Moderators: Dave Moll, Steve Anderson
ppppenguin wrote:I'm rather late to this party but I have a copy of the EMI Photomultiplier catalogue from 1970. I've scanned and uploaded the relevant pages for the 9524.
Many years ago I worked with PMTs in Cintel telecines and elsewhere. The HT needs to be very smooth indeed but you'd probably get away with an inverter and plenty of smoothing.
This is easy at the low currents involved. The voltage needs to be very finely adjustable to vary the sensitivity. And of course it needs to be very stable. The cheap and cheerful answer for lab work used to be a string of type 126 90V batteries. Not really an option now but I suppose you could fit a lot of PP3s together
n an earlier post I saw a circuit with a string of zeners feeding the dynodes. This feels instinctively wrong as you want the dynode voltages to track the overall voltage. You might well use a 150V zener from the cathode to the first dynode as recommended in some EMI notes. Otherwise the current in the dynode chain wants to be at least 10x the anode current. The mean anode current should rarely be more than 100uA so a few mA down the chain is about right.
Hope this helps.
ppppenguin wrote:Glad I could help.
Actually 10x 126 batteries wouldn't be a very big or heavy lump. But dangerous as you suggested. I suppose up to 100x PP3 isn't totally absurd. You're unlikely to need more than 900V.
Many years ago ISTR making a very simple flyback inverter to power a vidicon or plumbicon tube. I don't have any details now but it was pretty crude. I think it gave about 800V which I stabilised with a string of zeners. You might get some decent results wth an old diode split LOPT driven by a very modest amount of switched power. I've kept a couple of old CRT PC monitors to provide not just the LOPT but also the drive circuits.
Return to Harry Dalek's Photomultiplier Tubes camera build
Users browsing this forum: No registered users and 1 guest