Re: The "Sussex" Homebrew Valve Tester.
 

I built my own valve tester, not the Sussex and used a LM317 variable 0-30v PSU using two TIP3055's as series pass trannies, this gets 0-30 @ 3A. I did rig it so it did fixed values too, IE 5, 6.3, 12.6v etc but found several valves tested exceeded their heater max voltage. The only problem though might be testing some directly heated filament type valves especially rectifiers, something to bear in mind.

Andy.

Re: The "Sussex" Homebrew Valve Tester.
 

If you want an AC heater that is variable I can recommend using a small Variac in front of a transformer with the maximum output voltage/current that you need, or the other way around.

You'll have to calculate the power necessary for the Variac and transformer and add some extra power to make sure that it works under full load. If you want this to work with regulation there are Constant Voltage Variacs that use a small motor to control the Variac by measuring the output voltage - with necessary scaling of the voltage in the feedback circuit you can get it to monitor the output voltage from the transformer too, not just the output voltage of the Variac.

There are also low-voltage Variacs which require a transformer in front of it to work, like the ones from Thalheimer Transformatorenwerke sold by Conrad, the KSS103 (42V@2.5A) and KSS105 (60V@5A) are just fine to use after a suitable transformer. Sizes and data here: https://ttw.world/index.php/ess-sing...tion-mode.html click the arrow on the bottom line (Input voltage 42 V; 60 V and 230 V; output 0 up to 42 V/ 60 V and 250 V) to see data, click the Variac number and then the arrow to see the sizes (70*55mm and 94.5*58mm).

It is not cheap nor is it small but it works very well whichever of these solutions you go for.

I have an isolated Variac for school use which works with the full mains voltage which I have used in conjunction with a transformer to get low voltages and high currents and it works like a charm.

/Martin

Re: The "Sussex" Homebrew Valve Tester.
 

Just a quick note in case this is of use to prospective Sussex builders. A couple of years ago, when I first considered building Mike Rowe's excellent design I sourced the meters from Asia. These are blue LED (not LCD) types with an explicitly stated isolated power requirement of 5V DC, so not universal AC/DC as some other meters.

Now I have started building the Sussex I decided to test the meters, all seems fine although the linearity of the 200mV AC meter leaves a lot to be desired.

However, and this is what may be of significance for budding constructors, being LED types they draw between 40 and 80mA each depending on the number of segments lit. This seemed rather high to me so I checked the other meters with the same results. I wasn't sure whether the 4 6V meter windings on Ed's transformer could cope with this current demand, so I contacted him and was informed that the meter windings and lead out wires are the same, so the current carrying capabilities should be no problem although the windings were not specified for this level of current. The extra demand on the primary winding should not be a problem as we are talking about a couple of Watts and the demand on other windings will be intermittent. (Ed, please correct me if I have got this wrong).

If you are using the now more common LCD meters, I would imagine that you will not have this problem.

Re: The "Sussex" Homebrew Valve Tester.
 

Hi Gents, as per Eddie's post; the meter windings are wound with stranded PVC insulated wire. This will carry the current required and will also give high isolation between supplies, but will cause additional heating due to the increased pri current. It will also cause additional droop in output voltages due to transformer regulation.
With 240v in on the 240v tap these windings typically give 7.5V out on no load; rectified this will give over 9v DC on no load, but possibly closer to 6v with a 40mA load. It will depend on the rectifier circuit used.

On Eddie's transformer I provided an additional meter winding as is available on request.

Note that variations are available on these transformers as long as the consumption remains within design limits. Note that a much bigger transformer is needed if you need to burn in power valves, as well as increased heatsinks on the regulators.

Ed

Re: The "Sussex" Homebrew Valve Tester.
 

Hi Everyone,

I have just completed the Sussex valve tester and because it is a cut down version on the original Sussex I've called it 'The Sussex Junior' - I hope I'm not busting any rules on the forum and it's OK to call this one 'Junior' and to post it here as part of the Sussex legacy.

I wanted to build a well designed tester but for it not to be as complicated as the original Sussex so I cut down on a few things but still leaving a very capable tester that can still do almost everything the Sussex can but all be it, in part 'manually'.

Electrically the HT & Screen circuits are the same and the grid circuit too but with a zener clamping the voltage to -20V as my meter from a far Eastern country only goes down to 20V.

What is different:
1) There is no gm oscillator or meter.
2) There are no dials but instead banana plugs for selecting different combinations of valve pins
3) The continuity test is done manually and there is a LED for this purpose.
4) I have taken all relays out.
5) There no other voltages for the heater apart from 6.3V.

Points worth mentioning:
1) I discarded the gm function as I can vary the grid voltage by half a Volt above and bellow the spec grid Voltage which will give me the same result as with a gm meter. I also had a small project box and could not fit the third meter in so went without.
2) I decided to use banana plugs as I did not have any room for dials, this was also simpler too construct.
3) I didn't want the complication of the continuity tester and also wanted to test every possible pin combination so I added a LED and it is checked manually.
4) As I didn't have the continuity function I took all relays out even the HT one and used a suitable switch instead for the HT.
5) As most of the valves I test are 6.3V I left it at just that. I have a bench supply which would give me all other voltages as required especially for the likes of UL41 etc... 100mA heater valves.

The 'Junior' might appeal to someone who has either a small project box, wants a smaller form or just wants a simpler to build tester but with the same proven HT, Screen and Grid design and is not too worried about doing some manual checks.

I have included some pictures testing a 6L6 and also using the heater voltage and the LED for continuity/shorts.

I'd like to thank Ed Dinning for winding the transformer, great work Ed and works well!

Happy building,
Berni

Re: The "Sussex" Homebrew Valve Tester.
 

Nice one Berni, looks very neat. A higher power version of this would do for those who want to "burn in " power valves

Ed

Re: The "Sussex" Homebrew Valve Tester.
 

Thank you Ed.

It would better if I had letraset or the skill to do nice lettering.

I forgot to mention that I used a veroboard and have tucked away the other heater wires incase I need them for the future as I thought I would use them in this project.

For the grid pot I have used a multiturn device and this has really improved the adjustability of the grid Volts when testing something like an ecc83.
The 20V meter reads two decimal places which is nice when fine adjusting with the multiturn pot.

I've made "Valve Spec Strips" which can be put by the pin terminals, which makes the wiring easy and you can read off the parameters quickly.

Berni

Re: The "Sussex" Homebrew Valve Tester.
 

I have the control panel part of the 2 panel AVO tester and also made up a patch panel to connect to the correct pins on the valve bases. (I have since got a full 2 panel AVO but that's another story.

To make connecting easier I converted the AVO valve switch setting manual to Excel and used the Vlookup function to add the valve pin connection by name (A,A1,G.C etc.). see screen shot below.

Its too big to post as an Excel file so I have zipped it.

Peter

Re: The "Sussex" Homebrew Valve Tester.
 

Electronpusher0,

Thank you for the file, it'll be very useful!

Berni

Re: The "Sussex" Homebrew Valve Tester.
 

Hi all,
here a couple of photos of my current project. It is still very much work in progress, but I have got all chassis bashing out of the way (I'm not the world's best metal worker). Although the aluminium panels were not cheap, I am pleased with the finish, I could never have achieved the same precision with the tools available here.

I still have to populate the PCB and connect it all up, however the valveholders and pin switches have all been wired up before installing, but still some way to go.

Sorry about the mediocre quality of the photos, but I hope you can see what I've done so far.

I will keep you posted on the outcome.

Re: The "Sussex" Homebrew Valve Tester.
 

That looks really good! I'm planning to have the same amount of meters as you.
How did you make the labels? And where did you get the enclosure?

Re: The "Sussex" Homebrew Valve Tester.
 

Hi, thanks for the kind words.

I got the housing off Ebay in Germany. See posts 1551 ff on this thread for more details.

I made cut outs, slightly larger than necessary on the case itself and had the two aluminium panels made by a german firm called Schaeffer in Berlin. On their website they supply a free software program to create the layout required, this includes text facilities for either printing or engraving. The software will also quote the price, I paid approx. 90 Euros for the larger panel und 47 Euros for the smaller. They took about 10 days to arrive and saved much work and as I mentioned above I would not have been able to make them to the same exact measurements.

PS just seen you are also in Germany, so shouldn't be any problem for you :-)

Re: The "Sussex" Homebrew Valve Tester.
 

Thanks for the tip! I will check it out.

Re: The "Sussex" Homebrew Valve Tester.
 

My Sussex shown in post 1020 has an aluminium panel with the cutouts and the printing was done on a sheet of A3 paper glued to the panel with a clear sticky plastic protection sheet applied. Has been used many time now and no sign of wear. Cheap to print and changes can easily be made prior to the final version which was applied.

Re: The "Sussex" Homebrew Valve Tester.
 

Looks very nice as well but a bit difficult to see in detail. Do you have a more high-res picture?

Re: The "Sussex" Homebrew Valve Tester.
 

The forum software reduces the image file but I think you can click on the thumbnail then the image and it should enlarge.

Re: The "Sussex" Homebrew Valve Tester.
 

vidjoman - I thought about the paper, transparent plastic, however I have found in the past that I either get annoying air bubbles in the plastic or the edges start to curl up and become loose.

Another advantage is that my cut outs didn't need to be precise, the underlying material being 1,5mm steel which is not that easy for me to work with. The CNC machined aluminium panels provide the necessary precision.

sven - I'll try to get a better image, possibly as a pdf.

Re: The "Sussex" Homebrew Valve Tester.
 

Hi Berni - I am very interested in your 'Junior' - I started out on this project some years ago and now with the COVID19 lockdown it seems as good a time as any to get back into it! Have you a slimmed down circuit diagram you could share? best regards and stay safe, Ramon

Re: The "Sussex" Homebrew Valve Tester.
 

Hi all,

I started to gather the components for Sussex almost 1 year ago and now finally i completed it.
For case i used a suitcase, available here in a DIY store, from china, and is made from pressed cardboard with a layer of thin aluminum (i think).
I manually winded the secondary in the transformer which was taken from an loudspeaker enclosure acquired from local flea market.
The valve sockets were acquired from the same local flea market.
To my shame, i lost a few hours figuring out the connections on board, until i found that the silkscreen contains the necessary info :)

Re: The "Sussex" Homebrew Valve Tester.
 

Hi all,

I needed some additional vacuum tube sockets to complete the Sussex and as they were not available at a reasonable price here in Romania I designed and 3D printed them.

Here is the link to FreeCAD files if anyone needs them:-

Vacuum Tube Sockets