#1
-Marshall DSL 201
-Was playing on 7-9 out of 10 (I usually play on 6 or less) then volume suddenly dropped
-No change when through pedals
-Volume is now very low but all effects still work
-When I put the volume to 10 there is very loud feedback but when I start playing, the feedback goes and the volume is still very low.
#2
Try plugging directly into the effects loop return. If you get proper volume then a preamp tube needs to be replaced. If the effects loop return does not do anything then you need to replace your power tubes.
#4
Quote by diabolical
with the amp on tab power tubes with eraser head of pencil

sorry, what?
#5
Quote by sandvika
sorry, what?
You turn on the amp, let the amp warm up, then turn it off standby like you are going to play it (or just turn it on and warm up if you do not have a standby). Dial up some volume on the amp. Take a pencil and tap lightly on the tubes with the eraser end of a pencil. If the tube is microphonic, it will amplify the tap greatly. Be sure to check all channels.

Have the tubes been changed in the amp at all, do you know? That amp seems to be an older series so if you bought it used or new and the tubes have not been changed since then, it is likely the tubes are just on their way out.
Last edited by Will Lane at Feb 11, 2016,
#6
Quote by Will Lane
Try plugging directly into the effects loop return. If you get proper volume then a preamp tube needs to be replaced. If the effects loop return does not do anything then you need to replace your power tubes.

I think is my power valves then. Just to clarify, I did get something, but low volume when put through the FX loop.
#7
Quote by sandvika
I think is my power valves then. Just to clarify, I did get something, but low volume when put through the FX loop.
Okay. Then yes I would think it is the power tubes. Keep the amp off and do not use it until you get a new set of tubes in there.

If the tubes in are the stock tubes, I would suggest to just get a new tube complement for it. You need 4 12AX7's (the preamp tubes) and 2 EL84's (poweramp tubes). I also think your amp is fixed bias so you will have to bias the new power tubes you put in there. Look up how to do that, and if you are not comfortable doing it take it to an amp tech.
#8
Quote by Will Lane
Okay. Then yes I would think it is the power tubes. Keep the amp off and do not use it until you get a new set of tubes in there.

If the tubes in are the stock tubes, I would suggest to just get a new tube complement for it. You need 4 12AX7's (the preamp tubes) and 2 EL84's (poweramp tubes). I also think your amp is fixed bias so you will have to bias the new power tubes you put in there. Look up how to do that, and if you are not comfortable doing it take it to an amp tech.

Thanks for the help. This manual says this: http://imgur.com/QJG5OJe cathode bias. What does that mean. Also if it is my power tubes do i need new 12AX7s like you said or just the el84s? thanks
#9
Read that portion of the manual again, and then the bit after the highlighted part. It is explaining why the amp is not cathode biased.

You should have a spare set of pre and power tubes, for diagnosing and fixing issues like this.
#10
Thank's all. I am new so I will just bring the amp to a tech and watch him
#11
I ended up replacing and biasing the power valves myself but it didn't fix the problem. It is also worth mentioning that before my amp lost its volume, using the build in reverb caused a fuzzy sound, and now when I put the amp on max volume, it is quite and has the same fuzzy sound. Anyone have any ideas on what the problem is?
#12
Have you replaced the preamp tubes? Can you re-seat them to make sure they are in all the way? Or could you roll a spare through each preamp position to see if you have a bad tube somewhere else?

If not, take it to an amp tech, they will get your amp straight in a jiffy.