Andrea wrote: I have a KX1, not a K2, however the point is taken. Nicola told me that meter was "low-voltage" and okay for solid state. How do I verify that it is so? And, most importantly, how do I check whether any damage was done?
Ok, I'll quit worrying about the resistance values and get a DMM to recheck the ripple. -------------------------------- You are probably okay then Andrea. Sorry for alarming you! There have been multi-meters made for solid state that are not DMMs, but they are fairly rare. As far as damage goes, most solid state either works or it doesn't. It is possible to degrade the performance of a solid state device - particularly insulated gate devices like some field effect transistors - but that usually happens because of high voltages at tiny currents produced by not following good electrostatic discharge procedures when handling them. I've never seen a case where allowing too much current through a device - such as an old-style ohmmeter does - 'degrades' the part. It usually kills it. So if your rig is working, either the meter was okay for solid state or you used it in a way that didn't damage the parts. One way to check a suspect meter is to check the current that it allows to flow in the ohms range using a second meter. Typically, the greatest current flows in the lowest range. Most DMM's that I've seen allow no more than about 1 to 1.5 mA to flow through the circuit under test at any time. My Fluke DMM never allows more than a few hundred microamps in the ohms ranges. By comparison, a typical pre-solid state volt-ohm-milliameter (VOM) typically allows as much as 100 mA in the low-ohms range! Yes, I wrote 100 mA - 0.1 AMPERES - in the low-ohms range. That can wipe out all sorts of integrated circuits and transistors! Those older VOM's seldom allow more than a milliampere to flow on the higher resistance ranges, so a knowledgeable user who knows a particular meter can get away with using it for certain resistance checks. I've serviced a lot of solid state gear "professionally" and I simply don't fool with ohms checks with an older meter. I do have an older VOM that I prefer for "peaking" an adjustment, but I never use it in ohms range. Another clue is that the newer low-current meters do not need a "zero" adjustment. If a meter has a zero adjustment, I assume it is an older VOM that will kill solid state parts in ohms range until proven otherwise. And one more clue is whether the meter has a separate "diode check" function. Modern meters designed for solid state typically do not apply enough voltage to positively turn a transistor or diode junction "on". The resistance measured across junctions will still vary widely, but not enough voltage is usually applied to do a valid test. So a separate "diode" check is provided that applies enough voltage and current to determine whether the junction is behaving properly. Still, the current is limited to about 1 mA to avoid damaging any sensitive integrated circuit or transistor junctions. The KX1 is a really cute rig! I have serial number 0004 which I built while writing the assembly instructions for the manual. It's a great rig that had been invaluable in public relations here in Oregon. I'll tell that story in a separate post "Elecraft Rigs as Public Relations Tools" if you're interested. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
