Ive been working on a fender deluxe 112 plus -which has a loud humm as soon you turn it on. with or without guitar plugged in or volume turned up. The two large capacitors 50v- 4700 uf seemed to move alittle bit. While the amp was on I moved the two capacitors which were connected together with a hot glue gun, and the hum stopped. I took both the capacitors out, checked them with a multimeter. they seemed to be charging with the multimeter set on 20k ohms. So I cleaned them up,along with the holes they went through, put alittle soldering paste on them and resolderd them back onto the board. When I turned the power on, the hum was gone but I could hear another noise and then 30 seconds later the fuse blew. I dont think I shorted anything out with solder paste, if you even can, but the noise I was hearing could have been the sizzle of soldering paste. After the fuse blew, I shut off the amp, unplugged it and touched the capacitors and the were very hot. Almost to hot to touch. What damage could I have done? Did I do the right thing? Any other thing I should be checking? ect.
Sounds like you put the caps in backwards.
Quote from: joecool85 on October 20, 2007, 07:54:14 AM
Sounds like you put the caps in backwards.
+1.
And very lucky they didn't explode all over you.
I just took it back apart and desolderd the caps. I did put them in right. I tested them again with my Dmm. What other tests can I do on these caps to check their condition?
I had the schemadic once but cant find it and dont remember where I downloaded it from. I've been to schematic heaven and the fender field guide but neither has this schematic. Any sites I should try? The board felt dry, I dont know if the paste I used could have squished together when I pushed the capacitors down on them to short out the caps. Any paste would have to be a good electrical conductor, wouldnt it? Dont know what I did wrong maybe I hooked one of the power lines on wrong. I really dont think so but Im going to find the schematic and double check everything before I try to plug it in again.
What solder paste are you talking about?
Flux?
Flux is essentially a cleaning agent. I've never thought about it being electrically conductive. Can't answer that.
With rosin core solder I've never had to use any extra flux for any electrical connection.
I believe the schematic can be found from Fender's website under the section titled "support - amplifier schematics". If not, PM me.
With that large amount of hum, and the Caps getting hot it could be that the rectifier is (partly) shorted and you are getting a high ac ripple. Check it out using the diode function on your DMM.
for the schematics try this site http://www.bnv-gz.de/~ooehmann/dexer.php?d=fender