Hi guys, bought this Road King recently on the bay and it has a pretty serious problem. This is the first bad buy I have made over eBay yet, but the seller has agreed to compensate me for the repair costs. So, that point aside, I would appreciate if you can tell me if you have ever encountered a problem like this with a guitar amp.

Mesa Road King Problem

An awful, tremolo like cut in/out noise.

Here's the details:
As you should know, the Road King allows the option of switching between different power tube types. It only makes this noise on the settings involving the 6L6 tubes and on the high gain/high volume settings especially. Being that I play in a death metal band, I have very little use for the 50 watt EL34 setting which is the only setting which works.

I have brought it to a tech and this is everything we have done.

We have checked all of the tubes and replaced 2 of them, the problem is still present. Checked and replaced worn out pre-amp tubes, the problem is still present. The amps circuitry has been checked over and there was nothing burnt out or broken.

This problem is still present, regardless of guitar or pedals, and it is not a speaker cabinet problem as I have tried it in 4 different cabs. I have eliminated all of the possible problems - it is definitely the amp itself. I have tried it in multiple power outlets and the problem was still there, however, I have not hooked it up to a power conditioner. Not sure if that would be worthwhile trying at this point.

So, it is not a power or pre amp tube problem, it doesn't appear to be a catastrophic circuitry problem, it is not a guitar or pedal creating the problem, it is not a speaker cabinet issue, and I don't think it an outlet problem.

Has anybody heard this problem before? Heard this noise from an amp and found out the problem? I would be really grateful if you guys could share your experiences if you are familiar with this noise/tremolo effect problem with any amp, or Mesa amps specifically. I am going to be sending it to a specializer in Mesa products and possibly back to Mesa if nobody else can figure this out.
First of all - that clip sounds atrocious. The amp is really hurting. Sorry man.

Secondly - I'm not an amp tech.

You've taken it to a tech and had everything checked out so I'm really not sure what to say. I am assuming the seller is saying it never did that before? It is cool that the seller has offered to pay for any repairs.

The fact that it only happens on one set of tubes (the 6L6s) is odd. At first I was thinking a preamp tube or rectifier tube but now I'm thinking it may be motorboating.

Last edited by 311ZOSOVHJH at Oct 10, 2013,
Get a refund?
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You only replaced 2 of the power tubes? Replace the other 2. Fluctuations/tremolo effects are definitely a symptom of dying power tubes.

While I admit it's likely your problem is more serious, you should definitely completely rule out the power tubes first.

Have you emailed Mesa? I would ASAP.
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The rest of the tubes have been tested and are 100%. Only 2 of the power tubes were completely done. I believe this is the older series, and a refund through the seller is not an available option (at this point). I will be e-mailing Mesa if their certified repair center in Vancouver, Canada cannot diagnose the problem.

That motorboating example is very interesting, however, the amp does not make that noise when I'm not playing, and the gain/EQ controls don't change it much. It is almost strictly a high gain/high volume problem on the 6L6 involving settings.