M50 Shutting Off and with No Protect

[wesleyb420]

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!

[lilviper]

Id recap it before it sets itself on fire.

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

[wesleyb420]

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?

[wesleyb420]

Pics below


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


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


https://imgur.com/boNhL26

[Silverhorse]

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...

[Silverhorse]

you also need to change the rail caps...

[wesleyb420]

I took the screws out...should I replace the caps?

[ttocs]

caps def need to go.......

[wesleyb420]

Are we speaking about the rail caps? The other ones will be here tomorrow.

[wesleyb420]

Does the shrink wrap on the rail caps indicate something? Got hot and slid down?

[ttocs]

means the caps are bad.

[wesleyb420]

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.

[lilviper]

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...

Sent from my SM-G960U using Tapatalk

[ttocs]

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

[Silverhorse]

take a look at this link:

http://www.phoenixphorum.com/viewtopic.php?f=6&t=11910

[wesleyb420]

take a look at this link:

http://www.phoenixphorum.com/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.

[Silverhorse]

it's a two-layer board

[wesleyb420]

Thank you, everyone, for the assist...everything works!!!