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PostPosted: 28 May 2011, 16:48 
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Joined: 14 Oct 2008, 17:35
Posts: 901
Location: Dartmouth, Nova Scotia
I was given a Pioneer SC-27 receiver last night, it was left behind taking up space in a shop for a few months, and for a very good reason, it has no power, only a standby voltage and a flashing Advanced MCACC light. :(

I did some reading and found this to be due to power outages or speaker shorts. I spent a few hours tearing the receiver apart and found no shorted transistors or blown up parts, the only part that was remotely suspicious was a diode on the front panel main board on the standby 5 volt rail, measured 166 ohms forward and around 5K backwards, a normal diode measures around 500-600 ohms and an infinite reverse resistance, this part is not a zener as it is in line with the 5 volt rail.

I put a 1N4002 diode in place of the tiny surface mount diode.... then a good 3 hours of reassembly, I hope never to do again. :down:

I later found a hard reset method here; http://www.polkaudio.com/forums/showthread.php?t=114191

After I got everything back together I pressed and held the "zone on/off" and "down" button on the panel and the power came on..... it said "POWER ON"..... :D

Too bad that is all I can get out of it, no output, no tuner and it won't even power off unless I unplug it. :(

Any advice on what to do next other than get replacement boards? I also don't have a remote, so that doesn't help, but I can get the MCACC light to flash again by disconnecting the main power transformer and turning the receiver on again. :?

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My Mini 12AU7 Tube Preamp, Pioneer SX-D7000, JVC XL-V221BK, JBL L80T, DCM TF700


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PostPosted: 19 Dec 2014, 20:52 
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Joined: 19 Dec 2014, 20:47
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Reponding to an old post.

I had a similar problem with a Pioneer SC-35. After a power outage, the unit would not power on, and I had a blinking MCACC light.

After several Google search iterations, I came across the above post, and the hard reset method worked. Simultaneously pressing and holding the "Zone On/Off" and the "Down" button reset the receiver, and the unite powered on.

Thank Gawd I did not try to open the ting up and "fix" it


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PostPosted: 20 Dec 2014, 22:24 
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Joined: 04 Jun 2008, 20:59
Posts: 3814
Location: Arizona, USA
Hi, It sounds a lot like a Harmon Kardon 391 I have here. I tracked it down to a bad processor chip. Basically a hopeless case, I had hoped to fix it up as it matches exactly my HK high end cassette recorder. Not to be. Good luck with yours. I would start to follow the power supply chain and see if something is not getting juice. If a schematic is available I would certainly get it as I'm sure you know it can save a lot of grief.

Good listening
Bruce

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PostPosted: 05 Sep 2016, 14:28 
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Joined: 05 Sep 2016, 13:34
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After a power failure, I discovered that the MCACC light was blinking on my Pioneer SC 27 Receiver. I was worried that one of the circuit boards had been fried, again. The current receiver is a replacement for the exact same model that failed several months ago after many years of good service. The previous receiver also exhibited an MCACC LIGHT THAT WAS BLINKING AND COULD NOT BE RESET. I took it to the local Pioneer authorized service center and was advised that one of the circuit boards had been fried by an apparent power surge and the repair would be cost prohibitive. I, accordingly, bought the replacement. I was fearing the worst. Could lightning strike twice in the exact same place? Long story short, I pressed and held the on/off speaker button and the down arrow simultaneously and, much to my surprise and delight, the power was restored and the previously deceased receiver came to life! I couldn't have been happier. Your forum saved me a ton of money and a huge amount of hassle disconnecting and transporting the receiver to the service center for repair. I just wanted to thank all involved for the existence of the forum and the invaluable information it provided me.


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