Help Diagnosing Amp Problem

My TornSun Combo Amp decided to stop working the other day .

The lights go on . The Tubes are cooking . The back is open so even the most non-technical dweebs like myself can easily see that all the wires and speaker connections are still functioning .

All my cables are working . Amp produces NO sound . Not even a buzz .

Any ideas I can try before I'm forced to take it to the shop ? I'm hoping for an easy fix.

Thanks in Advance .


  • Dinosaur David BDinosaur David B Posts: 16,199
    edited July 2017
    Have you checked the fuse? That would be the easiest fix. Find out what kind of fuse it takes and get about five of them. Always smart to have replacement fuses on hand. The varying power supplies at venues can cause them to blow. Replace the fuse and all might be well. If it keeps blowing fuses, it's the amp.  This happened with my Hoffmann Marshall. It would work for 10 minute and then blow the fuse. It needed re tubing.

    How new are the tubes? And are they all lighting up? Most amp problems are tube related.  If they have a ton of hours on them, it may be time to retube.

    I have a book on troubleshooting amp problems. It says first you rule out stuff:

    The guitar -- I know it sounds stupid, but plug in your other guitar.
    The cable -- try a different cable

    1. Turn Off and/ or unplug the effects loop circuitry.
    2. Plug your amp into the same speaker using a different speaker cable.
    3. Plug your amp and speaker cable into a different speaker.
    4. Plug your speaker cable and speaker into another known good amp to double check that these two components are operational. 
    5. Unplug the speaker cable from the amp leaving the other end plugged into the speaker cabinet. Use an Ohmmeter to measure the resistance between the tip and the sleeve of the speaker cable’s free end. The reading should be slightly less (Ohms) than your speaker’s Ohms rating.
    6. Check the power cord to make sure the connections are secure and the power cord is not physically damaged.
    7. Plug your guitar straight into the Effects Return jack (if applicable), and turn On the Effects Loop.

    If you DO have sound, the power amp is not the source of the trouble.

    If you DON’T have sound, The problem is can be in either the power supply or, more likely, the power amp. Time to go to a tech.

    Post edited by Dinosaur David B on
    Life is easier, so much easier, life is easier now.
  • yngwie666yngwie666 Posts: 6,466
    Probably a fuse or a dead tube, otherwise an issue with the power supply. The 6.3V power supply to heat the tubes (called "heather") is separated from the amp circuit power supply (called "B+" : from 250V to 500V), so the tubes can glow but the amp circuit itself can be dead or not powered.
    As you stated that you're not very good at fixing stuff,I strongly advise you not to put your hands in there because of the lethal voltage.
  • jebbuddajebbudda Posts: 5,030
    It turns on . Lights up and everything .

    Chords are all good .  All the speaker wires are in place .

    No sound . Not even static .
  • Probably a blown fuse. Check the fuse.
    Life is easier, so much easier, life is easier now.
  • jebbuddajebbudda Posts: 5,030
    Probably a blown fuse. Check the fuse.

    That would be an easy fix .

    I always thought nothing would light up if the fuse was blown ? That's why I never checked it .
  • yngwie666yngwie666 Posts: 6,466
    edited August 2017
    There are usually 2 fuses:
     - one for main power (if this blows nothing lights up)
    - one for HT (High Tension): this one is only for the amp circuit power supply (not the tube heathing power supply)

    Post edited by yngwie666 on
  • jebbudda said:
    That would be an easy fix .
    It could be, or it could be blowing fuses because it needs a re-tube, or whatever. That's what happened to my Hoffmann Marshall 2 years ago.   If you change the fuse and all is well, you're fine. If it blows again, you need it checked.
    Life is easier, so much easier, life is easier now.
  • SanchoSancho Posts: 18,303
    I have never had a fuse blow because it was a bad fuse. Whenever I needed to replace a fuse, the new one blew instantly. It's usually a symptom of a deeper problem. Tubes most likely.
  • OskyOsky Posts: 859
    My 1975 Marshall Super Lead started blowing fuses very occasionally about 15 years ago... initially I just put it down to bad mains etc but the frequency increased and turned out in the end to be the mains transformer.
  • I think stuff like inconsistent voltage in the power coming into the amp CAN make them blow -- such as a power surge or a drop (most people use surge protectors for that reason), but if that didn't happen, if it's not event-related, something is going on in the amp. 
    Life is easier, so much easier, life is easier now.
Sign In or Register to comment.