Chameleon Labs 7720 - Intermittent Hiss/Crackle in one channel - Questions

[nanjo]

Hi all,

My Chameleon Labs 7720 (silver metal pots version) has intermittent noise (crackle and hiss) in the left channel output, occurring whether the compressor is either inserted or disengaged, and when the unit has no line inputs connected.

I have replaced all 4 DC Regulators, like for like, but the problem remains.

I am now considering replacing all capacitors on the board, and figure I might aswell install higher grade than the stock JH brand aluminum capacitors, unknown brand ceramic disc capacitors, and two unknown brand film caps.

I have spent countless hours looking at GSSL threads in attempt to find solutions, and recommended capacitors, but to no avail.

So, I would be very grateful for responses to the following questions:

1. What could cause intermittent hiss/crackle in the left channel?
2. What is the best solution/product for the upgrade of disc capacitors?
3. Would swapping a 2.2uf 63v +-5% film cap, for one of the same capacitance but higher voltage be sensible (having trouble sourcing 63v)?
4. Are audio grade aluminum capacitors suitable for the main board and side chain?

Any advice would be greatly appreciated.

Thank you.

 

[pucho812]

Shotgunning parts is a last resort effort to address a problem.
A problem on one channel and not both channels indicates a problem with the channel and not the power supply.
Intermittent issues are usually bad solder joint/joints.
It could also be a failed part or a broken part like a ceramic disk where it sometimes makes connection sometimes does not.

The hardest part here is getting it to noise again and for long enough that you can probe and compare channels.

 

[nanjo]

Shotgunning parts is a last resort effort to address a problem.
A problem on one channel and not both channels indicates a problem with the channel and not the power supply.
Intermittent issues are usually bad solder joint/joints.
It could also be a failed part or a broken part like a ceramic disk where it sometimes makes connection sometimes does not.

The hardest part here is getting it to noise again and for long enough that you can probe and compare channels.

Thanks for your reply and advice. I've spent some more time taking readings since, and isolated the problem to a ceramic capacitor.

I will be replacing this same capacitor on both channels.

I have the option of ceramic or polypropylene film capacitors.

Can anyone advise/give opinion on which capacitor type would be best suited in terms of audio quality/function, and whether or not I should be concerned about voltage specifications? The original ceramic capacitor is marked 101 (underlined), so I know I need 100pf, but am uncertain about which voltage specification.

Thanks.

 

[pucho812]

Why are you replacing on both channels when only one is the problem?
I would only replace it with same kind unless you have a specific reason to stray?

As for voltage, where is the cap located? That would easily tell you what voltage rating you need or what voltage rating you can get away with if you can’t find the part. Remember sometimes we stuff with what’s on hand.

 

[nanjo]

Why are you replacing on both channels when only one is the problem?
I would only replace it with same kind unless you have a specific reason to stray?

I intend to replace the ceramic capacitor on both channels as I do not have a like for like replacement of the original. So I will have to buy new/different anyway, and want to avoid introducing possible imbalance into the audio stereo image.

As for voltage, where is the cap located? That would easily tell you what voltage rating you need or what voltage rating you can get away with if you can’t find the part. Remember sometimes we stuff with what’s on hand.

Of all capacitors on the audio board, the maximum voltage among them is 100v.
The only replacements for the broken ceramic available to me in supply are either:

1. Polypropylene Film Capacitor, 63 V ac, 100 V dc, ±5%, 100pF
or
2. Ceramic Single Layer Capacitor 100pF 1kV dc ±5%

Does anyone know if either are suitable?

Thanks

 

[scott2000]

(having trouble sourcing 63v)?

Here's some Kemet....Surely there are others?
https://www.mouser.com/c/passive-co...f&capacitance=2.2 uF&voltage rating dc=63 VDC

The original ceramic capacitor is marked 101 (underlined), so I know I need 100pf, but am uncertain about which voltage specification.

I've always like the Goldmax....250v is usually good for circuits like this..Maybe others can chime in...

https://www.mouser.com/c/passive-co...cc-leaded/?q=goldmax 100pf&capacitance=100 pF

 

[nanjo]

....250v is usually good for circuits like this..

Thanks for your links- they've shown me another option- MLCC caps. I have also looked at the other suppliers you linked, however their delivery is expensive.

Are MLCC Capacitors a suitable replacement for Ceramic Capacitors in a circuit like this, and why would a 250v rating be recommended?

My preferred supplier has these 'Goldmax' MLCC's in stock, where I can collect for free, but they are 200v, will these also be suitable? (100pf MLCC 200v, replacing original 100pf Ceramic Disc 100v)

https://www.kemet.com/en/us/search.html?q=C322C101J2G5TA&t=558

 

[scott2000]

Are MLCC Capacitors a suitable replacement for Ceramic Capacitors in a circuit like this

multilayer ceramic capacitor= MLCC
guess it could depend but, looking quick at schematic yes.

and why would a 250v rating be recommended?

old habits... there is quite a bit of information here and online if it interests you enough to learn about the different materials used in ceramic capacitors, temperature coefficients,voltage dependant capacitance...etc

I can collect for free, but they are 200v, will these also be suitable?

replacing original 100pf Ceramic Disc 100v

yes

 

[nanjo]

multilayer ceramic capacitor= MLCC
guess it could depend but, looking quick at schematic yes.


old habits... there is quite a bit of information here and online if it interests you enough to learn about the different materials used in ceramic capacitors, temperature coefficients,voltage dependant capacitance...etc





yes

Thank you for your time and assistance.