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Everything posted by guyatone

  1. I was able to fix the "black bars" issue on my 212 Mk1. The problem was that one of the solder joints of the voltage regulators on the DSP/preamp board came loose and it didn't supply the required +5V any more. If (and only if!) you have the necessary experience to work with the insides of a high voltage device like a tube amp, it's quite simple to diagnose. The preamp board has test points for the various voltages and you can probe them with a multimeter. Once you find that one of these DC voltages is missing, you can find the matching voltage regulator (IIRC there are three, two through-hole and one SMD) and see if the regulator itself is broken (there are reports of them overheating) or if it's only a dead solder joint.
  2. Now this is just a blind guess, but if one relay already was broken, it might be another relay causing this. If one output tube gets switched to triode, but the other tube either is stuck in pentode mode, then the asymmetry in the push/pull stage could lead to hum.
  3. Firmware updates go through MIDI, so safe mode needs working MIDI - and I should be able to get Line 6 Monkey to see the amp in safe mode, shouldn't I? Factory reset is holding the voicing switch down and the pentode switch up while turning the amp on. I've done this at least a dozen times, it made no difference.
  4. What does your amp do when you start it in safe mode? That is, holding the channel selector down to "B" for 15 seconds when turning on the amplifier? Does the amp behave normally afterwards, play and allow you to switch channels and topologies or is it mute and unresponsive? I'm trying to diagnose a MIDI problem with my amp*, and safe mode for me is showing the latter behaviour. I don't know if that is correct or if my amp is faulty. * https://line6.com/support/topic/60000-diagnosing-a-broken-midi-input/
  5. Thanks for your help. I know we technical users aren't the easiest :) I got this amp used just a couple of days ago, I don't know how old those tubes are. They are EH tubes, so either a correct replacement or they're 10 years old... I tried replacing the 12AX7s with known working EH tubes that I have, with no difference. I don't have any EL34s for testing. The amp, when I got it, did have a blown heater filament fuse, so there's that... Voltage drop due to high current draw was also on my mind. I tried it with all tubes removed, but that didn't make any difference either. Getting new tubes put in by an authorized dealer, well, that's the aforementioned half-day trip to Switzerland in which case I might just as well have them look at the MIDI port while they're at it. For any other amp, I'd have service points nearby to get new tubes in (Bogner authorized even), but as you say, the DT50 has a special procedure that goes beyond a basic bias adjustment and those specs aren't public. One thing I might take a look at, which I know is not recommended, is to check the test points on the digital PCB for correct voltages. Line 6 is doing a great job at labeling their boards, I have to say. Still, the one question that I'd like to get answered: What is the expected behavior of an amp in safe mode? Is it supposed to be "frozen" and quiet or should it still be amplifying sound and react to the switches?
  6. I know the script. Try resetting the amp. Try rebooting the computer. Update your drivers, update your operating system. Try a different MIDI cable. Try a different MIDI interface. Try a different computer. That's what the script for "troubleshooting firmware update" says. I have done all that. I'm not even at the point where the firmware update is my concern. The current status is that there is no reaction, whatsoever, to any MIDI input of the amp. MIDI is a dead simple protocol. UART, 31250 bits per second, 5V. The MIDI command to change the channel on a DT50 is a whole three bytes, nothing more. Sending that simple signal to the amp does nothing - I can send it from a hardware MIDI controller, I can even send it from an Arduino - nothing. If I can't get that simple command to work, there's no point in even going through operating system and driver updates, because they aren't even playing a role yet. And, my question from above again: What is the expected behavior of the amp in safe mode? I see others reporting that when they start the amp in safe mode, it will respond to MIDI signals and switch channels and topology. When I boot mine in safe mode, it does not respond ot anything. Safe mode on mine means that "B", "Class A" and "Class A/B" light up and stay lit, the lights on all the other switches stay off and the amplifier responds to nothing. Is that how it is supposed to be or does my amp have trouble with safe mode?
  7. - Windows 10, all updates installed - no USB hub - I don't have the UNO model, but my MIDI interface is made by M-Audio Again, this is not just limited to Line 6 Monkey or the computer USB, but even with simple hardware interfaces (no computers, operating system or USB involved at that point) sending nothing more than CC19 on MIDI channel 1 I get no reaction from the amplifier. According to all the documentation I read so far, that MIDI command alone should cause the amplifier to switch channels, which it doesn't.
  8. What should I be doing? A bit of reading in this forum tells me that I’m not the first one who can’t get Line 6 Monkey to recognize a DT50/DT25, and I have tried everything that was suggested in those threads, such as different cables, different computer, different MIDI interface, safe mode and reset. I would love nothing more than a solution that doesn’t require me to take it apart, but I don’t know of one.
  9. If I can avoid it, I'll be happy to keep the thing closed. What other options to I have to get MIDI input (and with it Line 6 Monkey) to work?
  10. I have done a reset, several times. It does reset properly, both channels are back to voicing I. I just can’t get the DT50 to react to any MIDI signal. Not from Line 6 Monkey, not from a hardware controller, not from DTEdit, not from Pure Data. The optocoupler is working, there isn’t really anything else between it and the MCU, so I’m leaning towards firmware issues. Besides the “pinch” reset and the channel B safe mode, are there any other diagnostic/reset possibilities that I have from the outside, other than breaking out the soldering iron and adding a JTAG connector?
  11. How many watts is our converter rated for? While the DT50 may output "only" 50W, the power intake is rated as up to 300W.
  12. I'm pretty sure he would. However, the closest Line 6 service point is not only more than two hours away, but I'd also have to cross two international borders to get there. I took out the I/O board earlier today, hooked up my bench power supply and meter and was able to verify that the optocoupler is working - MIDI signals coming in through the DIN connector read correctly at the PCB connector. I've seen people refer to "safe mode" in this forum, including someone writing that they were able to use DTEdit when the amp was started up in safe mode. Safe mode, when I try it, leads to an amp that gets stuck with both Class A/AB lights on and does not respond to any switches, MIDI signals or guitar input. Is that the intended behavior or does my amp have a software problem?
  13. Plug your guitar into the "Power Amp In" on the back of the amp. If you still hear the same noise, it's the tube stage that needs service. The Preamp Out and Power Amp In are exactly right between the digital and anlog boards of the amp. Any signal coming out o the Preamp Out has been touched only by the modeling stage but not the tube stage, and any signal going into the Power Amp In will only be going through the tubes.
  14. Excessive noise can be a sign of aging tubes, especially when there is crackling/popping. Aging capacitors and resistors create noise too, but there we’re talking about decades of aging. A simple test would be to pull the 12AX7 tubes and see if the amp still has the same noise. In that case, it is very likely that the power tubes could benefit from a replacement.
  15. If sound is coming out, then all tubes are working (and glowing). It might just be too much ambient light to see it properly. The 12AX7 tubes have smaller heating filaments than the EL34s, so that could be why it appears as if there were only two glowing.
  16. I recently purchased a used DT50. When trying to find out if needed a firmware update, I was unable to get Line 6 Monkey to recognise the amp. I tried a different MIDI interface, with no success. I am able to receive MIDI signals from the DT50, for example, the channel selector sends CC19, but I cannot get the DT50 to recognise the same CC when I send it via MIDI controller to it. Now, I know my way around the insides of a tube amp (discharging caps, etc), and would like to diagnose further why the MIDI input isn't working rather than having to send it in for (costly?) repair. Looking at the I/O PCB, it looks like the optocoupler is a likely candidate - are those known to fail? Other than this and the connectors between the I/O and the digital board, are there any other components that I should be checking?
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