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To do this repair, you must have experience in SMT soldering. It's very important because components on the motherboard are very small and 2 components to change out of the 3 are SMT.
1) First, you must open the Jag (and remove the metal cage).
2) Once the Jag is open, search for the capacitor C134 (330uF 16V) just above the U38.
In my Jag, this component was blown.
You must remove this capacitor. Do not replace it before the next instruction : it will be
easier to replace the next component.
3) You can see the U38 (MC34163DW) in the right of the MC68000 and below the C134.
This component is a power switching regulator (9V->5V 3A MAX) and it doesn't like it very much when the polarity is inverted. You can see heat damage on the surface of this component as shown below ( yours might not be bad as mine):
You shall replace it with the same part.
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!!!!!!!!!!!!!!WARNING : BE CARFUL WHEN YOU SOLDER SMTs!!!!!!!!!!!!!!!!!!!!!!
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If you don't find the MC34163DW you can use the MC33163DW, the difference is in the operating temperature range : the MC34163DW = 0 to 70°C and the MC33163DW = -40 to 85°C.
When you have replaced the U38, you can replace the C134.
4) Another component shall be replaced : It is the REG1 (LM78L05ACM) (in the sound circuit).
This component is a DC/DC converter (9V->5V 100mA MAX) and it is used for the audio power.
As the U38, if it is dead, you can see heat damage on the surface as below :
If it is dead, you don't have sound when the Jag works.
You shall replace it with the same part.
Normally, if you replace these components with success, your Jag should work.
All information came from AA user SCPCD with his permission.
