Very bad crackling noise from small amp.

[slidincharlie (Carlo P)]

I bought a Pignose Hog20 off ebay. It looks like new. 20W peak output, 6.5" speaker, solid state.
When I play a low-end note on the 5th or 6th string most anywhere on the fretboard, a horrible loud crackling noise comes out the speaker. This starts with the volume around 6-7 on the dial. The higher the volume, the worst the noise.
Is this normal for such a small amp? I mean, is it a matter of power handling?
Is there a way to check the speaker integrity?
I have never played through a Pignose so far, but I usually play through small tube amps without such a problem.

Carlo

[Amp Kat]

Not much different troubleshooting this one as the last one you had and is just a process of elimination. Sounds like the speaker is bad by your description. You can ohm it out to see if it is ok or visually inspect it for cone cracks or throw it on another amp output. The output transistors are working because your getting sound but they may be out of bias and getting some crossover distortion. If you take a signal from the preamp before it gets to the power section and send it to another amp you can eliminate that part and move on. Any way you do it you'll have to eliminate either preamp,output and speaker. Another key element to troubleshooting these SS amps is making sure your rail voltages +/- are there on the op-amps and output transistors. When a device blows it usually pulls one of these down with it and until you replace the faulty component it won't return to it's normal nominal voltage. The emitter resistors will open up as well but you'll have to pull one side to correctly check the output xistors and when they go you usually get no sound at all but a large hum.

[slidincharlie (Carlo P)]

Thank you Amp Kat, I am a bit scared when it comes to ss amps (this is my first one).
I'll try to troubleshoot it anyway.
I'll also ask the schematic diagram to the Pignose guys.

Carlo