I'm guessing these PSU caps have had it?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
MikeHunt79

MikeHunt79

Member
Joined 2003
I fitted an IEC socket to my Numark SA3000 today, and saw this:
An externally hosted image should be here but it was not working when we last tested it.


The amp works fine, but I'm guessing it would work better if I put some new caps in?

The existing ones are 3600uF, while my replacement ones are 4800uF, all 80V.

Higher capacitance should be fine for PSU caps tho should'nt it?

I just want to check before breaking out the soldering iron. :) :smash:
 
D

dave_gerecke

Member
Joined 2007
Hey Mike, The increase in the cap value should be fine, might even clean the supply up a little more. Those caps do look at wee bit stressed. Kind of like I felt today. Even if the amp works now, they look likely to burst and then it makes a big mess and usually stinks. Good luck and have fun!:)

Peace,

Dave
 
MikeHunt79

MikeHunt79

Member
Joined 2003
poynton said:
I'd love to see the picture but something seems to have happened to it.

Andy
Click to expand...
Imageshack seem to have lost the pic, so I re-uploaded it:

An externally hosted image should be here but it was not working when we last tested it.


I've now replaced them, and the amp is working fine:

An externally hosted image should be here but it was not working when we last tested it.


I have no idea how old this amp is as I bought it used, but there was so much dust in there, I've got most of it out now. The originals were actually 3300uF, and there's now 4700uF caps in there. :)

I haven't measured the rail voltages, but I will next time I have the lid off. :smash: The original caps were rated at 80v tho.

EDIT: The caps had already started to leak, I had to wipe some of the brown stuff off the PCB:

An externally hosted image should be here but it was not working when we last tested it.
 
poynton

poynton

Member
Joined 2005
It is quite common for caps with the plastic top-cover to appear to bulge.

If you remove the top plastic piece, is the case bulging ?

The brown stuff on the pcb is anti-vibration glue, commonly used.
Having said that, I cannot tell from the photos if the caps are leaking as well or not.

Andy
 
B

Bigred

Member
Joined 2007
poynton said:
It is quite common for caps with the plastic top-cover to appear to bulge.

If you remove the top plastic piece, is the case bulging ?

The brown stuff on the pcb is anti-vibration glue, commonly used.
Having said that, I cannot tell from the photos if the caps are leaking as well or not.

Andy
Click to expand...

Clearly those caps sh*t the bed.
 
MikeHunt79

MikeHunt79

Member
Joined 2003
* goes and grabs caps from bin * :D
poynton said:
It is quite common for caps with the plastic top-cover to appear to bulge.

If you remove the top plastic piece, is the case bulging ?
Click to expand...
Yep:
An externally hosted image should be here but it was not working when we last tested it.

poynton said:
The brown stuff on the pcb is anti-vibration glue, commonly used.
Having said that, I cannot tell from the photos if the caps are leaking as well or not.

Andy
Click to expand...
Both goo's are brown, but the light brown (glue) is soft and squidgey, while the dark brown stuff (electrolite?) is dry and had to be scraped of the PCB:
An externally hosted image should be here but it was not working when we last tested it.


They're going back in the bin now, unless they have to be disposed of in some special way? :confused:
 
MikeHunt79

MikeHunt79

Member
Joined 2003
Just a quick question, one of the channels is now not working... The "limit" light lights up the whole time, and the sound is very distorted thru this channel, at very low volume...

Could it be that there are 2 caps for each channel and I have put 2 in the wrong way around?

Or could I have triggered some sort of fault by taking the PCB out?

I don't have my scope right now, but I should have access to it tomorrow, as I have only been able to measure 1 rail voltage so far, which is 67v. :smash:

EDIT: It's not the caps, they are all in the right way, and all of them are getting 67v across each one.

I'll have another look tomorrow, when i've got my scope handy...
 
B

Bigred

Member
Joined 2007
Originally posted by MikeHunt79
Could it be that there are 2 caps for each channel and I have put 2 in the wrong way around?

Or could I have triggered some sort of fault by taking the PCB out?
Click to expand...

If you got the polarity wrong on those PS caps you would CETAINLY know about it. I suspect its not 2 caps per channel but 2 for the + rail and 2 for the - rail but I could be wrong as I'm unfamiliar with that amp. You have got other issues.
 
MikeHunt79

MikeHunt79

Member
Joined 2003
Bigred said:


If you got the polarity wrong on those PS caps you would CETAINLY know about it. I suspect its not 2 caps per channel but 2 for the + rail and 2 for the - rail but I could be wrong as I'm unfamiliar with that amp. You have got other issues.
Click to expand...
I've just checked each one with the PCB out and all the caps are in the right way and getting charged to 67v each...

I have a feeling it's a grounding issue, I'm gonna have to have a look into how the limiting circuit works....
 
MikeHunt79

MikeHunt79

Member
Joined 2003
Tony said:


You can also have output offset voltage, is there a relay in there that does not click?
Click to expand...

There is a relay for each channel, and it clicks around a second after you turn the amp on. No turn on thump. I found a short was causing the limiter to kick in, I've now insulated the spade connector and it's working perfectly.

I've also checked for DC offset on the speaker output, and it's less than 0.5v so that seems fine.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom