What makes EF86 noisy?

[dougietamson]

Originally Posted by cathoderay57

Thanks Doug, good of you to go to so much effort Jerry

I've been meaning to test those EF86's!

I tested with the same 200mVpp sine and eyeballed the amplified trace:

Philips Miniwatt 1963 27Vpp
Mullard Holland 1960 25Vpp
Mullard Holland 1951 27Vpp
Mullard Holland 1956 26Vpp
Mullard Blackburn 1958 25Vpp
Mullard Blackburn 1951 19Vpp
Mullard Blackburn 1950 27Vpp
Mullard Blackburn 1959 27Vpp
GEC Made in USSR 27Vpp

All matched quite close except one out of the bunch is a bit low, l'll use it in a guitar preamp.

Doug

[GrimJosef]

There's a report here http://www.r-type.org/timeline/time-098.htm of the EF86 appearing as a new valve at the 1953 Earls Court Radio Show. So I suspect your 1950 and 1951 valves are 1960 and 1961, not that it affects the data of course.

Cheers,

GJ

[Maarten]

That should be easy to confirm. 1950 an 1951 valves used the old date coding system for which a lookup table is needed to decode. Later 1950's valves may also be from the 1960's or even 1970's. Not 1950's if they have a 4 character factory/date code, though.

To confirm date codes, I've found checking revision codes quite helpful.

[dougietamson]

Originally Posted by Maarten

That should be easy to confirm. 1950 an 1951 valves used the old date coding system for which a lookup table is needed to decode. Later 1950's valves may also be from the 1960's or even 1970's. Not 1950's if they have a 4 character factory/date code, though.

To confirm date codes, I've found checking revision codes quite helpful.

Thanks GJ and Maarten.
I'll check them again, most have 3 digit manufacturing revision and a 3 digit factory/date code and I thought 60's always had a 4 digit factory/date code.

Doug.

[GrimJosef]

Do we know when the transition from long-mesh to short-mesh took place ?

Cheers,

GJ

[MotorBikeLes]

If you want to re-heat ONLY the getter, surely a focussed light beam is the way to do it. A clear sunny day and a big magnifier may get it hot enough.
If not, move to Portugal and try again, if not, try in Death Valley or up on Mt. Palomar.
Les.

[RichardGM]

Originally Posted by GrimJosef

And a pair of EF184s was used by Radford as the phase-splitter/driver in their STA100 https://www.radfordrevival.co.uk/wor...uctions-P2.jpg.

Cheers,

GJ

With, notably, a cascode for the first stage, avoiding the partition noise mentioned in this thread.

[daviddeakin]

Originally Posted by cathoderay57

I mean a background rustling noise:
1. What is happening inside the valve that actually generates the noise?
2. I have recently experienced the background rustle originating in my Quad22 control unit, and the noise was intermittent.

I have a power amp that rustles occasiaonally (6N1P and EL84s). I have never been able to identify exactly where it is coming from since it seems to happen a few times than stop for months on end, and tapping the valves doesn't seem to affect it when I do catch it happening. My guess would be bursts of leakage current inside the valve, maybe caused by static charge build up on some element suddenly discharging

[cathoderay57]

Hi folks, I have now received a replacement EF86, kindly provided by Doug, and all is well with the Quad22 so I'll bow out of this thread and leave it to the guitarists to continue the debates! Cheers, Jerry