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5F11 Mulligan

Discussion in 'Shock Brother's DIY Amps' started by JuneauMike, Nov 27, 2017.

  1. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska
    Spent some of the Thanksgiving holiday tearing down a 5F11 kit that I built almost 2 years ago. It had some nagging problems that made me want to take another run at this thing now that I'm slightly smarter than I was back then. I've been collecting parts for it while I was buying for a scratch build Champ.

    I was able to do most all the desoldering in one sitting. While doing it I found all kinds of goobered solder joints and other problems, including a ground wire that was mechanically secured to the ground but not soldered (hmm, I'll bet that was where my intermittent 120hz was coming from).

    But I also found this: It looks like at one time there was an "event" at V2 somewhere between the 5th and 8th pins. Anyone recognize what's going on here?
    burn.gif burn2.gif

    That's a good pic of it. The substance was brown, and it behaved like welding slag for those who have ever stick welded. It was stuck on, but scraped off with some pressure.

    Also, for the benefit of others who don't know what they are doing either, I McGuyver'd a really convenient way to desolder the sockets. There was globs of solder on the 12ax7 sockets and I was worried about those globs liquefying and rolling down into the pin sockets. So I just desoldered them upside down. Anyway, it worked for me.

    socket.gif

    Maybe a half turn of the wood screw gave it enough bite to secure it so I could put a soldering iron against the pins.

    socketvise.gif

    Anyway, I'll be posting periodically here as I make progress. Wish me luck.
     
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  2. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska

  3. dan40

    dan40 Tele-Holic

    659
    Aug 19, 2015
    Richmond Va
    The residue looks a lot like normal brown flux residue leftover from the soldering process. Did you happen to add extra flux to that area when you originally soldered it? I usually see that residue around the turrets in my builds because I like to add a touch of extra flux to the turrets before soldering them. The residue turns brown and crystallizes after the joint cools and will easily flake away with a small screwdriver or dental pick.
     

  4. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska
    Ah, got it. I don't recall adding extra flux there, but its possible. Glad its not evidence of arcing, which is what I first suspected.
     

  5. Wyatt

    Wyatt Tele-Holic

    842
    Nov 3, 2004
    In an amp, evidence of arcing is usually black carbon.
     

  6. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska
    That makes sense, but welding slag and spatter can be caked in a brown or rust coloured dust. That's why I wondered. Glad it's not.
     

  7. corliss1

    corliss1 Tele-Afflicted Gold Supporter

    Sep 13, 2008
    Lansing, MI
    Lots of people stick an old tube in the preamp sockets to avoid the solder situation you're talking about :D
     

  8. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska
    Yep. I don't have one of those. Also, I don't understand the benefit of using an old tube when you can just use gravity. But whatever works.
     
    Last edited: Nov 28, 2017

  9. jhundt

    jhundt Poster Extraordinaire

    Age:
    63
    Mar 23, 2003
    Netherlands
    my favorite way of desoldering is to use my big old Weller soldering pistol, and blow the solder off with an air compressor. Of course it is probably absurdly dangerous, and I should warn anyone who is fool enough to try it to wear safety goggles, asbestos gloves and a fireproof Nascar racing suit.

    But it works, and it's quick!
     
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  10. printer2

    printer2 Poster Extraordinaire

    May 24, 2010
    Canada
    I desoldered boards by heating up the foil side with a heat gun and smacked board foil side doen on the table. The solder goes flying. Forget the asbestos, rawhide work gloves are fine.
     

  11. corliss1

    corliss1 Tele-Afflicted Gold Supporter

    Sep 13, 2008
    Lansing, MI
    Once you go to a good desoldering station like a Pace unit, there is no going back. Your life will forever be changed. Not even joking.
     

  12. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska
    What exactly is a desoldering station? I was curious about them (not going to buy one since I don't desolder very often, this project aside).

    I sorta use a combination of soldering sucker and desoldering wick. Both work really well.
     

  13. corliss1

    corliss1 Tele-Afflicted Gold Supporter

    Sep 13, 2008
    Lansing, MI
    Pace and Hakko both make 'em. It's a soldering iron with a hollow hole in the center. You heat up your joint, press a button to activate the vacuum, and the solder is sucked up into a container that is easy to clean out inside the handle. It's night and day difference from a suction bulb or spring unit, and it's amazing on circuit boards where you need to get in and out quickly.

    They aren't a cheap tool, but if you're doing a lot of work, especially on boards, it's the only way to go. I will never not have one now.
     

  14. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska
    Crap, now I have to have one of those ....
     
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  15. jhundt

    jhundt Poster Extraordinaire

    Age:
    63
    Mar 23, 2003
    Netherlands
    air compressor is cheaper!
     

  16. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska
    LOL. Dude, I fear I'm going to read about you in the papers someday. "Man Uses Soldering Iron and Air to Blind Himself and Everyone he Knows"

    kidding ....
     

  17. jhundt

    jhundt Poster Extraordinaire

    Age:
    63
    Mar 23, 2003
    Netherlands
    no, since I moved to Holland I no longer have my air compressor. I sure do miss it when I strip an old scavenged chassis!
     
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  18. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska
    Making progress. I built the board some time ago and then sorta put it on pause until the holidays when I could spend some time with it. Due to the shear number of wires coming off this board, I decided to tag them to make tracing leads a little less daunting.

    boardfront.gif

    So basically, signal wire is yellow, trem circuit wire is white and power is red, although I used some small 20 AWG from Hoffman on the backside that happened to be red because it was handy. Hoffman wire was nice because would fit comfortably inside the turret shafts with room for more wire at the two lugs that needed to accommodate that sort of thing. One is at the bias circuit and the other is at the grid leak carrying B+.

    boardback.gif

    Holy crap, look at this mess? I quit.

    wiring.gif

    Kidding.

    Wired up the tube sockets and the PT connections to the board last night. Doing this, and moving the heater wires around to get into the back socket pins I noticed one of the stranded heater wires had broke a number of strands (I'd say about half of them). This has happened twice while I was dealing with stranded wire. Not crazy about that stuff, but its what I've got.
     

  19. corliss1

    corliss1 Tele-Afflicted Gold Supporter

    Sep 13, 2008
    Lansing, MI
    It's more likely that your wire cutters cut through some of the strands when you stripped the insulation than having them seemingly break off, at least that would be my guess.
     

  20. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska
    I think its a bit of both. My handyman grade wire strippers aren't the best and they have cut and nicked wires in the past. But I also pushed and moved those heater wires around quite a bit while trying to make some space to solder the back pins on the sockets. I was pretty rough on em, I'm sure that didn't help matters. But I guess its good to find out about it at this stage rather than fire it up and have to trace it down later.
     

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