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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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26th Nov 2020, 10:23 pm | #1 |
Pentode
Join Date: Mar 2019
Location: Monmouth, Monmouthshire, Wales, UK.
Posts: 166
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Cossor 185BTA Valve.
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. |
26th Nov 2020, 10:59 pm | #2 |
Pentode
Join Date: Mar 2019
Location: Monmouth, Monmouthshire, Wales, UK.
Posts: 166
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Re: Cossor 185BTA
Anode and supports look very similar to Cossor MIL spec 6L6 CV1947??
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26th Nov 2020, 11:08 pm | #3 |
Moderator
Join Date: Dec 2010
Location: Exeter, Devon and Poole, Dorset UK.
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Re: Cossor 185BTA
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
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27th Nov 2020, 10:22 am | #4 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,194
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Re: Cossor 185BTA
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 |
27th Nov 2020, 12:34 pm | #5 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: Cossor 185BTA Valve.
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.
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27th Nov 2020, 3:23 pm | #6 |
Heptode
Join Date: May 2017
Location: Konongo, Ghana
Posts: 513
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Re: Cossor 185BTA Valve.
On page 42 of this valve guide the 185BT and the 185BTA are mentioned: https://worldradiohistory.com/UK/Ber...lve-Guide1.pdf
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Robert |
27th Nov 2020, 8:19 pm | #7 |
Pentode
Join Date: Mar 2019
Location: Monmouth, Monmouthshire, Wales, UK.
Posts: 166
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Re: Cossor 185BTA Valve.
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.....
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27th Nov 2020, 8:21 pm | #8 |
Pentode
Join Date: Mar 2019
Location: Monmouth, Monmouthshire, Wales, UK.
Posts: 166
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Re: Cossor 185BTA
Thats was my theory........I think it may be loosely based on a 6l6
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27th Nov 2020, 8:38 pm | #9 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,194
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Re: Cossor 185BTA Valve.
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 |
27th Nov 2020, 9:17 pm | #10 | |
Pentode
Join Date: Mar 2019
Location: Monmouth, Monmouthshire, Wales, UK.
Posts: 166
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Re: Cossor 185BTA Valve.
Quote:
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. |
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28th Nov 2020, 11:15 am | #11 |
Heptode
Join Date: May 2017
Location: Konongo, Ghana
Posts: 513
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Re: Cossor 185BTA Valve.
A little bit more data.
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Robert |
1st Dec 2020, 10:29 pm | #12 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,147
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Re: Cossor 185BTA Valve.
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. |