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 Post subject: M100...another jewel that was fiddled with
PostPosted: Mon Aug 27, 2018 5:54 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 26
So on the heels of getting the M50 working, i opened up the M100 to see what the issues were with this guy.

1. Input Caps...replaced them and one was bad. Replaced the bad one.
2. Resistor mod...done very badly by the PO. I tried to repair but the resistors tested good. I will mark that as good, just horrible looking.
3. Dim green LED...It is dim but it is on. Not really sure what this means but my guess is that something is wrong.

Any suggestions on where to start? the M50 was straightforward enough and had not been touched...this one has been messed with and I dont know where to start troubleshooting. From my testing of the IRFz44 transistors, they seem open.

Thanks again for the help.


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Tue Aug 28, 2018 10:56 am 

Joined: Sat Aug 06, 2011 1:18 am
Posts: 63
pictures of the board?
maybe the amp pulls to many current so you have a voltage drop.
Can you measure how many amps it uses? What is your power source?


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Tue Aug 28, 2018 11:00 am 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 26
pictures of the board? - I will post some tonight...be warned...it's bad.
maybe the amp pulls to many current so you have a voltage drop. - Possible, see below
Can you measure how many amps it uses? What is your power source? I am using a computer power supply which "should" supply 12v 18A. I know it is on the low side, but the amp still should start, right? I didnt even think to measure how many amps it is pulling, ill check that tonight as well.


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Tue Aug 28, 2018 12:43 pm 

Joined: Sat Aug 06, 2011 1:18 am
Posts: 63
12v 18A power supply is ok for testing.
if the amp uses more than 3 amps idle than something is wrong.
is the red LED also lighting up?


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Tue Aug 28, 2018 4:14 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 26
No red light, just an extremely dim green light.


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Tue Aug 28, 2018 5:08 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 26
Draw at idle is 4.7a. Red light turns on then goes off normally during startup.


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Tue Aug 28, 2018 5:32 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 26
Here are some photos. Let me know if they are too crappy.


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Wed Aug 29, 2018 1:44 am 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
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have you checked the voltage on the led yet?



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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Wed Aug 29, 2018 10:42 am 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 26
Yes, it is 1.75V


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Wed Aug 29, 2018 12:10 pm 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
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I am not a pro but that seems low. what voltage are the other leds reading?



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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Thu Aug 30, 2018 9:32 am 

Joined: Sat Aug 06, 2011 1:18 am
Posts: 63
seems like a bad connection somewhere. Maybe a bad via.
this is a difficult one...


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Thu Aug 30, 2018 4:11 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 26
This may sound silly but would the vias for the resistor "mod" that was done, cause this? I can take them out along with the caps to check everything.

Should i/How can i rule out the transistors? I have seen ways to test them but I have no experience with it. The PO said that 4/6 power side transistors were bad but he also said that this board had not been messed with.


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Fri Aug 31, 2018 10:36 am 

Joined: Sat Aug 06, 2011 1:18 am
Posts: 63
I'm not an expert, the experts are stil on holiday I think :(
What I would do:
- take out all the components that are not original ( the 4 white ressitors to start...)
- take out the 4 IRFZ 44 and test them individual when they are out
- take out the 6 PSU caps
- take out other components that are looking not good
- when they are removed, remove all the solder with desolder braid or desolder pump
- check that you have connection between both sides of the PCB (when the via is pulled out you have no connection)
- if you have a bad via restore them (you can find info on this forum how to do this)

- put the 4 resistors back in
- put back the other components that you have removed, when they are discoloured or burnt replace them with new
- put the 4 IRFZ 44 back in (if you have new FET's in stock, use them)
- put back 1 capacitor
- put back the heatsink on the board (never power up without heatsink)

- power up the amp back up, use a 10 amp fuse
- when it powers up fine you can place the other 5 PSU caps


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Fri Aug 31, 2018 1:08 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 26
Where can I find the irfz transistors?

Whats a solid procedure to test the transistors?

I had to do a few via holes on the m50 so I’m familiar with that process...good call on testing them.


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Fri Aug 31, 2018 2:08 pm 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
Posts: 14383
https://www.youtube.com/watch?v=b0jCUsenNsY



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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Fri Aug 31, 2018 5:27 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 26
The guy in that video says his method will not work with fets...I have not found a swell video yet.


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Fri Aug 31, 2018 6:28 pm 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
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https://www.youtube.com/watch?v=RkWy1EirEu8



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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Sat Sep 01, 2018 11:34 pm 

Joined: Sat Aug 06, 2011 1:18 am
Posts: 63
you can buy them here:
https://www.digikey.com/products/en?keywords=IRFZ44ZPBF


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 Post subject: Re: M100...another jewel that was fiddled with
PostPosted: Fri Oct 12, 2018 9:08 pm 

Joined: Mon Jun 11, 2018 10:13 am
Posts: 26
Replaced the 4 irfz44 and she is back in action!!! Thanks guys!!!!!


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