The "Sussex" Homebrew Valve Tester.

[Mike Brett]

I am in the process of testing the following valves on my Sussex, UY85,UL84, UABC80,UCH81, UF89,and UCC85. What is the best reliable source of information on identifying the valve pins to set the Sussex pin switches. I have tried the National Valve Museum but I find some of the valves confusing.
Mike

[mole42uk]

They are all in the AVO Valve Data Manual. PM me if you haven't got a copy and I'll email mine. It's 7.7Mb though!

Richard

[Mike Brett]

Hi Richard
P M sent.
Many thanks Mike

[gainworld]

Hi discovered this thread just now, and have read through it. and i am very impressed with the design. Now I must build this tube tester.
Wondering if it still is possible to order the circuit board and transformer.

Tony.

[G8UWM-MildMartin]

I still have (28) PCBs for sale at cost (8.12 GBP).
Plus, maybe, the cost of a padded envelope, depending on whether any suitable used ones are being thrown away at work, plus the ever-increasing Royal Mail postage cost, minus the discount from using the franking machine at work, plus any applicable curency transfer or exchange fees.
Best regards,
Martin.

[Ed_Dinning]

Hi Tony, yes I still wind transformers for this tester on demand, nearly 50 sold to date; cost, including post to Sweden would be £95.

Best regards, Ed

[adriaanhendrik]

Hi all,

Just to keep you informed. I finished my Sussex in the last weeks since my former post.
It works as expected and I have tested as much valves, as I have here.
Most readings confirm what is in the VALVO manual, so I trust I did a good job.
I have used a double HEATER switch and an extra relay, to be able to measure DC and AC in the same action on the extra HEATER meter on the left.
I sneaked in an extra DC position on that (AC)meter just after the diode to be able to measure both (an extra resistor is in place to compensate for reading the right Voltage). The relay switches the wire before and after the diode on the meter pcb. I may have overdone it there as a solution, but I like it anyhow

The only strange thing I came upon is, that the 'cont.' LED in the '0' pos. lights up only dimly and then brightly, as I switch to 'LEAK1' and 'LEAK2' only to become dimly again in the 'TEST' pos. Maybe I made a mistake there..
I have to recheck my wiring once more..

Until now I didn't dare to short the Anode or Grid pins to test the other LED's.
Les, I have followed your wonderful 'my version' doc for this build and i thank you for its clarity, but is this safe to do, when not in the 'TEST' pos.?

Regards,
Ad

[Top Cap]

Hi Ad, that looks a fine job you have done there. The HEATER CONT LED should only light up when you are at the HTR CONT position of the Function switch.
The HTR CONT LED is isolated by Relay 2 which is de-energised for the LEAK and TEST positions. Check Relay 2 is energised at HTR CONT but not at the other 3 positions of the Function switch.I have attached the circuit of this section again, it is different to the original to stop valves with heater cathode shorts from shorting the -45v supply. This supply also does the leak tests so the main High Voltage tests are not switched on at the LEAK positions. Just don't try it with the Function switch set to TEST

[adriaanhendrik]

Hi Les,

I must have overlooked that one in the many posts regarding the Sussex.
I'll change the wiring the next time i plan to do some soldering
Thank you for your answer about the other leds. For some reason i keep on getting confused about Anode / Cathode funtion in a Led or any diode for that matter. But then again, I only spent the last 45 years with technology as a hobby...

Regards

[gainworld]

Originally Posted by G8UWM-MildMartin

I still have (28) PCBs for sale at cost (8.12 GBP).
Plus, maybe, the cost of a padded envelope

Hi Martin you got a PM
Tony

[mole42uk]

Hi Folks,

I was doing some modifications to the Sussex the other day, changing the current limiter on the anode voltage supply.

Before and after those mods, on any valve that requires more than about 15mA on the anode, the Ia meter is unsteady - it will flicker about plus or minus 3 or 4 mA during test. The Gm meter shows a similar unsteadiness.

If I test a smaller valve, using up to about 15mA the meters are steady and consistent.

I at first thought it was the current limiter operating, but having increased the current limit point I am still seeing this wavering on the meters. The grid voltage meter is steady under all conditions.

Has anyone any thoughts?

Richard

[adriaanhendrik]

Richard,

I get the feeling that maybe a cold soldering point might cause this.
Also, have you tried feeding the meter(s) with a DC supply, or are they DC already?

Regards,
Ad

[mole42uk]

Hi,

You might be right. I used an awful lot of parts from the spares bin, and I do remember a few bits that needed extra care with soldering because the leads were not bright and shiny.

I'm not sure that the meter supply is likely to give trouble - they are all AC from the independent windings on the transformer, and the Grid volts meter is steady when the other two are drifting about.

I'll have a look at the anode voltage circuit, see if there's a bit of rogue solder in there.

Richard

[Top Cap]

While restoring a Sobell 515P I re-valved the set but the sound output was very distorted at anything above half the rotation of the volume control. Everything looked right, bias and other voltages all spot on so could it be the EL84? I had done a precautionary check of all the valves as received on the Sussex and all looked fine. So I tried the 50 odd year old blackened EL84 in the set and presto! Magic sound. So what was wrong? Why did the Sussex tell me all was right with the new valve when clearly it was not.
Now it was always regarded that a valve tester cannot reproduce the same conditions as the actual circuit the valve sits in, but it was annoying to think that the Sussex had given this valve an erroneous Green light.
One thing you can do with the Sussex is record the Ia at different settings of the Grid Voltage control, then the results can be put into a spreadsheet like Excel, plotted and compared with the manufacturers factory curves.
I have done this countless of times when matching up valves so I decided to try this with the suspect EL84. As you can see by the attachment, the valve sits at zero Anode current for quite some time (Red graph) before eventually getting started which is contrary to the makers curve (shown in Green). The valve then runs out of steam as more current is demanded, as if the cathode itself has insufficient coating to provide the electrons required. In contrast, the other attachment shows the chart from the blackened and worn out Mullard. It still just passes the AVO spec figures being the equivalent of 'just in the Green' but it does start conducting at the low end compared to the new valve. The Red line strays away from the Green due to the poor thing trying to give emission that it clearly cannot do, but it does a good job of keeping with the curve shape.
So after all of this, I am now inclined to do a much fuller check on the valves I test, happy in the knowledge that if I used a 'quick test' instrument I would still be wondering what is wrong. The Sussex has given me a greater insight into how some of my valves actually perform and is a tip I am happy to share with other owners.

[mole42uk]

It's a good morning!

Martin suggested, with reference to my problem with the Sussex, that maybe it was parasitic oscillation. It was. A 1nF capacitor between the grid wire on the selector switch and ground was all that it took to cure.

Now I get sensible results from the EL34s I bought recently.

Thanks Martin!

Best regards,
Richard

[Mike Brett]

TC
Thanks for sharing the information with us, most interesting, lesson there to be learned me thinks.
Mike

[Theopholis]

Hello everybody. I am new to the audiophile scene, and found this "Sussex" valve tester. I would like to try to build it, but it would have to be for U.S. power. Is there a simple modification that I can do?

Thanks for your replies.

[Ed_Dinning]

Hi Theopholis, transformers are available for US power (120V); you could use it on your 220v circuits or you could add a 110/240 auto transformer.
The price gets pretty high because of the large postal charges to the US.
PM me with your e-mail address if you need further details.

Ed

[Alezar17]

Hi, Ed
I would like a PCB and transformer please. How much including shipping to the 06360, Ct. US.
Thank you in advance.

Alezar

[Ed_Dinning]

Hi Alezar, I'm afraid I only do the transformers, but I believe one of the other forum members still has some PCB's available.
PM me you e-mail address and I'll send you details.

Best regards, Ed