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triode wrote:
Having suffered for years with tiring audio on my R71, decided to fix it. These are one of the best radios ever made, worth hanging on to. Hello Triode: With your permission, I would like to post your solution and schematic from Mods.DK on the R71 yahoo group. OK? Thanks, Dave The problem is the switching diode D75. The Emitter follower Q26 is enabled for AM reception, the 3 volts or so being used to forward bias D75, thereby passing the audio to IC6a. The current through the diode being only a few hundred microamps is insufficient to turn it on fully, causing the forward dynamic `resistance to be modulated with the audio, causing distortion. The fix is simple. Replace R202, (100k) to 15k, and replace R128 (1K) with a jumper. This increases the current to a more satisfactory.3 mA or so. The results are great. |
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