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Onkyo m-506RS runs hot

Houas07tc

Houas07tc

Well-Known Member
I just got me a good condition Onkyo M-506RS amp this morning. Run it for 30 minutes and check DC offset and L side is 3.7mv, R side .2mv. Units was hot. Let it sit and tried it again. Same thing. Switch over to by DBX BX-3 and ran it for 30 minutes and it's barely warm. Is it normal for Onkyo or is there something wrong. Any help is appreciated.
 
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I've had my M-506RS since I bought it new in 1985. I've pushed it may times over the years and recently, and it has never ran hot. I'm not sure what's going on in your case, but it seems something may be a little off. Good luck with the amp.
 
Follow the procedure in the service manual and check the bias, too high and it will run hot.

Flip the amp over and pull the bottom cover off. Inspect the outermost output transistor on each side. There will be a diode package with the body of the diode glued to the center leg of the output transistor. This diode is part of the bias circuit and in essence "reads" the temp of the transistor. If it's not attached any longer the bias will run quite high as the amp heats up. If the diodes are properly attached try adjusting the bias per the manual, but you may have a fault or component that's out of spec thats causing the issue.

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I have a M-504 that runs quite warm. I wouldn't say hot, but the temperature gets high as it pushes speakers for a while. How hot is "hot" in your case? My bx-3 do not run as hot as the Onkyo...if that means anything in this case.

I guess another important question to ask is what speakers are you pushing with the amp at what load?
 
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gogofast said:
I have a M-504 that runs quite warm. I wouldn't say hot, but the temperature gets high as it pushes speakers for a while. How hot is "hot" in your case? My bx-3 do not run as hot as the Onkyo...if that means anything in this case.

I guess another important question to ask is what speakers are you pushing with the amp at what load?
Click to expand...

Half way through an album and it is very warm. Don't want to go on any further. The DBX BX-3, I can listen to for hours and only slightly warm.
 
Theremust be a typo on the maual becuase it says board NAMA-1781. I don't have that board instead I have NCMA-1780. The resistors are correctly lable.
 
Idle current set. I think it is the warm air that is heating up the vents. I ran it without the cover and it seems fine. After replacing cover, the vents get hot. I also made sure the diodes are glue to the middle pin of transistors.
 
No change. Still getting hot. Inspect the board and can see there is heat stress where 2sc1626 is. D511, D411, D507, D407, R481, and R581 are next to 2sc1626. When I was setting idle current the procedure said to adjust fully clockwise semi-fix resistor R433 and R533, but they are not adjustable. This is confusing since all the boards in the manual does not match the actual boards in the amp. Unit hasn't shut off or go into protection mode yet since I turn it off when it gets hot. The hot area in int the middle area of the fins, but not the outside area. How do I measure the transistors? De-solder it or leave in.
 
Don't know if this is cause of running hot, but i can sure feel a lot of heat from this area within 5 ti 10 minutes of operation vs other area.
 

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