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4070 quad amp

  1. quadmatrix82

    Marantz 4070 transistor substitute

    Hi all, currently repairing a Marantz 4070 can I use a 2sa970BL transistor in place of 2sa641 for h701-704? I’ve seen other posts that recommend bc556bta but looking at specs and what I have on hand I think the 2sa970 would suffice but I’m no expert, thanks!
  2. ZCurves

    Marantz 4070 - Super Shrieking

    Greetings ! I have a 4070 Quad Amp with the SQA-2 board. It was working fine- plays for a while then out of the blue it starts Shrieking and Screeching at very high volume. There is no way to turn it down, it is just full-on Shrieking and Screeching assault. I have to power off to preserve...
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