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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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Old 11th Jan 2019, 5:04 pm   #21
G8HQP Dave
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Default Re: 6Q7G Valve, what brand ?

As far as I know, Brimar never used alphanumeric codes. Just numeric codes. Y10M may or may not be a Philips code, but it looks more Philips-like than Brimar-like.

My guess is that a British maker simply copied an American design, as there was a war on. As Brimar did this for almost all their range they must be the prime suspect, but it could have been someone else.
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Old 11th Jan 2019, 9:59 pm   #22
tri-comp
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Default Re: 6Q7G Valve, what brand ?

The Y10M code looks like it was handwritten with a pencil on the glass pinch inside the valve.
I'll see if I can get my camera to focus on it tomorrow and post the picture.
Could it be just a partno.-indication for possibly the completed valve construction ready to be put in a bulb and finished ?
Sort of a warehouse stockno. ?
Oh, and since I have 2 NOS Boxed 6Q7G's I'll check the other as well for any code on the pinch.
Didn't think of that until just now.

/Torben
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Old 12th Jan 2019, 5:33 pm   #23
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Default Re: 6Q7G Valve, what brand ?

At first I tried to take pictures out in the daylight.
It didn't work out too well for photographing the text on the pinch.
Then I tried indoors under a LED lamp.
As you can see that turned out quite well.
The second valve has STA63N written inside.
There's absolutely no relations between what's written inside the two valves imho.
As you will also notice the second valve has had a label attached with a string.

/Torben
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Old 12th Jan 2019, 7:21 pm   #24
RF Burn
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Default Re: 6Q7G Valve, what brand ?

That 'N' embossed on the base pretty well confirms that it is of UK manufacture. Now looking at the attached label, the Service Valve Equivalents Guide gives the CV587 as 6Q7G (USA), DH63 (MOV) and the ZA manufacturers code as 'MOV Gateshead' which strengthens the MOV (Marconi Osram Valve company) connection. Is that information strong enough to fix a result?

Brimar also copied the 'stop sign' or hexagonal border for their early valves from their USA originals, after all the company was named BRItish MAde American Range (BRIMAR) for a reason . . .

Other British manufacturers normally produced 'equivalents' or 'substitutes' to USA type valves using their own standard type numbering systems (e.g 6Q7 = EBC33, DH63; 6J5 = L63; 6F5 = H63; 6K7 = EF39, KTW63 etc.)

Also, do not forget the flood of 'tubes' from the USA during & after WW2 as parts/spares for the US and British military and on 'lend/lease' that were marked and distributed by British manufacturers.

Adrian.

Last edited by RF Burn; 12th Jan 2019 at 7:34 pm.
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Old 12th Jan 2019, 8:58 pm   #25
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Default Re: 6Q7G Valve, what brand ?

Quote:
Originally Posted by RF Burn View Post
That 'N' embossed on the base pretty well confirms that it is of UK manufacture. Now looking at the attached label, the Service Valve Equivalents Guide gives the CV587 as 6Q7G (USA), DH63 (MOV) and the ZA manufacturers code as 'MOV Gateshead' which strengthens the MOV (Marconi Osram Valve company) connection. Is that information strong enough to fix a result?

Brimar also copied the 'stop sign' or hexagonal border for their early valves from their USA originals, after all the company was named BRItish MAde American Range (BRIMAR) for a reason . . .

Other British manufacturers normally produced 'equivalents' or 'substitutes' to USA type valves using their own standard type numbering systems (e.g 6Q7 = EBC33, DH63; 6J5 = L63; 6F5 = H63; 6K7 = EF39, KTW63 etc.)

Also, do not forget the flood of 'tubes' from the USA during & after WW2 as parts/spares for the US and British military and on 'lend/lease' that were marked and distributed by British manufacturers.

Adrian.
Yes, your conclussions are good enough for me.

There must have been some wide tolerances for substitution as the amplification factor and Ra for 6Q7 is ~60 and 50KOhm as opposed to 30 and 15KOhm for the EBC33.
Would that have been normal ?
I'm asking because I'm putting together a rather extensive list of settings for the B&K 607/667 emission valve-tester when testing B&K non-listed valves. The list is already some 80+ A4 pages and I have obviously no chance of testing each and every valve in-the-flesh. So, I'm depending on what cross-ref. tables and books that have been published, like The Sams-series and the RSGB Service Valve Equivalents besides data from radiomuseum.org, The CV-register etc. etc.
Unfortunately I don't have a NOS EBC33 here, actually none at all, so I won't be able to hold the readings against the 6Q7 for this valve xref, and perhaps I should be more carefull in the future about recommended substitutions that could display far off data from the original.

/Torben
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Old 12th Jan 2019, 9:08 pm   #26
G8HQP Dave
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Default Re: 6Q7G Valve, what brand ?

You need to bear in mind the difference between a substitute and an equivalent. A substitute has roughly the same pinout and sufficiently similar characteristics that it will work reasonably well in most circuits; someone trying to sell you a substitute may stretch the truth. An equivalent is almost the same thing as the original; it could be identical, or only have minor differences which will almost always be of little consequence in almost any circuit.

6Q7 and EBC33 may be substitutes, but not equivalents. 12AU7 and ECC82 are equivalents.
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Old 12th Jan 2019, 9:24 pm   #27
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Default Re: 6Q7G Valve, what brand ?

I understand that.

So, I went and checked a NOS Tungsram EBC3 (EBC33 with a P8A socket) with a suitable socket-adapter and with the same tester-settings as for the 6Q7.
Both diodes are spot-on and the triode in the EBC shows about 10% more emission than the NOS 6Q7G.
I'd say that's fully acceptable for an emission-test and as my wife says I can't afford an AVO VCM or such I'll leave it with that

/Torben
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Old 13th Jan 2019, 8:09 pm   #28
Maarten
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Default Re: 6Q7G Valve, what brand ?

Quote:
Originally Posted by G8HQP Dave View Post
As far as I know, Brimar never used alphanumeric codes. Just numeric codes. Y10M may or may not be a Philips code, but it looks more Philips-like than Brimar-like.
Unfortunately, I know next to nothing about Brimar markings so I'll take your word for that.

Philips did indeed use alpha/numeric/symbol markings, but this code doesn't really make a lot of sense according to what I know of their coding systems. The valve was meanwhile identified as not being a Philips/Mullard made valve, so that's a bit of a moot point anyway.
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Old 13th Jan 2019, 11:40 pm   #29
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Default Re: 6Q7G Valve, what brand ?

Quote:
Originally Posted by G8HQP Dave View Post
You need to bear in mind the difference between a substitute and an equivalent. A substitute has roughly the same pinout and sufficiently similar characteristics that it will work reasonably well in most circuits; someone trying to sell you a substitute may stretch the truth. An equivalent is almost the same thing as the original; it could be identical, or only have minor differences which will almost always be of little consequence in almost any circuit..
By your definition, I would say that most equivalent lists are substitute lists and in many cases they are not even a good substitute with different heater currents and characteristics. Worse than that, manufacturers changed the performance of their valves and I have an example of a 30's Pye set with a label saying you should not replace a particular valve with a newer version of the same type without circuit changes.
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Old 14th Jan 2019, 12:57 pm   #30
G8HQP Dave
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Default Re: 6Q7G Valve, what brand ?

The lists put out by Mullard were generally quite good, as they mentioned issues like change in heater currents. If they said something was equivalent then it usually was a genuine equivalent.

Ones which I found amusing were the Brimarisation adverts which as well as changes in heater current and gain, in some cases even required a change of valveholder!
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