The "Sussex" Homebrew Valve Tester.

[unitelex]

I have ordered a DCDC boost converter from China which claims to achieve up to 60V
Once it arrives I will test it and report on its performance.

Chris

[mole42uk]

Originally Posted by G8UWM-MildMartin

Is it possible that one of the modules that comes up on a Google search for "DC Buck Boost Converter CC CV 0.5-30V 4A Power Module Adjustable" would be any use?
They have a display showing current and voltage and an adjustment knob.

I've used a couple of those briefly but they are not very stable and I wouldn't use one for a supply that I needed to be 'in calibration'.

[Diabolical Artificer]

I just built a regulated 50v supply for my heater supply using a LM317AVH and a couple of 2N30055's as series pass. I tried using selectable resistors to give various fixed DC voltages IE 6.3v, 12.6v etc but it works better as a variable supply; with a 10 turn pot you can dial V in for each valve.

Andy.

[Electronpusher0]

I also used a variable DC heater supply for my version of the "Sussex"

Peter

[Ed_Dinning]

Hi Folks, note that a single 50v winding at about 0.5A can be provided on the Sussex transformer in place of the multi tapped heater winding if requested at the time of ordering

Ed

[unitelex]

Originally Posted by Ed_Dinning

Hi Folks, note that a single 50v winding at about 0.5A can be provided on the Sussex transformer in place of the multi tapped heater winding if requested at the time of ordering

Ed

Thanks Ed, noted.

I have a transformer reclaimed from some Taiwanese built equipment. Have had it in my transformers box for a long time, forgot what it was taken out of. Yin Nan brand, It is dated May 1980 weighs 1.6Kg Iron core is 75 x 65 x40. Might have been from a dot matrix printer? but the copper leakage shield suggests audio or tape drive?

It has many secondaries:
0, 130v 150R
0, 152v 41R Will combine these in series for 282 AC, 400V unloaded DC for the HT. Will check cap voltage etc on the PCB.

0, 33v, 40v 39R and 0.9R respectively - intend to use this for the grid bias as this is a lower current winding

0, 10v, 20v 1.3R and 0.8R respectively
0, 10v 1.9R
0, 19V 1R
0,30V 1.2R Will combine some of these to get circa >50V for the heater supply via linear or switched-mode regulators.

I have a lot of surplus compact SIL and DIL isolated DC/DC converters which I will use to isolate each meter supply.

Hope to complete it over the XMAS break

Chris

[Diabolical Artificer]

It has a 220v primary, might get a bit hot as is, might be worth using a bucking tfmr or running that tfmr off another's primary if it has 10 0 110 220 230 240 primary taps. Secondary voltages will be higher too. Depends on how long your tester is going to be on for.

Andy.

[Imillar]

I have given up looking for an AVO valve tester at a sensible price. But have just discovered the Sussex valve tester. Are PCBs and transformer still available?
It looks to be a very well designed, quite an impressive piece of work.

Ian Millar

[Ed_Dinning]

Hi Ian, I still do the transformers, but wind on demand these days. If you PM me I'll give you the details.
It was some time since the last batch of PCB's was ordered but another forum member used to supply these and should be able to answer you.
I believe there is also a full manual available in the forum posts

Ed

[chriswood1900]

The forum member who was doing the PCBs was G8UWM-MildMartin you could try sending him a PM.

[tempbond]

Hello everyone,
I joined this forum very recently and I'm really glad I did ! I'm planning on building my own tester and started to look for parts, but was having a hard time finding the meters. I finally found the holy grail of meter sellers on Aliexpress, the "Super meter store"...the name says it all.

So I'm going to order all 3 meters from them, but don't know if I should go with a DC 200V or 500V meter. I plan on using a "real" power transformer to power the filaments, cathodes, plates... in order to have "real use" voltages to test the tubes, so 200V is too low. But not having had the time to check out all I need to check, maybe the tester is designed to use a lower voltage and still gives good results. So I might not be able to use "real" voltages, I guess I'll find out after reading all the documentation and posts (but maybe one of you has the answer ?).

Anyway, here's the link to the Super meter store : https://www.aliexpress.com/store/1747583

[chiilyuk]

I've dipped in and out of this thread, so I don't know the full history, yet! I'm really interested in building a valve tester and having looked around the Sussex looks to be a rewarding to build and use. I wondered if the PCBs be are still available and whether any build instructions or guidance was put together?

Ta.

[Red to black]

You would need to read the massive thread on here, there is a vast amount of technical detail included.

[David G4EBT]

Originally Posted by tempbond

Anyway, here's the link to the Super meter store : https://www.aliexpress.com/store/1747583

Just remember that almost all digital meter modules, whether for measuring current or voltage, must not share a common ground with the circuit being measured, and must have a separate power supply. The attached info makes that clear.

[joebog1]

David is absolutely correct ( as always ).
To get around this problem I found some isolating inverters for, if I remember correctly $2 each. ( pic 1 )
THey have 1000 volt isolation supposedly. They take 12 volts in and supply 5 volts out fully isolated.
Part number B1205S-1W

To simplify the power transformer requirements I also found another inverter that takes 240 directly in, and outputs 12 volts DC. So I run one 240 to 12 volts DC "black box " that feeds five isolation inverters that supply the five meters I am using.
Part number HLK-PM12

The 12 volt to 5 volt units are rated at 1 watt total power. ( about 3 times what any of the meters I have examined will take ) and the 240 to 12 volt inverter will supply 250 mA, again about 5 times what I need for 5 meters.

I have found it really simplifies everything. ESpecially the mains transformer.
Data for the two modules are freely available on the net.

Joe

[vidjoman]

In The UK, Ed Dinning (of this forum) can supply exactly the correct transformer without having to make any workaround to get required supplies. Saves a lot of time and maybe problems sorting it out.

[Electronpusher0]

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

[retailer]

Originally Posted by Electronpusher0

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.

Peter

Back when I built my first Steve Bench design valve tester, I had similar reservations about digital panel meters - not sure about the "high end" brands but the 200mV AC Chinese made budget versions available on Ebay or Aliexpress I found to be non linear at the low end of the scale, measuring anything much below 15mV couldn't be trusted. I ended up developing an opamp circuit similar to yours but not quite as elaborate - a 1Khz band pass filter followed by precision rectifier to drive a 200mV DC panel meter. I found your post interesting and will keep an eye out for the next one.

[Guitarist28]

Happy New Year to all
Its been a very long time since I was here and I'm pleased to see that the work on this is still continuing from dear Mike Rowe's original terrific project.
Alas, I never finished the work on this having only built the circuit boards etc., but have all of the parts etc., to complete the work from back in 2010.
Now that I'm on the point towards full retirement I'm not sure that I have the capability of really finishing this. I did note the point from Paul Stenning, would it be possible for one the Sussex 'experts' to be able to explain/draft a document as to how to really construct this? I know the Les Carpenter (Top Cap - I do hope you are well sir) wrote an excellent book on the subject but I'm still short of the mark. Perhaps this is a project too far for me to do.
Best Regards to all

Rob

[chiilyuk]

Originally Posted by Guitarist28

Happy New Year to all
Its been a very long time since I was here and I'm pleased to see that the work on this is still continuing from dear Mike Rowe's original terrific project.
Alas, I never finished the work on this having only built the circuit boards etc., but have all of the parts etc., to complete the work from back in 2010.
Now that I'm on the point towards full retirement I'm not sure that I have the capability of really finishing this. I did note the point from Paul Stenning, would it be possible for one the Sussex 'experts' to be able to explain/draft a document as to how to really construct this? I know the Les Carpenter (Top Cap - I do hope you are well sir) wrote an excellent book on the subject but I'm still short of the mark. Perhaps this is a project too far for me to do.
Best Regards to all

Rob

Hi Rob,

I wonder if you would be willing to sell the parts on and the completed cct board?

I'm just at the start of my Sussex build, well more of the musing and thinking stage, but I would welcome being able to purchase a completed board and any other parts you have.

Ta.