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Old 28th Apr 2021, 10:58 am   #1
agardiner
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Default U30 Valve

Does anyone have a U30 valve in good condition that they will sell me please?

Thanks,

Adrian.
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Old 28th Apr 2021, 9:56 pm   #2
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Default Re: U30 Valve

It seems these valves are very rare and expensive, what piece of equipment is it used in?
John
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Old 29th Apr 2021, 8:36 am   #3
Ed_Dinning
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Default Re: U30 Valve

Hi Adrian, there will be plenty of suitable rectifiers about but you will need to change the base to a B4/5 type or make up an adaptor.

Ed
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Old 29th Apr 2021, 8:45 am   #4
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Default Re: U30 Valve

Hi Adrian

ISTR this valve has the ability to be used as a voltage doubler is that facility being used in this case?

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Old 29th Apr 2021, 4:40 pm   #5
agardiner
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Default Re: U30 Valve

Hi all,

Thanks for the comments. Yes, I think I will need to resort to changing the base and using something else.

It is only being used as a simple rectifier for a radio; must have been an easy choice for the manufacturer in the day as I haven't seen one used in a radio before; they tend to be the more common 5Z4G.
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Old 29th Apr 2021, 5:21 pm   #6
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Default Re: U30 Valve

If it is used as a half wave rectifier in the radio, the U30 valve heaters are 26 volt .3 amp, a cheap abundant substitute would be a PY32 or PY33 valve which has a heater 29 volt .3 amp, you would have to change the base to octal or make up an adaptor.
John
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Old 29th Apr 2021, 5:26 pm   #7
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Default Re: U30 Valve

Quote:
Originally Posted by jonnybear View Post
If it is used as a half wave rectifier in the radio, the U30 valve heaters are 26 volt .3 amp, a cheap abundant substitute would be a PY32 or PY33 valve which has a heater 29 volt .3 amp, you would have to change the base to octal or make up an adaptor.
John
Yes, just used as a double half wave rectifier. The heaters are in series though, would this be much of a problem?

Thanks.
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Old 29th Apr 2021, 10:12 pm   #8
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Default Re: U30 Valve

Quote:
Originally Posted by agardiner View Post
Quote:
Originally Posted by jonnybear View Post
If it is used as a half wave rectifier in the radio, the U30 valve heaters are 26 volt .3 amp, a cheap abundant substitute would be a PY32 or PY33 valve which has a heater 29 volt .3 amp, you would have to change the base to octal or make up an adaptor.
John
Yes, just used as a double half wave rectifier. The heaters are in series though, would this be much of a problem?

Thanks.
If the anodes are strapped together along with the cathodes then the valve is being used as a standard 1/2 wave rectifier, the PY33 being a standard 1/2 wave rectifier would be fine, 3 volts difference in a series heater chain will not be a problem as long as all the valves have 300ma heaters which they obviously have, For interest would the radio be a HMV 340 by any chance?
John
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Old 30th Apr 2021, 12:07 pm   #9
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Default Re: U30 Valve

Thanks John.

No not an HMV set, but a Marconi 382.

Regards,

Adrian.
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Old 30th Apr 2021, 1:31 pm   #10
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Default Re: U30 Valve

Quote:
Originally Posted by agardiner View Post
Thanks John.

No not an HMV set, but a Marconi 382.

Regards,

Adrian.
In that case a PY32/3 would do the job admirably especially as the radio uses a Half wave rectifier and barretter tube in the heater chain. is the U30 completely US, if the glass bulb is broken you could use the base as an adaptor, if not may be worth keeping as a collectors item. The PY32/3 are easy to get hold of as they were used in their thousands in monochrome televisions,may even be worth a ask on this Forum.
John
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Old 30th Apr 2021, 1:38 pm   #11
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Default Re: U30 Valve

Thanks John.

So, fingers crossed I might have sourced a U30; would be nice to keep original. Otherwise I will indeed go down the modification route.

Pretty certain the U30 is dead - one side of it is completely dead and the other side tests low emission. The HT in the set is very low and so the set is not working. I have replaced the main electrolytics; they were replaced in the 80s but now completely open circuit. The sets owner loves the radio and it is in every day service! So I suspect worn/faulty valve probably finished off by overload as the caps failed.
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Old 30th Apr 2021, 1:57 pm   #12
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Default Re: U30 Valve

If the U30 is cosmetically good I would keep as it is probably worth something to a collector. If you have an old seven pin broken glass valve it would be easy to make an adaptor up so it is just plug in, instead changing the base to IO. some one on here may be able to help with that.would be great if you have managed to source a U30 though.
John
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Old 30th Apr 2021, 2:38 pm   #13
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Default Re: U30 Valve

You could always leave the U30 in the heater circuit and use silicon under the chassis with a series resistor for rectification.
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Old 30th Apr 2021, 2:40 pm   #14
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Default Re: U30 Valve

Quote:
Originally Posted by PJL View Post
You could always leave the U30 in the heater circuit and use silicon under the chassis with a series resistor for rectification.
I had considered this, and will still consider it if the U30 I have hopefully sourced doesn't appear. What sort of value of resistor would you recommend?
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Old 5th May 2021, 1:01 pm   #15
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Default Re: U30 Valve

I have sourced and received a U30. Many thanks to all for their various suggestions.

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