Recapping a mixer?

T

theshoemakerstu

New member
Hi folks, I've often seen old mixers on sale on ebay and sites like that, and it often says that the mixer has been "Recapped".
What does that mean?
I've noticed my old Soundcraft mixer scrattles, and I think it's because of the capacitors. Is that why people desire their old mixers "Recapped"? :o
 
theshoemakerstu said:
Hi folks, I've often seen old mixers on sale on ebay and sites like that, and it often says that the mixer has been "Recapped".
What does that mean?
I've noticed my old Soundcraft mixer scrattles, and I think it's because of the capacitors. Is that why people desire their old mixers "Recapped"? :o
Click to expand...

It means they replaced the capacitors.

Electrolytic capacitors, especially older ones, have a limited life. When they get old they might leak a little DC, which can cause scratchy pots. But the first thing to try is simply cleaning the pots, and see if that fixes the problem.
 
mshilarious said:
It means they replaced the capacitors.

Electrolytic capacitors, especially older ones, have a limited life. When they get old they might leak a little DC, which can cause scratchy pots. But the first thing to try is simply cleaning the pots, and see if that fixes the problem.
Click to expand...

Im not sure that failing electrolytics has anything to do with scratchy pots but I do know that failing caps will result in considerably higher ripple currents in DC power supplies (result = noise)
 
Yes thats what I've been getting. Frequent Static and noise now and then, but it come and goes.
Im talking about the caps in the Pre amp stage, they run about 63 volts max. Well thats the description on the capacitor itself, 47uF and 63 volts.
Should I be carefull about shock hazard? If so, I do know how to discharge them :)
I've got some basic electronic skills.
Thx for the info!
 
theshoemakerstu said:
Yes thats what I've been getting. Frequent Static and noise now and then, but it come and goes.
Im talking about the caps in the Pre amp stage, they run about 63 volts max. Well thats the description on the capacitor itself, 47uF and 63 volts.
Should I be carefull about shock hazard? If so, I do know how to discharge them :)
I've got some basic electronic skills.
Thx for the info!
Click to expand...

Those are probably the input decoupling caps, or interstage decoupling (although those would usually be lower voltage). They won't kill you. They might not be the source of your problem though. Bad caps can mean scratchy pots if the caps are intended to keep DC off the pots, and they are failing at it.

The power supply caps are the ones that can store a larger charge, but even then in a typical mixer voltages are low enough merely to piss you off if you touch them. Caps in a tube amp are much higher voltage and potentially more dangerous.
 
Ah ok, coz you got me confused there.
Well, I cant explain the frequent noise in the line in stage, and its wierd that it dissapears when turn up the Gain on the line in section.
Either way, im getting some testing equipment soon, so I should be able to nail the problem. I just needed some hints on where to start. And you gave me alot of hints :)

out of subject: I've heard about amp's getting their caps "exploding".
Some guy I know played a gig in UK, and his amp (1970's Fender) didnt like the UK current, since we run 220 DC current here. So his caps just kinda "exploded" and the sound was so loud that the drummer fell of his drumseat and started running out of the building.
Im glad I never tried that.
The guitarist said it's like getting a car tyre filled with gas and then exploding right infront of your face. And believe me he tried that as well...
 
Oops, I should have told you guys long time ago. It's only channel 2 and 3 that scrattles on the line in section :o :o :o :o
All the other channels are fine.
 
theshoemakerstu said:
out of subject: I've heard about amp's getting their caps "exploding".
Some guy I know played a gig in UK, and his amp (1970's Fender) didnt like the UK current, since we run 220 DC current here. So his caps just kinda "exploded"
Click to expand...

You have 220V AC voltage. And yes, if you greatly exceed the voltage rating of a cap, they have a pressure relief vent that will "explode".
 
I haven't had to completely recap any of my mixers yet in 25 years (knock on wood), except for the PS and a couple caps in the signal chain that were just flakey after about five years.

- Clean faders and pots... check
- Rework ground (earth) connections... check
- Replace electrolytics in the PS... check

All done.

:)
 
theshoemakerstu said:
hmmm, we have 220V DC and 230 AC, it depends what it's used for. Well I think so, im from the Faroe Islands.
Click to expand...

Interesting. I'd heard of people running low-voltage DC in the wall for lighting, but I didn't know anywhere was running high-voltage DC as well. You'd have to have gear specifically built for that though, otherwise use the AC plug with appropriate voltage setting or transformer! If you plug an amp into DC . . . I don't think anything would happen as the DC wouldn't pass the transformer, but it might overheat in the process . . .
 
well things around here work different than in America.
Our Computers, TV's and PSU run on 220 volts DC. The transformer transforms it to lower voltages so it can work on low voltage circuts.
But this is kinda offtopic eh? :P
 
theshoemakerstu said:
well things around here work different than in America.
Our Computers, TV's and PSU run on 220 volts DC. The transformer transforms it to lower voltages so it can work on low voltage circuts.
But this is kinda offtopic eh? :P
Click to expand...

Well, no, it isn't, because if you're going to work on electronics it's helpful to learn something about them. The first thing is that transformers cannot pass DC, only AC. Therefore all of your appliances cannot run off DC unless they use DC converter circuits. This would be very unusual.

Read up on the AC vs. DC battle between Edison and Tesla:

http://en.wikipedia.org/wiki/War_of_Currents
 
mshilarious said:
Well, no, it isn't, because if you're going to work on electronics it's helpful to learn something about them. The first thing is that transformers cannot pass DC, only AC. Therefore all of your appliances cannot run off DC unless they use DC converter circuits. This would be very unusual.

Read up on the AC vs. DC battle between Edison and Tesla:

http://en.wikipedia.org/wiki/War_of_Currents
Click to expand...

Way to go rehashing the "mac vs PC" argument of the 1880s :D

to theshoemakerstu:

Your power is AC. No one on the PLANET gets 220V DC out of a wall(maybe the spacestation). You would need a power plant in every house to supply that in any relevant current. There are 4 types of power standards for normal use: British, European, Japanese, and Australasia and all are AC
 
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