Cap Orientation Question

[Siegfried Meier]

Hey guys,

I'm just recapping our console and was wondering about a specific cap that's on every channel.

At first I figured the long leg would be the positive side, but now I'm wondering if the indented band is actually the positive?  These came from Colin - it's for our TAC Magnum console.

Any ideas?

Thanks!
Sig

 

[Siegfried Meier]

Pretty sure it's the long leg, as most caps are - if I put the positive lead of my meter on the long leg and negative on the short leg, it begins to charge and read a positive ascending value.  Reverse of that gives me a negative value, and it descends.

Can anyone confirm?

 

[Brian Roth]

There are no polarity markings on the cap?  Hmmmm...perhaps it's a bipolar?

Bri

 

[Siegfried Meier]

Hmmmmm...well I don't think so.  There is a band that has ------- written on it, as  you can't see on the other side.  And the cap it's replacing is polarized.

I'm gonna place bets on the longer leg.  There are similar looking caps in the Neve clones that I've built up, and in those cases the indent indicates the + side, which is why it's confusing.

 

[zamproject]

Vishay BC series asm 021/031...

You have a BIG mark on it ,on the other side not showed in your pict

Clearly pointing the neg leg like this ->->->->

 

[Siegfried Meier]

HAH!  Can't see the forest for the trees!  Didn't even notice the arrow in the abstract art that was the negative symbol...

You are correct.  Although, it seems odd that they would have the long leg be the negative, doesn't it?  Now I have to go back and make sure I didn't accidentally orient any the wrong way.

Would these have blown if I fired the console up?  Can't tell where they are, but my guess is in the mic preamp stage.

Thanks,
Sig

 

[Brian Roth]

Another clue for many/most polarized axial lytics....the wire lead for the positive end comes through a "rubber" gasket, while the negative end attaches to the (bare) metal can.

Bri

 

[ruffrecords]

Is it metsal at one end where the lead comes out and plastic at the other?. If it is then the metal end is the negative.

Cheers

Ian

 

[zamproject]

You are correct.  Although, it seems odd that they would have the long leg be the negative, doesn't it?  Now I have to go back and make sure I didn't accidentally orient any the wrong way.

Would these have blown if I fired the console up?  Can't tell where they are, but my guess is in the mic preamp stage.

Thanks,
Sig

They don't like reverse polarity like all polarized caps...
My experience with this Vishay axial series is that they are leaking boiled electrolith trough the positive side (around the rubber) .
Maybe you have to cleen the PCB  :-X

 

[Siegfried Meier]

I'll have to check - I only did this to 3 channels that I started working on today, fired up the console for only 10 minutes.  The rest are correct, as I'd already done them earlier this year.  Guess I started working, saw the long leg and just didn't think about it...

;-)

 

[Siegfried Meier]

Nothing at all on the PCB to clean, and I can't even see anything leaking.  Do you think 10 minutes wasn't long enough for them to blow?

 

[3nity]

whats the rating of the cap?
is it a filtering cap?

 

[Siegfried Meier]

They're 2200uF 16v.  They're in the mic preamp section of the console, which we don't use anyway, but I'm not sure what the job is?  Is it related to phantom power?

Either way, I pulled those out and measured them, they don't appear to be blown or anything.  Reading the exact same as a fresh new cap.

 

[Brian Roth]

I don't have schematics for that desk, but from your description, my hunch is the cap is in series with the mic gain pot.  Of so, the polarity can be relatively arbitrary since there will be very little DC across the cap.

Bri

 

[joaquins]

I don't think a 16V cap is related to phantom, they normally are around 220u and over 60V... Brian idea seems right to me.

JS

 

[Siegfried Meier]

Yup, I think you're right.

Onwards and upwards - thanks guys!

Sig

 

[3nity]

i agree with Brian Roth.

I don't have schematics for that desk, but from your description, my hunch is the cap is in series with the mic gain pot.  Of so, the polarity can be relatively arbitrary since there will be very little DC across the cap.

Bri

 

[3nity]

the console a Magnum? My einstein had the same value of cap at the gain pot!