Rudimentary Valve Tester

[Sparks]

I am now well into my rudimentary valve tester.    I found an ancient wooden box on the car boot sale that was ideal.     I can always polish it up if the tester works OK.    The first task was to fit a wooden rim around the inside onto which the front panel will bolt.   Two panel meters will be fixed in the front panel, whilst two "cheapo" multimeters will be in the lid for anode and screen current.      I have checked that the lid OK.         The worst part is now over, being the drilling of the aluminium front panel.   It was quite an effort to cut the two rather jagged meter holes in it.    Bit of a mess, but they will be hidden by the panel meters.    I have almost reached the stage where I discover that I have either drilled a hole in the wrong place, not drilled enough of them, or drilled too many!     The next task is to smooth and spray paint the front panel.       The HT and LT will come in from external supplies.
Bob

[Sparks]

The light is going a bit, so latest image a bit fuzzy.     I had forgotten to put the grommet holes in for the two sets of multimeter leads.   Also the hole for the grid bias pot.     Fortunately, spotted these omissions before painting.     Sprayed it with grey matt primer from Halfords, and fitted the metres, sockets and controls.     All that now remains is to wire it up.
Bob    

[pwdrive]

Looks the job, hope it all works.

Lawrence.

[Sparks]

Thansk,
It worked OK when I built it roughly, so should be OK.
Bob

[Sparks]

I completed it, and it does work, but with the same rather erratic results that my Avo Mk1 tester produces!   Different valves of the same type give different readings.   It is easy to say that some are better than others, but they all have one thing in common, in one valve radio circuits, there is no audible difference in performance!   It is more consistent with triodes!  The more I read about valve testers, the more sceptical I become, and wonder if in many cases they were just an excuse to say that a valve was low in emission, and needed replacing.   (I am talking about the 40s, 50s, and 60s now!)    I have no doubt that modern versions can analyse a valve 100%, but in the end, if it works OK, that is all that matters.     I will probably end up dismantling this one, and going back to my original, that tests the valves in a one-valve receiver circuit, whilst providing monitoring for anode current.
Bob

[pwdrive]

It all depends on the valve's application, for regen detectors a low emission valve will work ok as long as there is enough emission in it to get the circuit to oscillate or just about oscillate, with a regen it's not usually a problem as the amount of regen coupling can be increased by advancing the regen control to offset the loss in emission.

But for instance in a superhet the emission of the oscillator valve is a bit more critical as the amount of regen coupling is fixed

Lawrence.

[Mike Watterson]

I'd recommend keeping it. You never know when it might be handy or be usefully enhanced.
I have two KK32, fine on LW, MW, SW1 but not SW2, the higher bands. They are not great on tester. Similarly I have some DK92 and only one is good on SW. I made up a B7G to Octal adaptor with 2.1V to 1.4V dropper resistor to try DK92 in the radio.