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newbie here need help diagnosing pioneer svx-821
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jgrice53




Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571


PostLink    Posted: Thu Dec 11, 2014 2:40 pm    Post subject: newbie here need help diagnosing pioneer svx-821 Reply with quote


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Hi to all, my first time here. I do a lot of electronic repairs but not a professional at all. I have a pioneer svx-821 that came in dead. customer said to have shorted the speaker outputs accidently when connecting speakers. When I plug it in and press the power/standby button, the display lights with "volume min" for approx. 5 sec. I hear a relay click and then the display changes to a blinking, " overheat" for a few seconds and then it shuts off. I removed the cover and unplugged all the connectors to the amp board, but that produced no change in response when powered on. I suspect the pcb main board to be the problem board because the speaker connections are on that board, plus disconnecting the amp board did not change the operation in any way. So, am I correct in looking at the main board?
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Nashou66




Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY


PostLink    Posted: Thu Dec 11, 2014 3:22 pm    Post subject: Reply with quote

Some times removing the amp board will not allow the power to come up with out jumping a relay on the power board so the transformer comes up. But any how i would check all output fets for shorts .

Athanasios

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jgrice53




Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571


PostLink    Posted: Thu Dec 11, 2014 3:56 pm    Post subject: Reply with quote

Thanks, I will start checking them and post my results.
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macgyver655




Joined: 22 Aug 2007
Posts: 8508



PostLink    Posted: Thu Dec 11, 2014 4:09 pm    Post subject: Reply with quote

In this case , disconnecting should of eliminated the error. So the error is most likely on the CPU board.
I would do a quick test on Q213,Q214,R264,R289,R341,R290 and R295.
If these all test ok then you need to test for DC voltage right on ic203 at pins 34 and 71.

So how are things in Marion?
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Nashou66




Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY


PostLink    Posted: Thu Dec 11, 2014 5:56 pm    Post subject: Reply with quote

Mac to the rescue !!!!!

Very Happy


Nashou

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jgrice53




Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571


PostLink    Posted: Thu Dec 11, 2014 6:58 pm    Post subject: Reply with quote

thanks mac, i will let you know what i find
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jgrice53




Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571


PostLink    Posted: Thu Dec 11, 2014 7:10 pm    Post subject: Reply with quote

mac should i be able to disconnect the cpu board to determine if it is causing the error before i get into testing the components on it?
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Jeremy112




Joined: 28 Sep 2006
Posts: 2645
Location: Fond du Lac, WI


PostLink    Posted: Thu Dec 11, 2014 10:51 pm    Post subject: Reply with quote

These Pioneers are the ones you can take the amps out and swap them with some Marantz or Denon Model AVR's... I had a VSX-821 I robbed the amp from for a Marantz, worked like a charm!

Mac will get you fixed up Thumbs Up

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macgyver655




Joined: 22 Aug 2007
Posts: 8508



PostLink    Posted: Fri Dec 12, 2014 2:46 am    Post subject: Reply with quote

jgrice53 wrote:
mac should i be able to disconnect the cpu board to determine if it is causing the error before i get into testing the components on it?


You should be able to disconnect CP404 on the CPU board to verify the problem board.
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jgrice53




Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571


PostLink    Posted: Sat Dec 13, 2014 12:17 am    Post subject: Reply with quote

Well mac, if cp404 is the 5pin connector on the top of the CPU board on the right from viewing the front of the receiver , I disconnected it and there is no change. It still comes on with overheat and shuts off. How would disconnecting cp404 verify the problem board? I have disconnected the amp board and basically ever cable one by one in an attempt to produce a change. I removed the cpu board and attempted to check the transistors and resistors that you listed, even though I could find them on the schematic I was unable to locate them all on the board. Even using a lighted desk magnifying glass they are sooooo tiny. How likely is it that the culprit be the cpu board? I can get a replacement cpu board for $35. Wouldn't one expect the amp board to have some blown output transistors when the speaker terminals were supposedly shorted by the speaker wires?
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macgyver655




Joined: 22 Aug 2007
Posts: 8508



PostLink    Posted: Sat Dec 13, 2014 4:32 pm    Post subject: Reply with quote

The actual protection circuit is on the CPU board. The parts I gave you to test where the protection circuit for the 2 temp errors. There should be zero volts coming in from the amp board on those 2 lines so if there was voltage coming on 1 of those lines to trigger an error, disconnecting that connector would remove that voltage going to the protection circuit and should then be no error. If there is still an error then something is going on, on the CPU board in the protection circuit.
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jgrice53




Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571


PostLink    Posted: Sat Dec 13, 2014 5:38 pm    Post subject: Reply with quote

I want to thank you for the information mac. I tested q213&q214 as well as a few of the other transistors on the cpu board and all tested good. I only have millivolts readings on all the 5 pins of cp404. I do have the cpu_+ 3.3v on cn704b. Even with cp404 and all the other connectors unplugged from the cpu board i still have the overheat and shutdown. So I am going to roll the dice and order another cpu board and see if that will at least get rid of the overheat error. Hopefully I will have it next week and I will post the results.
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macgyver655




Joined: 22 Aug 2007
Posts: 8508



PostLink    Posted: Sun Dec 14, 2014 5:13 pm    Post subject: Reply with quote

I can never agree with just changing a board and hope. Even with what has been done here so far does not exclude other possible boards. Maybe you will get lucky. I find luck only prevails a small percentage of the time.
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jgrice53




Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571


PostLink    Posted: Sun Dec 14, 2014 5:49 pm    Post subject: Reply with quote

You are right mac. And I do expect their to be problems on at least the amp board. While I have experience troubleshooting and repairing to component levels, I could not get a handle on this cpu board. Of course that means that I should not attempt a repair on this unit with my competence level in the first place. But I do think that I will be able to complete a repair once I am able to rule out the cpu board.
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macgyver655




Joined: 22 Aug 2007
Posts: 8508



PostLink    Posted: Sun Dec 14, 2014 7:07 pm    Post subject: Reply with quote

Well you do know I could guide you thorough the CPU board testing, right? Smile Well providing you can use a DMM, soldering iron and follow directions, lol.
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jgrice53




Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571


PostLink    Posted: Sun Dec 14, 2014 8:35 pm    Post subject: Reply with quote

That would be great mac and highly appreciated. I did not want to nit pic you with every little detail of the testing and troubleshooting because it is a lot to ask. I do have the service manual for this receiver, a DMM and of course a soldering iron. So, my first question is should I remove the back panel and all the rear panel connectors to facilitate testing?
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macgyver655




Joined: 22 Aug 2007
Posts: 8508



PostLink    Posted: Mon Dec 15, 2014 12:12 am    Post subject: Reply with quote

Are you able to take pictures and post them?
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jgrice53




Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571


PostLink    Posted: Mon Dec 15, 2014 12:34 am    Post subject: Reply with quote

yes i can post pictures
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macgyver655




Joined: 22 Aug 2007
Posts: 8508



PostLink    Posted: Mon Dec 15, 2014 2:06 am    Post subject: Reply with quote

When looking at the front of the receiver I need a picture of the right side of it. I believe there is a board on the side and it is the CPU board. Try to get a clear pic.
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jgrice53




Joined: 10 Dec 2014
Posts: 165
Location: marion, sc 29571


PostLink    Posted: Mon Dec 15, 2014 2:28 pm    Post subject: Reply with quote

okay mac. here are a few of the cpu board. if they are not clear enough for you i will take more.


pvsx821-a1.jpg
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