Re: The "Sussex" Homebrew Valve Tester.
 

Hi Gordon, well spotted! The diodes are correct on the circuit diagram.
D12 and D14 are shown the wrong way round on the board layouts.
I have placed amended sketches into my handbook on:-

http://homepage.ntlworld.com/lez/Sus...%20version.doc

Many thanks for the feedback, Les

Re: The "Sussex" Homebrew Valve Tester.
 

Fig 11 on page 11 of the linked document seems to tie up with the text of the post.

Re: The "Sussex" Homebrew Valve Tester.
 

Page 11 doesn't have any text apart from the component lists.
The Document is about a Commercial - Philips - Valve Tester, which is hardly the context of the current Thread nor the Poster's comments on his own unit.
Is he saying that he did the same and it worked?
Alan

Re: The "Sussex" Homebrew Valve Tester.
 

It's the right link and it is Fig 11. Quoting F. Langford Smith, p1283, Radio Designer's Handbook available as free download here;

http://www.tubebooks.org/technical_books_online.htm

"Parasitic oscillations often occur at frequencies of the order of 100MHz with leads from valve sockets forming resonant circuits, and with a feedback path provided by a few pF of capacitance between plate and grid circuits."

Placing a capacitor between control grid and earth, but remote from the socket, won't eliminate parasitics under all operating conditions because there is still a good lead length. The 100R resistors and 270pF capacitors soldered right on each of the valve pins do.

It's normal design practice to use grid stoppers soldered as close as possible to g1 and g2 (and in extreme cases to anode) socket pins but this isn't possible here.

Proof of concept can be tested before committing, by testing, for example, an EF183 or EF184 and soldering just three RC pairs with short leads to g1, g2 and a (pins 2 and 8 and 7) of the B9A socket base. They should have no effect on DC voltages used during leak testing etc. or on your 1KHz test signal but I confess that I haven't fully studied the design. Values aren't critical and cheap 5% 1W resistors and 1000V 220pF ceramic capacitors would suffice.

On my curve tracer design, there were extreme current and voltage surges, or constant current effects on the XY recorder without these in place when testing EF183, though I could successfully trace ECC82 characteristics. My first thoughts were to build an adapter with 240R stopper resistors soldered close to each pin with small switches to short out those not required. A clumsy solution. Then I came across this thread researching other options. I continued, wondering how it was done historically and came across the simple Philips design. Tried proof of concept, and it worked.

Regards,

Bob

Re: The "Sussex" Homebrew Valve Tester.
 

Fig 11 shows a resistor and capacitor in series connected from every pin of the tester's valveholder to earth. This is exactly what getters refers to in the text of post #500 of this thread.

Re: The "Sussex" Homebrew Valve Tester.
 

.... and Post #505 answers my question. It was copied from a Commercial Design and it did work in the home-brew version.
Alan

Re: The "Sussex" Homebrew Valve Tester.
 

WOW!

I stumbled on this incredible project about a week ago, but it seems that I'm a little more than a year behind. Sure have some catching up to do!

I've read almost 400 of the posts and am getting geared up to build this thing, but hope that I haven't missed the boat on getting a transformer and PCBs. I even read that someone talked about getting a few kits together, but I assume that time has passed beyond that idea.

I don't yet have PM credentials, but would like to get a post up that I'd like to get a transformer (USA version) and PCBs if they are still out there.

Someday I'll be a big kid and will be able to send PMs.

Thanks,
Ed

Re: The "Sussex" Homebrew Valve Tester.
 

Welcome to the forums. You are now a big kid.

Re: The "Sussex" Homebrew Valve Tester.
 

Hi Ed, transformers still available, PM sent.

Ed

Re: The "Sussex" Homebrew Valve Tester.
 

Hello Ed, I'm interested in the transformer, could you please send me a pm with the details?
Also, is there a pcb available as well?

Many thanks
Alejandro

Re: The "Sussex" Homebrew Valve Tester.
 

Alejandro
Martin probably has some PCBs left, look through the earlier postings

Mike

Re: The "Sussex" Homebrew Valve Tester.
 

Hi Mike,
Many thanks for your response and great work by the way!
I've been testing my valves with a breadboarded simple voltage regulator, CCS and driving the grid with an audio oscillator to measure GM.
Recently I saw the RAT tester and started modifying the circuit with some enhancements and changes.

I also got a set of LCD meters from eBay which are sourced by 8-12V AC/DC.

Question: does each one of the meter need a separate floating supply to ensure there is no loop currents across them to avoid burning?

Thanks for the help
Cheers,
Ale

Re: The "Sussex" Homebrew Valve Tester.
 

Hi Ale, PM sent.
Yes, the meters need seperate supplies in this application.
My transformer covers heater voltages from 4 to 12.6; the US version with a 110v primary also has a 2.5 v heater tap for the power triodes that were popular there. It would make for a very bulky and costly transformer if I included all heater voltages up to 110v, so it is suggested that you use an external power supply for the odd values.

Ed

Re: The "Sussex" Homebrew Valve Tester.
 

Hi,

I found my way to this thread (a year late, it would seem) as a result of my request for a reasonably priced valve tester on the "wanted" section. WOW! What can I say, you guys have really mapped it all out. I have not yet found the neccessary twenty hours to read all the posts, but am really interested. Are the Transformers and PCB's still available? Parts lists? Wiring diagrams?And from whom?

Thanks,

Barry
PS. Sorry if all these questions have been asked before

Re: The "Sussex" Homebrew Valve Tester.
 

Hello all,

I'm a newbie to this Forum as well. I understand from reading some of the previous posts by 'swordholder' that the pcb might still be available from "Martin"?
Much obliged if Martin can please indicate if this is so..many thanks...

Re: The "Sussex" Homebrew Valve Tester.
 

Hi,

Has anyone considered using thumbwheel switches (either edge wheel or pushbutton) instead of the 9 pin selector switches? They would seem to be closer to the AVO style selector and would take up far less panel space. Most of the ones I have looked at, have poor current switching ability (200mA) but at 1Amp current carrying capacity seem to be up to the job. As I recall the rotary switches are also poor at current switching. Here is a link, NOTE: the decimal switch, not the BCD coded version.

http://www.farnell.com/datasheets/310077.pdf

Barry

Re: The "Sussex" Homebrew Valve Tester.
 

11 undrilled PCBs left (plus 2 reserved) at £10 ea. including UK post.
(Plus £1 for EU or £3 for the rest of the world.)
I have also built 10 (including mine!) PCBs up, but not tested them yet, price TBA.

Re: The "Sussex" Homebrew Valve Tester.
 

I am intending to try thumbwheel switches in my version of this tester.
But I have hunted out some huge thumbwheels to help with both current carrying and high voltage requirements. The main thing is not to expect the switches to be moved when carrying current. I never move the Avo tester switches when a valve is being tested anyway.
PM me if you want to try this option as I had to buy a large batch and have quite a lot spare. I could easily make up a 9-way set for you!
(PS Avo photos coming soon as requested)
regards
Jeremy

Re: The "Sussex" Homebrew Valve Tester.
 

Hi Gents, Sussex transformers wound as required, £65 including UK postage. I also have a version with a US (110V) primary available.

Ed

Re: The "Sussex" Homebrew Valve Tester.
 

All my spare thumbwheels now gone - that was quick!