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Yamaha CR-1000 buzz and occasional popping

sssboa

sssboa

Super Member
Hi

I just noticed that I have background buzzing on my CR-1000, the same level irrespective of how far I turn the volume knob, it doesn't change whatever I do, I can't hear it when the volume is up to some point, not very disturbiing thing but I don't think I had it before. It is present on all sources. Nothing changes when I use any tone switches or sliders.
Besides I also have single pops in speakers (sounding like electrical discharge), quite occasional, about 1 pop per 5 minutes or so, also I didn't have it before.
I would appreciate any ideas.
Thank you,
Andy
 
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Thank you for interest.
Yes, both channels exactly the same if we speak about buzzing. To be honest I noticed it today so still must test a bit, maybe there is a banal cause in my system.

As the occasional popping, I noticed it weeks ago. I was checking cables for the cause.
The popping, to clear this up, it is not deep bassy pop like with switching off an amp, it is high pitch pop like static on radio or a pop from a scratch on a vinyl record, and rare like 1 pop per 5 minutes.
 
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Seperate the pre-amp from the maim amp with the coupler switch and have a listen.
 
OK. So first of all, we may forget buzzing, it's gone, something from source probably.
But the popping is real.
So I connected the preamp of a non-popping CA-1010 to the power amp of the popping CR-1000 and so far I have no popping as the result and really beautiful sound. I will keep testing for some time to be 100% sure.
What does it say if it stays like this? Well, obviously that the preamp of CR-1000 causes the pop. Could it be the sliders/switches that are all over the CR-1000?
 
Have a look see at the pass transistors solder connections in the regulated power supply for the EQ amp(pre-amp).
 
Yeah. It's single pops so I am not sure if every pop is heard in both but definetly I heard the popping in either channel.
The receiver was fully recapped half a year ago and cleaned in a specialized repair shop.
 
The background low-level buzzing could be caused by the mic board. It's possible the slider doesn't fully turn it off. You can easily remove the mic board to test that theory.
 
Though the popping still persists. After the receiver is switched on I have 2 or 3 in a space of 10 minutes or so then it's clear for hours or 1 pop per hour or so.
I have the pops both on speakers and headphones. Thank you for your help!
 
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powersupply.jpg
Is it the power supply we are talking about?
powersupply2.jpg
When I tap on this thingy :) with the radiator in the south east corner on the board (I suppose it's a transistor) I have identical pop or pop + crackle (and yes it's popping and sometimes crackling now after the pop). But maybe it's normal that a transistor like this crackles when tapped (I tapped on the radiator). The next to it identical transistor also pops a bit when tapped but much less. Another pair in the opossite corner of the board does not make any noise when tapped.
 
Check your solder connections under that corner of the board.
 
Yes those are transistors, and they run pretty hot. Everything with a heatsink (radiator!) could probably use a touch up.
 
OK. So I found the transistor with the heatsink in the corner of the board gets extremely hot, as hot as it gets, similarly the small transistor nearby (in front of the big one in the picture and without a heatsink). They both produce pop and crackle when lightly tapped, also just after switching on when not hot yet. The soldering looks good to my eye though the big one was probably resoldered in the past. The next transistor with a heatsink to the left from the ones in the pictures gets only warm/slightly hot. It produces a pop sometimes when tapped but less and must be heavier tapped. The other transistors with heatsinks on the left upper corner get only tepid and don't make any noises when tapped. transistor1.jpg transistor2.jpg transistor3.jpg transistor4.jpg
 
Is it possible to replace the transistors with something new? Below is the one that gets just slightly hot, but also a suspect.
transistor5.jpg
 
Ohm out the copper traces around those pass transistors. Especially the resoldered ones. You have a bad connection somewhere on that board.
 
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