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Pioneer SC-1227 A/V Receiver issue ... need some help ...

Discussion in 'Audio' started by Journey11, Jul 4, 2021.

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  1. pedroafonso

    pedroafonso

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    Sep 7, 2021
    20210822_130509_2-min.jpg Here is the picture with the pins circled. That's the right side of the radio
     
  2. pedroafonso

    pedroafonso

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    Sep 7, 2021
    The last pin to the right is the fan err line and in my radio shows 4.5 volts and the fan spins around one or two seconds after the radio is switch on!!
     
  3. Journey11

    Journey11

    82
    1
    May 23, 2018
    Yeah ... I will be getting back to that unit again tonight. I set it aside for a couple months now ... I know where those ERR signal test points are as I went checking them last time I was working on it and found all was good there.
    I will let you know soon what I find. What I did find was any signal or voltage for the fan speed ctrl pin. I tested the fan on the bench and it spins up but would have to setup a PWM control to see if the speed ctrl on the fan itself still works.
     
  4. Journey11

    Journey11

    82
    1
    May 23, 2018
    Awesome ... thanks !
     
  5. pedroafonso

    pedroafonso

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    Sep 7, 2021
    Ok. Do you remember where to check for that fan.crtl.pin.is so I can measure it in my radio and report it back to you
     
  6. pedroafonso

    pedroafonso

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    Sep 7, 2021
    I know that there is a line that detect fan locked and triggers a fault signal so if yours is not running for a reason then radio shuts down
     
  7. Journey11

    Journey11

    82
    1
    May 23, 2018
    Hi Pedro,
    It worked ! Disconnected +15v allows the unit to stay on ... problem is that power feed runs the FET drivers. So at least I know that is where the problem is ... either a bad FET new out of the tape reel OR one of the driver IC's is bad causing one or two FETS to go into overload. Sure the unit will stay on BUT you will not get any sound output. Also with unit staying on ... the fan is NOT running at all. So a couple of issues now.
     
  8. Journey11

    Journey11

    82
    1
    May 23, 2018
    I'll get back to you when I find the fan lock detect signal again but it is not running so we have a problem with the fan. However the unit is not reporting a fan error now that it will stay on.
     
  9. pedroafonso

    pedroafonso

    15
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    Sep 7, 2021
    Hi journey
    Well good discovery mean good news
    That 15 volts line intriguing me. Looks like the -B line is running on top of it. The interesting thing is this 15v line is only used to feed the FETs drivers ic thought a dedicated low noise 12 volts regulators ic on each audio channel!
    So from where you discover looks like is feeding more circuits than just the drivers.
    They service manual is not that well, is missing some info. Al least on my radio SC-82
    I'm curious now if I can lock my radio fan to see what happens. Hahahah
     
  10. pedroafonso

    pedroafonso

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    Sep 7, 2021
    Did you check the radio error logs??
     
  11. Journey11

    Journey11

    82
    1
    May 23, 2018
    No not yet ... now that I got the unit to stay on, I can get into the service mode and check error log. Still looking for a test point for the fan lock. My unit is a little different than yours ... the pic with the test points you showed ... mine are scattered all over that V-reg brd.
     
  12. pedroafonso

    pedroafonso

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    Sep 7, 2021
    ok, Did you check DC on outputs?? I have 1.8 volts when the radio comes on without the 15+ volts line. I think thats my problem but the service manual states that the dc detect will come low when the dc voltage on outputs is higher than 7 Volts dc. so im a little confused on how much DC would be normal on a speakers output
     
  13. Journey11

    Journey11

    82
    1
    May 23, 2018
    Hi again,
    What is the log reporting on your unit ? DCERR or OLERR ?
    My manual says the same thing ... speaker output DC should be less than 7vdc.
    Update on my progress ... I removed all the new FET's and checked for faults ... found none so put them all back and still same issue OLERR. So I'm thinking now a bad driver IC ? I also checked all the original FET's for faults and 11 out of 14 had leakage between gate and source pins. They also had visible signs of over heating on the underside ... drain casing discoloration.
    I was thinking if a guy could remove the driver IC's one by one to find a bad driver but I'm thinking with those drivers missing the FET gates would be floating ... not sure if that's gonna work or not.
    Only other option would be to just replace all driver IC's ... problem is no one has stock in N.Amer. ... I think ALiExpress had some sellers with stock.
     
  14. pedroafonso

    pedroafonso

    15
    0
    Sep 7, 2021
    Hi Journey.
    My radio report dc error on the log.
    OLERR is over load detect circuit. Also i try to manually lock the fan and the radio will shut down after 2 seconds.
    Did you check the 5 volts regulators on the amplifier board? there is two of them for +5 volts
    Can you check the dc voltage on the speakers terminals in your radio, mine has +1.8 volts in all of them.!!
    Im suspecting also those drivers IC. I think Newark electronics have them in stock for like 3$ a piece
    What bugs me is that 15 volts line, if i check taking the regulator ground as reference then the voltage is ok, if i use chassis ground then show 50 volts on the pin 12 (VCC) on the driver ic .IRS2092SPBF Maybe a floating voltage.
     
  15. pedroafonso

    pedroafonso

    15
    0
    Sep 7, 2021
    Newark electronics shows exact replacement this, and cost like 1.2$ at arrow electronics
    IRS2092STRPBF
     
  16. Journey11

    Journey11

    82
    1
    May 23, 2018
    OK so your problem is DCERR ... If 1.8V then should be good ... well under 7v. When measuring the 15v supply you have to use that GND and not chassis ... they are separate. Just probe across the two pins on that connector. One labelled -B+15 the other -B and it checks ok at 15 ... but according to manual it comes down to 12v at the amp brd apparently ... but if I remember I get 15 right at the amp connector so then it goes thru some stuff before it hits the regulator and becomes VSS+12v.
    Haven't check my 5v regs on amp brd just yet ... I suspect they are fine.
    I'm wondering if the DCERR can be caused by another DC voltage elsewhere ?
     
  17. Journey11

    Journey11

    82
    1
    May 23, 2018
    I just seen those 5v regs on the schematic and one is +5, one is -5 and they both feed the driver IC's which I didn't see before. Gotta check them for sure now.
    Seems at Newark website no has any stock available. AliExpress has them but are way more expensive oddly enough.

    Hey have you ever worked on Plasma TV's ? I got one that had picture issues and after removing and checking a few IGBT's it has no picture now ... the IGBT's tested ok (I think anyway) ... they were on the Zsus brd which I think is responsible for the vertical scanning ...
     
    Last edited: Sep 16, 2021
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