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tutor turtle

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1/4W Resistor

1/4W Resistor (3/21)

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  1. Update: The +12volt supply had bad capacitors (discolored dark, high ESR measurement) The 8 ground screw connections tying the power supply to the chassis had a little oxidation going on. Now the loudest sound at idle is the mechanical hum of the power transformer. This unit does not have the toroidal transformer. The customer complains of a popping sound through the speakers when he plugs it in. It does do that. Not horrible, but noticeable. Is that normal?
  2. DC on the AC mains? That would be an impossibility. Or the +/- 130VDC rails internally? Yes, the internal power is to spec.
  3. I've been on and off the site for a few years now, as Caver equipment come through my shop. Your site has been a wealth of information and advice in getting broken Cavers back in action and back to their grateful owners. While I'm an old school guy who loves tube-based amplifies and those speakers that mate best with them Altec-Lansing Voice of the Theater, Klipsch Heritage Series.... I am not a technology Luddite, I digitized my record and cd collection to a Synology media server, using Blue Sound Node as the host and streaming device. Blue Sound is a very affordable steaming device that has MQA decoding built in. Blue Sound has about two dozen radio stations (i.e. Tidal). Radio Paradise, for example, offers MQA steaming free of charge. I believe you can add stations as you find them.
  4. Thanks for the welcome. I have visited a few years back when I inherited a 500-T with matching pre-amp and tuner, then again when I first got the Sunfire in for service. Folks here have always been kind and helpful.
  5. 50 years experience as a technician, last 35 years at MIT, now retired. I ran a vintage hifi restoration business on the side for most of those years, also retired from. I still like to dabble in tube electronics, but I mostly focus on enjoying life without a time-clock.

  6. I received this Sunfire Cinema Grand Signature (type II) in for repair of a noise and hum issue. I replaced all of the capacitors and diodes in the power supply circuit, including those on the individual amplifier cards where they were mounted too close to power resistors and had discolored. This fixed the issues. The customer never came back to pick up the unit. I held on to it for over two years, then put it on consignment. It sat in consignment for another two years before a customer bought it. Within a month, the noise and hum problem is back. Noise: Slight buzzing sound, all speakers, with the power off; AC power plugged in, on "Auto", Slight Hum all channels when running. All output transistors check good with a DVM, all fuses are good, no burned parts or traces. I have since retired from the repair business, but I would love to not lose all the time, effort and money I have invested in this unit. Has anyone had a similar noise issue with their Sunfire Cinema Grand Signature? Please help.
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