Troubleshooting Vox AC4TV8 help.

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by ai3gtmc, Mar 30, 2015.

  1. ai3gtmc

    ai3gtmc Member

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    Oct 10, 2013
    Hey guys, I've got a little dilemma here, my Vox AC4TV8 suddenly stopped working. I was just playing at practice when suddenly it went silent. No sound, LED still ON, just a little faint hum.

    I turned it off for 30 minutes and turned it on again, there was a LITTLE sound at first then 3-5 seconds later it went out again like turning down the volume but really fast. tried it again a couple of hours later, no more sound not even a little except for that really FAINT hum and the led indicator still ON.

    I changed the tube, same problem. The fuse doesn't seem to be blown, if they're blown the led indicator wouldn't go ON right?(if I'm getting this right)

    I'm in Japan and the closest Amp tech is like 400 Kilometers away so I'd rather try and fix this myself if I can.

    Thanks in advanced!
     
  2. Tone Meister

    Tone Meister Member

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    Just replaced an output transformer in one of these that was arcing internally. No explanation for the failure other than it just quit one day. It's a simple swap if that's the problem
     
  3. Kurzman

    Kurzman Supporting Member

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    I had a similar problem with my AC4. After researching the amp on line I found they had a run of amps with bad diodes (rectifier).
    Probably best to pull the chassis (it's light) and mail it to the tech telling him about the diodes.
    Good luck.
     
  4. ai3gtmc

    ai3gtmc Member

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    Someone on another forum pointed out about the Fuse, it looked normal so I didn't really check it. Upon checking, I found out that FS2 Fuse is not working. I checked it with a multimeter and it's not registering anything.

    It is labeled as 160mA 250v which seems kinda weird because upon my research everyone seems to find a 125mA. I can't even find a 160mA in my usual online stores. I'll just get a 125mA to try it out and some new tubes.

    Best case scenario it's just the fuse, otherwise I'm checking out the diodes.

    thanks guys!
     
  5. Kurzman

    Kurzman Supporting Member

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    One of the internal fuses on mine went also. At the time I had two problems....a bad old Telefunken EL84 in the amp and the bad diodes. I don't know which took out the fuse.
     
  6. ai3gtmc

    ai3gtmc Member

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    I wish my diodes are alright. Do you happen to remember the values of the diodes? just in case.. thanks!
     
  7. Kurzman

    Kurzman Supporting Member

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    Sorry, my buddy did the work. I told my buddy about the diodes and he installed them. I'm sorry I can't be of more help. I'm not a tech.
     

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