| Electronics > Beginners |
| NAD 218 THX amplifier Repair. |
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| SantaClaw:
Right, time to get to work. Cleaned it a bit |
| SantaClaw:
No connectivity between any pins on Q317 and Q319 other than a short blip. I made sure I had good connections D301 .636v - Right Channel: D302 .637v D303 .640v - Right Channel: D304 .637v D305 .637v - Right Channel: D306 .638v D307 .640v - Right Channel: D308 .639v D309 .631v D311 .634v D312 .537v D313 .638v D317 .658v D319 .661v D321 .594v D323 .535v D325 .669v So the diodes I could find, looks good ? The small transistors: C4793: 1 Q333 B=143 Vf = 614mV 2 Q329 B=143 Vf = 614mV 3 Q321 B=173 Vf = 605mV A1837: 1 Q331 B=160 Vf = 603mV 2 Q335 B=188 Vf = 571mV So far no fault, I suppose starting to check resistors is next ? |
| SantaClaw:
Any suggestions ? |
| Richard Crowley:
--- Quote from: SantaClaw on February 21, 2019, 01:40:37 pm ---No connectivity between any pins on Q317 and Q319 other than a short blip. I made sure I had good connections --- End quote --- Not sure what this means? What does "no connectivity" mean? Tested how? Out of circuit? With what? POS tester? with a DMM? with a curve-tracer? What does "short blip" mean? --- Quote ---So far no fault, I suppose starting to check resistors is next ? --- End quote --- I would say that "no connectivity" and "short blip" seem to indicate that Q317 and Q319 are blown. Unless we are misunderstanding your testing methods and results? What do you find when the corresponding transistors (Q316, Q318) in the other (good) channel measure by the same method? Out of circuit in all cases. |
| SantaClaw:
I put my DMM meter in diode check mode, and it briefly beeped when I measured between the legs. So I need to de-solder q317 and q319 ? |
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