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Re: TR-4 Resistance Chart
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One thing to keep in mind, regardless of the measuring equipment used, is that most (but not all) of the resistors in these radios are 10% tolerance.? That means that, at a minimum, your readings can be +/- 10%.? If there are more resistors involved in the path to ground, those resistors are also +/- 10%, so the tolerance stackups can be greater than 10% and the resistors can still be technically good. I have found with the voltage and resistance charts that it will give you an indication of any major deviations.? If the chart says 5k, a reading of 4k wouldn't really raise an eyebrow with me but it its in megohms or very low resistance, there's likely a problem. It's the same with voltages -- especially if you're using a DMM or a VTVM because the readings were done with something similar to a Simpson 260.? What you're looking for are places that are way off from the expected reading -- especially in circuits that can be close to zero, like -2V and your meter is telling you 0 or even +1. Related but not reading voltages, I am working on an early TR-4 that's in very good cosmetic shape.? The owner told me he changed a few tubes by substitution and it worked somewhat better.? My Hickok 6000A tube tester identified 4 definitely bad tubes.? After I replaced the bad ones, the performance of the set was markedly improved.? This shows that not every method is 100%.? Tube testers have their place but aren't a cure-all.? Using the group of test equipment helps you greatly towards fixing any problems. 73, Steve Wedge, W1ES Time flies like an arrow.? Fruit flies like a banana.
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On Tuesday, April 15th, 2025 at 10:18 PM, Gary Follett via groups.io <xntrick1948@...> wrote: Also, while the type of voltmeter used can radically affect voltage readings, due to the loading effects of low resistance meters, differing ohmmeters should read relatively closely, whether they are VOM, VTVM, DMM etc. as long as they are in calibration. Good DMM¡¯s can offer capability of reading very high and very low resistances not possible with older types of meters, but should still read the same values for given resistances within the range of any given meter type, albeit with fewer significant figures. |
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