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Old 3rd Mar 2015, 2:15 pm   #1
mark pirate
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Default Can a B&K 470 be used with a triode CRT?

Some time ago I made up a universal adaptor for my B&K for testing my older CRT's.
I want to test emission on an Emiscope 3/16 and a 3/18, but these do not have a G2 connection, the same applies to the Mazda CRM92.
Is there a way round this?

Mark
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Old 4th Mar 2015, 9:38 pm   #2
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Default Re: Can a B&K 470 be used with a triode CRT?

I also know that these types of tube can be tested with my Taylor valve tester via an adaptor (Taylor 445) this is plugged in to the tester via an octal socket.
It is tested in the 'Diode' position.
Has anyone either got or used one?

Mark
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Old 5th Mar 2015, 8:34 am   #3
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Default Re: Can a B&K 470 be used with a triode CRT?

Hi Mark,

The B&k does not test those for some reason (460, 470 and 490 tried) I always use the Taylor 445 of which I have two types. Basically the same but with different tube adapters on the block. Comparing results between them proves also that the B&K is on the mean side when it comes to emission, giving between 5-15% lower result. This has also been discovered by other forumites who tested their tubes on the old VRAT site.
The only downside to the 445 is it is slightly heavy so you have to be careful if the tube base is at all loose.
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Last edited by Freya; 5th Mar 2015 at 8:45 am.
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Old 5th Mar 2015, 9:40 am   #4
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Default Re: Can a B&K 470 be used with a triode CRT?

Hi Stephen, Looking at the Taylor adaptor it does appear to be quite a heavy item. As you say, not something you would want hanging off the back of your CRT!

It would be quite simple to make up a lead, I think there are only five wires from the octal plug. These could be terminated with small insulated crocodile clips to connect to the CRT under test.

Do you have any info on the wiring and which octal socket it plugs in to on the Taylor?

I do have some NOS octal plugs kicking round, so would like to knock up a lead to use with my early tubes.

I think the B&K will only work with a CRT that has a G2 connection. I already have a 467 and have just got the 470, it seems to function ok, but only came with one base.
I have the wiring diagrams, so will make a universal adaptor for it.

Mark
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Old 5th Mar 2015, 10:36 am   #5
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Default Re: Can a B&K 470 be used with a triode CRT?

Cant find the booklet in amongst the piles of taylor stuff I have accumulated.
Here is the wire colour info from the octal plug to B12A socket.
PLUG

2 white
3 black
4 green
6 blue
7 red


B12A

1 white - heater
2 blue - grid
10 green - A1
11 black - cathode
12 red - heater

Hope you can interpret it ok, bottom left is the mazda Octal for CRM92 etc.
There are a small percentage of tubes that have a lower beam current (50uA) that may read bad on the scale when they are actually ok. Remember the meter is 200uA FSD.
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Last edited by Freya; 5th Mar 2015 at 10:54 am.
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Old 5th Mar 2015, 11:00 am   #6
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Default Re: Can a B&K 470 be used with a triode CRT?

Thanks Stephen, It should be easy enough to work out from the info you have given. Two wires will be the heater connections, the others will be Cathode, G1 and G2.

I have the list of CRT info in my valve chart, but it does not state which octal socket to plug the adaptor in to. I am guessing it will be IO2.

I will make up a lead this afternoon and give it a try.

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Old 5th Mar 2015, 11:09 am   #7
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Default Re: Can a B&K 470 be used with a triode CRT?

Valve tester socket number 12 which is IO-1. switch setting 2-0-1. set to diode.

Have added the grid, a1, cathode etc on previous post

Remember to use thick enough wires for heater current.
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Old 5th Mar 2015, 2:29 pm   #8
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Default Re: Can a B&K 470 be used with a triode CRT?

Hi Stephen,
Quote:
Valve tester socket number 12 which is IO-1. switch setting 2-0-1. set to diode.
I should have added my tester is the 45A, so possibly a different socket identity.
Unfortunately the Emiscope 3/16 & 3/18 can only be tested on the later 45C
But most use the 2-0-1 setting.
I guess the Avo two panel tester could also be adapted to test CRT's?

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Old 5th Mar 2015, 2:42 pm   #9
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Default Re: Can a B&K 470 be used with a triode CRT?

Yes of course the two panel can be used, just a matter of working out the selector sequence to give the same output on the octal plug. Must admit that I hadn't spotted the Emiscope 10-0-1 setting, how disappointing you cant get that high on the 45A.

Might have a go on the two panel later if I get a chance.
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