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Old 20th Feb 2011, 9:11 am   #521
Mr_Klaatu
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi,

I know I am simply showing my ignorance, but I have to ask

I understand that the three meters need to have a separate power supply from the circuit they are measuring. But would it be possible to run all three meters from a single supply so long as it was isolated from the rest of the circuit ?

If not, could anyone explain to me just why not ?

Thanks in advance !

Last edited by Mr_Klaatu; 20th Feb 2011 at 9:23 am. Reason: spelling corrections
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Old 20th Feb 2011, 2:50 pm   #522
julie_m
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Default Re: The "Sussex" Homebrew Valve Tester.

No. The meters' supplies need to be isolated from one another, because they are not all referenced to the same "ground".

The grid voltage meter is referenced to the cathode, but the anode current and gain meters are in series with the anode supply.
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Old 20th Feb 2011, 3:15 pm   #523
Guitarist28
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi AJS,
I'm still working on my Sussex - are you indicating that each meter needs it own power supply??

Regards

Rob
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Old 20th Feb 2011, 6:23 pm   #524
swordholder
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Default Re: The "Sussex" Homebrew Valve Tester.

Rob,
Each meter needs its own supply, Eds transformer has 3 separate 6v windings, one for each meter

Regards
Mike
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Old 20th Feb 2011, 9:40 pm   #525
Ed_Dinning
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Gents, the meter windings on my transformer are white insulated wire and are tri-filar wound so they all see the same voltage and are well insulated from each other. The lead-outs have either 1, 2 , or no knots in them for ID.

Ed
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Old 20th Feb 2011, 10:32 pm   #526
Guitarist28
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Default Re: The "Sussex" Homebrew Valve Tester.

Thanks Ed,
This is a timely reminder that I should finish what I started and complete my tester!

Regards

Rob
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Old 22nd Feb 2011, 9:20 pm   #527
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Default Re: The "Sussex" Homebrew Valve Tester.

Here's a few pictures of my Sussex testing a 40 year old Dynaco branded ECC83. Some valves just seem to go for ever!

The case is from an old subwoofer amplifier which had lost its side panels, so I made the curved wooden side pieces as a nod to the Avo MkIV.

A big thanks to everyone who helped simply through your posts to this forum and especially to Mike (swordholder) for sharing his original project.

Gordon
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Old 26th Feb 2011, 2:52 am   #528
valvoline1298
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Gordon,

That's a very handsome looking tester unit you got there!... very well done indeed.

What did you use for the letterings for your Sussex panel faces..did you use white 'Letraset' transfers?

Regards...Gary
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Old 26th Feb 2011, 2:02 pm   #529
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Default Re: The "Sussex" Homebrew Valve Tester.

Gordon, congratulations! What a great job you've made of that. Want one ... How did you apply the lettering?
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Old 27th Feb 2011, 9:53 pm   #530
Foggy Road
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Default Re: The "Sussex" Homebrew Valve Tester.

Thanks for the kind words -yes, it is white Letraset - bit of a pain to apply, but easy to remove if you make mistake - which I did numerous times! Once on it's quite durable - I have some valve amps I built many years ago where the lettering is still in good condition. In hindsight I wish I'd used 3mm letters instead of 5mm as it's a bit congested in the centre of the case - still, as age will no doubt take its toll on my eyesight using the larger letters might be beneficial in years to come!

Gordon
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Old 3rd Mar 2011, 9:12 pm   #531
neun elf
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi,

Can one of you who have already completed their tester please help. What should be the RMS value of the control grid signal 100mV or 1V? Reading through the complete thread I have found references to both values. Thanks in advance.
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Old 3rd Mar 2011, 9:42 pm   #532
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Default Re: The "Sussex" Homebrew Valve Tester.

100mV
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Old 4th Mar 2011, 9:57 pm   #533
neun elf
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Default Re: The "Sussex" Homebrew Valve Tester.

Thanks Top Cap,

I found your drawings and notes inspirational. I will post pictures of my tester when the darned meters turn up!
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Old 5th Mar 2011, 12:26 am   #534
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Default Re: The "Sussex" Homebrew Valve Tester.

Many thanks for the compliment. I tried to explain in the notes how the 100mV signal was seen as a voltage across the 10 ohm load resistor such that the meter gave a direct reading of gm. However, writing technical notes is like writing software, one thinks everyone can understand it but only when someone tries to follow it you realise the deficiencies in ones work. I even get the same problem when sending Morse code, people come back at ridiculous high speeds (not to them) and I find it so dis-heartening to keep up that I give up. However, on this Forum, one finds everyone wiling to do whatever it takes to help someone, whatever the problem. Something that makes this Forum such a wonderful place so never be afraid to ask. Hope you have final success with your 'Sussex VT', you will find the project to have been very worthwhile.
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Old 6th Mar 2011, 12:48 am   #535
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
Originally Posted by swordholder View Post
I have designed and built a valve tester just to prove to myself that I could
Hi I am new to the forum and I have just come across this how do I get all the detail I need to build it?
Peter
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Old 6th Mar 2011, 5:28 am   #536
gulfstream
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Default Re: The "Sussex" Homebrew Valve Tester.

Peter.
You just start to read from page 1, it is all here in this thread

Joe.
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Old 6th Mar 2011, 6:42 pm   #537
Mogliaa
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi everyone,
I'm still working on my updates and tweaks to the Sussex. Question: is there any particular reason why it wasn't added the mu meter as in the RAT tester?

Les, Ed,
Many thanks for your notes and help, it has really helped me a lot in making some good progress in the circuit updates. Hopefully I can etch the new PCBs and test the circuit soon...

Cheers,
Ale
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Old 6th Mar 2011, 8:28 pm   #538
timohaveri
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Default Re: The "Sussex" Homebrew Valve Tester.

I just bought some thumbwheel switches from Ebay (item number: 290538529383). They have only 6 segments so I bought two so that I can combine them. Do you think these will be suitable for the Sussex? The datasheet says they are rated 28 VAC or 28 VDC at 125 mA but they can handle max. 3 amps non-switching. Does the voltage rating apply in non-switching conditions? Normally you don't ever need to switch these under load. The datasheet also says that the dielectric strength is 750 VRMS so I'm hoping it'll be able to handle the anode / screen voltages as well. What do you think?
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Old 6th Mar 2011, 10:45 pm   #539
Brian R Pateman
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Default Re: The "Sussex" Homebrew Valve Tester.

As these are used in a non-load breaking application they will probably be OK.
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Old 8th Mar 2011, 8:53 am   #540
swordholder
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Default Re: The "Sussex" Homebrew Valve Tester.

Hello All,
Although I havent tried them, I found these on the net
http://www.sourcingmap.com/pcs-elect...-p-111670.html
Looks like a very good price, maybe worth a punt if you are looking for a roller switch.
Mike
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