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-------- Original message --------From: - <rrrr6789@...> Date: 11/30/20 11:47 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Resistor in series ? That's good information Menahem. Thanks for posting it.?? I'll just add that I have a large number of 40-ish year old AllenBradley carbon comp resisters, many of them still in the factory sealedpackages. I have probed through the packaging and measured many of them andthey're ALL well out of spec!? So don't trust old carbon camp resisterseven if they've never been used.? Seeing how far out of spec that many ofthese resisters are, it amazes me that any of this old equipment that usesthem still works!On Mon, Nov 30, 2020 at 3:50 AM M Yachad <yachadm@...> wrote:> Jeff> Choosing a substitute resistor type, as others mentioned here, is not a> simple matter.> You really need to know what its function is in the circuit.>> Carbon Comp resistors are the only absolutely suitable choice, if the> circuit has current surges.> Film resistors of all types simply cannot handle the range of current> surges.>> If you really cannot find a Carbon Comp (and the circuit requires it),> then a Ceramic MAY be a good substitute, and if you are still really stuck,> then the next possible substitute is a Metal Oxide type. BUT, Metal Oxide> starts to introduce inductance into the circuit.>> Carbon Comps also have no inductance (inductance kills - as in obliterates> - performance in RF circuits).>> Now, Ceramics come in two types - Inductive, and non-Inductive. Again, For> an RF circuit, ONLY a NON-Inductive is suitable.>> Notice that I haven't even mentioned film resistors.> On these vintage machines, you really want to investigate using Carbon> Comp or Ceramics first, to solve the problems, without introducing new> problems!>> Your choice was correct to use Carbon Comps, but I would recommend buying> new production pieces from Mouser or Digikey. Highly unlikely that you'll> find significant deviations due to moisture in cracks, or whatever..>> Menahem Yachad> CondorAudio>>> >>>