1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Post Your Repair Tips And Links!

Discussion in 'Repairing Electronics' started by ElectroMaster, Feb 10, 2011.

  1. throbscottle

    throbscottle Well-Known Member

    Joined:
    Feb 1, 2012
    Messages:
    1,802
    Likes:
    113
    Location:
    Nuneaton, Warwickshire, UK
    Can't say I've noticed a big difference in that respect, Jim, but it's a long long time since I've done any really "heavy" de-soldering (oh the heady days of my youth, raiding the TV rental repair place skip for junk boards to strip for parts. *sigh*). OTOH, I haven't had a clogged nozzle for a very long time either. I hadn't made the connection, but maybe the spray is helping!
     
  2. gmphadte

    gmphadte Member

    Joined:
    Jun 23, 2003
    Messages:
    30
    Likes:
    0
    If you have a solid state discrete amp with dual supply and you get high dc offset at the output, check voltage across the LTP bases. It should be near zero if your power amp is good.

    gmphadte
     
  3. fezder

    fezder Well-Known Member

    Joined:
    Dec 11, 2011
    Messages:
    1,665
    Likes:
    100
    Location:
    Mikkeli, Finland
    what is LTP?
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. gmphadte

    gmphadte Member

    Joined:
    Jun 23, 2003
    Messages:
    30
    Likes:
    0

    Long Tailed Pair
    The two transistors at the input of a power amp where the input signal and the feedback signal from the output(mostly) of the amp is fed.

    gmphadte
     
    • Thanks Thanks x 1
  6. fezder

    fezder Well-Known Member

    Joined:
    Dec 11, 2011
    Messages:
    1,665
    Likes:
    100
    Location:
    Mikkeli, Finland
    ok, thanks mate!
     
  7. granddad

    granddad Active Member

    Joined:
    Jan 18, 2015
    Messages:
    758
    Likes:
    76
    Location:
    Worcestershire UK
    Just sharing my recent grapple with an Asus EN210 SILENT/DI/1GD3/V2(LP) , Graphics adapter , But could apply to any card with a large heatsink arrangement.... Having moved this card to a different PC (due to a PNY card fail), the whole machine became slow ... really slow after trying several asus (Nvida) drivers i gave up and reluctantly placed it in the suspect box ! and ran with on-board graphics.. not 1920 x 1080 i wanted, The chap next door gave me a similar card but one with a fan , nice chap but his card sounded like a tractor ! brain-wave to swap the fan heatsink / no fan heatsink ....bad to not so bad , thought I would have to force the big lump of fan less aluminium off the chip.... not so it just came away ! and this turned out to be my slow PC problem , I think the graphics chip was cycling through overheating / shutdown ? After i replaced the heat pad I was up and away no problems .. gave the chap his tractor card back and told him he was Mr Fix-it !
     
    Last edited: Sep 27, 2015
    • Like Like x 2
  8. cowboybob

    cowboybob Well-Known Member Most Helpful Member

    Joined:
    Oct 22, 2011
    Messages:
    3,037
    Likes:
    478
    Location:
    James Island, SC
    Good job, granddad!

    One of those unexpected fixes that turn out so satisfying :woot:...
     
    • Thanks Thanks x 1
  9. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

    Joined:
    Oct 30, 2010
    Messages:
    9,934
    Likes:
    1,099
    The measurement I pay attention to is the difference between the output transistor bases. That basically should be Vbe*2. 0 is bad and your amp may suffer from cross-over distortion. In my amp (the leach amp), https://www.google.com/search?q=lea...iLi7wAbwM:&usg=__vFDJUeIda-GDjdQNerwF1R88SJI=

    The output stage is wierd, but between the C of Q12 and C of Q13 should be about 3.6 V. (3*0.6)*2. Q18 and Q19 don't count.
     
  10. Quantumleap

    Quantumleap New Member

    Joined:
    Mar 13, 2016
    Messages:
    2
    Likes:
    3
    Location:
    USA Maryland
    APC SUA1500 Ups problem.
    This ups was in the junk pile for a high pitch squeal whenever the unit was plugged in. Found a apparent short at one of the caps near the micro-controller. After de-solder of the suspect cap, the short appeared in the pc board where the component was removed. Traced this back to the micro-controller. After removing the micro-controller the short was gone. The micro-controller is a P87C51FB-4A. I was able to read the program code off the damaged micro-controller and burn it to a new P87C51FB-4A. Installed the new micro-controller and re-soldered the cap. Unit now restored to full working order.
     
    • Like Like x 3
    • Informative Informative x 1
  11. cowboybob

    cowboybob Well-Known Member Most Helpful Member

    Joined:
    Oct 22, 2011
    Messages:
    3,037
    Likes:
    478
    Location:
    James Island, SC
    Welcome to ETO, Quantumleap!

    Ballsy and remarkable fix :cool:! Just curious, what do you do for a living (I ask because your fix demonstrates a pretty high level of competence in a number of technical arenas)?

    Especially just to repair a trashed UPS :woot:.
     
  12. fezder

    fezder Well-Known Member

    Joined:
    Dec 11, 2011
    Messages:
    1,665
    Likes:
    100
    Location:
    Mikkeli, Finland
    Indeed, United parcel service can be pain in the butt sometimes :)....
     
  13. Quantumleap

    Quantumleap New Member

    Joined:
    Mar 13, 2016
    Messages:
    2
    Likes:
    3
    Location:
    USA Maryland
    Thanks for the reply,
    I work as a Networking /Electronics Tech. building custom high performance network raid servers for the High End Computer Network (HECN) at Nasa. We use a lot of APC gear in our server racks, but this unit was from a home computer system in my neighbor hood. I put this out here in hopes to help someone else, because APC won't give you the time of day when it comes to repair or trying to buy parts. So I have been repairing myself for some time now.
    BTW most problems with older APC ups units are battery related. Can't tell you how many I have brought back to life just by getting good batteries with the right charge in them.
     
  14. throbscottle

    throbscottle Well-Known Member

    Joined:
    Feb 1, 2012
    Messages:
    1,802
    Likes:
    113
    Location:
    Nuneaton, Warwickshire, UK
    Those are big hefty beasts - I installed a load of similar ones a couple of years ago (Ah found it, Smart UPS 750). The ones I put in weighed 13Kg apiece. Worth the effort of repairing - well done.
     

Share This Page