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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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19th Aug 2019, 7:20 am | #1 |
Heptode
Join Date: Jan 2016
Location: Gateshead, Tyne and Wear, UK.
Posts: 504
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Valve identity
Pulled from a working set , just cant remember which one lol
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19th Aug 2019, 7:44 am | #2 |
Octode
Join Date: Dec 2018
Location: Llandeilo, West Wales, UK.
Posts: 1,092
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Re: Valve identity
EL84 (or similar output type 6BQ5 etc.)
Alan
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19th Aug 2019, 7:49 am | #3 |
Pentode
Join Date: Feb 2018
Location: Nottingham, Nottinghamshire, UK.
Posts: 229
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Re: Valve identity
I've heard that if you freeze valves, it can temporarily reveal the valve markings on the glass envelope.
Never done this myself, but might be worth a try? |
19th Aug 2019, 8:20 am | #4 |
Octode
Join Date: Dec 2018
Location: Llandeilo, West Wales, UK.
Posts: 1,092
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Re: Valve identity
... should have asked how many pins on the base. 7 or 9?
If it is a Mullard (Philips family) valve there could still be a code round the bottom.
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Never Leave Well Enough Alone... Last edited by snowman_al; 19th Aug 2019 at 8:28 am. |
19th Aug 2019, 9:05 am | #5 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
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Re: Valve identity
If the other valves are "U" types, then UL84
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19th Aug 2019, 11:19 am | #6 | |
Rest in Peace
Join Date: Nov 2010
Location: North Hykeham, Lincolnshire, UK.
Posts: 515
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Re: Valve identity
Quote:
Two rows, one identifies the valve type, the second the date and place of manufacture. Full details - including a translation of the type codes - here: https://frank.pocnet.net/other/Phili...CodeListAB.pdf |
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19th Aug 2019, 2:05 pm | #7 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,996
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Re: Valve identity
Yes I'd say it's an EL/UL84-series. The anode isn't big enough for it to be a 5763.
Sometimes if you breathe on the envelope it can reveal the markings - could this (or rather the condensation that would form on the cold glass) be the same idea as the putting-it-in-a-fridge trick? Ultraviolet light (from one of those hand-held forged-banknote-detectors) could be worth a try too - residual markings might glow! |
19th Aug 2019, 2:27 pm | #8 |
Octode
Join Date: Dec 2017
Location: Morden, Surrey, UK.
Posts: 1,557
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Re: Valve identity
I can only see 7 pins - EL90?
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19th Aug 2019, 8:46 pm | #9 |
Heptode
Join Date: Jan 2016
Location: Gateshead, Tyne and Wear, UK.
Posts: 504
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Re: Valve identity
Can't see any numbers, I have tried with uv lighting. It's a 9 pin. My guess was a UL84 but that was just a guess. Had it for a while so couldn't say which set of valves it came out of.
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19th Aug 2019, 8:54 pm | #10 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Valve identity
If they are intact, a check of the heaters cold resistance should indicate whether it's a UL84 or not.
Lawrence. |
19th Aug 2019, 9:20 pm | #11 |
Heptode
Join Date: Jan 2016
Location: Gateshead, Tyne and Wear, UK.
Posts: 504
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Re: Valve identity
71 ohm cold resistance pins 4 & 5
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19th Aug 2019, 10:17 pm | #12 |
Dekatron
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,270
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Re: Valve identity
my EL84's more or less read short when cold, might be a P series?
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Kevin |
20th Aug 2019, 7:11 am | #13 |
Octode
Join Date: Dec 2018
Location: Llandeilo, West Wales, UK.
Posts: 1,092
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Re: Valve identity
I've just measured a UL84 cold and have 69 ohms.
(Also a couple of UL41s at 70 to 71 ohms - they are 45 volt 0.1 amp heaters same as the UL84) Checking an EL84 heater resistance, it is less than 1 ohm. Alan
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25th Aug 2019, 1:33 pm | #14 |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,199
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Re: Valve identity
Unfortunately, Philips never etched those codes so they can and sometimes are rubbed off. They used a somewhat better ink since it had to survive the chalk print process and then a few years to have proof of warranty.
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26th Aug 2019, 4:15 pm | #15 |
Rest in Peace
Join Date: Nov 2010
Location: North Hykeham, Lincolnshire, UK.
Posts: 515
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Re: Valve identity
I have seen codes printed on bakelite bases and on the underside of B8A valves but all B7g and B9A valves I've ever seen have had the code etched in the glass and large numbers of valves sold in the UK under the Mullard trademark were manufactured in Dutch factories.
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26th Aug 2019, 5:47 pm | #16 |
Octode
Join Date: Feb 2009
Location: Bletchley, Buckinghamshire, UK.
Posts: 1,219
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Re: Valve identity
I think what Maarten is saying is that technically, they aren't etched. It's actually an "almost-indelible" ink.
I have seen a few valves where it has partly rubbed off, but that is unusual. |
26th Aug 2019, 7:22 pm | #17 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,932
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Re: Valve identity
Put 6.3 volts across the heaters and all will be revealed,UL or EL.
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27th Aug 2019, 12:11 am | #18 |
Heptode
Join Date: Jan 2016
Location: Gateshead, Tyne and Wear, UK.
Posts: 504
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Re: Valve identity
Sorry for the late reply its a UL84 just tried it in a set, works good sounds nice. Thank you
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27th Aug 2019, 2:48 am | #19 | |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,199
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Re: Valve identity
Quote:
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27th Aug 2019, 11:34 pm | #20 |
Heptode
Join Date: Jan 2016
Location: Gateshead, Tyne and Wear, UK.
Posts: 504
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Re: Valve identity
I will have anther look tomorrow for etched numbers but to be honest im thinking theres none there
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