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benwake 24th January 2012 09:19 AM

Audison Millenium Power 4 protect mode
Hi all,

I have an Audison Millenium Power 4 amp which is going into protect mode.
In the beginning, it were 2 output transistors which have failed. I replaced them, worked for 30 minutes, and is again in protect mode now.

I have (again) a failed output transistor (one of the 2 I replaced).

I have two solutions now:
- Repair the amp and make sure it will work
- Exclude the part that is broken, and use half of the amplifier (I only have to use it for the woofer).

My question is:
How can I repair it permanently so the output transistors won't fail again?
If no repair possible, how can I exclude the part that is broken?

A couple of pictures:
How to repair an amplifier in safe mode | Benwake (my first repair) (2 transistors I've replaced) (the result now)

Thanks in advance for your help.


Perry Babin 24th January 2012 10:56 AM

Were the replacement transistors the exact same part number as the originals?

Were they purchased from a reputable seller?

Did you notice how much current the amp was drawing at idle after the amp was repaired?

Did you readjust the bias after repairing the amp?

Did you remove the old heatsink compound and replace it with new compound before reassembling the amp?

benwake 24th January 2012 12:03 PM

Thanks for the quick reply, these are the answers:

- The exact same partnumber (if 2N6488 and 2N6491 is what you mean)
- Purchased in the most known seller in Belgium
- No, but if you tell me how, I will certainly check it
- No, because the bias potentiometer had the same resistance as the other 3. If it has to be done, guide me and I will at next repair. I didn't knew it.
- Yes, I cleaned everything and putted new thermal paste (with the mica plate)

Again, thanks for helping me out, I really appreciate it :)

Perry Babin 24th January 2012 02:25 PM

What are you using to power the amp when testing?

benwake 24th January 2012 02:50 PM

I don't have a testbench or something, so I always use my car.
Is it worth to buy the 5 transistors? Or is there a chance he will fail again?

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