Cambridge Audio minix x200 CA609 Testing Caps - VLoss Changed, why?

[Pizarro]

Hi,

I'm a noob trying to fix my sub-woofer.
I have obtained some simple tools and the circuit diagram, but have seen some odd behavior with one/some of the capacitors.

The problem is I don't know enough, to know what terms I should be searching for (so I can understand what happened).


Issue:
I used a simple "multi-function Tested T7" to check some of the capacitors (in circuit). Specifically a "330uF 10V JWCO" electrolytic capacitor, with my tool stating it was:

"304uF ESR=0.39 VLoss=15%"

I know that measuring in circuit is not ideal, so I de-soldered it and tested it again. This time it measured with a "VLoss=1.6%"

I soldered the capacitor back into the circuit and tested it again. It measured with a vloss of 1.6%.


Does anyone know why (or what I should search for to explain), the measured vloss went from fifteen percent, down to one point six percent?


Or is it just a bad cap? i.e. should I just replace the capacitor with a new one?


Thanks in advance.

[kaboom]

Re: Testing Capacitors - VLoss Changed, why?

Specifically a "330uF 10V JWCO" electrolytic capacitor, with my tool stating it was:


Or is it just a bad cap? i.e. should I just replace the capacitor with a new one?


Thanks in advance.

Could be a bad internal connection, which comes & goes with handling; besides, JWCO is junk in general...

[stj]

Re: Testing Capacitors - VLoss Changed, why?

vloss relates to the internal resistance,
your first test also saw the resistance of other parts on the board.
1.5% is about right.

[eccerr0r]

Re: Testing Capacitors - VLoss Changed, why?

easiest explanation: you broke something in your circuit while desoldering

[Pizarro]

Re: Testing Capacitors - VLoss Changed, why?

Thanks for the info. It was already not working, so I'm not fussed if I have broken something (else).

I will probably replace the caps with some new ones, and see if that helps.
They are part of the circuit generating the +3v and +5v lines, and those seem to measure between 13% and 15% VLoss across the cap (in circuit).

I'm hoping that the problem with the rest of the circuit is just noisy power. As it seems to still be producing the voltage correctly (according to my cheap multi-meter).

[stj]

Re: Testing Capacitors - VLoss Changed, why?

you can check the ripple(noise) by simply setting your meter to AC.
it will ignore the dc voltage and just show the noise.

[Pizarro]

Re: Testing Capacitors - VLoss Changed, why?

I'm not sure my meter is accurate enough to measure the ripple(noise).

e.g. the +5v line measures 4.9v (dc) and 10.0v (ac). So I would guess that the ripple would be +-0.1v ?

The 10v makes sense, as I assume the meter is measuring the peak voltage, but with it set to AC it assumes that it is half of a "sin wave" (so it doubles the value). Flipping the leads causes it measure 0.0v (actually it flips between "0.0" and "-0.0").

[stj]

Re: Testing Capacitors - VLoss Changed, why?

your meter doesnt like my trick - it should be showing mV levels
what meter is it?

[petehall347]

Re: Testing Capacitors - VLoss Changed, why?

put a small capacitor in series with meter probe .

[Pizarro]

Re: Testing Capacitors - VLoss Changed, why?

FYI... The meter is a cheap and nasty "Draper 60792 Digital Multimeter".

Useful for checking to see if the house electrics are live or how dead my batteries are, but not really designed for analyzing digital logic circuits.

I have ordered myself a "JYE Tech Wave2 Portable Oscilloscope DIY Kit", and will come back to trying to fix my subwoofer, after it arrives.


Thanks for the info and the help

[R_J]

Re: Testing Capacitors - VLoss Changed, why?

Maybe you could give us the make and model along with what the actual problem is with the sub, its not always a capacitor problem.
Some clear pictures would also help.

[Pizarro]

Re: Testing Capacitors - VLoss Changed, why?

FYI... Comparing the service manual schematics with the circuit board components....

The schematic states they caps are "330uF 16V", but they built it with "330uF 10V" caps.

The under rated caps are the one with aprox 15% vloss on them.

[Pizarro]

Re: Testing Capacitors - VLoss Changed, why?

The problem is with a "Cambridge Audio minix x200 CA609 Digital Subwoofer", not producing sound.


I do have a copy of the service manual, but that is just an exploded diagram of its parts and the circuit schematics for both the power board and amplifier board.

The audio signal can correctly pass though from "audio in" to "audio out" (so it is not the signal source), but something with the powered sub.

The power led lights up ok, but no sound is being generated.
I have tried with the "standby feature" both in "auto" and "always-on" mode (this is a switch on the back).

FYI... The internal power supply is generating:

• 7.2v for the +7v line.
• 6.8v for the -7v line.
• 47.7v for the +48v line.

I can't seem to measure anything outputting to the speakers, but my meter might not be sensitive enough.


As stated before, the +3v and +5v lines (created by the amplifier board) do appear to be generating the voltage, but the caps that create those two lines are the ones that (according to the circuit diagram) are below spec.

I'm hoping that after I get my little oscilloscope, even if it is not super accurate, it might mean I can trace the signal though the circuit and figure out where/when it disappears.

Also, there are no obvious burnt or blown components that I can see... I do hope its not a cold solder joint somewhere.

[Pizarro]

Re: Testing Capacitors - VLoss Changed, why?

The problem might be on one of the signal lines going into or out of one the chips (AK5358 , STA309A , R5F211A4 or STA516B ).

If I can figure out where I loose the audio signal, I can backtrack to see if one of the chips are broken or if there is a fault/short/floating-signal/etc on one of the lines.


Oh, I have also tried turning up the volume control (I even measured the pot to check that turning it did change its resistance).

[Pizarro]

Re: Testing Capacitors - VLoss Changed, why?

If you are interested, this is the service manual / circuit diagram, obtained from "Cambridge Audio" (as they have discontinued this model/version and replaced it with a newer one).

[rajembt]

Re: Cambridge Audio minix x200 CA609 Testing Caps - VLoss Changed, why?

Hi did you manage to work out what the problem was?
I have the same sub woofer with the same symptoms. I.e. powers on but no sound

[wobby]

Re: Cambridge Audio minix x200 CA609 Testing Caps - VLoss Changed, why?

Same to me... Solutions are welcome, thanks!