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Post subject: Mustang 3 ver: 1 Power Amp
Posted: Sun Jun 21, 2015 8:24 am
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Finally couldn't take that buzzing brittle, sitar Fizz any longer.
Took the amp down into my basement workshop and opened it up.
I took the clamp that holds the power amp chip down onto the heat sink so as I could find out what was being used.
Turns out that the 3, and possibly the 4 and 5 all have this same chip. Its a TDA 8950J 2 X 150 watt class D amplifier. For the 3 they only use the right side output. The left hand output is not used.
I was quite shocked to see so many cold solder joints. Very dull, not shiny and the component wire ends loose, barely contacting the solder around them. More in the power amp section than the power supply end of the board.
So I carefully re-soldered the joints that looked poor.
Under the power amp section of the board are two power resistors. The type you see in CRT power sections of TV's. Square and about 1.5 inches long. These are heat sinked to the metal chassis via large amounts of white thermal paste.(Horrible stuff to get on your hands or clothes) They had cold solder joints. So they to were re-soldered and had the thermal paste reapplied.
Blew all the boards off with Dust Remover Spray from RS, replaced the power chip clamp and bench tested.
Buzz/Fizz/Brittle sound Gone!!. Back to the great sounds of before.
Buttoned it up and now its back in my music room (Minus all the dust from 3 years)

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Post subject: Re: Mustang 3 ver: 1 Power Amp
Posted: Sun Jun 21, 2015 8:36 am
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Sorry, wrong forum. How do I erase this?

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Post subject: Re: Mustang 3 ver: 1 Power Amp
Posted: Sun Jun 21, 2015 4:44 pm
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JohnR242 wrote:
Finally couldn't take that buzzing brittle, sitar Fizz any longer.
Took the amp down into my basement workshop and opened it up.
I took the clamp that holds the power amp chip down onto the heat sink so as I could find out what was being used.
Turns out that the 3, and possibly the 4 and 5 all have this same chip. Its a TDA 8950J 2 X 150 watt class D amplifier. For the 3 they only use the right side output. The left hand output is not used.
I was quite shocked to see so many cold solder joints. Very dull, not shiny and the component wire ends loose, barely contacting the solder around them. More in the power amp section than the power supply end of the board.
So I carefully re-soldered the joints that looked poor.
Under the power amp section of the board are two power resistors. The type you see in CRT power sections of TV's. Square and about 1.5 inches long. These are heat sinked to the metal chassis via large amounts of white thermal paste.(Horrible stuff to get on your hands or clothes) They had cold solder joints. So they to were re-soldered and had the thermal paste reapplied.
Blew all the boards off with Dust Remover Spray from RS, replaced the power chip clamp and bench tested.
Buzz/Fizz/Brittle sound Gone!!. Back to the great sounds of before.
Buttoned it up and now its back in my music room (Minus all the dust from 3 years)


I for one am glad this showed up here ... its the type of thing that nerds like to know about '''

'Space


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Post subject: Re: Mustang 3 ver: 1 Power Amp
Posted: Mon Jun 22, 2015 6:28 am
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Yes - most interesting - I'm not having any "fizz" problems but I recall reading posts from others.

Just realized that it may be that I don't have any "fizz" because my Mustang III is a version .2 - just tons on amazing chime and character! :mrgreen:

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Post subject: Re: Mustang 3 ver: 1 Power Amp
Posted: Mon Jun 22, 2015 8:16 am
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You hit the nail on the head Strataholic. The new Mustang 3, 4 and 5 version 2, have an improved Fizz free power amp. I would love to find out what they did to it.

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Post subject: Re: Mustang 3 ver: 1 Power Amp
Posted: Mon Jun 22, 2015 9:19 am
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JohnR242 wrote:
I would love to find out what they did to it.

They probably figured out how to use lead-free solder.


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Post subject: Re: Mustang 3 ver: 1 Power Amp
Posted: Mon Jun 22, 2015 8:28 pm
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ChrisH1 wrote:
JohnR242 wrote:
I would love to find out what they did to it.

They probably figured out how to use lead-free solder.


Right - lead-free solder with unobtainium! :lol:

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