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 Post subject: M50 Shutting Off and with No Protect
PostPosted: Wed Aug 08, 2018 7:26 am 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 22
I bought an M50 the other day that is in pretty good shape cosmetically. The PO said that nothing had been replaced and he didn't want to deal with fixing it. I hooked it up and it turned on fine. The problem comes when I adjust the gain up (past 30%) the amp just turns off. The green light just fades out with no protect light at all. I am going to replace the caps but wanted to see if I need to check anything else. Sorry for the low amount of details but those are the ones I have. Thanks in advance!


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Wed Aug 08, 2018 11:27 am 

Joined: Tue Nov 06, 2012 9:30 pm
Posts: 97
Id recap it before it sets itself on fire.
wesleyb420 wrote:
I bought an M50 the other day that is in pretty good shape cosmetically. The PO said that nothing had been replaced and he didn't want to deal with fixing it. I hooked it up and it turned on fine. The problem comes when I adjust the gain up (past 30%) the amp just turns off. The green light just fades out with no protect light at all. I am going to replace the caps but wanted to see if I need to check anything else. Sorry for the low amount of details but those are the ones I have. Thanks in advance!


Sent from my SM-G960U using Tapatalk


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Wed Aug 08, 2018 6:02 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 22
I clearly stated that the caps are getting replaced. I took the caps off and not a lot of leaky ones (1). What would cause the amp to just cut out?


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Wed Aug 08, 2018 6:41 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 22
Pics below

Image
https://i.imgur.com/2dgOgdv.jpg

Image
https://i.imgur.com/2ef21CN.jpg

Image
https://imgur.com/boNhL26


Last edited by wesleyb420 on Thu Aug 09, 2018 9:53 am, edited 1 time in total.

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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Thu Aug 09, 2018 5:32 am 

Joined: Sat Aug 06, 2011 1:18 am
Posts: 60
Hello
the power supply fets (IRFZ44) and the 2 diode (SF163) are not bolted to the heatsink. If you didn't take out the screws yourself look no further...


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Thu Aug 09, 2018 5:35 am 

Joined: Sat Aug 06, 2011 1:18 am
Posts: 60
you also need to change the rail caps...


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Thu Aug 09, 2018 9:48 am 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 22
I took the screws out...should I replace the caps?


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Thu Aug 09, 2018 12:04 pm 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
Posts: 14380
caps def need to go.......



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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Thu Aug 09, 2018 7:03 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 22
Are we speaking about the rail caps? The other ones will be here tomorrow.


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Thu Aug 09, 2018 7:05 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 22
Does the shrink wrap on the rail caps indicate something? Got hot and slid down?


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Thu Aug 09, 2018 7:21 pm 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
Posts: 14380
means the caps are bad.



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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Fri Aug 10, 2018 8:51 am 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 22
Ok, so one rail cap tested bad. I took them out but I lost a solder pad in the process. From what I can tell, the solder pad does not have a trace on the bottom side. Is that pad just to hold it and the actual trace is on top? Can I just use the superglue method and re-attach it?

thanks for the help on this and please overlook the excess solder...I have not used the solderwick yet, just the sucker.


Attachments:
Amp Macro-1.jpg
Amp Macro-1.jpg [ 184.2 KiB | Viewed 390 times ]
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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Fri Aug 10, 2018 9:42 am 

Joined: Tue Nov 06, 2012 9:30 pm
Posts: 97
If you navigate to the how to section of these forums, there is a very good tutorial on the repair process, and a few posts under the stickys on how to repair the through holes. If i recall correctly pg used a 4 layer board? I could be wrong there. But broken is VIAs generally bad if not repaired...

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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Fri Aug 10, 2018 2:31 pm 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
Posts: 14380
there is a few ways to repair it. Its not hard to lift a via and loose it. I finally got a repair kit to make it easier and better looking but it was not cheap



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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Sat Aug 11, 2018 9:40 am 

Joined: Sat Aug 06, 2011 1:18 am
Posts: 60
take a look at this link:

viewtopic.php?f=6&t=11910


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Sat Aug 11, 2018 11:50 am 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 22
Silverhorse wrote:
take a look at this link:

viewtopic.php?f=6&t=11910


I did end up finding that after scrolling.

Can anyone verify that this is just a two-layer board, not a four-layer that someone mentioned above? I am not seeing any traces between the layers, just on the bottom and top.


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Sun Aug 12, 2018 12:00 pm 

Joined: Sat Aug 06, 2011 1:18 am
Posts: 60
it's a two-layer board


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 Post subject: Re: M50 Shutting Off and with No Protect
PostPosted: Mon Aug 27, 2018 5:45 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 22
Thank you, everyone, for the assist...everything works!!!


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