The "Sussex" Homebrew Valve Tester.

[Ed_Dinning]

Hi Gents, please note that this is a valve tester, not a designed for soak testing of valves.
Please do not run valves, especially power valves, for extended periods of time as the transformer and probably regulators are not designed for this use and my well overheat.


Ed

[Top Cap]

As an update to post 420, I have observed that the leak LED does not always light up after testing. I have just done a batch of 6K7 and 6V6 without the effect showing so maybe the other valves did have a fault. Also I must correct my original findings, the Leak LED when it does glow only lights while the capacitor on the regulated HT line discharges and is not dependent on the heaters as these are of course still on in the leak test position of the Function switch. Apologies if I caused some confusion here, the grey matter often confuses me at times but I refuse to hang up the soldering just yet.

[Bero]

Thanks for advice
It really was due to parasitic oscillation.
I've hook up scope probe between cathode and g1,
all seems to be OK till current 5mA.
There was only a 1 kHz input signal (see picture nr.1).
Picture 2 shows probably point where oscillation starts.
Picture 3 shows how looks like after this point, there is much more of traces behind those visible.
I even don't know frequency of those oscillations, seems to be much more than one visible.
On picture 4 you can see magnified trace.

I've try to use ferrite beads around the wires connected to valve socket.
Seems this helps, but only for a few milliamps more, and then an oscillation backs.

Like you suggest top-cap, I've tamed them with a 1nF ceramic disc across cathode and g1 onto valve socket.
Seems this has influence on pilot tone 1 kHz, it's a little attenuated now.

[Bero]

About ferrite beads, I've read somewhere in this thread.
Can someone give a comment about best position, where to put them in such type of circuit?
(around the valve socket, repeat somewhere inside of wiring, is there any rule using this?)
I have two types of ferrite, I've use those from first picture.
Didn't try those from second picture.
Any comment here?

[Bero]

According to my question from post 417-419,
I still don't know how this thing with current limiter works.
After curing wild oscillations, all seems to be OK now; there isn't positive voltage on g1.
Contrary, there is 6.2 volts negative respect to cathode.
According to the valve data book, with 250V on anode and screen, -7.3V on g1, EL84 will give 49.5mA current.
This -6.2V is really close to book value of -7.3V.

[0108vesa]

Hello!

First test made with "Sussex" and ecc85, tube looks to be ok. Or tester not...

Vesa

[Guitarist28]

Hi 0108vesa,
I do like your tester and I'm pleased to see that its working.

Well done

Regards

Rob

[swordholder]

Hi Vesa,
A super example of home made equipment.... Well Done.
I like the idea af a heater voltage meter, presumably to set the mains input correctly where mains fluctuations are a problem.
Can I ask what the "high/low" switch at bottom left does? I notice you are using a "test button", but your hand is covering what appears to be another couple of buttons, what are the purpose of these.
If you have modified the original circuit. I'm sure others apart from myself would be interested to know what you have done, after all ideas are meant to be improved upon, a concept I fully agree with.
Regards and well done

Mike

[0108vesa]

HI!

I have dc heater power, 0 to 25V and 0 to 50V, 2A, and high/low selects between them. 2 x 18 volts toroidal transformer happened to be in this box... Behind the hand are power on/off and g1 potentiometer. Anode and screen voltages go to sockets through relay by pushing that test button. I have not yet diode/rectifier testing working. Tester has given really fine results. I tested many old ech81 tubes, most poor, compared to new one, which gave results, like in manual.

Vesa

[swordholder]

Hi Vesa
All understood. Let us all know what results you get from the rectifier testing.
I'm glad the testing results are meaningful and useful.
Regards
Mike

[rayG3NOD]

Originally Posted by G8UWM-MildMartin

I now have the PCBs.

HELLO MARTIN
I have just recently found this article and am very interested in building the Sussex valve tester. Do you have any P.C.B's still available. If so I would like to buy one.
Ray Burton G3NOD.

[swordholder]

Ray,
Ed Dinning may well have some transformers for the design if you are interested, suggest you contact him direct.
Welcome to the "Sussex Gang", as you can see several have/are being built, so far with no great problems.
Kind Regards
Mike

[rayG3NOD]

Hello Mike
It certainly is a very impressive unit, ive always wanted a valve tester. I thought that Martin was dealing with the P.C.B,s and Ed was dealing with transformers, and that I would start with the P.C.B first. However will see what happens before contacting Ed. I have a lot of old valve radio,s so looking forward to checking valves during the process of rebuilds etc:.
Thanks again for such a good article

Ray

[G8UWM-MildMartin]

Hello Ray,
Yes, still about 40 PCBs left..
Regards,
Martin.

[rayG3NOD]

Hi Martin.
Many thanks for your reply to my request.
I take it that your address will be in QRZ, and the price of the P.C.B is still £10.00 ?. I so I will send a short note & cheque over the weekend.
Ray.

[Darren-UK]

Ray,

You might be best confirming Martin's address and other details via PM (Private Message).

[rayG3NOD]

Hi Darren
Many thanks for that information. I will try by PM
Ray

[G8UWM-MildMartin]

PMs exchanged, thanks.

[Top Cap]

Just had a requirement to reform some electrolytic's and realised that the Sussex had most of what I wanted i.e. variable HT supply with metering. I decided to make an accessory to plug into the Top Cap Anode and Cathode sockets and that would also allow both charging and discharging.
I had added an extra 50V option on the HT switch of my Sussex which is very convenient for checking 63V capacitors. The circuit is pretty simple, the key component I think is the isolator Diode 1N4007. Also, the Diode option on my Sussex allows me to lower the charge current down to 5mA if required but so far I have had no problems using the Anode supply.
Les

[timohaveri]

I've been following this thread with great interest and I have started to gather the parts for the Sussex. I'm sure I'll have much questions later when I start actually building it.

I have already bought the panel meters (arrived yesterday). In case there are other cheapskates around I thought I should mention that I got the 3 meters for 21 USD including shipping from a seller called "a-suntek". Just use the "make offer" button or contact the seller directly. I'm sure many other sellers would give a discount too if asked.

I have one question about the panel meters. Some of the pictures attached in this thread show meters without the text "mV" in the display and in some it is clearly visible. Mine has the text. Are there different versions around or is it possible to get rid of the "mV" in the display by removing a resistor or something? It would just be a bit confusing if the display says "mV" if the meter actually is measuring anode or grid current. I have used similar meters before with LED displays and there was a jumper that could be used to change the position of the decimal point or remove it altogether so I thought that maybe it is also possible with these meters.

Timo