Spec 4 mistake

Discussion in 'Pioneer Audio' started by bendoggie, Jan 1, 2018.

  1. bendoggie

    bendoggie AK Subscriber Subscriber

    Messages:
    109
    Location:
    Plantation, Fl.
    Just did a terrible thing. My Spec 4 had not been adjusted for a long time and it seemed to me that the right channel was slightly lower than the left. I adjusted the left Ok and when I did the right channel i touched the adjacent pin and it sparked. I checked the outputs and sure enough one of the 2sb554 transistors was blown. I replaced all the outputs with on semis from digikey as recommended here by the folks that know a great deal more than me. Once I turned it on the 50mv i was trying to adjust just ran away. Now I am an electrician by trade and I know enough electronics to make me dangerous. It seems to me that the device regulating this current is also blown. Visual inspection shows no burnt components. My next step is to replace all the transistors on that power board. Any suggestions will be greatly apreciated.
     
  2. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time

    Messages:
    20,659
    Location:
    Bensenville,Illinois
    When replacing transistors also check the resistors, EACH with one leg lifted (VERY important!!). You may have popped some - and be SURE to check the high power ones (0.5? ohms) connected to the output transistors.

    A LOT of new arrivals have missed out on my YEARS of hammering in one DIRECTIVE - INSULATE ALL BUT THE TINIEST PORTION OF THE TIP OF YOUR TEST PROBES.
    Also ANY screwdriver you wave at or near a board should ALSO BE INSULATED.

    AND
    WHEN TAKING MEASUREMENTS use clip leads that are affixed WITH THE POWER OFF!!!!!!!!!!

    Everyone's in a HURRY, or too CHEAP to get a pack of clip leads, and they INVENTIVELY end up spending MORE time and money.

    Electronics is NOT for the impatient, PATIENCE is a necessity.

    Juice is UNFORGIVING.


    edit - post your PROSPECTIVE parts list, so we can spot problems before the trigger on the order is pulled.
     
    Last edited: Jan 1, 2018
  3. bendoggie

    bendoggie AK Subscriber Subscriber

    Messages:
    109
    Location:
    Plantation, Fl.
    Impatience is definitely what got me. I have the correct leads and I had shut the unit off. It still sparked it must have been a cap discharging (maybe I am not an expert by any means ). This is the list I came up with, thanks.




    KSA1381ESTU
    KSC3503DSTU
    KSC2073TU
    KSA940TU
    KSA1013YBU
    KSA1381ES
    KSC2383YBU
    KSD1616AGBU times 2
    KSC2383YTA
    KSC1845FTA times 2
    KSC945CYTA times 2
     
  4. KingBubba

    KingBubba "Too Much Stuff" Subscriber

    Messages:
    8,862
    Location:
    Brooksville, Fl.
    The same happened to me with my SA-9500II. It was unplugged but had not be off long enough for the filter caps to discharge. I too was using minigrabbers. I ended up recapping and redoing the whole thing. It was a true learning experience.
     
  5. Jon1982

    Jon1982 Member

    Messages:
    51
    I've destroyed a couple of capacitor testers by assuming a cap was discharged when it wasn't. Doesn't even take a very large cap to have enough stored clout to do damage.These days I put the dmm across it first if I'm in doubt. It seems also that in crappily designed or faulty circuits where there is no discharge path, that capacitors will hold their charge for a very long time. And of course with high voltage caps it is entirely possible to do ones self a mischief if not careful.

    My personal favourite F**k up seems to be putting the DMM into current measurement mode and then forgetting... D'oh..
     
  6. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

    Messages:
    4,152
    Location:
    Las Vegas Nevada
    With the original problem. More than likely you were going to be messing with it, one way or the other ;)

    Matt's Spec 4 resto Thread. With a recap and component list.
     
  7. slimecity

    slimecity Super Member

    Messages:
    2,055
    Location:
    New Zealand
    Hi OP, I assume in you perusals of this site you will have come across the recommendation to build and use a DBT?

    Mite be a good idea as you work thru the diagnosis process on this unit......
     
  8. bendoggie

    bendoggie AK Subscriber Subscriber

    Messages:
    109
    Location:
    Plantation, Fl.
    Yes I built a DBT some time ago when I was experimenting with old tube amps. going to start checking the resistors today
     
  9. bendoggie

    bendoggie AK Subscriber Subscriber

    Messages:
    109
    Location:
    Plantation, Fl.
    ITS ALIVE !!! The Spec is back in action thanks to that great Spec rebuild thread by Matt and the responses from other helpful members. My subscribtion to AK is the best investment ever. I replaced Q4, Q10, Q11 on the Right power amplifier assembly and that did the trick I am now going to proceed and rebuild both sides completely. Since Q4 is one of the outputs I replaced all 8. many thanks
     
    slow_jazz likes this.
  10. slow_jazz

    slow_jazz Lunatic Member

    Messages:
    13,405
    Location:
    SE Michigan, Downriver....
    Glad it's working....
     
  11. Awesomeaudio

    Awesomeaudio AK Subscriber Subscriber

    Messages:
    969
    Location:
    Sydney, Australia
    Get yourself some ceramic screwdrivers to adjust your pots. Plenty on ebay and plenty safe..
    If not then insulate as Mark has mentioned.
     
  12. bendoggie

    bendoggie AK Subscriber Subscriber

    Messages:
    109
    Location:
    Plantation, Fl.
    I don't know if this should be on a new thread or not, but I am trying to do a meter board adjustment and it does not make sense to me. On page 15 of the service manual it says to increase the input voltage to 34.64 volts then adjust the pot until the output reads 0 ?? And also what position should the level control on the front panel be at when you are doing this ? I connected a frequecy gen as indicated and a voltmeter as indicated. is this a typo should it be mV ?
     
  13. bendoggie

    bendoggie AK Subscriber Subscriber

    Messages:
    109
    Location:
    Plantation, Fl.
    Ok, my two brain cells woke up and I got it
     
    satellite65 likes this.

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