12-05-2022, 09:50 PM
Well, I have been in the game since I was about eight, when dad and I constructed my first radio.
So I have been looking at a valve tester all my life
and I have discovered that its cheaper and easier to build one rather than buy one. Buying on the normal auction sites can be a disaster,
although I dont think everybody would be out to make a killing. I have been collecting digital panel meters, but so far cannot find a useful one at the right price,
AND that has a floating ground power supply so I can hook up six of them to a single supply for the digital readouts. All of them I have found so far are common earth
for the measurement zero and the power supply zero. That makes things go boom and let the magic smoke out.
I have been designing and winding transformers all my life, and although its easy enough to wind an extra ?? six supplies, I still have to rectify them to get DC,
and ideally would use a little regulator to make readings as stable and repeatable as possible.
I have assembled a set of iron, a set meaning HT, and screen on one transformer, Bias and heater on another so that I cannot switch on the HT without having a hot valve and at least some bias on the grid.
Valves go boom and let the magic smoke out too, if there is no bias.
So I have 500 volts DC available at about 1 amp, which will supply my HT and screen voltages using 807's or CV 428 ( same as 807 but in a loctal bottle ) as the series elements, initially two for HT and one for screen, but upgradeable by adding another the same to each supply if they struggle at low HT voltages. Bias will be -100 volts and will be gas regulator stabilised and have a small amount of positive ( so I can test in class B ) controllable through a ten turn pot. All of these supplies will have volt and milliamp meters so I can see and plot very easily what a particular valve is doing.
I will also be able to match valves for more critical applications.
So my posting and explaining myself is post one of the fifteen required to access the the archive. I am patient and have discovered quite a few interesting posts here to read in any case so it wont take long.
I have collected every piece of information I can find on the net regarding valve testers in general ( problem being an ex engineer, you require documentation ) and W.T. Cocking did some work starting almost a century ago, that I dont have yet. I am hoping all the information mixed into a big pot of soup, will fetch me a real, decent valve tester when its dished up.
Thanks to all for you interest and comments. I will keep you all posted.
Joe
So I have been looking at a valve tester all my life
and I have discovered that its cheaper and easier to build one rather than buy one. Buying on the normal auction sites can be a disaster,
although I dont think everybody would be out to make a killing. I have been collecting digital panel meters, but so far cannot find a useful one at the right price,
AND that has a floating ground power supply so I can hook up six of them to a single supply for the digital readouts. All of them I have found so far are common earth
for the measurement zero and the power supply zero. That makes things go boom and let the magic smoke out.
I have been designing and winding transformers all my life, and although its easy enough to wind an extra ?? six supplies, I still have to rectify them to get DC,
and ideally would use a little regulator to make readings as stable and repeatable as possible.
I have assembled a set of iron, a set meaning HT, and screen on one transformer, Bias and heater on another so that I cannot switch on the HT without having a hot valve and at least some bias on the grid.
Valves go boom and let the magic smoke out too, if there is no bias.
So I have 500 volts DC available at about 1 amp, which will supply my HT and screen voltages using 807's or CV 428 ( same as 807 but in a loctal bottle ) as the series elements, initially two for HT and one for screen, but upgradeable by adding another the same to each supply if they struggle at low HT voltages. Bias will be -100 volts and will be gas regulator stabilised and have a small amount of positive ( so I can test in class B ) controllable through a ten turn pot. All of these supplies will have volt and milliamp meters so I can see and plot very easily what a particular valve is doing.
I will also be able to match valves for more critical applications.
So my posting and explaining myself is post one of the fifteen required to access the the archive. I am patient and have discovered quite a few interesting posts here to read in any case so it wont take long.
I have collected every piece of information I can find on the net regarding valve testers in general ( problem being an ex engineer, you require documentation ) and W.T. Cocking did some work starting almost a century ago, that I dont have yet. I am hoping all the information mixed into a big pot of soup, will fetch me a real, decent valve tester when its dished up.
Thanks to all for you interest and comments. I will keep you all posted.
Joe
