Tweet
Hi yall. I posted on here before about my Fender HRD. Had a switching problem and it turned out to be the 5W power resistors. All was fine until recently. I was playing a gig at an outdoor festival everything was good, but it ended up raining on us just as we finished our set. My amp got rained on for about 30 seconds before I was able to cover it. I thought it would okay because I had it unplugged at the time. I let it dry for several days with a fan on it. But when I played it last I was getting a really bad crackle and static that seemed to come and go. Even when the all knobs are turned down. I also noticed that the "crackle and static" changes pitch when I switch channels. I tested the 5W power resistors, they're fine. I was told it could be the plate load resistors aswell. I also noticed when testing the bias point the bias increases during the crackle and static. Any possible ideas? Thanks
-
-
It is likely to be due to the onset of corrosion. A careful inspection for residue from evaporated moisture, corrosion "cancer", and trapped moisture under components would be a good beginning. If there is remaining moisture, a lab grade alcohol flush of the component side of of boards can absorb moisture and wash it away. Methyl Alcohol is the best for this but it is also very flammable, more so than other heavier alcohols like isopropyl alcohol is safer and more readily available. The type found in the pharmacy often has a relatively low purity...mostly water. Even Reagent grade is cheap however.
The noise is probably coming from one of several developing sources so stopping and mitigating the corrosion is more important than just finding the current source, or else the amp will never have long term reliability.
Water under component mounted down tight on a board can retain fluid water for a very long time, after the rest of the amp has dried, due to capillary action that prevents normal evaporation. Noise and corrosion usually is worse some time after the electronic assembly has gotten wet and appears to be dried out. It only gets worse with time. Some types of corrosion responds well to deoxidizer chemicals such as Caig Laboratories De-Oxit D-5.
Good luck -
Right on. I'll give it a thorough cleaning. Last night I had the back open probing it over and over with my dmm when I noticed it seemed like alot of the solder joints on the smaller pcb holding the tubes were very dull so I reflowed all of them and the problem seemed to go away. But I'll give her a good cleaning with some alcohol aswell. Snag some spots before they get to become a problem. Thanks again for the advice.Comment
Comment