Pioneer A400 power on relay problem - diyAudio
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Old 4th February 2011, 02:07 AM   #1
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Default Pioneer A400 power on relay problem

Hi,

A few weeks ago my much loved A400 started misbehaving. Occasional loud noises were happening after powering up, then the power up relay click started taking longer than usual to kick in. Then it wouldn't kick in at all. I opened it up and removed the relay (Omron G5R-2282C-PA) for inspection - looked fine. After giving it a squirt of electrical contact cleaner for good measure I re-soldered it back onto the board and power it up. Much to my dismay R308 started to smoke !. I replaced it with a new 100R .25W and the same thing happened, in fact the resistor burst into flames!.

I think this is part of the DC detection or Overload detection circuit. Hoping there's an electronics guru out there that knows a bit about the A400 and can help me trouble shoot. I have schematics if anyone would care to take a look. Thanks.
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Old 4th February 2011, 09:00 PM   #2
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I used to work for pioneer and may have a diagram for the a400 in the loft - will take a look. They used the same protection circuit in most of their amps so any design from the 90s will do .
Will try and look over the weekend
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Old 4th February 2011, 11:13 PM   #3
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Thanks raymondo, would be much appreciated. The A400 has been my main amp since I bought it back in the early 90s. Would hate to see it die because of a shorted transistor or something.
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Old 5th February 2011, 01:57 AM   #4
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Quote:
Originally Posted by raymondo View Post
I used to work for pioneer and may have a diagram for the a400 in the loft - will take a look. They used the same protection circuit in most of their amps so any design from the 90s will do .
Will try and look over the weekend
Sorry, but I have a similar problem with a Pioneer VSX-9500S A/V receiver.
Pioneer VSX-9500S A/V Receiver under maintenance, need support...
There are some burnt tracks, along with a faulty output.
I need the plans for the PCBs, alongside with schematics, in order to rebuild the tracks and change some dead electrolyctics (maybe 1uF/50V, x3).
Could you help me too, Raymondo?
Thank you very much!
Regards,
Max.
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Andres
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Old 5th February 2011, 03:15 AM   #5
jkeny is offline jkeny  Ireland
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You'll find the schematic here HiFi Engine | Download Free User/ Service Manuals, Amplifier, Receiver, CD, Tape, Tuner, Video
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Old 5th February 2011, 03:57 AM   #6
jkeny is offline jkeny  Ireland
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Pioneer A400 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
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Old 5th February 2011, 09:25 AM   #7
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Quote:
Originally Posted by jkeny View Post
Very nice link, indeed. Thank you very much!
But it seems mine is not there. I found only VSX-5500 schematics.
I will take a look to see if 5500 resembles 9500 somehow, though.
Regards,
Max.
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Andres
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Old 8th February 2011, 12:13 AM   #8
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I have the schematic now but not the answer as to what's gone wrong. The outputs, measured at L402 and L401, are way high: -40 V and -20 V respectively. Also Q237 and Q238 (voltage regulators?) have +41 V and -41 V (resp.) on all three legs. Can anyone suggest something that might be causing these strange readings ?
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