The "Sussex" Homebrew Valve Tester.

[Chicoull]

Forgot to ask - is there a way of knowing a valve is Directly Heated - such as the two battery valves I tested?

[Station X]

A directly heated valve has no cathode.

[Ed_Dinning]

Hi, if valve is internally visible then the filament wire can be seen on directly heated types, a cathode cylinder on indirectly heated types.
For battery valves (1.4,2,4 and 6 volts ) it is best to use an external DC supply.
Directly heated mains valves (PX4 and some rectifiers ) will be fine with the appropriate AC voltage

Ed

[George G4EUF]

Hello Les, Did you rx my last PM to you?
George.

[George G4EUF]

Hello all,
I have now at last completed the "Sussex" and carried out all the test procedures and apart from dropping one or two clangers on the connections to both the electrode switch and the function switch all seems to be working correctly apart from getting a relatively high GM reading on most valves tested.
I would like to take this oportunity to thank all those involved with this project, in particular to Les, (top cap) and others who helped me sort out one or two problems in the bias supply department, again my thanks to everybody !!.
Regards.
George.

[DaveBacon]

Hello,

I'm just starting to locate parts for my own Sussex Valve Tester and have come across a problem locating a couple of transistors. Could you kindly recommend a location where the following transistors could be purchased?

BC307
BC237

Most places have indicated these as being obsolete.

Originally Posted by Chicoull

I was looking for a Valve Tester, found this link and was instantly hooked! I have started ordering component parts - PCB and transformer already organised.

Charles, where did you source (purchase) the relays from?

Thank you,

Dave Bacon

[DaveBacon]

I also asked Martin about where I might locate BC307 and BC237 transistors (as they seem to be obsolete) and his reply was extremely helpful:

The BC307 and BC237 transistors aren't at all critical.
The oscillator will run with almost any PNP ones (originally BC307) such as BC557B or 2N3906.
The NPN (BC237) in the short detector could equally be something like a BC547B or 2N3904.
( The 2N ones have reversed pinout)

Thank you Martin

[Boater Sam]

Loads on ebay but they may be of doubtful parentage.
These are fairly simple NPN general purpose transistors, I can't imagine that they are critical, near equivalents will likely do OK.
Perhaps someone who knows this tester is better to advise on substitutes.

[KeithsTV]

As Sam says they are general purpose transistors and can be substituted by many alternatives. The BC307 is PNP and BC237 is NPN. The only thing to be aware of is that the Vceo should be 45V or greater.

Keith

[Boater Sam]

2N3703,BC307,BC512,BC557,BC251 & BC212 are listed as Equivalent to BC307 PNP

BC107/108/109 are listed as equivalent to BC237 NPN

You need to check the ratings as Keith said and the pin outs, some very common transistors there.

[DaveBacon]

Hello, looking at post #1353, would someone be able to explain what a "grid stopper" resistor is?

I'm assuming the "grid stopper" resistor would be connected to and close to the control grid pin on the octal valveholder. Correct?

And, what value should the resistor be?

Thank you,

Dave Bacon

[Boater Sam]

Typically I use 33ohm to 100ohm on my home made tester but only if I need to stop the parasitic oscillations.
Yes, close as possible to the pin.

[Omegaman]

I used 2N3904/6 in mine. No problems.
The relays were from Rapid Electronics.

[Top Cap]

I used these relays on my build (see attachment), available from many suppliers e.g. RS 680-3947P or Mouser 655-RTE24048.
Les

[DaveBacon]

Hello, please excuse this lengthy post.

I've searched this forum concerning the wire used to connect all of the components in the enclosure and still have a few questions.

The current Sussex Valve Tester manual recommends using wire rated at 3A.

1. For the majority of the connections (e.g. between the rotary switches and valve base pins / excluding the heater pins) what gauge of stranded wire is recommended. 20 gauge?

2. I see in the forum post #659 that using a solid core wire for the heater connections is recommended as twisting the wires can reduce hum. It's my understanding that solid core wires can generally handle more current than stranded. What solid core wire gauge is recommended for the heater connection wires? 24 gauge?

3. Concerning the use of screened wire between the switches and valve base pins. I understand that it may not be possible (due to space limitations to use screened (shielded) wires on all of the valve base pins. At a minimum, which valve base pin connections should use screened wire? And what gauge is recommended for the screened wire?

4. Another question on the screened wire, is it also recommended to connect the screen to ground? Both ends of the screen?

And lastly, are there any recommendations on where to purchase high quality wire? I like the idea of using a different colored wire (based on the resistor color codes). But I'm concerned about purchasing wire from an unknown eBay seller.

Thank you for your time responding to my questions.

Dave Bacon

[Top Cap]

Hi Dave, I think most folks building the Sussex used whatever wire was to hand. I used some 19/.15 (22 AWG) and some 7/0.2 (24 AWG). I also used some coloured flat cable (Rainbow wire) which although only rated for 300v has not given any problems and is 7/0.15 (26 AWG), this is rated 4 Amps. Its smaller size allows you to fit ferrite beads close to the tube holders and should make using screened wire unnecessary.
Typical ribbon cable is Mouser 523-111-2609-010 available per foot.
Single wire could be Mouser 650-55A111-22-9-9, also available per foot and other colors apart from White are available.
No doubt others will chip in with their ideas as this is a very wide open question.
Les

.

[6110c37]

As regards the screened wire for the valve bases I found that good quality fully wired Scart cables have a selection of coloured cables in them.
Martin

[vidjoman]

I would be wary of those Scart cables - they only need to be rated at about 12 volts as the only voltages present will be for switching inputs. The tester needs cables rated at 500 volts to be on the safe side.

[George G4EUF]

Hello All,
Can someone please tell me how to upload some pictures of my "Sussex", Have tried a couple of times without success.
Regards.
George.

[Boater Sam]

There is a sticky that explains it in detail George.