Roadster - Loss of Bass Freq CH 4 on Modern

[fjk1138]

Hi All,

I just switched on the Roadster, put it on CH 4 Modern and the volumed dropped off a bit, stayed at that lower level, and now the channel plays like someone took the bass knob and turned it completely off. Moving the bass knob now makes no difference, but the treble knob works fine. Ch 3 in Vintage mode sounds a bit darker than normal (or maybe it just seems that way since the bass seems to be sucked out of Ch 4?) and Channels 1 & 2 seem to be fine.

I assuming a tube is on it's way out -- any idea which one(s)/position(s)?

Thank you kindly to whoever can identify it.

 

[fluff191]

Try switching your V2 and V3 preamp tubes and see if the problem happens on another channel.

 

[fjk1138]

Done....but no change. Ch 1-3 sound fine.

Adjusting the mid knob and bass knob on Ch 4 = no response.
However, the treble knob now acts like a volume knob. Turn the treble knob off and it almost totally kills the volume.

Should I just take it to the Mesa dealer? It's still under warranty (about 1.5 years old).

 

[fluff191]

I would absolutely take it to the amp doctor.

 

[fjk1138]

I called Mesa and they think it might be a J Fet (spelling?), which controls the internal switcing for the channels. It will
go to the authorized repair center tomorrow or Friday and I will report back the results.

Thanks.

 

[fjk1138]

UPDATE: Authorized Mesa tech cannot hear the problem. I am more than a little nervous because I know I am not imagining it. I will try to talk
to him tomorrow. Maybe the guy just can't hear it because he is not familiar with the amp?

In the meantime, anyone know what the Mesa policy is on an intermittent problem that an authorized tech cannot find? Would they just replace the entire insides completely "just to be safe" if they cannot fully diagnose the problem?

 

[pokerrules47]

UPDATE: Authorized Mesa tech cannot hear the problem. I am more than a little nervous because I know I am not imagining it. I will try to talk
to him tomorrow. Maybe the guy just can't hear it because he is not familiar with the amp?

In the meantime, anyone know what the Mesa policy is on an intermittent problem that an authorized tech cannot find? Would they just replace the entire insides completely "just to be safe" if they cannot fully diagnose the problem?

Don't fret too much about this. Go down to the shop and show him. Most decent techs will allow you into the shop. The last time I had major issues with my amp, the tech made me show him what I meant before I left after dropping it off!

 

[fjk1138]

I visited the tech today. They were very nice to deal with, but forwhatever reason the amp appears to be OK now. It was treated as a warranty repair, so it didn't cost me anything. I'll keep an eye on it. Thanks you guys for your advice, and also to Mesa for their help -- they
were very nice on the phone.

 

[jbird]

Ya know, I once had that same thing happen to my old y2k Dual Rec! I drove it down to Petaluma in the morning, picked it up in the afternoon, they said it checked out fine? The problem was gone, and it never happened again! They said they did nothing, but I could see it appeared the treble pot had possibly been replaced? Weird?