filter cap corrosion

[Joe Blow]

playing around with a friends fender hot rod deluxe and getting a grainy ratting sound. looking at the board I notice yellowish corrosion around 2 of the filter caps. Im not getting any hum or other noises, just a crappy playing sound. Can or how can filter caps compromise the sound?

[HotBluePlates]

The most common symptom of a failed filter cap is hum.

After that, you may experience motorboating or other oscillation effects, if there are enough cascaded stages connected to the affected cap(s). The though is that the failed cap no longer performs its decoupling function properly. But this requires that there are at least 3 plate-loaded stages cascaded which could be coupled through the power supply by the failed cap. I say 3 because with 2 cascaded stages, the signal currents drawn from the supply are opposite phases, and shouldn't result in positive feedback.

Your present symtpom is non-specific. Do you get this grainy sound on clean or distortion settings? At all volume levels? Could there be a speaker issue? Or maybe a contact issue (jacks, molex connectors, etc)? I would think those would be more likely to cause the sound you're describing.

[plexi50]

When filter caps get saturated they will make your notes or the amp just sound bad. Each PS cap is doing a job. That job is to filter and store that voltage for each section of the amp that depends on being regulated. A PS cap wont necessarily blow right away. But in the meanwhile you get bad tone and fuzzy or unclear notes and chords. Remove and flip the PCB over. I just finished working on one where 3 of the PS caps were just laying on the board and were no longer soldered to there traces that supply the nodes of the amplifier. It only worked because of shear luck and being so close to the traces them selves is all i can figure. I bet you have the same sitiuation to some degree if not just plain old bad caps. The machines that solder these boards occasionally miss or get very little solder on the board and the parts themselves

Also check those 470 ohm white ceramic resistor solder connection. You can cook eggs and bacon on them. They get very hot. I change them to a 10 watt rating