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Old 19th Jan 2023, 4:34 pm   #1661
Guitarist28
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Default Re: The "Sussex" Homebrew Valve Tester.

Having looked over this again after all this time I have decided to have another go at finishing what I've started.
Over time I have managed to get a spare Avo 9 rotary switch as used in the old Avo two panel, mk1&2 etc valve testers. I'm going to use this to replace the bulk of switches that need to be used so it should cut down some work to be done?

I do hope that I will eventually be successful.

Best Regards

Rob
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Old 17th Mar 2023, 12:58 pm   #1662
Ibis 911
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Default Re: The "Sussex" Homebrew Valve Tester.

Hello everyone,
I recently joined the forum. I've been following the sussex tube tester thread for a few years now and the time has come to start building. I would like to thank everyone who has participated in the development of such an outstanding project so far.
I started with the case, which is made of oak wood and aluminum panels. I plan to make the pin selector in the AVO VCM style with a 3D printer. I'll attach some pictures of the project next time.

Best Regards

Igor
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Old 25th Jun 2023, 7:04 pm   #1663
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Default Re: The "Sussex" Homebrew Valve Tester.

Hello everyone,
What a fabulous site and this Sussex project is proving a great challenge. I've had a quick scan through the 80+ pages and picked up lots of good tips and ideas, so many thanks to all those who have forwarded their personal variations and upgrades. Can someone please advise if the latest version of the circuit boards are still available to purchase
Kind regards
Jack MM0JYR
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Old 26th Jun 2023, 9:08 am   #1664
Ibis 911
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Default Re: The "Sussex" Homebrew Valve Tester.

Some pictures of the construction of the case. As I mentioned, it is made of wood and aluminum panels.
Making such a case is very simple and anyone can make it themselves.

Regards,
Igor.
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Old 10th Jul 2023, 8:34 pm   #1665
jackrae
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Default Re: The "Sussex" Homebrew Valve Tester.

That's one beautiful piece of woodwork !
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Old 11th Jul 2023, 6:55 am   #1666
Ibis 911
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Default Re: The "Sussex" Homebrew Valve Tester.

For those having trouble powering DVMs. With this solution, you only need one free voltage between 10 and 15V on the transformer, and you can supply up to 5 DVMs.
DC/DC converters B1212S-1W are used. Each DVM is powered by 12V DC.
If you use the LM7809 instead of the LM7812 regulator, the supply voltage will be 9V DC, since the DC/DC converters transform the voltage 1:1.

Best regards,
Igor
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Old 11th Jul 2023, 8:04 pm   #1667
Ed_Dinning
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Folks, I normally fit 3 windings to power DVM's, but a 4th winding can be added when it is wound.
To upgrade an existing transformer, simply add 19 turns of thin insulated wire on whatever small spaces exist round the bobbin.

Nominal voltages of these windings is 7 volts

Ed
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Old 12th Aug 2023, 7:14 pm   #1668
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
Originally Posted by Ibis 911 View Post
Some pictures of the construction of the case. As I mentioned, it is made of wood and aluminum panels.
Making such a case is very simple and anyone can make it themselves.

Regards,
Igor.
How is it jointed, out of interest?
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Old 11th Sep 2023, 6:55 am   #1669
Ibis 911
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Default Re: The "Sussex" Homebrew Valve Tester.

I apologize for the late reply due to the floods in Slovenia.

The wooden parts are glued together and fixed with screws. The screw holes are closed with wooden plugs so that they are not visible.

Regards,
Igor
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Old 13th Nov 2023, 4:25 pm   #1670
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Default Re: The "Sussex" Homebrew Valve Tester.

Very interested in this by our departed Swordholder. I am tired of messing around with the ancient units of the day. This looks like a very good device.
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Old 5th Feb 2024, 3:13 am   #1671
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Default Re: The "Sussex" Homebrew Valve Tester.

. . .A note from me regarding Thumbwheel BCD Switches!

. . Given that cheap BCD pressbutton switches of the up/down KM2 type are readily available on AliExpress and eBay in plentiful quantities, its easy to adapt them for use in a valve tester!

. . .Connect the Common to +5V, the '1', '2', '4' and '8' terminals to 0V via pull–down resistors to 0V, then link the '1', '2', '4' and '8' Switch terminals to the 'A', 'B', 'C' and 'D' inputs of a BCD–decimal decoder IC, the Q1 to Q9 outputs (if you want to test ten–pin B10B valves use the '0' position of the switches and the 'Q0' output for pin 10 on the B10B base) to suitable relay drivers that can link each valve–holder pin bus–bar to the various heater, cathode, control–grid, screen–grid and anode supply points on the tester!

This will save chasing about for decimal thumbwheel or button switches that are a lot harder to find and horrendously expensive when theturn up!

. . .There's no need to use a decoder with special internal design to ignore "1001 to "1111" as BCD switches normally never give illegal codes!

. . .Anybody who's good at Arduino's or PICs can probably devise a BCD–to–1 of 10 decoder without too much difficulty !

. . .I'll draw a circuit in due course!

Chris Williams
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Old 5th Feb 2024, 5:27 am   #1672
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
Originally Posted by TheJunkDr View Post
Very interested in this by our departed Swordholder. I am tired of messing around with the ancient units of the day. This looks like a very good device.
It is indeed.

Unlike the AVO Valve Characteristic Meters, the valve being tested is biassed with DC, which can therefore be easily measured and calibrated.

It's a real mutual conductance tester, with an audio oscillator applying a test voltage to the valve's grid, and the ensuing sine on the anode current is measured. Both the stimulus and the measurement are easily calibrated.

To go through the AVO calibration process, you need a standardised valve, measured on a calibrated DC tester. The Sussex *IS* one of those, itself. You don't need specific meters with known responses to half-wave rectified waveforms as well.

So it's a valve tester whic can have its calibration proven with a trusted multimeter.

You can build it with whatever socket types you chose.

It has a number of things it cannot do. It isn't a high power tester... but we've had a distressing number of people appear on the forum with a dead AVO that they've tried to use to burn-in valves. It just turned out that it wasn't the valve which got burned!

The biggie is that the avo machines, espacially the later models has a special glamour. They are trusted utterly even if they've never been calibrated sinc ehtey were made. "AVO Tested" is a phrase which boosts the price of valves put up for auction. A picture of the valve (you can always trust all photos, of course ) gives a further boost.

If you have a load of valves to test and sell, you need an AVO. No-one will ask when it was last calibrated or if it even works. Enough people believe the sound is improved by being tested if it's the right model of tester.

If you want to use the tested valves, then the Sussex is a much better option.

The Sussex lacks some of the gas and leakage tests that the AVOs can do but these seem to be rare problems, and a lot can be deduced from other results.

You're free to add a few other digital panel meters. Heater current, G1 current and G2 current for example.

The machine can be used as a true DC bench for plotting valve curves.

David
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Old 5th Feb 2024, 9:55 am   #1673
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Folks, just to reiterate David's comments.
I have wound over a 100 transformers for the Sussex and people have made up their own transformer "collections"
I have had 1 of my transformers fail and I have been asked about damaged testers by a few people. In all cases this has been due to the use of the tester to "burn in" power valves.
Very few testers are designed for this. I state a duty cycle of 30% for my transformer
This keeps both the size and cost of the transformer down and reduces stress on the power supplies in the tester itself.

I have built special testing transformers to specifically "burn in" valves; these are larger and more expensive. They do not need the sophistication of the Sussex to operate.
Test on Sessex first; run for as long as needed on specific, simplified burn in rig; retest on Sussex to compare.

Ed
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Old 14th Feb 2024, 12:41 pm   #1674
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
Originally Posted by Electronpusher0 View Post
I have a Sussex tester made using several transformers to get all the secondaries I need but have always been unhappy with the floating meters and the need for floating supplies for them.

I have also been unhappy with the fact that the gm meter only uses a tiny portion of its full scale capability.

I have been working on a circuit to allow all the voltages, currents and gm to be measured using a single (well +/- 15V) supply and every measurement referenced to 0V.
This would be much safer and would allow further expansion if required, say for a curve tracer.
I have been developing the design and have designed a pcb.
This is assembled and is undergoing testing, I am also writing a test procedure as I go.

The key element is a high voltage differential amplifier constructed using closely matched resistors. Compensation has been added to null out errors due to loading by the measurement circuit itself.
GM is measured by injecting a 100mV 1kHz Sine wave to the grid, the oscillator for this is on the measurement board. The ac Anode current is sensed across a 100 ohm resistor and is amplified and filtered to eliminate 50Hz and precision rectified. The output is a dc voltage of 2V (or 200mV) for a reading of gm=20
I attach the schematic and a picture of the assembled board.

I will do a full write up and post it under “Homebrew” since the board could be used in any homebrew tester or to convert an existing tester to measure gm (which is what I will do to my MHSVT).

And yes, I will offer pcbs in the appropriate section.

Peter
I'm a retired engineer and have started to build the Sussex valve tester and I have read in thread 83 of The "Sussex" Homebrew Valve Tester, that you have been working on a circuit to allow all the voltages, currents and gm to be measured using a single (well +/- 15V) supply and every measurement referenced to 0V.

This appears to be an elegant design.

Do you have the PCBs for this project?

Best regards,

Malcolm
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Old 15th Feb 2024, 7:59 am   #1675
Electronpusher0
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Default Re: The "Sussex" Homebrew Valve Tester.

Its odd but this subject has just recently resurfaced, another member pm-ed me asking the same question.
I do have a pcb design and a few spare pcbs.
I need to finish the write up including set up procedure.

You can have one of my pcbs for £6 including postage.

pm me with your address and I will reply with payment details.

Oh dear, I may have to order some more boards if this becomes popular.

Peter
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Old 15th Feb 2024, 1:36 pm   #1676
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Default Re: The "Sussex" Homebrew Valve Tester.

I have checked and I have a further 5 PCB's available, I will post them in the "offered" section but it will not be until towards the end of next week when the documentation is done.

Please wait until it's posted before sending more requests for boards.

In the unlikely event this proves popular I will order more boards.

Peter
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Old 21st Feb 2024, 10:39 am   #1677
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi All,

A long way back I made a request that this thread should trigger a new thread to consolidate the current design, and look at possible revisions. This is a great thread to read, but a bit arduous to trawl through in order to allay uncertainty about the current state of play.

This new PCB by Peter (Electronpusher0) is quite a significant improvement I think.

My Sussex sits 90% complete, just awaiting the final wiring of the top plate to the PCB. I am not a huge fan of screw connectors, and having to rely on so many of them from the top plate left me looking for other solutions - I think someone here used a 38pin D connector? Those sorts of connectors can be quite cheap, so a board that incorporated that could be useful, or grouping connections so that standard multi-way connectors could be used. I would prefer connectors grouped by function to simplify testing and simplify the wiring for different layouts.

I suppose a request like this comes back to someone who can own the next revision and coordinate responses? Or can a collective effort work?

Last edited by Richardgr; 21st Feb 2024 at 10:48 am.
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Old 22nd Feb 2024, 12:17 pm   #1678
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Default Re: The "Sussex" Homebrew Valve Tester.

Has anyone come across a reasonably priced 2 pole 7 way switch suitable for the heater voltage selection?
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Old 22nd Feb 2024, 2:00 pm   #1679
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Default Re: The "Sussex" Homebrew Valve Tester.

When I made my version I used small 12 volt relays, meant fot automobile use, which had 10amp contacts. About the size of am OXO cube and used a standard switch and a small 12 volt power supply to drive them. Couldn't find a suitable switch at the time as most had 150 max max rating.
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Old 22nd Feb 2024, 2:24 pm   #1680
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Default Re: The "Sussex" Homebrew Valve Tester.

I have started a new thread on my measurement pcb.

https://www.vintage-radio.net/forum/...d.php?t=208750

I am also offering pcbs in the appropriate section.

Peter
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