WHAT IS THIS WRAP ON THESE MARANTZ TRANSISTORS ?

boatdrinks77

Well-Known Member
I have been fighting this damned Marantz 300DC amp for a while. The right channel cuts out when it gets hot. I THINK it is one of these two transistors wrapped together Q707/708......



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What is the wrapping on them ? Does the wrapping help dissipate heat ? Or is it just heat shrink ? Where do I get new stuff when i cut this off ? I have plenty of heat shrink....

ALSO, does anyone have a copy of the service manual. The one on HiFiEngine has the page cut off on the parts list of the amp board......UGH

Thanks in advance, Dan :music:
 
It's just heat shrink. It's used there so these two transistors stay at the same temperature. Usually it is used for the differential pair so that the DC offset is stable as the temperatures inside the amp rise and fall.
And no it does not help dissipate heat, rather the opposite...
 
It's just heat shrink. It's used there so these two transistors stay at the same temperature. Usually it is used for the differential pair so that the DC offset is stable as the temperatures inside the amp rise and fall.
And no it does not help dissipate heat, rather the opposite...


Thanks Bert 1100. On the left Channel board the heat shrink is cut flush at the top of the transistors and I can see the two transistors have heat sink paste sandwiched between them.
 
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