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The trouble with my fender stage 160

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  • #1

    The trouble with my fender stage 160

    hi folks,
    My fender stage 160 have no sound and it keep burn the fuses out! I tried to check the problem. I found one pair transistor TIP 142 and TIP147 broken. So I replace them with new ones. But the fuse burn again when I turn the volume louder. Yes, the transistor is broken again (Only one TIP 142 , there're 3 pairs of Tip142 and 147). I replace with new one again..... Now I use the lamp for current limiter. I found the amp will work in the low volume but the lamp will be lighter when I turn the volume up. I think it is the reason the fuses burn. But now I don't know what to deal with it. Does any thing wrong with my amp? English is not my native language and sorry for my grammar, spelling, expression etc....
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  • #2
    If ENglish is not your language, then can I assume your amp- runs on 240v mains instead of 120v? That is important.
    Education is what you're left with after you have forgotten what you have learned.

    Comment

    • #3
      Originally posted by Enzo View Post
      If ENglish is not your language, then can I assume your amp- runs on 240v mains instead of 120v? That is important.
      Hi Enzo,
      I saw you answered a lot of questions about the fender stage series!
      Yes, this amp runs on 110V. I use the fuse with 4A. At the first time two transistors were short with the Base and the emitter. But at the second time the transistor was not short just defective.

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      • #4
        OK, 4A fuse correct for 110/120v operation.

        When you install TIP142/147 transistors, make sure the insulator under them is good. make sure no contact between the aluminum heat sink bar and the transistor tabs. Check with your ohm meter.
        Education is what you're left with after you have forgotten what you have learned.

        Comment

        • #5
          Originally posted by Enzo View Post
          OK, 4A fuse correct for 110/120v operation.

          When you install TIP142/147 transistors, make sure the insulator under them is good. make sure no contact between the aluminum heat sink bar and the transistor tabs. Check with your ohm meter.
          Thanks for your reply, Enzo.

          I checked these transistors again and make sure there's no contact with the tab and the heat sink (Gorund) by multimeter. The way I determine TIP142 is put the black probe on the collector, put the red probe on the emitter. Turn the multimeter to 10k ohm. If the pointer remain in the leak area means it's fine. Testing TIP147 is just change the red probe with the black one.

          The thing I feel strange is the resistance between the emitter of TIP142/147 and ground is only 0.8 ohm. Is it fine or not?

          According the schematic of the fender stage 160, I checked TP1-7, TP29-39:
          [My Value] / [Factory Value]
          TP1 62.6VAC / 66.7VAC
          TP2 38.7VDC / 45.2VDC
          TP3 -38.7VDC/-45.2VDC
          TP4 16.17VDC/17.8VDC
          TP5 16.22VDC/17.9VDC
          TP6 16.05VDC/16.5VDC
          TP7 -15.91VDC/ -16.8VDC
          TP29 1.21V(normal) 1.215V(Drive)/ 1.22V(normal and drive)
          TP30 15.13(N) -14.5(D)/ 15.6 -15.6
          TP31 -15.9(N) -0.05(D) / -16.8 -0.05
          TP32 0.48(N) 9.55(D) / 0.51 9.66
          TP33 -10.89(N) -5.09(D) -4.8(More Drive) / -11.8(N) -5.14(D) -4.82(MD)
          TP34 -0.047(N) -0.047(D) -9.68(MD) / -0.5 -0.5 -9.63V
          TP35 -14.43(N) -14.43(D) 15.6V(MD) / -15.5 -15.5 15.7VDC
          TP36-0.04(N) -0.045(D) -16.02(MD) / -0.025 -0.025 -16.9
          TP37 -0.05VDC/ -0.05VDC
          TP38 -0.064VDC/ -0.64VDC
          TP39 -16.2mVDC -14.47VDC(Plug in)/ 0V, -15.3VDC(plug in )

          It seems all matched. I also check all 5W resistor are fine.(measure for 0.8 ohm)
          Any suggestion?

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          • #6
            I check all the diodes, capacitors , resistors , transistors near the TIP 142/147. These components are no problem.
            By the way, I use the TIP147 with TO-247 package because I couldn't buy TO-220 package one here. Does TIP142/147 must be matched to each other? (special pair?). I don't know how to tell. Or any transistor called TIP142/147 will work?

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            • #7
              TO247 is fine. I think Fender used TO218. I don't know anyone using TO220s.

              This is a grounded emitter output stage. Look at schematic, the emitters of the outputs connect to ground. The speaker is wired between ground and the power supply center tap.
              Education is what you're left with after you have forgotten what you have learned.

              Comment

              • #8
                I try to use normal AC110V power without the lamp current limiter and it works. I think the lamp current limiter will bright because the more volume , the more current will go into the power amp. The 3 pair of TIP142/147 can handle amount of the current. But I don't figure out why do the transistors be dead in the begining, I think it will be: 1) After ten years hard working and It's time to die. 2) It played at maximum volume for long time, these transistors got very hot and damage. 3) Too much volume into this amp, it can't handle because too much current. I guess.

                It seem to be fine.......I hope it will not burn another fuse one day......

                Thanks! Enzo.

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