Another Pionner sx 1250 repair

Discussion in 'Pioneer Audio' started by Joe Stem, Mar 9, 2017.

  1. Joe Stem

    Joe Stem Member

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    @zebulon1 per your post i rechecked pins 8,9,10,12 just to make sure i had meter set right the 1st time

    Pin 8 if measured in DC as you stated i get 10.8VDC if i checked it in AC as i did my 1st test i still get 23VAC which is correct?

    Pin9 VDC 41.1 IF measured on VAC as i did in 1st test i get 85VAC
    Pin10 VDC -41.9 if measured in AC on meter i get -0.0VAC
    Pin12 VAC i get 3.9VAC

    as for diodes can you give me some idea of the correct readings i should get... im not very familiar with diode testing... i have the correct settings on the meter i think and am getting test result im just not sure how to interpret what im seeing on the meter
     
  2. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

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    All the readings I'm asking for are in DC:
    The stabilizer board once again. AWR-106.
    (-) means you should expect a negative reading.

    Pin 1 = (-)
    Pin 2 =
    Pin 8 =
    Pin 6 =
    Pin 7 =
    Pin 9 =
    Pin 10 =
    Pin 11 =
    Pin 13 =
    Pin 14 = (-)
    Pin 15 = (-)

    Don'y worry about the diode's as yet. A good visual inspection is all that's needed for now.
    HiFi Engine has a fairly good service manual to follow.
    https://www.hifiengine.com/manual-library.shtml
    The site is free, required is to sign up. It's a safe site and won't bother you with spam.

    upload_2017-3-14_15-5-10.png
     
  3. Joe Stem

    Joe Stem Member

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    @zebulon1
    Board 106
    1 -32.2
    2. 34.5
    3 GND
    4 .54
    5. .56
    6. 39.6
    7. 10.4
    8. 10.3
    9. 9.7
    10. 20.7
    11. 41.1
    12 Gnd
    13. -41.3 maybe + dont remember if i put red to the pin or Black lol
    14 -21.2
    15 -43.2
     
  4. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

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    The stabilizer voltages don't look too bad.
    All are there and low due to the DBT drawing current.

    Time to look at the Protection board voltages.
    All the readings I'm asking for are in DC:
    Black probe to Chassis ground.

    Pin 1 =
    Pin 2 =
    Pin 3 =(-)
    Pin 5 =
    Pin 6 =
    Pin 9 =

    upload_2017-3-14_17-20-44.png
     
  5. Joe Stem

    Joe Stem Member

    Messages:
    61
    will if the big filter caps weren't bad one of them is now.. i went to get a smoke and came back and found the pioneer had the same thought one of the big filter caps was smoking and pouring electrolyte out nOW ive got a mess... the unit was on its side and now there is shit all over the connections
     
  6. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

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    You can clean the mess up with Contact cleaner.
     
  7. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

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    We (I) should of had you check the Voltage (AC and DC) on the cap terminals.
    I'll send you some serviceable caps tonight.
    Sorry we'er on hold until I can get you the caps.
     
  8. Joe Stem

    Joe Stem Member

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    Is it safe to turn power on with that filter cap popped
     
  9. Joe Stem

    Joe Stem Member

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    sorry didn't see your last message lol
     
  10. KingBubba

    KingBubba "Too Much Stuff" Subscriber

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    It looks like you are making decent progress JS. You have great people giving you a hand. Quite a few years back, I had the idea that I would do the work my 1250. I bought all the parts from MTF's and mattsd's lists, but after ruining a few smaller projects, I decided that I was safer to send my beast to mattsd for the full Monty. Even with the added costs, I am fully satisfied I spent the money. A wise old inventor friend once told me that is was better to spend the money on the things you want because after a very short time you will no longer feel the pain from the financial loss. He was absolutely right.

    I created a thread in which I tried to combine parts list and important quote regarding proper steps in repairing the 1250. In doing this, I found that keeping the parts list up to date was very difficult due to changing products on the market. That was the reason that I did not continue the thread.

    Have fun with your Monster. It is so nice to have them back again when they are done. Keep an eye open for those pimples on the bottom of the filter caps. If you have the funds, I would advise replacing them, even if they test good. Just my opinion.
     
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  11. Joe Stem

    Joe Stem Member

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    thanks for the advice... this receiver means a lot to me... it's not one i just picked up second hand, so i have had the thoughts of bite the bullet and send it off but I want to do it my self so bad because it was my dads and he was able to build amps do this stuff too... I feel its almost a rite of passage for me to get this right... He also gave me a Knight kit 35W stereo amp that he built in the 60's... it is in need of repair, and i'd like to restore it and give it to him for Christmas... but that thing is all Point to Point and i dont have schematics for it so I'm not ready to tackle that yet i don't think... Unless anyone knows anything about them.... I can start another thread if need be. I really enjoy this stuff... It's something i think i could do for a living if there was still a need for people to repair these awesome monsters and i had enough training and practice...
     
  12. Joe Stem

    Joe Stem Member

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    @zebulon1 i re installed new Filter caps (All 4)... cleaned up mess, plugged unit into DBT, and bulb is REAL bright, then immediately dims and 4 seconds later i hear the click.... if i shut unit off and turn back on light stays dim, doesnt get bright then dim down and no click... BUT if i leave unit off for 2-3 min it will act normal... almost like the big caps have to discharge some before it will work again or is it some sort of built in thing...
     
  13. KingBubba

    KingBubba "Too Much Stuff" Subscriber

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    You can almost guarantee that it will take 10 seconds to numerous minutes for the caps to discharge. This is why it is suggested to use a resistor to discharge the caps before working on a piece of equipment. This is how I ruined my Pioneer SA-9500MkII. I turned it off and immediately started probing it without using minigrabbers on my meter. I crossed two contacts with the positive meter probe. I killed the outputs on the right side and spent months getting it back up to snuff. Be careful out there.
     
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  14. tsd71

    tsd71 RIP Tom Petty Subscriber

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    Both relays should engage if there is no other issues. What wattage bulb are you using?
     
  15. Joe Stem

    Joe Stem Member

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  16. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

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    Update:
    We been using the PM system to work on this 1250's issue.
    Joe replaced the big filter cap that blew it's cookies and the replacement is only reading half of the twins voltage and getting hot.
    Both amp boards have been disconnected.
    Its narrowed down to the rectifier diodes on the stabilizer board, Pin one (1) for the S5151R diode.
    He's removing the diode to check it for serviceability.

    We should be discussing this on the forum as it seems a rare failure.
     
  17. tsd71

    tsd71 RIP Tom Petty Subscriber

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    You got that right Bob, it is a rare failure.
     
  18. Joe Stem

    Joe Stem Member

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    well im having some issues de soldering the rectifier diode, the solder is so heavy and so old my litlle solder sucker is having a hard time
     
  19. paultlaw

    paultlaw Active Member

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  20. markthefixer

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

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    desoldering the diode wire lead from the PC board or the metal strap from the pc board?

    I don't think it's possible to desolder the diode from the metal strap.
     

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