Cossor 185BTA Valve.

[Megatron]

Does anyone have any information on 185BTA cossor valve?
I have always built amplifiers using slightly out of the ordinary valves, and in my stash have kept quite a few of these because they look like they may be a likely candidate for a small PP amplifier, however only have very basic info from TDSL.
there must exist a data sheet somewhere?
was kind of hoping they would be related to a better known audio type, like a lot of sweep tubes are.

[Megatron]

Anode and supports look very similar to Cossor MIL spec 6L6 CV1947??

[Cobaltblue]

As you probably gathered it's a Line Output Valve.

The very Basic Information is available here

http://www.r-type.org/exhib/aaq0448.htm

Cheers

Mike T

[Ed_Dinning]

Looks like it should work OK for audio, possibly like an 807, so it may need quite a low RL
for best matching.
As it is an older generation LOP valve it should not have been optimised for pulse performance and should be nicely linear

Ed

[Herald1360]

Some characteristic curve measurements would provide a good basis for comparison with similarly PA rated audio valves. I would think the valve would be fine up to around 500V anode / 300V screen for audio output duty, adjust bias for around 20W max standing anode dissipation.

[Robert Gribnau]

On page 42 of this valve guide the 185BT and the 185BTA are mentioned: https://worldradiohistory.com/UK/Ber...lve-Guide1.pdf

[Megatron]

Yes there doesn't seem to be much detailed data out there. guess I will have to do some curve plotting when I get time, I guess 5 grid voltages with 10 data points will be enough to see if its similar to something else.....

[Megatron]

Originally Posted by Ed_Dinning

Looks like it should work OK for audio, possibly like an 807, so it may need quite a low RL
for best matching.
As it is an older generation LOP valve it should not have been optimised for pulse performance and should be nicely linear

Ed

Thats was my theory........I think it may be loosely based on a 6l6

[Ed_Dinning]

I have a Geloso amp using 807's in UL mode and it sounds quite good.
It will complicate the opt slightly to use UL but should be worth the effore. Mine runs with the bias at -34V and about 400v on the anodes

Ed

[Megatron]

Originally Posted by Ed_Dinning

I have a Geloso amp using 807's in UL mode and it sounds quite good.
It will complicate the opt slightly to use UL but should be worth the effore. Mine runs with the bias at -34V and about 400v on the anodes

Ed

I have a home made amp using 807 in Ultralinear too. opts were for KT88 ultralinear 5k a-a so work well with parallel 807's
In fact I made it switchable from triode to UL to full pentode, it has too about 400V in triode & Ultralinear, and in pentode mode 575V and 250v on the grids.
Sounds best in triode mode, but Ultralinear is very good too, but has more feedback to sound good. fortunately when I set the feedback right in pentode mode it worked well in triode mode too less feedback afforded by the lower open loop gain.
power output is quite suffecient.

[Robert Gribnau]

A little bit more data.

[Heatercathodeshort]

The English Electric 1550 TV has five 185BT valves.
Line output, Frame output, video output,
Sound output and a 185BTA [higher insulation] for EHT generation.
It has an odd heater voltage, 18V @.45a.
John.