The "Sussex" Homebrew Valve Tester.

[Dekatron]

Timo,

Some of these digital meters have soldered jumpers on the PCB which says "Hz", "AC", "DC", "A", "mA", "V" and "mV" but some don't. You will just have to unsolder that small jumper of solder in the "mV" position to remove the text, but that only works on some of these modules as some demand a solder blob in either "V" or "mV" or any other position. But if you want to change it to say "mA" that should be ok, just make a new solder jumper in the "mA" position and remove the "mV" solder jumper. Some modules can be programmed via a serial interface to display different texts and they usually lack these jumpers. Unfortunately not all modules can be modified like this so it is good to check with the seller which modules he is selling and if it is possible to change the text.

[TuningIndicator]

I've found 'Lascar' meters (from RS) pretty good, we used some at work not long back.
They are small and compact, and don't have jumpers, you just 'blob' some solder on two adjacent pads on the pcb to illuminate (or not) V, Hz, mV, move the decimal point, etc.
So you could solder wire to the pads and connect to a switch.

[TommY_BuRnZ]

Wow, 2 hours reading and what an amazing thread! I am thinking about building this valve tester, and I have the BOM and have picked highlights from the previous threads just in case any debug is required. Does anyone know if the custom transformer is still available and also the custom PCB?

Thanks,

Tom

[Guitarist28]

Hi Tom,
Send a PM to Ed Dinning who I am sure will have some left and will be happy to help.

Regards

Rob

[swordholder]

Hi Tom,
Welcome to the Forum, I'm fairly certain Martin has some PCBs available.
There will be plenty of help available for you if you get going,

Mike

[timohaveri]

Originally Posted by Dekatron

Some of these digital meters have soldered jumpers on the PCB which says "Hz", "AC", "DC", "A", "mA", "V" and "mV" but some don't.....

Thanks for the tip. I took a better look at the meters and indeed they have these jumpers that you described. Also there are jumpers marked with letter "P" and a number. I assume these are for the decimal points. They are bridged with zero ohm SMD resistors. I haven't experimented with them yet but I will when I have the time.

[Top Cap]

I have had problems (unlucky ones I think) where the Anode Mosfet has gone short circuit, killing the current monitor circuit at the same time. This is not too bad as it is easily repaired but unfortunately the gm meter has blown, necessitating a long wait for replacement. I am now trialling a diode, D15 in the attached circuit, which I hope will prevent damage by keeping the meter terminals from going more than 600mV apart in potential. As the sine wave is only at 100mV, the diode does not affect the normal gm measurement. Only time will tell if it does the trick but using isolating capacitors or current limiting resistors does upset the gm meter so this is my only option, me thinks!
There is a link on the PCB that connects the HT relay output to the drains of the Mosfets. I have replaced this link with an open style 20mm fuse holder, fused at 250mA A/S at present (though I may try lowering this later) which I hope will also prevent too much damage if the current limiters go defective. Thought I would post this up, anybody else had failures of the gm meter?
Cheers, Les

[leccigas]

Originally Posted by G8UWM-MildMartin

I now have the PCBs.

Do you have any left as I am looking for one.

[TommY_BuRnZ]

I've just ordered my PCB from Martin....oh eck - am I really going through with this??!! Better make sure there is plenty of room in my garage and the mrs doesn't mind me spending time on another homebrew project :-p !!!

[G8UWM-MildMartin]

Tee hee!

I've only got as far as getting the PCBs (35 or so left...) and a set of the meters and finding a flight case and some transformers I've had knocking about for years.

I'd be happy to get a few kits of components if anyone's interested, as it's little much effort than ordering one set for myself.

But can anyone supply pairs of "front" and "valve base" panels, ideally drilled and punched, and overlays to suit a common size of flight case?

(I really hate my poor efforts at metalwork and my fingers don't heal as quickly as they used to...)

If so, and with Ed's transformers, it would be an even more attractive project.

Best regards,
Martin.

[leccigas]

Originally Posted by swordholder

I have designed and built a valve tester just to prove to myself that I could.......

Hi there, I would like to build your valve tester and have spoken to Martin Crossley about buying a circuit board from him. I have a copy of the circuit diagram which I copied from your site. Is there any more info or construction details or anything else you could send me to help in my labours. Art.

[Brian R Pateman]

Hello Art and welcome to the forum.

I think that you'll find all the information which exists is somewhere in the 450 odd posts in this thread.

I think that every one of the "Sussex" testers will be unique, especially in terms of the housing and mechanical construction.

[Ed_Dinning]

Hi Gents, I'll be winding some more transformers shortly, so let me have your orders if you need any. Note that I can do units for 110V (US mains) as well as 240V.

Ref the valve base panels; I can probably do some of these to your design on 1mm Ali as long as it is not much larger than A4 size. Punched for standard valveholders (say upto 20 off,but not drilled for base fixing centres as these vary.
£10 including postage to UK addresses.

Ed

[Counting_Frame]

I stumbled across this forum when searching the web for valve tester information, finding I have more and more need for a tester as time goes by. I was thinking about building Steve Bench's RAT tester, mentioned elsewhere in this thread, when I came across the Sussex valve tester. This looks like a much better proposition as it is a current project and there is lots of feedback from people who are building it. Congratulations to 'Swordholder' for all your hard work. It's great that those of us who aren't so adept in the design department can benefit from this. Many thanks! Having spent the last couple of weeks reading all the posts, I have started gathering the parts together and hope to start building my version of the 'Sussex' any time now.

Andrew

[swordholder]

Originally Posted by Top Cap

I am now trialling a diode, D15 in the attached circuit, which I hope will prevent damage by keeping the meter terminals from going more than 600mV apart in potential.

Les,
Anything to report yet on the use of the diode?


Mike

[Top Cap]

Not yet Mike, I have not had any Mosfet failures since the last repair so I will only find out then lol. I cannot see why the gm meters otherwise failed as their supplies are fully floating but as the diode does not affect the readings it may be useful to add it anyway. I don't really want to do any overload testing on my present gm meter in case it goes faulty, so it could all be a red herring or a saviour. Hoping for feedback from others on this, in case they have had similar problems.
Les

[Counting_Frame]

Nobody seems to have mentioned this so I may be wrong, but apart from the 'on' LED, aren't the other LEDs shown connected the wrong way round in the circuit diagram? Maybe I've missed something..

Andrew

[Bero]

No you didn’t.
I have noticed the same, when trying to incorporate shorts test into my design.
Didn’t try other LEDs except LED3.

[FRANK.C]

Hi Guys
I am still working away slowly on my Sussex I've got a long way to go yet.
One problem that I came across with my build was that the amplitude of the oscillator's output was temperature sensitive. I came across this by accident while trying to set it up for 100 mV output.

For a 20C rise in ambient temperature the output would increase by almost 70%. This is probably not a problem for most if the Sussex would be kept in a place where the temperature would not change all that much, but the temperature in my shack can easily change by 20C between winter/summer.

The transistors appeared to be the main culprits so I tried changing the transistors for less sensitive ones this did help somewhat but there still was a considerable increase in output.

In the end the only way I could stop the output from changing too much was to substitute the oscillator for one I found on the net sometime ago with output stabilization ( I had a look for the web site but cant find it now) I substituted and changed component values to ones that I had to hand, the lamp I got from Rapid. I have attached the circuit below. The output now keeps within 5% for a 20c change in ambient temperature.
It can be easily built on a small piece of strip board.

Frank

[jimmc101]

This one?
http://www.4qdtec.com/singen.html

Jim