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Two Fender Frontman 212R same issue

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  • #1

    Two Fender Frontman 212R same issue

    A guy brings me two Fender Frontman 212Rs that don't work. Both of them had the same problem, the connection at one of the cement resistors, R144. Almost exact, one had broken free from the top hole, and one had a broken pad at the bottom hole. What are the chances? Or is this a thing with this model? Good thing is, I got the second one apart and back together a lot faster than the first one, once I knew the PT has to be removed before the board can come out.

    Oh, and the first one also has two blown speakers, which of course I only realized after fixing the amp, but that's another story.
    It's weird, because it WAS working fine.....
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  • #2
    R144 is the dropper resistor to drop +42V down to the +16V zener diode. The schematic says it's a 5W resistor. Is it one of the sand box style? I've noticed that the ones I get these days have really weak leads.
    WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
    REMEMBER: Everybody knows that smokin' ain't allowed in school !

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    • #3
      Yes, it is, but I don't think was the resistor's fault in either case. One backed out of the solder, and the other had a pad come away from it's trace.
      It's weird, because it WAS working fine.....

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      • #4
        It isn't "this model", it is any model constructed in similar manner. Larger parts like that resistor are often glued down in amps so they can't shake around as much from vibration. That causes solder to break, leads to snap, and traces to pull up.

        I myself call those Fenders "wedge chassis" models. The chassis is bend sheet metal with a narrow front face and a wide rear face. So the side views of the chassis makes it wedge shaped. To me. I find that more often than I would like, the main filter caps sticking up from the board can crack their solder. And large cement resistors can break loose.

        Whenever I am in an amp, if it has large cement resistors I wiggle or poke them, and I look close at the solder if the board is out. And other large parts like filter caps get inspection too.
        Education is what you're left with after you have forgotten what you have learned.

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        • #5
          Especially the one with the blown speakers. Run the amps a while. I've had a couple with bad diff amps. When they randomly change in hfe it sounds like a shotgun going off with max rail on the speakers. I actually like these amps. A great versatile and attractive compromise for an inexpensive amp. Still haven't figured out the random rice Crispies they tend to get.

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          • #6
            I don't know about running the amps for a while to see if more problems arise. I fixed the problems they came in with, and they are working and sounding good. If something else goes awry later, I'd rather not have it happen to me. These are inexpensive amps, and it seems prone to failure. If a mechanic replaces your brake pads because they are shot, he doesn't drive your car to see if the master cylinder also may act up. He gives it back after the repair, if the master cylinder goes bad next week, that's another repair.
            It's weird, because it WAS working fine.....

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            • #7
              it is one thing if it blows up a month from now, it is yet another thing if it blows up the first time the guy uses it. He will blame you.

              I myself don't think these are prone to failure, they are made with the same materials on the same processes as all the other cheap Fender amps. But this model is just SO popular that there are a zillion of them, so we hear about a lot of them failing. The same percentage of some lesser model fails but it is only a few in total number.

              It is also a complex amp, so when they do blow up, it is harder for the less experienced to get them running.
              Education is what you're left with after you have forgotten what you have learned.

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              • #8
                Originally posted by Enzo View Post
                it is one thing if it blows up a month from now, it is yet another thing if it blows up the first time the guy uses it. He will blame you.

                I myself don't think these are prone to failure, they are made with the same materials on the same processes as all the other cheap Fender amps. But this model is just SO popular that there are a zillion of them, so we hear about a lot of them failing. The same percentage of some lesser model fails but it is only a few in total number.

                It is also a complex amp, so when they do blow up, it is harder for the less experienced to get them running.
                Every shop I ever worked in had a "cook bench", sometimes just a cart off to the side, sometimes several, sometimes a separate room for it. Nothing destroys your bottom line and reputation like call backs. I always ran most units half a day after a repair. I learned very early on there is a difference between fixing a unit and making it work. Especially when something is aging, abused, or under continuous use.

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                • #9
                  Heat running is good but issues that occur due to mechanical shock/vibration are hard to simulate on a bench.

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                  • #10
                    Rubber mallet or your fist, whack the end of the chassis and along its edges. The amp should NOT react, if it does, something is loose.
                    Education is what you're left with after you have forgotten what you have learned.

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