Emc 215 tube tester manual12/17/2022 "Hell, there are no rules here-we're trying to accomplish something!"Ĭhris108 and Dennis H - Thanks for the replies. Might be worth opening it up to see if there is a series resistance inside. You realize that a 5-mA meter with a 1,500 ohm resistance would actually be a DC voltmeter (0-7.5 volts to be exact). If the original meter had a moving coil on pivots between the poles of a permanent magnet, it was a d'Arsonval type movement, which only would have been DC (unless it had some kind of rectifier mounted inside the case). The cap would not have worked out so well if AC was applied to the meter.Īnother way to look at it is this. But it is often a pulsating form of DC which would cause the meter needle to vibrate in a blur, so the cap is there to smooth out the pulsations and keep the needle steady. Sophisticated tube testers contain DC power supplies to develop the various test voltages needed simpler tube testers apply AC voltages, and let the tube under test do the rectification. Oh, the new meter cost $8.00 so it's not a big loss if my jerry-rigging doesn't work, but I would love to get this tester to work! Thanks all. Am I just burning my brain up over this? Can anyone post their thoughts? Any help would be appreciated. That's not going to produce a deflection similiar to the deflection I would have with a 350 ohm meter movement. It seems to me that the current flow would be divided approximately 25% thru the 1500 ohm meter and 75% through the 470 ohm resistor. But, will this give me the same needle deflection as the original would have? As I'm asking this I'm starting to think that it won't. I'm thinking that by doing so I will now have the (approximate) total resistance that the original meter presented to the circuit. My question is this: I know that if I put a 470 ohm resistor in parallel with the meter the total resistance will equal approximately 360 ohms. However, the new meter ohms shows a resistance of 1500 ohms. It took a little "customizing" but it matches very, very close to the position of the former "0-50 Ma" face plate. I've also very carefully opened the new meter and swapped the old meter face ("Bad-Weak-Good") into it. I've gotten a replacement 50 Ma meter which will physically fit the opening on the front panel, so mounting is not a problem. The schematic identifies it as "50 Ma - 350 ohm". I have a preevious post about my EMC tube tester meter being open and unrepairable. I'm wondering if someone has advice or help with my problem.
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