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Thread: Removal of ICs with bent pins from DEC PCBs?

  1. #1
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    Default Removal of ICs with bent pins from DEC PCBs?

    All the DEC made boards in the LAB-8/E I am restoring have their IC pins bent presumably to keep them in place during assembly.
    The soldering looks terrible so I don't think these were wave soldered but rather soldered by hand. The LAB-8/E was made in Puerto Rico so labour cost was cheaper than fancy equipment.

    Until now I had to only remove a single 14 pin TTL IC (74H40), but it defeated my de-soldering station because of the bent pins.
    Normally I can desolder each pin and the IC just falls out, but not on these DEC boards.

    I ended up cutting every pin at the point where it exits the IC body and then using a tweezer and soldering iron removed each pin individualy. Even this was painful because of the sharp bend of the pins and the quick dissipation of heat once you touched the pin with the tweezer. It took a lot of effort (and a few four letter words) to succeed.

    What is the best approach for the removal of ICs with bent pins on these DEC boards?

    Thanks and best regards
    Tom Hunter

  2. #2

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    You care about preserving the PC board, so cutting the pins off the ICs is exactly right. Use a high powered temperature-controlled soldering iron, with the biggest tip that will fit in the space, set to around 600 degrees F (315C) to minimize the potential for lifting traces, etc. I like my Hakko FX951 for this, but anything that supplies tons of heat without exceeding the temperature limit is good.

    I would have the board held vertically (Panavise PC board vise if you have one) so that I could grip the pin with the tweezers from the front while heating the joint from the back. I would add fresh 63/37 solder before trying to remove each pin to ensure optimal heat transfer. Heat and pull gently. Wreck a pair of tweezers by heating them with the joint if you have to; smaller tweezer tips will draw less heat.
    Last edited by Uniballer; January 1st, 2021 at 05:32 AM.

  3. #3
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    I concur - this is the only viable way of doing it whilst preserving the PCB.

    With more practice you will get better!!!

    Dave

  4. #4

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    Thinking about this a bit more, if the pins are straight then you can usually just "lift" the pins out from the top of the board using the soldering iron tip and the little "hook" left over from cutting the pins right next to the IC body. I'm sure this will be more difficult with the bent pins, but maybe you will get an idea from the technique.

  5. #5
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    I cut the pins next to the IC body and from the component side either use the soldering iron tip melt the solder and lift the pin from the PCB, or use hot tweezers to heat and pull the pin through the PCB. Then use the desoldering iron to remove the solder from the plated through hole. I have replaced a LOT of DEC ICs, so I am pretty good at it and don't damage the boards.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  6. #6
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    For this sort of work, I find that the cheap Chinese stainless hollow needles are invaluable for getting any stubbord bits out of component holes.

  7. #7

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    Ha, just yesterday I removed a 16 pin part from TRS-80 motherboard to install socket for floppy re-mapper. The pins on this tandy board are all bent to inside as well. I was using the technique I described here in this post. Took me 10 to 20 seconds to remove the chip pulling it up, the pins unbent by themselves from pulling, no tracks were hurt.
    Last edited by vldmrrr; January 1st, 2021 at 07:37 PM.

  8. #8
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    Quote Originally Posted by vldmrrr View Post
    Ha, just yesterday I removed a 16 pin part from TRS-80 motherboard to install socket for floppy re-mapper. The pins on this tandy board are all bent to inside as well. I was using the technique I described here in this post. Took me 10 to 20 seconds to remove the chip pulling it up, the pins unbent by themselves from pulling, no tracks were hurt.
    I would not dare to use that technique on valuable DEC boards. Also the Z80 CPU you removed using this method may work for a short time but it would be permanently damaged and will fail anytime soon. You have absolutely no temperature control with a butane torch.

    If the chip is valuable you could use Chip Quik's low temperature bismut based solder to help remove the chip.

    Thanks but no thanks. I won't go near any PCB with a butane torch.

    Tom Hunter

  9. #9

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    Quote Originally Posted by thunter0512 View Post
    Thanks but no thanks. I won't go near any PCB with a butane torch.
    Well, me neither. The torch is used on the side to heat up the copper tool to melting point of solder on contact surface. Then the heated copper pipe is placed on top the chip, one-two-three, pull the chip with forceps -- and job is done. The site is left in pristine condition without any cleaning liquids.

  10. #10

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    Now that you have the failed (or suspected faulty) IC removed from the PCB what is the recommended 'best practice'?
    i316boz.jpg
    Do you just solder in a replacement IC or is it better to solder in an IC socket and place the replacement chip in the IC socket?

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