Center channel sounds okay, but all other channels have super loud buzzing/popping noises and high-pitch squeeze that come from them.
Channels make this noise only when the input is connected.
And the volume of the noise is dependent on the volume of the input.
Any one know what this could be?
Guess it's DC at the outputs eh?
Channels make this noise only when the input is connected.
And the volume of the noise is dependent on the volume of the input.
Any one know what this could be?
Guess it's DC at the outputs eh?
Last edited:
No. DC wouldnt depend on volume and would blow the speaker fuses.
This sounds like a ground loop of some kind
This sounds like a ground loop of some kind
I seem to have exactly this guy's problem:
Rotel RMB-1075 noise issue ? Polk Audio
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Rotel RMB-1075 noise issue
jflail2jflail2 Posts: 2,658
April 2016 in Electronics
Hey guys:
A buddy of mine has a Rotel RMB-1075 that he picked up for cheap. Apparently it was cheap for a reason, as when we plug in source cables, there is an instant, very extremely loud noise, like 100+dB static hum combined. If we unplug RCA cables = no noise.
Another friend suggested an AC input filter cap(s) may be bad, so I'm curious if anyone knows how we could go about testing that, and if bad, how difficult it is to replace.
The unit has no ground built into it - Polarized AC input.
Any input would be appreciated.
Thanks!
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Comments
SCompRacerSCompRacer Posts: 6,309
April 2016 edited April 2016
I'd look at the RCA blocks ground into the circuit boards. I have a RB 985MKII which has a similar RCA input scheme. RCA blocks held to rear panel with screw, circuit boards attached to right and left side panel heat sinks. When it was shipped to me, the package was mishandled and chassis must have twisted, breaking a ground pin on one of the outer RCA blocks.
Rather than search for an RCA block, I soldered a ground wire from board to RCA ground.
An example of a board mounted RCA block.
-------------------------------------------------
Rotel RMB-1075 noise issue ? Polk Audio
-------------------------------------------
Rotel RMB-1075 noise issue
jflail2jflail2 Posts: 2,658
April 2016 in Electronics
Hey guys:
A buddy of mine has a Rotel RMB-1075 that he picked up for cheap. Apparently it was cheap for a reason, as when we plug in source cables, there is an instant, very extremely loud noise, like 100+dB static hum combined. If we unplug RCA cables = no noise.
Another friend suggested an AC input filter cap(s) may be bad, so I'm curious if anyone knows how we could go about testing that, and if bad, how difficult it is to replace.
The unit has no ground built into it - Polarized AC input.
Any input would be appreciated.
Thanks!
0 0 0 New
Comments
SCompRacerSCompRacer Posts: 6,309
April 2016 edited April 2016
I'd look at the RCA blocks ground into the circuit boards. I have a RB 985MKII which has a similar RCA input scheme. RCA blocks held to rear panel with screw, circuit boards attached to right and left side panel heat sinks. When it was shipped to me, the package was mishandled and chassis must have twisted, breaking a ground pin on one of the outer RCA blocks.
Rather than search for an RCA block, I soldered a ground wire from board to RCA ground.
An example of a board mounted RCA block.
-------------------------------------------------
Ground loop RCA block broken
For future reference of course
If some one helps you fix something you should help some one in return
I've heard that cashiers say that the people that take a penny always take and never give and the people that give always give and never take
Really makes you think
For future reference of course
If some one helps you fix something you should help some one in return
I've heard that cashiers say that the people that take a penny always take and never give and the people that give always give and never take
Really makes you think
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same problem
I have exactly the same problem with my Rotel MK-985 MKII. The buzzing happens only on right surround and right front channels. Other channels work just fine. The buzzing starts as soon as I connect RCA middle pin (not even touching the ground yet).
I measured the bias voltages on all the channels. They were between 3-4 mV. I did not warm up the amplifier as instructed since I don't have proper speakers for load.
The components seem to be ok with visual check. I also checked the diodes D903, D904, D905, D906. They are ok.
I uploaded the service manual if someone finds it useful here.
Could someone identify the AC input filter caps from the schema, please? Should I start by replacing them?
I have exactly the same problem with my Rotel MK-985 MKII. The buzzing happens only on right surround and right front channels. Other channels work just fine. The buzzing starts as soon as I connect RCA middle pin (not even touching the ground yet).
I measured the bias voltages on all the channels. They were between 3-4 mV. I did not warm up the amplifier as instructed since I don't have proper speakers for load.
The components seem to be ok with visual check. I also checked the diodes D903, D904, D905, D906. They are ok.
I uploaded the service manual if someone finds it useful here.
Could someone identify the AC input filter caps from the schema, please? Should I start by replacing them?
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