Diagnosing a Haysee30

[Jonny toetags]

I'm having an issue with a Hayseed 30.
A friend asked me to look at it, complaining of half volume/no volume.
First thing I noticed were 2 completely burnt resistors (shown in the pic).
I replaced them with a couple 110ohm 2W metal oxides I had in stock and turned the amp on.
I get no sound from the guitar but do get a hum and popping, then a burning smell slowly started.
After shutting the amp off, i noticed that one of the same resistors was starting to turn brown.
Any ideas?

[Chuck H]

Those are screen grid resistors. It looks like you may have different color codes on the ones you installed. One looks to be 110R and the other a 100R. Unless that's just an affect of light in the photo or a result of a partial cook

Replacing burned resistors is almost never a repair for a tube amp. In tube amps, resistors generally fail because something else over stresses them. So the repair needs to include a diagnosis of WHY the resistors might have failed rather than just recognizing that they have. I expect you have one or more bad power tubes and/or a shorted bypass cap in the bias circuit for the power tubes. At least that's what I would check first. Don't fire the amp up again with tubes in until you have this sorted out.

[MarkusBass]

Screen grid resistor fail when the tube is shorted. Replacing the resistors (without replacing the tubes) in this case is a very bad idea - the new resistors will fail again. Remove the tubes first (the first one and the fourth), connect a meter to one of the resistors and switch the amp on. If you get high voltage, switch the amp off and keep looking for the problem. If you don't get high voltage, I would check the resistors (most probably replaced them) and buy a new set of tubes.

Mark