Roadster Combo Channel Three Issue

[kcocking]

I have a Roadster 2x12 combo. Occasionally, channel three will change from sounding smooth and crisp to just plain rotten. Suddenly, the low E string will sound a LOT louder than any other string and the general crispness of channel is replaced by a muddy sound.

I don't have this problem on any other channels and the problem is intermittent. Sometimes I will play channel three and it will be great. Other times, it will sound as described.

I was told that changing a pre-amp tube would fix the problem, but I don't know which pre-amp tube to change. Can someone tell me which tube? I see the v1-v6 diagram, but don't see anywhere in the manual or amp where it tells you which tube affects which channel.

Any help would be appreciated. Thanks in advance.

 

[LerxstLee]

I have a Roadster 2x12 combo. Occasionally, channel three will change from sounding smooth and crisp to just plain rotten. Suddenly, the low E string will sound a LOT louder than any other string and the general crispness of channel is replaced by a muddy sound.

I don't have this problem on any other channels and the problem is intermittent. Sometimes I will play channel three and it will be great. Other times, it will sound as described.

I was told that changing a pre-amp tube would fix the problem, but I don't know which pre-amp tube to change. Can someone tell me which tube? I see the v1-v6 diagram, but don't see anywhere in the manual or amp where it tells you which tube affects which channel.

Any help would be appreciated. Thanks in advance.

I am NOT sure if the roadster uses the same preamp "map" as the roadking, my thoughts would be using the roadking as a reference it would be:

V2A = 3rd gain stage-ch 1 & 2
V2B = 3rd gain stage-ch 2 & 3


V3A = 4th gain stage-ch 3 & 4
V3B = Tone stack Driver


My best guess would be to swap out V2 for a known good 12ax7 and fire it back up.
If the problem continues I would then switch V3 out for a known good 12ax7
fire it up.
Let me know if that is the fix. I hope this works for you.

have fun
be safe

 

[KH Guitar Freak]

Could be preamp or poweramp valves that are going. Also, have you tried running your amp thru a power conditioner???

 

[kcocking]

it turns out i had a tube that lost its seal. that is now fixed, but now there are volume issues on channel three. when i turn the volume all the way down, you can still hear sound. the sound is very low, but it won't turn all the way off like on other channels.

then when you turn the volume up to 12 o clock, the volume is not as loud as the other channels. any ideas?

 

[LerxstLee]

Am I correct in understanding that the tube "lost its seal" means lost the vacuum?
If so, if you look at my above post there are more than one PRE-AMP tube, I am also not
sure that is what tube you replaced. That said I would think you may have another tube
that could be replaced, the tube before or after the one you replaced.
Pre-amp tubes V2 and V3 each affect channel three has you can see below.



V2A = 3rd gain stage-ch 1 & 2
V2B = 3rd gain stage-ch 2 & 3


V3A = 4th gain stage-ch 3 & 4
V3B = Tone stack Driver

This said, it could be many other problems. I tend to think replacing the simplest items in the equations can result
in an easy fix as opposed to sending your amp away. Yet, many will say after this post, no, it must be xy or z, this
is just my best attempt to help you with what may be a simple issue, simular to ones that I have ran across before.
/cheers

 

[LerxstLee]

You are correct, I did look at the manual and there are no instructions for the V1-v6 pre amp tubes.
I would still think that V2 and V3 are where this problem could exist.
Yes, it could be plenty of other problems but lets start there.

Am I correct in understanding that the tube "lost its seal" means lost the vacuum?
If so, if you look at my above post there are more than one PRE-AMP tube, I am also not
sure that is what tube you replaced. That said I would think you may have another tube
that could be replaced, the tube before or after the one you replaced.
Pre-amp tubes V2 and V3 each affect channel three has you can see below.



V2A = 3rd gain stage-ch 1 & 2
V2B = 3rd gain stage-ch 2 & 3


V3A = 4th gain stage-ch 3 & 4
V3B = Tone stack Driver

This said, it could be many other problems. I tend to think replacing the simplest items in the equations can result
in an easy fix as opposed to sending your amp away. Yet, many will say after this post, no, it must be xy or z, this
is just my best attempt to help you with what may be a simple issue, simular to ones that I have ran across before.
/cheers