Yes, that was going to be my next suggestion, only I expected to see what´s visible on speaker output.
That looks definitely ugly, cracked open, burning around comes from the electric arc (always VERY hot) caused by current jumping the gap.
Those big heavy capacitors wiggle them free by vibrations, doubly so in a Bass amp.
Although you will eventually replace those caps as suggested above, forn testing repair those joints,those caps were working 1 week ago, "aging" is sloooowwww.
So unsolder and remove both to better clean solder pads, apply fresh solder to them, melt and wipe it away to carry all the crud with a small ball pf paper, clean area with alcohol and a ball of cotton or rag or an old toothbrush, lightly scratch away any carbon you see, and resolder caps with fresh solder.
I bet it will work.
With the time and work involved why not just replace the caps while he's at it? It would be a shame if one failed shortly after fixing the solder joint and he had to redo the job. 2 caps less than $20CDN
https://leeselectronic.com/en/product/8152-8152ELECTROLYTICCAP63V4700UFRUBY.html
https://leeselectronic.com/en/product/8152-8152ELECTROLYTICCAP63V4700UFRUBY.html
Ok, thanks everyone for helping, I'll try this when I've some free time 👍
I was wondering, would it be better to exclude the preamp pcb (by disconnecting the red circled connector below) for testing or it can cause problems?
I'm also disconnecting 1, 2 , 3, 4 and 5 to exlude the speaker and horn.
Do not throw new variables into the problem, just-do-as-instructed and post results.
99% that your problem is there.
You will burn nothing since your problem is mechanical, not electrical.
99% that your problem is there.
You will burn nothing since your problem is mechanical, not electrical.
Oh, replace them if you wish.
I am trying to find now whether that´s the problem or something else, not wait 1 or 2 weeks for new capacitors to arrive.
I am trying to find now whether that´s the problem or something else, not wait 1 or 2 weeks for new capacitors to arrive.
I've followed what you suggested for the capacitors joints, I've also redone some other solder joints that seemed bad.
This is the results with no speaker connected. (+/- 45V on power supply rails, with full mains voltage)
GO-OO-ODDDD!!!! 🙂
Call it "repaired" 🙂
Replace them if you wish, for peace of mind, but it´s already working, ready to rock onstage 🙂
No more hum on speakers, of course.
Call it "repaired" 🙂
Replace them if you wish, for peace of mind, but it´s already working, ready to rock onstage 🙂
No more hum on speakers, of course.
No more hum of course... thanks to you!
I ask my friend if he likes me to replace them, maybe with some Vishay ones.
Is there any good way to avoid the vibrations problem? (there was some kind of glue on the caps before)
Now I guess the "up and down of volume" issue was caused by those caps? Can it be anything else?
Thanks again
Glue them down in place.
I don´t like "rigid" adhesives because they crack on impact (so not hot glue), much prefer slightly elastic ones.
You can draw a bead all around the perimeter with silicone sealant, the kind used for windows and fish tanks.
In principle, it is "not exactly recommended" in Electronics because for the first hours it exhales acid fumes, literally, acetic acid (white vinegar) which is used as a preservant, but that attacks copper if applied to solder tracks , etc.
This reinforcing bead will be between "plastic" PCB surface and plastic capacitor sleeve, so no problem.
Just leave that chassis open overnight or for 24 hours so all acid evaporates.
If you wish, there is acid free silicone, you´ll probably have to special order it; Forum members will certainly suggest some brand.
Personally I use and prefer a bead of neoprene/rubber contact cement, since I always have some around for my speaker assembly, you can buy a little squeeze tube at the Dollar Store, generally sold to repair sports/rubber shoes.
In general anything that prevents vibration will help.
I don´t like "rigid" adhesives because they crack on impact (so not hot glue), much prefer slightly elastic ones.
You can draw a bead all around the perimeter with silicone sealant, the kind used for windows and fish tanks.
In principle, it is "not exactly recommended" in Electronics because for the first hours it exhales acid fumes, literally, acetic acid (white vinegar) which is used as a preservant, but that attacks copper if applied to solder tracks , etc.
This reinforcing bead will be between "plastic" PCB surface and plastic capacitor sleeve, so no problem.
Just leave that chassis open overnight or for 24 hours so all acid evaporates.
If you wish, there is acid free silicone, you´ll probably have to special order it; Forum members will certainly suggest some brand.
Personally I use and prefer a bead of neoprene/rubber contact cement, since I always have some around for my speaker assembly, you can buy a little squeeze tube at the Dollar Store, generally sold to repair sports/rubber shoes.
In general anything that prevents vibration will help.
One last thing there was some glue on front panel leds too, to keep em still and to prevent leads from touching.Glue them down in place.
I don´t like "rigid" adhesives because they crack on impact (so not hot glue), much prefer slightly elastic ones.
You can draw a bead all around the perimeter with silicone sealant, the kind used for windows and fish tanks.
In principle, it is "not exactly recommended" in Electronics because for the first hours it exhales acid fumes, literally, acetic acid (white vinegar) which is used as a preservant, but that attacks copper if applied to solder tracks , etc.
This reinforcing bead will be between "plastic" PCB surface and plastic capacitor sleeve, so no problem.
Just leave that chassis open overnight or for 24 hours so all acid evaporates.
If you wish, there is acid free silicone, you´ll probably have to special order it; Forum members will certainly suggest some brand.
Personally I use and prefer a bead of neoprene/rubber contact cement, since I always have some around for my speaker assembly, you can buy a little squeeze tube at the Dollar Store, generally sold to repair sports/rubber shoes.
In general anything that prevents vibration will help.
Is this good for this purpose too?