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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 10th Apr 2018, 7:12 pm   #1
Calanta
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Default Valve ID Help

Hi. I'm looking for some help identifying the valve shown in the pics.
It is used as the output stage to provide the HT for an old Bush radio. I'm not entirely sure if its actually faulty as yet, as I'm still testing the PSU which has other problems, however I thought if I can at least understand what it is that would help regardless. It has seven pins.
I've had a look through the National Valve Museum site which is amazing, but not managed to find this. I'm sure it will be a common type, I'm just not familiar with this era of technology.

Many thanks for any help / advice.

Hugh
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Old 10th Apr 2018, 7:15 pm   #2
vidjoman
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Default Re: Valve ID Help

Which Bush radio ?
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Old 10th Apr 2018, 7:17 pm   #3
Calanta
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Default Re: Valve ID Help

It's an SB21
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Old 10th Apr 2018, 7:19 pm   #4
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Default Re: Valve ID Help

Could it be an OB2 stabiliser http://www.r-type.org/exhib/aaa0357.htm ? In your second pic above the letters SK I think I can just about make out a faint B2. Take it out into the daylight (if we ever get any !) and see what you can see with a magnifier. It should look something like this

https://www.picclickimg.com/d/w1600/...-Old-Stock.jpg

Cheers,

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Old 10th Apr 2018, 7:19 pm   #5
RF Burn
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Default Re: Valve ID Help

Hi Hugh,

That looks like a Voltage Regulator valve. The type number was printed on the glass just above the SK with white background. Usually if you breath on the glass to form condensation and then look at it at an angle you should be able to make out the type identifier characters which are currently unreadable in you photo.

Post what you find here and someone should be able to tell you what the device actually is.

Adrian
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Old 10th Apr 2018, 7:22 pm   #6
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Default Re: Valve ID Help

Just looking at it it looks a lot like a stabiliser tube like this one.

http://www.r-type.org/exhib/aai0227.htm

What model of Bush is this?

Your description suggests a rectifier but they look more like this http://www.r-type.org/exhib/aaa0851.htm

Its possible someone has stuffed any old valve in the socket.

Oops crossed.

Cheers

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Old 10th Apr 2018, 7:24 pm   #7
Calanta
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Default Re: Valve ID Help

Quote:
Originally Posted by GrimJosef View Post
Could it be an OB2 stabiliser http://www.r-type.org/exhib/aaa0357.htm ? In your second pic above the letters SK I can just about make out a faint B2.
Many thanks GJ, I'll have a go at the condensation trick and see if I can make out the letters.

Thanks Adrian also.
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Old 10th Apr 2018, 7:27 pm   #8
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Default Re: Valve ID Help

That valve isn't original to the SB21 so it must be part of a later mains power supply for this 1935 battery set

Cheers

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Old 10th Apr 2018, 7:30 pm   #9
Calanta
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Default Re: Valve ID Help

Thank Mike. Yes I should have said that, it's a separate PSU I'm fault finding.
I believe the valve heater output is fine, just the HT.
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Old 12th Apr 2018, 11:00 am   #10
Calanta
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Default Re: Valve ID Help

Looks like this is a voltage rectifier OB2. Seems the likeliest.
I still can't fully see the markings but there is a resemblance of a B and 2.
So thanks for everyone's help, much appreciated.

Having looked at the design, I'm going to abandon this PSU and go with a better / safer option probably based on info from here:-

http://www.dos4ever.com/battery/battery.html

Cheers again.
Hugh
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Old 12th Apr 2018, 10:45 pm   #11
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Default Re: Valve ID Help

Just out of interest - could you post the circuit of the present power supply?
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Old 16th Apr 2018, 11:45 am   #12
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Default Re: Valve ID Help

Quote:
Originally Posted by Calanta View Post
Looks like this is a voltage rectifier OB2. Seems the likeliest.
I still can't fully see the markings but there is a resemblance of a B and 2.
So thanks for everyone's help, much appreciated.
.
Hugh
That should be voltage regulator.

The 0B2 behaves similarly to a zener diode- it has a relatively stable breakdown voltage over a range of operating currents so it can be used with a suitable series ballast as a shunt type voltage regulator.
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