Currently Being ModeratedMay 9, 2012 1:41 AM (in response to Atminstone)Re: dt25 112 combo bias adjustment
make sure you're in NFL1, pentode and class AB. make sure the amp is fully powered on with the master volume control at min and with no guitar plugged into the input.
If the bias still reads so high then it needs adjusting. you may want to have an amp tech or line 6 service centre do this as you may need to remove the chassis slightly to get to the bias pot, or use a special tool that only LIne 6 service centres have. usually it's just a screwdriver though, so it's strange that you can't get to it.
could you send a photo of where it is?
could you make a small L shaped tool to get access to it?
Currently Being ModeratedMay 9, 2012 6:51 AM (in response to Rowbi)Re: dt25 112 combo bias adjustment
I made sure I was in NFL1, pentode and class AB. Got pretty much the same results. I'll borrow a better multimeter tomorrow from work just to check (I got 14 mV from the "Ground" to the chassi?). Then I'll hunt for a L-shaped screwdriver, do you know/guess what kind of screwdriver it should be? (I can't really see the trim pot)
Here's a few pictures:
Not the easiest place to put a trim pot
Currently Being ModeratedMay 9, 2012 7:52 AM (in response to Atminstone)Re: dt25 112 combo bias adjustment
Maybe, you can find this thread interesting http://line6.com/support/message/333390#333390. Answer #8 from Andrewtorres. It seems that you might need to remove the amp out of the chasis to do so. However, I have never done this with my DT 25, so I cannot talk about the experience.
Currently Being ModeratedMay 9, 2012 12:10 PM (in response to daferalo)Re: dt25 112 combo bias adjustment
Thank you daferalo!
This solved my problem. At first I hesitated to open the amp, but the post by andrewtorres in the other thread and the fact that there is only 4 screws holding the amp in the chassis (two of them are in the handle) made me brave enough. Just unscrew them and the amp comes sliding from the chassis. Then I placed the amp with knobs down on two large books and CONNECTED THE SPEAKER and power cables. It's very easy to measure and set the bias voltage when the amp is removed.
Here's one more picture to show the amp removed from the chassis: