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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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20th Feb 2011, 9:11 am | #521 |
Retired Dormant Member
Join Date: Jun 2009
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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 |
20th Feb 2011, 2:50 pm | #522 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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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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If I have seen further than others, it is because I was standing on a pile of failed experiments. |
20th Feb 2011, 3:15 pm | #523 |
Heptode
Join Date: Dec 2009
Location: Hockley, Essex, UK.
Posts: 575
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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 |
20th Feb 2011, 6:23 pm | #524 |
Rest in Peace
Join Date: Aug 2009
Location: East Preston, Sussex
Posts: 162
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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 |
20th Feb 2011, 9:40 pm | #525 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,172
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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 |
20th Feb 2011, 10:32 pm | #526 |
Heptode
Join Date: Dec 2009
Location: Hockley, Essex, UK.
Posts: 575
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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 |
22nd Feb 2011, 9:20 pm | #527 |
Retired Dormant Member
Join Date: Dec 2010
Location: Co. Durham
Posts: 7
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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 |
26th Feb 2011, 2:52 am | #528 |
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Join Date: Feb 2011
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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 |
26th Feb 2011, 2:02 pm | #529 |
Heptode
Join Date: Jun 2004
Location: Ilkley, West Yorkshire, UK.
Posts: 656
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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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Colin Armstrong |
27th Feb 2011, 9:53 pm | #530 |
Retired Dormant Member
Join Date: Dec 2010
Location: Co. Durham
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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 |
3rd Mar 2011, 9:12 pm | #531 |
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Join Date: Aug 2010
Location: Gravesend, Kent
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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. |
3rd Mar 2011, 9:42 pm | #532 |
Octode
Join Date: Mar 2006
Location: Watford, Hertfordshire, UK.
Posts: 1,270
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Re: The "Sussex" Homebrew Valve Tester.
100mV
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4th Mar 2011, 9:57 pm | #533 |
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Location: Gravesend, Kent
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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! |
5th Mar 2011, 12:26 am | #534 |
Octode
Join Date: Mar 2006
Location: Watford, Hertfordshire, UK.
Posts: 1,270
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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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Whether the Top Cap is Grid or Anode - touching it will give you a buzz either way! |
6th Mar 2011, 12:48 am | #535 |
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Join Date: Jan 2011
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Re: The "Sussex" Homebrew Valve Tester.
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6th Mar 2011, 5:28 am | #536 |
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Location: London
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Re: The "Sussex" Homebrew Valve Tester.
Peter.
You just start to read from page 1, it is all here in this thread Joe. |
6th Mar 2011, 6:42 pm | #537 |
Retired Dormant Member
Join Date: Feb 2011
Location: London, UK.
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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 |
6th Mar 2011, 8:28 pm | #538 |
Pentode
Join Date: Sep 2007
Location: Parkano, Finland
Posts: 131
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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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6th Mar 2011, 10:45 pm | #539 |
Nonode
Join Date: Jun 2005
Location: Western Lake District, Cumbria (CA20) - UK
Posts: 2,136
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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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Brian |
8th Mar 2011, 8:53 am | #540 |
Rest in Peace
Join Date: Aug 2009
Location: East Preston, Sussex
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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 |