Micro terror feedback

[Gus]

Hi,
I have a micro terror dark and it has a really bad feedback issue. As soon as I stop playing the feedback starts instantly and is very loud.
I had initially put it down to using a bad speaker cable, but after using it on a new cab and cable yesterday it continues....could it be a wiring problem? Or any other ideas?
I live in Vietnam so getting it checked under warranty is not an option.

Thanks

[bclaire]

Have you tried replacing the tube?

[Gus]

Sorry, does tube mean the valve?
I haven't tried this as its brand new so I didn't think it would be a problem.
Please let me know and I can try.
Thanks

[Randy Bass]

I would suspect a microphonic valve/tube to be the most likely culprit. Be certain that you are connecting the amp to the speaker cab with a dedicated speaker cable (unshielded) and not an instrument cable (shielded) though.

Valves/tubes are the most likely component to fail inside the amp, and they are considered to be consumables as such. It is fairly common for defective or weak valves/tubes to reveal their flaws early on. It is also common for valves/tubes to be damaged in transit to the end user by rough handling which is usually attributed to parcel couriers. These problems are common to all valve/tube amp brands since they source their valves/tubes from the same manufacturers and ship their amps via the same parcel couriers. It is good practice for any owner of a valve/tube amp to keep spare valves/tubes on hand in preparation for the inevitable failure of said consumables.