Sunfire Cinema Grand Signature Noise and Hum

[tutor turtle 7]

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.

 

[itchitch 4,517]

Welcome to the site!

 

Be patient and one of the members will respond soon. 

[Yamacarver 806]

On 3/22/2022 at 9:22 AM, tutor turtle said:

Slight buzzing sound, all speakers, with the power off

Does it have a triac? I'd try and figure out why it's not powering off.

 

[itchitch 4,517]

IIRC these units never power off. They just mute to output when in “off mode”(dimming the meter light)

[tutor turtle 7]

On 3/23/2022 at 12:28 AM, itchitch said:

Welcome to the site!

 

Be patient and one of the members will respond soon. 

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.

[Sk1Bum 11,513]

Hello tutor turtle, and welcome to thecarversite.com. We're glad you're hear. There is a lot of information here, much technical know how, and a pretty good bunch of folks that are happy to help. I wish I had the knowledge to point you in the right direction, but I do not. Hopefully, someone will notice this thread that has solved a similar issue.

Once you get to Novice status, please consider uploading some pics of your gear in the Members Systems area. We all like pics of all kinds of audio gear.

In the meantime, kick your shoes off, turn up the music, and welcome aboard.

 

 

[tutor turtle 7]

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.

[Balok 1,677]

I wonder if the new owner has DC on the mains?

[tutor turtle 7]

DC on the AC mains? That would be an impossibility.

Or the +/- 130VDC rails internally? Yes, the internal power is to spec.

[tutor turtle 7]

On 3/22/2022 at 12:22 PM, tutor turtle said:

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.

 

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?

[Balok 1,677]

54 minutes ago, tutor turtle said:

DC on the AC mains? That would be an impossibility.

Or the +/- 130VDC rails internally? Yes, the internal power is to spec.

 

My Sunfire Ultimate Receiver is quite sensitive to any DC on the main line.  DC from appliances such as my humidifier.  Even a few millivolts causes the Sunfire transformer to buzz.