My Acurus A150 which I’ve had and used without any issues for more than 20 years with the Acurus surround processor preamp and another 3 channel Acurus amp suddenly began producing a loud buzzing in the speakers. It happened last night when watching something that went from fairly low volume to high volume. The buzzing is LOUD. Even with the lines in from the preamp removed the buzzing continues. It’s not the low hum you might expect from a ground loop issue. I’ve swapped speakers to make sure I hadn’t blown the pair. The buzzing is still there. Before I take the system apart and do a rebuild I figured I’d ask if anybody has seen this issue or something similar on an Acurus amp or others.
If it’s happening in both speakers I would suspect something has gone in the power supply. Acurus uses really good caps in there products but as much as you have used the amp the main power supply caps could be failing.
The first thing I would check would be the main power supply caps.
After that the bridge rectifier.
The first thing I would check would be the main power supply caps.
After that the bridge rectifier.
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Thanks a ton for the quick response! Anybody have a schematic or a link to one for the A150? Anything that would have ohms info to do some testing?
Any recs on what power supply caps to use as replacements?
Any recs on what power supply caps to use as replacements?
Halo, I’m the owner of A250 that I modded quite heavily. Much of the info I got from this thread:
Acurus A250 and starground | Audiokarma Home Audio Stereo Discussion Forums
Try to ask there as there are some Acurus experts there.
Cheers
Acurus A250 and starground | Audiokarma Home Audio Stereo Discussion Forums
Try to ask there as there are some Acurus experts there.
Cheers
I just ordered United Cemicon caps from Digikey. The pricing is not that bad. Get your capacitance value and working voltage and I can help. I will look for a schematic for your amp. I think I have the 3 channel version.
Thanks for the responses! Here's an update as to where I am.
I have a "spare" 3x100 Acurus amplifier that I was not using. The bridge and capacitors matched up with what was in the A150. I swamped out the bridges but still had the speaker buzzing. So I returned the bridges to their correct boxes.
I then removed the caps from the A150 and ohms tested them with a multimeter. ZERO reading on either of them. I removed the caps from the 3x100 and tested them. These caps were good as the values consistently ticked up the longer the multimeter leads were in contact with the cap. The caps from the A150 were the same as the 3x100 (the Cornell Dubilier model numbers were identical). So, I decided to install the working caps in the A150. I was very careful to reconnect everything identically to their starting positions.
Once the caps were installed in the A150, I connected the power cord and the speaker wires. When I turned it on, I got a slight electrical smell. Not seeing the telltale flickering light on the power switch, I feared a fuse blew. Sure enough, the rear fuse had blown.
I'm not sure what I did wrong. So a few questions for the group. First, above the fuse in the back is a connector. I can't recall if I removed that and reinserted it a few days ago when first probing the problem. I plan to compare its position to the one in the 3x100 (which I just thought of), but wonder if anybody knows exactly how it's supposed to be positioned in the unit.
Before I put another fuse in and fire it up again, I'd love to hear what the issue might be.
Thanks!
I have a "spare" 3x100 Acurus amplifier that I was not using. The bridge and capacitors matched up with what was in the A150. I swamped out the bridges but still had the speaker buzzing. So I returned the bridges to their correct boxes.
I then removed the caps from the A150 and ohms tested them with a multimeter. ZERO reading on either of them. I removed the caps from the 3x100 and tested them. These caps were good as the values consistently ticked up the longer the multimeter leads were in contact with the cap. The caps from the A150 were the same as the 3x100 (the Cornell Dubilier model numbers were identical). So, I decided to install the working caps in the A150. I was very careful to reconnect everything identically to their starting positions.
Once the caps were installed in the A150, I connected the power cord and the speaker wires. When I turned it on, I got a slight electrical smell. Not seeing the telltale flickering light on the power switch, I feared a fuse blew. Sure enough, the rear fuse had blown.
I'm not sure what I did wrong. So a few questions for the group. First, above the fuse in the back is a connector. I can't recall if I removed that and reinserted it a few days ago when first probing the problem. I plan to compare its position to the one in the 3x100 (which I just thought of), but wonder if anybody knows exactly how it's supposed to be positioned in the unit.
Before I put another fuse in and fire it up again, I'd love to hear what the issue might be.
Thanks!
Maybe something was making contact that should not have been with the replacement caps? I also noticed that the caps leads were not at 12 and 6 perfectly. I'm guessing when I tightened the set screw on at least one cap the cap shifted. Will realign the caps, and then tighten the cage around the cap a bit more before tightening the set screws.
What else can I do? Even though the caps had the identical model number on them, might they be different somehow?
What else can I do? Even though the caps had the identical model number on them, might they be different somehow?
Noob error. After staring at before and after photos I figured it out. I relied on the company stamp on the caps to line them up, but they weren't in series when I did that. Put them both on the multimeter. They both still work thankfully. So - rotated one to line up +/- properly. Have to wait for a fuse to arrive from Amaz to start it back up. 3x100 are 8amp fuses not 6amp. SO have no extra fuses to throw in.
Thanks again for the help. Will update when I test.
Thanks again for the help. Will update when I test.