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Old 21st Oct 2020, 3:13 pm   #1601
Ed_Dinning
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Default Re: The "Sussex" Homebrew Valve Tester.

Yes, voltages on tube sockets should be taken under load and should be within 10% of nominal value.Grid stoppers (in series with grid pin) are typically about 1000 ohms.

If you have a scope you could look at the valve electrodes, but note that with this sort of oscillation the scope probe my well stop it !

Ed
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Old 7th Nov 2020, 5:17 pm   #1602
oldgeezer
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Default Re: The "Sussex" Homebrew Valve Tester.

Having spent the last few days reading this excellent thread, I've started collecting the parts for my build of the 'sussex'.

Meters ordered from ebay, pcb on way. Transformer - still looking st the pile of transformers in the attic as I'm sure one (or two) can be put to use.

Wish me luck in the lockdown!!!
Keith
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(just wondering - anyone in 2m radio range of St Albans?)
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Old 7th Nov 2020, 7:12 pm   #1603
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Default Re: The "Sussex" Homebrew Valve Tester.

Best of luck. It’s an excellent valve tester but I would recommend that most leads are fitted with ferrite beads to avoid any possibility of oscillation. It’s easy to get and difficult to eradicate. I built mine with plenty of beads and never had any problems. Make sure that all the meters are fed from separate power supplies.
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Old 11th Nov 2020, 5:12 pm   #1604
marcoamf
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Default Re: The "Sussex" Homebrew Valve Tester.

Getting back to thank you and mention that I installed the ferrite beads and the tester is now working like a charm.
Thank you, guys! You rock!
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Old 21st Nov 2020, 2:12 pm   #1605
theschoolmaster
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
Originally Posted by G8UWM-MildMartin View Post
I still have (28) PCBs for sale at cost (8.12 GBP).
Plus, maybe, the cost of a padded envelope, depending on whether any suitable used ones are being thrown away at work, plus the ever-increasing Royal Mail postage cost, minus the discount from using the franking machine at work, plus any applicable curency transfer or exchange fees.
Best regards,
Martin.
Hi Martin.
I would very much like to buy a set of PCBs - if you have any left this late in the day!!

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Old 21st Nov 2020, 2:14 pm   #1606
theschoolmaster
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
Originally Posted by Ed_Dinning View Post
Hi Folks, Sussex transformers are still available and are wound to order. PM me if you need one and I'll get it wound on my return.

Ed
Hi Ed.
Any chance you can still supply these? What would the cost be?
Thanks,
David
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Old 22nd Nov 2020, 8:11 pm   #1607
oldgeezer
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Default Re: The "Sussex" Homebrew Valve Tester.

Meters arrived from China...
Have pcb from Martin....

Just got to check BOM vs PCB holes and order the bits!

(and find a case!)
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Old 3rd Jan 2021, 1:49 pm   #1608
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Default Re: The "Sussex" Homebrew Valve Tester.

I have built the PCB, and have been accumulating parts for an eventual build.

(Anyone interested in thumbwheels? I am watching 8 sets of 12 thumbwheel switches on a local auction. Perhaps I could buy them and distribute?).

Anyway, it was not an easy journey to get to where I am because this has become a very long thread, and there have been quite a few fairly major revisions along the way. It seems to me that it would be quite brave of someone to attempt a build of this device today since the thread has lost some of its momentum, so help is not always forthcoming in a short time.

I would like to propose that the Sussex Valve Tester is relaunched in a completely new and sticky thread as the 'Sussex VT 2.0'. The first task would be to set the new baseline, with latest circuit, BOM, parts availability and documentation. That would enable people to build the current PCBs with confidence.

Next, I think it would be good to plan some improvements. From a tube testing POV, I think the original circuit has been great, and some enhancements from different users have cemented the design. However, as a keen valve enthusiast, I think it would be very nice if the power supply could be seperated from the valve tester. I would love to have a bench supply with supplies for B+ (up to 400V), screens (up to 400V), grid (up to 100V), and a variety of heaters. I.e. exactly what the power supply of this tester has to deliver. It ought to be possible to combine the functions of the tester and a PSU, making this the perfect device for a tube enthusiast.

The world of tube testers has changed a lot since the inception of the thread. I built a uTracer, that came in a complete kit with superlative instructions for €200. It does things that are tricky on an AVO, but the AVO also does things that it is not capable off (for example gas test and non-PCM filament heating).

That means there is still a big market for a device like the Sussex.

Would there be any interest in a combined Bench Supply/Tester? It is probably adaptable from the existing PCB, but some of the construction issues would need to be ironed out.

Anyway, just throwing the suggestion out there, to see if the tube lights up and a crackle comes out the speaker ;-)

Happy New Year All, or God Fortsättning, if you prefer ;-)
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Old 3rd Jan 2021, 1:57 pm   #1609
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Default Re: The "Sussex" Homebrew Valve Tester.

Hejsan,

What does the thumbwheels look like?

I still haven't got to building my Sussex, I have all the major parts though like transformer, case, meters etc. And yes it's a bit of work to gather all data for it in this enormous thread
I have to doublecheck my pcb versions and so on once more, just to see if all is matching.

God fortsättning!
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Old 3rd Jan 2021, 2:14 pm   #1610
Richardgr
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Default Re: The "Sussex" Homebrew Valve Tester.

Thumbwheels BCD

They are Binary Coded Decimal, so not sure if they are adaptable to an AVO setup.
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Old 3rd Jan 2021, 5:24 pm   #1611
FRANK.C
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
Originally Posted by Richardgr View Post
I would love to have a bench supply with supplies for B+ (up to 400V), screens (up to 400V), grid (up to 100V), and a variety of heaters. I.e. exactly what the power supply of this tester has to deliver. It ought to be possible to combine the functions of the tester and a PSU, making this the perfect device for a tube enthusiast.

Why not just bring the B+, screen, grid and heater supplies on the tester out to banana sockets on the front of the tester? That's what I have done on my Sussex. Have to admit I have never yet used the supplies.

Photo of it on post #483


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Old 3rd Jan 2021, 6:02 pm   #1612
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Default Re: The "Sussex" Homebrew Valve Tester.

I have used the HT supply for testing paper caps for leakage and reforming electrolytics. Used the A, G, K banana sockets on the top panel which are there for top cap connection.
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Old 3rd Jan 2021, 7:15 pm   #1613
Ed_Dinning
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Gents, please note that the PSU on the Sussex is designed to test valves, on a low duty cycle.
It is not designed to "burn in" audio power tubes or act as a continuously running high current bench power pack.
The transformer for this duty would be much larger and more costly

Ed
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Old 3rd Jan 2021, 9:42 pm   #1614
Richardgr
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Default Re: The "Sussex" Homebrew Valve Tester.

As Ed pointed out, the spec of the transformer for a PSU should be min 100ma, maybe 200ma.

I don't think heater winding taps should be necessary, but a means to produce a regulated heater supply up to 50V, such that lower voltages had higher currents.

It requires a new implementation.
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Old 6th Feb 2021, 6:01 pm   #1615
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Default Re: The "Sussex" Homebrew Valve Tester.

I bought this pcb from G8UWM-MildMartin in Nov17 and since then have not made any progress, and have rather lost my way. I now am trying to get my head round the latest tweaks.

So, before I start populating this board, I would like to know if there are any significant board updates available, and what circuit areas are affected. Happy to splash out on the latest version to keep the job tidy. Are boards available?

Otherwise, if my existing board is reasonably up to date, can someone please point me to the appropriate circuit(s) and BOM.

Thanks,
Keith
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Old 25th Mar 2021, 8:57 am   #1616
Steve Gibson
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Default Re: The "Sussex" Homebrew Valve Tester.

I have just finished building this device and it has passed all of the tests in the construction manual up to the Gm Tests.

The manual says to use an ECC82 but I do not have one of these tubes. Is there a reason why this tube in particular was used for the Gm Test, or can I use an ECC83/12AX7 and check the readings against the spec sheet for that tube?

Also, the Av and Gv2 voltage selectors are down by around 2v across the range with VR3 at full adjustment. Is this an issue or can I adjust resistances in the circuit to get the voltage correct?

This has been a great project, although identifying the correct documentation to use from amongst these posts has been a project in itself. Thanks to everyone who posted in this resource it was a great help, and especially Ed and Martin for the circuit boards and transformer.

Steve
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Old 25th Mar 2021, 10:55 am   #1617
Paul Stenning
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Default Re: The "Sussex" Homebrew Valve Tester.

I think it would be really useful if someone who understands this project could compile the relevant information for building one of these today, from these 1600+ posts, into a new thread. That new thread would of course be made sticky.
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Old 25th Mar 2021, 12:26 pm   #1618
mole42uk
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Default Re: The "Sussex" Homebrew Valve Tester.

I don't see any reason why a particular valve is used for the Gm setup testing. I think I probably used any handy low-power valve when I built mine, but that was many years ago (I just looked back on this thread and it was 2013)! The anode and g2 voltages on my tester are quite a lot lower than spec but it hasn't made any real difference.
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Last edited by mole42uk; 25th Mar 2021 at 12:49 pm.
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Old 28th Mar 2021, 12:35 am   #1619
Steve Gibson
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Default Re: The "Sussex" Homebrew Valve Tester.

Thanks for the feedback guys

I have tested the ECC83 and all is well

However. I have tested some EL84's with differing results (Anode and Grid @ 250v):

I have a couple of EL84's that measure 19.2 and 19.4mA @ -8.3volts control which is the closest I could get to some sort of documented spec at the end of the El84 data sheet for 2 tubes in AB push pull (i.e. 2 x 20mA)

At the standard -7.3volts control (Class A) where the data sheet says 48mA these tubes only read 28 - 29mA. which is way down on spec.

Also, on another set of valves (Russian EL84 equivalents), these read in the mid to high 20's at -8.3volts, BUT when come back from Test through Leak 2 and Leak 1, the led lights indicating a 'Leak' at Leak 2 until the valves cool down.

Do I have a bad set of Valves or is there something I'm missing when testing these valves?

Many Thanks

Steve
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Old 28th Mar 2021, 8:35 am   #1620
mole42uk
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Default Re: The "Sussex" Homebrew Valve Tester.

I don't think you'll ever get results that exactly match the book specification. After all, most valves are old, or they are made on old machines. You don't say where the first two valves are from - are they NOS, pulls or something else? If the Russian ones are overheating, have you checked all the voltages at, and connections to, the socket? Do you have ferrite snubbers on the wires connecting all the sockets - it has been known for valves to go into high-frequency oscillation on the Sussex tester, indeed on many testers there is that possibility....there are comments on this somewhere on this thread, I know it's a pain to read through though!
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