models of tube receivers which used tubes very conservatively. Systems that needed precision require full alignment whenever tubes were replaced but the tubes were still supposed to be plug compatible. A wide variation in Gm simply meant they were bad tubes and would be rejected, then sold to consumers in the public retail channel. What your amp to be roadworthy.... do as the military did, run a 6L6 at 15-17w dissipation. Pushing tubes with high idle dissipation is not compatible with reliable roadworth amps. You can still get tube saturation compression. The tubes in a head should, if kept within design limits, last 5-15 years in an amp. You can also get increased life by cooling, particularly with small bulb tubes like EL84 or 5881 where there is less glass surface area to plate surface area ratio. Large bulbs have more surface area to absorb and re-radiate the IR energy radiated from the plate. Every try pulling a hot small bulb tube out with your fingers compared to the large glass bulb types, using the same exact tube interior components?
Is gaining 0.5 db in spl that could not be heard, really worth investing in hundreds on tubes every year?

I have come to the conclusion that the biggest risk to amp performance/reliability and "tone" is players reading the internet, not bad tube brands, and certainly not the often argued over capacitors.

[Leo_Gnardo]

FWIW my pet theory for the 5881's good fit for mil use is - more can be carried in a spares box than regular 6L6 varieties common in the early 50's when it was developed. One among several other reasons. Active cooling systems Stan mentioned = fans.

One of my favorite shop tools for checking power tube operation, a "laser thermometer" probably same/similar to "IR gun" mentioned by another correspondent. I got mine on sale @ $25 from Parts Express. In the case of amps using multiple output tubes you can quickly tell which are running cool or hot. Of course the electrical measurements are important but our eyes only see a problem when a tube goes red-plate or worse. The laser thermometer or IR gun sees infrared at wavelengths our eyes don't, and interprets that as a temperature reading on its screen. Good for checking temps on hot power transformers, resistors, transistors etc as well. What a handy item, at $25-35 very affordable too.