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Old 22nd Nov 2013, 8:06 pm   #981
crackle
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi
Please can any one confirm who I can get the printed circuits from.
Thanks
Mike
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Old 23rd Nov 2013, 8:33 am   #982
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
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I wondered if you guys on here would like to ponder over a problem I had and which I dont fully understand exactly what happened and the sequence of events which lead to the bang..
What happened to the HT fuse? Was that destroyed as well?

Richard
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Old 23rd Nov 2013, 9:51 am   #983
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Default Re: The "Sussex" Homebrew Valve Tester.

I am not sure now but think the fuse was intact (because it was over sized, oops!). I have since found D3 4 & 5 were also blown.
I have replaced components and tested the HT supply again on no load, but the voltage is way too high, does this circuit need a dummy load resistor to test it successfully?
Also the zener diodes, zd1 - zd7 are getting warm, the voltage across the zener's is 304v
Mike
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Old 23rd Nov 2013, 12:24 pm   #984
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Mike just read through your problem, it seems to me that with a HT of 410V the MPSA92 has to drop 110V and at approx. 4ma to supply the zeners this makes for a little over 400mW dissipation. It is riding close to its limits so either you need to reduce the HT feeding or substitute another transistor with higher dissipation spec such as MJE350.

Dave
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Old 23rd Nov 2013, 9:23 pm   #985
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
Originally Posted by crackle View Post
Please can any one confirm who I can get the printed circuits from.
Mike,
Take a look at my post #942 in this thread. Sorry to sound like a smartass, but while it may be a big ask of anyone, almost everything you want to know is in the thread; just read through it. You could maybe even try a search.....
Colin.
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Old 23rd Nov 2013, 10:23 pm   #986
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Default Re: The "Sussex" Homebrew Valve Tester.

Thanks Colin I have sent a PM to Mildmartin
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Old 23rd Nov 2013, 10:49 pm   #987
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Default Re: The "Sussex" Homebrew Valve Tester.

I have added some links, which I hope are useful, to the first post in this thread.

Is there anything else that could usefully be included?
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Old 23rd Nov 2013, 11:03 pm   #988
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Graham
That will be very useful, I did spend some time searching through posts for details of the printed circuit, but it started to get too much and I started to go cross eyed.
Cheers
Mike
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Old 24th Nov 2013, 2:07 pm   #989
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Default Re: The "Sussex" Homebrew Valve Tester.

Just a thought... Because this thread is now approaching 1000 posts, it would be very difficult for someone considering building the project to find all the key information. The discussion above illustrates the problem.

Perhaps it would be a good idea if someone who knows a lot about the project could create a new thread containing all the important information someone would need to build the valve tester, including circuit diagram, parts lists, PCB and transformer suppliers, operating instructions etc?

If that thread was then just updated when key details were changed (such as an agreed circuit modification) with general discussions remaining here, it would be a really useful reference.

We would of course make that thread sticky. It could possibly be left closed too except when an edit is needed?
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Old 24th Nov 2013, 2:11 pm   #990
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Default Re: The "Sussex" Homebrew Valve Tester.

Good idea Paul. It's hard to find a post that you know had some details some time ago and have to look at so many to find it.
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Old 24th Nov 2013, 2:20 pm   #991
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Default Re: The "Sussex" Homebrew Valve Tester.

1000 posts is an indication of both the quality of the original work, and about how well it was suited to the interests of the group.

David
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Old 24th Nov 2013, 2:43 pm   #992
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Default Re: The "Sussex" Homebrew Valve Tester.

Absolutely, it is a huge credit to the design and designer. That's why I think the information should be made as clear and accessible as possible, especially now several other constructors have refined it.
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Old 24th Nov 2013, 7:51 pm   #993
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Default Re: The "Sussex" Homebrew Valve Tester.

When the information is collected together, it would be a nice gesture to find a magazine to publish it, to the benefit of Swordholder's widow. Subject to the approval of the subsequent contributors. PW maybe?

Being a true DC conditions valve tester it has the advantage that it can be calibrated against a DMM, and can even make the calibrated valves needed by Avo owners.

David
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Old 25th Nov 2013, 8:23 am   #994
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Default Re: The "Sussex" Homebrew Valve Tester.

Information on the best place to get the little digital meters from, or make and model, would be useful.
Also the rotary switches, are the shorting/non-shorting 150mA 250v ones OK such as below.
Do you think they would be suitable for the heater switch
Mike
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Old 25th Nov 2013, 8:45 am   #995
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Default Re: The "Sussex" Homebrew Valve Tester.

That realy is an excellent idea to "sanitise" and write a streamlined guide for this project, I too have started collecting parts, have got with me that there is a modification to the circuit board but little else. It is a daunting task to trawl through nearly one thousand postings despite it being an absolutely brilliant project from the onset way back.

Hope someone can see their way to posting a revised ciurcuit diagram, components list, "in house" suppliers of the transformer and circuitboard, and perhaps some advice on the imortance of component choices regarding switches, ferrite beads etc, etc. The cabinet / chassis is a relative walk in the park once the parts are in hand.

Thankyou everybody
Tony

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Old 25th Nov 2013, 11:16 am   #996
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi
This is a question about the layout and use of switches.
Rather than switches for the selection of electrodes etc. I was intending to use a patch bay so I could use a short banana plug patch lead to connect supply to electrode. By using this |I thought that if needed I could also insert additional components.
Have members any advice or comments about this.

I notice from various posts that the inclusion of ferrite beads on the cables to the valve sockets. Does this mean that there could be problems with "RF noise" being picked up. Is the length of wiring between selector switches/patch bay and the sockets critical for the same reason, will this influence the results of the valve test.

I may have to completely redesign my layout as I have the valve sockets some way from the patch bay.
thanks
Mike
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Old 25th Nov 2013, 6:40 pm   #997
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Default Re: The "Sussex" Homebrew Valve Tester.

A patch bay sounds like a good idea - if you could make it conform to the AVO switch numbering somehow it would save having to re-write their valve characteristic tables.

The use of ferrites is discussed along with grid stoppers and wiring loops somewhere in the 1000 posts - and likened to the AVO practise on their testers. It isn't so much RF that you have to worry about as local oscillation generated by feeding the VUT with a 100mV sine wave on the grid and the optimum conditions on the rest of the elements to make the valve self-oscillate at various harmonics of the original. The ferrets and other tricks stop this happening. (why does my spell-checker insist on calling those little grey beads 'ferrets'?)

Richard
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Old 25th Nov 2013, 6:44 pm   #998
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
Originally Posted by Paul Stenning View Post
<snip>

Perhaps it would be a good idea if someone who knows a lot about the project could create a new thread containing all the important information someone would need to build the valve tester, including circuit diagram, parts lists, PCB and transformer suppliers, operating instructions etc?
I'll volunteer to help editing and suchlike, but I don't think I have time to lead the documentation project.

Richard
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Old 27th Nov 2013, 3:44 pm   #999
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Default Re: The "Sussex" Homebrew Valve Tester.

I thought you might be interested in my Sussex Valve Tester that passed the 'Glass and rain' test after the storm damage a few weeks ago. A concrete ridge tile came through the glass conservatory roof and then it was rained on for about 6 hours until I woke the next day. All cleaned up and now continuing with the build.

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Old 28th Nov 2013, 12:42 pm   #1000
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Default Re: The "Sussex" Homebrew Valve Tester.

A very attractive realisation of design. Since there is a CPC box in the background is the case a CPC line? I would be interested to see the internals prior to the assault by the roofing tile (or after the debris has been cleared) and also a similar shot of the complete build with the critical dimensions.

I have had all the parts for several years and planned to build mine into an aluminium flight case similar to Maplin Code: GL34M. Only the motivation to assemble them is missing. This may restore that missing essential.

Regards - Alan
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