Hi I picked up an old technics sa-eh760, the amplifier is warm on the top and sides which I think is just fine, but ont the bottom in the corner it's red hot, I took the cover off and tge hot area is being caused by a component I'm not sure what it is or if it's supposed to get really hot, it's pcb with 3 transistors and a heatsink/clamp holding the transistors to the bottom case/chassis. The fact it's got a clamp holding it to the body says its supposed to get hot, but how hot?
It heats up even if there's no music playing, and cools very fast when turned off, I'm guessing it's some kind of voltage regulator?
Any help would be great thanks Ben
It heats up even if there's no music playing, and cools very fast when turned off, I'm guessing it's some kind of voltage regulator?
Any help would be great thanks Ben
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Those are transistors, the D and B is actually prefixed by '2S' so they are 2SD2734 and 2SB1548.
They could well be used as voltage regulators. If you can hold a finger on it (when its on the heatsink... never ever run with it free) for 5 secs without burning yourself then its OK as far as the devices go. The fact that the PCB material looks non-discoloured also suggests they are probably not as hot as you might think.
They could well be used as voltage regulators. If you can hold a finger on it (when its on the heatsink... never ever run with it free) for 5 secs without burning yourself then its OK as far as the devices go. The fact that the PCB material looks non-discoloured also suggests they are probably not as hot as you might think.
It looks like one 2SD2374 is missing, and the board could even be a small dual amplifier as it has two pairs of these medium power transistors. The SA-EH760 has many outputs for mids/woofers/centre/surround speakers, this may just be two of the amplifiers, or at least the output stages..
Check all solder joints on that board - particularly the transistor connections.
Then smear some thermal grease on the back of each transistor and re-attatch it to the chassis.
Those are regulators.
The joints look pretty typical of most such equipment... probably OK but there are possible signs of cracking on quite a few.
Have a look at the last couple of images in post #1 here:
Sony CDP790 and KSS240 Restoration Project
Have a look at the last couple of images in post #1 here:
Sony CDP790 and KSS240 Restoration Project
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Actually having a good zoom in and look about there could be or close to some cracks, not a great image by me there, when I pop it back open to put the paste on, I'll have a good proper look at them, many thanks
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