Hi my name is Andy. I have lurked here for a long time learning what I can but have not posted.
I have come into a Sunfire True Subwoofer Signature that is in need of servicing. This is a Bob Carver design and uses a high current amplifier based on a tracking down converter instead of a beefy power supply.
I opened it up and found the switches for volume, crossover and phase were dirty but some deoxIT took care of that. I have found several electrolytic capacitors are bad, bulging or even a little leakage on the power supply and I also think the signal detection on/off and signal.
I know this is a very common problem for these amplifiers and has been blamed on the use of cheap Chinese caps used in manufacturing. I would like to go through it and replace them myself in order to learn something instead of just sending it out for service. Plus I figure Inwill save a bundle.
I have done some soldiering before on through hole boards (which this is) to install sockets for OpAmp rolling in a DAC, etc. I have a Weller solider station, some lead free solider one of those “sucker” things to pull solider off the board and some solider wicking tape.
I realize the biggest issue for me will be not shocking the cap out of myself when doing this so I have been looking for a spark pen to drain the charge of the existing caps. Beyond removing the old ones noting polarity and replacing them with the same rated caps from a good brand (Panasonic, Vishay, etc) is there anything eles I should be aware of? When I go parrt picking at Mouser, I see a million choices for caps. Are there features I want to look for like %variance? Vibration resistance (boards are in the sealed sub enclosure), etc.? Should the caps be replaced in pairs? Are only the electrolytic caps the ones I need to be concerned with? Only the failed or all?
Am I foolish to take this on as a first project?
If anyone else has experience with the amps, that would be a great help as well. I’d love to stumble across a parts list and the caps that need replacing ID’d.
Thanks all.
I have come into a Sunfire True Subwoofer Signature that is in need of servicing. This is a Bob Carver design and uses a high current amplifier based on a tracking down converter instead of a beefy power supply.
I opened it up and found the switches for volume, crossover and phase were dirty but some deoxIT took care of that. I have found several electrolytic capacitors are bad, bulging or even a little leakage on the power supply and I also think the signal detection on/off and signal.
I know this is a very common problem for these amplifiers and has been blamed on the use of cheap Chinese caps used in manufacturing. I would like to go through it and replace them myself in order to learn something instead of just sending it out for service. Plus I figure Inwill save a bundle.
I have done some soldiering before on through hole boards (which this is) to install sockets for OpAmp rolling in a DAC, etc. I have a Weller solider station, some lead free solider one of those “sucker” things to pull solider off the board and some solider wicking tape.
I realize the biggest issue for me will be not shocking the cap out of myself when doing this so I have been looking for a spark pen to drain the charge of the existing caps. Beyond removing the old ones noting polarity and replacing them with the same rated caps from a good brand (Panasonic, Vishay, etc) is there anything eles I should be aware of? When I go parrt picking at Mouser, I see a million choices for caps. Are there features I want to look for like %variance? Vibration resistance (boards are in the sealed sub enclosure), etc.? Should the caps be replaced in pairs? Are only the electrolytic caps the ones I need to be concerned with? Only the failed or all?
Am I foolish to take this on as a first project?
If anyone else has experience with the amps, that would be a great help as well. I’d love to stumble across a parts list and the caps that need replacing ID’d.
Thanks all.
You can discharge large capacitors with a 1k resistor across the terminals.
High ripple current and 105C capacitors are better for power amplifiers.
All the electrolytics should be replaced, but film capacitors should not normally
need replacement. Check for burned/out of tolerance resistors also.
Newer caps are more volumetrically efficient so you may find caps with matching value and voltage are smaller than the originals. It doesn't hurt to use higher V caps to get the sizes you want.
As suggested, 105C caps will last longer than 85C ones.
Other than that, use reputable brands: Vishay, Nichicon, BHC, Kemet, Panasonic, Rubycon, Epcos, to name a few. There are some good "audiophile" caps, like Mundorf, but they are 2 or 3 times the price and may not make a significant difference.
I am not familiar with the Carver design; try to establish whether any pairs of caps need to be closely matched in value. Typical electrolytics are only 20% accurate.
As suggested, 105C caps will last longer than 85C ones.
Other than that, use reputable brands: Vishay, Nichicon, BHC, Kemet, Panasonic, Rubycon, Epcos, to name a few. There are some good "audiophile" caps, like Mundorf, but they are 2 or 3 times the price and may not make a significant difference.
I am not familiar with the Carver design; try to establish whether any pairs of caps need to be closely matched in value. Typical electrolytics are only 20% accurate.
All great advice here, thanks! I continue to scour the interwebs for more info on this amplifier and have had a little luck. I have also read overwhelming that the amplifier is of an innovative but poor design that will overstress it’s parts and likely fail in another 6-10 years. Oh well, the fun is in the process.
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