Line 6 MM4

[Jazz P Bass]

Had a Line 6 MM4 come in.
Would not power on.

Checked all of the voltages, which where good.
3.3Vdc came up when a cord was inserted into the input jack.
Pressing any key did nothing.
Tried a master reset at power On (Hold A and D keys down, power On)
Nothing doing.
Scoped the crystal. Oscillating fine.
OK. Now what.

I used a 10X magiifier a looked at the main microcontroller.
Some of the solder pads looked iffy at best.
So I hit it with my Weller 750 degree heat gun and then popped it in the freezer for 10 minutes.

Lo and behold!
It works.

Thought I would pass this on.)

Here is a voltage measurement schematic.
And a brief of how the power supply functions from a gentleman in Scandinavia.

[g1]

Is the freezer part some trick or just so you can handle it?

[Jazz P Bass]

More than anything, I wanted to make sure the core of the ic was cooled down.

[Jazz P Bass]

Well, after 3 hours running , it locked up.

Pulled the Eprom out & gave the pins a quick wipe with DeOxit.

Now it's working again.

Stay tuned.