06-05-2024, 09:05 AM
I have a lash up bit of scrap chassis, tag strip, b9a base, couple of switches and 10 turn pot for grid voltage, plus suitably connected 4mm sockets for test leads to connect. I have a couple of lcd multimeters bought 50p each at a rally, minus leads and battery but both working, plus my usual bench lcd meter.
I have a Solartron 500V 100mA variable psu that also gives 6.3V, plus my small Farnell 30V 1A bench psu for grid voltage.
For some protection of ht current, I have an les 4V 60mA or so bulb in a holder fixed to the ht + terminal in series with supply when testing low current valves. I have a stock of maybe 100 bulbs! Usually blow with a brilliant flash when I accidentally short something within my lash up!
This jig is for ecc and with my adapter lead also 6sn7 or l7 etc. I put some ferrite beads on the leads close to the base.
For audio output valves, I have another similar lash up with my base wired for el84, again adapter leads for 6v6, 6bw6 etc.
Comparison checks show the cheap meters as within 2% accuracy and good enough to measure valves with.
Just need to be careful where I put my fingers sometimes with ht around from my meaty psu!
My ht psu would be better if stabilised for small changes in load, as being to the rear of my bench I reach across to vary the voltage, it could also do with a fine pot as well, the wirewound within seems a bit jumpy around 250v setting.
I suppose I ought to modify the psu with a stabiliser circuit and fine / coarse controls, but that is still on the to do list, has been for 10 years or so!
Rob
I have a Solartron 500V 100mA variable psu that also gives 6.3V, plus my small Farnell 30V 1A bench psu for grid voltage.
For some protection of ht current, I have an les 4V 60mA or so bulb in a holder fixed to the ht + terminal in series with supply when testing low current valves. I have a stock of maybe 100 bulbs! Usually blow with a brilliant flash when I accidentally short something within my lash up!
This jig is for ecc and with my adapter lead also 6sn7 or l7 etc. I put some ferrite beads on the leads close to the base.
For audio output valves, I have another similar lash up with my base wired for el84, again adapter leads for 6v6, 6bw6 etc.
Comparison checks show the cheap meters as within 2% accuracy and good enough to measure valves with.
Just need to be careful where I put my fingers sometimes with ht around from my meaty psu!
My ht psu would be better if stabilised for small changes in load, as being to the rear of my bench I reach across to vary the voltage, it could also do with a fine pot as well, the wirewound within seems a bit jumpy around 250v setting.
I suppose I ought to modify the psu with a stabiliser circuit and fine / coarse controls, but that is still on the to do list, has been for 10 years or so!
Rob
