Hi guys,
I've scoured the forums a bit, and every thread I read about these types of issues tends to be a preamp tube in a specific position, or poweramp tubes (which I'm not able to swap for another set as of today due to living rurally). This problem is in a Mark V 25 head dated October 2014 on the chassis.
So, here's the problem:
- Amp hums, on both channels, gets worse with increasing gain on all settings on both channels. Much louder on Ch2, and with increasing gain modes. Can only hear it on Ch1 in fat or crunch with the gain way up but its there and wasn't before.
- Turning the EQ on or off has some effect, similarly to adjusting the gain but not as drastic.
- Ground from the input jack to the ground out pin on the mains shows 0 resistance with a multimeter as it should. But when I touch the power switch, the hum lessens slightly.
- 10W and 25W mode BOTH have the hum (which is why I DON'T think its a power tube problem)
- I don't know that this is not a normal amount of crackle, but when I tap on V1 is crackles when every other preamp tube doesn't. I know V1 is a more sensitive tube that way, but there is zero sound from other tubes when I do this.
What I've tried:
- Swapping, one at a time, each preamp tube. I only has a set of 2 Sovtek 12ax7's sitting around, and I used each of them trying to swap into each position of the Mesa tubes. Nothing improved at all, with either of the sovteks (which both worked fine last time i used them) in any of the positions.
- Swapped positions of the power tubes for shits and giggles, and it did nothing.
- Plugged the amp into several jacks in my house on different breaker circuits, did nothing.
- Tried different guitars, leads, and a surge protecting powerbar and none of that did anything.
Any ideas to check for would be greatly appreciated. Thanks in advance!
I've scoured the forums a bit, and every thread I read about these types of issues tends to be a preamp tube in a specific position, or poweramp tubes (which I'm not able to swap for another set as of today due to living rurally). This problem is in a Mark V 25 head dated October 2014 on the chassis.
So, here's the problem:
- Amp hums, on both channels, gets worse with increasing gain on all settings on both channels. Much louder on Ch2, and with increasing gain modes. Can only hear it on Ch1 in fat or crunch with the gain way up but its there and wasn't before.
- Turning the EQ on or off has some effect, similarly to adjusting the gain but not as drastic.
- Ground from the input jack to the ground out pin on the mains shows 0 resistance with a multimeter as it should. But when I touch the power switch, the hum lessens slightly.
- 10W and 25W mode BOTH have the hum (which is why I DON'T think its a power tube problem)
- I don't know that this is not a normal amount of crackle, but when I tap on V1 is crackles when every other preamp tube doesn't. I know V1 is a more sensitive tube that way, but there is zero sound from other tubes when I do this.
What I've tried:
- Swapping, one at a time, each preamp tube. I only has a set of 2 Sovtek 12ax7's sitting around, and I used each of them trying to swap into each position of the Mesa tubes. Nothing improved at all, with either of the sovteks (which both worked fine last time i used them) in any of the positions.
- Swapped positions of the power tubes for shits and giggles, and it did nothing.
- Plugged the amp into several jacks in my house on different breaker circuits, did nothing.
- Tried different guitars, leads, and a surge protecting powerbar and none of that did anything.
Any ideas to check for would be greatly appreciated. Thanks in advance!
