I am trying to replace the output capacitors in my KEF 30b subwoofer amplifier. I cannot get to the under side of the capacitors as the circuit board is connected to two transistors that seem to be stuck to the heat sink? Any ideas on how to unstick these?
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Put a few drops of iso alcohol, will reduce the adhesion of dried heat sink compound.
Then a tap with a strong knife, or aluminum / wood block to chisel made of power hacksaw blade, at the edge of the transistors to pry them loose.
Those blades are 400 x 25 x 1.6 mm, I get broken / old ones from a friend.
Quite suitable for this type of work, you can spread out the force.
Less chance of device damage.
Then a tap with a strong knife, or aluminum / wood block to chisel made of power hacksaw blade, at the edge of the transistors to pry them loose.
Those blades are 400 x 25 x 1.6 mm, I get broken / old ones from a friend.
Quite suitable for this type of work, you can spread out the force.
Less chance of device damage.
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Thank you for the suggestions I will try tomorrow. What is strange is that the material that you can see behind them is loose??
Sheet material is loose with respect to heatsink or loose re the transistors? Both?
Try carefully starting board removal. Do you see stress appearing at the transistor leads? Maybe that will provide insight.
Try carefully starting board removal. Do you see stress appearing at the transistor leads? Maybe that will provide insight.
I don't think you need to stick them back on as long as you have good thermal contact (and electrical insulation) between the transistors and the panel. Most likely they just became stuck over time.
Put new heat sink compound before fitting.
Or silicone rubber pads.
To take up gap between transistor and heat sink.
Or silicone rubber pads.
To take up gap between transistor and heat sink.
The reason they were stuck in the first place is because they did a good job of properly applying heat sink compound. Properly done, the surface tension is strong and it’s a bitch to get apart - even with fresh compound. Youre not supposed to use a lot of it - it’s a mistake many builders make.
Thermal compound (aka thermal grease). Wakefield 120 or 126 is what I use.
Exactly. You're only supposed to fill the voids between the transistor package and the heat sink.
Tom
'Thin film' is the right amount.
Some computer CPU thermal compounds are adhesive, they come in a syringe, be aware about that.
They are difficult to remove.
Some computer CPU thermal compounds are adhesive, they come in a syringe, be aware about that.
They are difficult to remove.
I ordered this, is it okay?
HEATSINK PASTE for Transistors, Diodes, CPU`s etc. - White - 25 g compound injection type https://amzn.eu/d/jgZWysv
HEATSINK PASTE for Transistors, Diodes, CPU`s etc. - White - 25 g compound injection type https://amzn.eu/d/jgZWysv