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QMX Rev 3 - transformer T501 check
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Hi Folks,
just a small quick question. Have finished output transformer T501 and performing the continuity check in step 17.
Continuity of A and B: OK.
Between A and B (primary / secondary):
Is it normal and ok to have several mega ohm resistance or should I be concerned and search for a problem?
VY 73 DE Thomas - DJ1TF - JJ1QPB
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On 30/12/2024 19:31, Thomas Fritzsche via groups.io wrote:
*In circuit* my cheap DVM measures a very high resistance of a several mega ohm.Thomas, If you are looking for a short circuit then millions of Ohms is no problem. With the vast number of connections between components in a circuit it is unlikely that there will be an infinite resistance between any two points. Unless the instructions specify a particular figure you may ignore high readings. Lower readings in the hundreds or thousands of Ohms may be normal, explained by examining the schematic. 73 Alan G4ZFQ |
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HI Stan, Hi Alan, thanks so much for your quick reply. Meanwhile I did some check on the schematics. Even it's embarrassing it looks like I did not check on the polarity of the DVM probes. If one is flipping the probes, the continuity seems to be able to pass D503/D504. At least after flipping the probes in the normal direction (black at ground plane) does not show any continuity. I should have listen to Hans advice and stopping further work in the night, but I even continued installing L401 (QMX High Band). Did just a tiny solder bridge to a ground plane pin when soldering loop at turn 8. I thought having solved it very quickly but could NOT find find the reason I have ground on all Pins (A-E) in Step 8 of Rev 3 instruction. I checked my old trusty Rev1 (low band) QMX, that does not have ground continuity. I did lot of desoldering (I'm not good at) to find the problem, but I should have just RTFM: Hans has changes this part of the schematics between Rev 1 und Rev 3. It looks like the ground that is not on the "Receiver" part of the schematics can be just seen in the "Transmitter" part. Here at label RX IN is a ground via L503. So indeed in Rev 3 all the points A,B,C,D,E getting ground. Some personal learning from desolder (the hard way): - Use lot of Flux - Add some fresh low temp. melting sold if you used other during solgering. ?Meanwhile I have restored L401) as it should be (hopefully). Soldered one connection at the top of the PCB, hope no problem. Thanks again and HNY. VY 73 DE Thomas - DJ1TF Am Di., 31. Dez. 2024 um 09:54?Uhr schrieb Stan Dye via <standye=[email protected]>:
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