Help identity blown part in Alesis Mixer PS

[Carm99]

Alesis Multimix 16 firewire
Small capaciter is blown and I dont know the size to get, as I can't get the Service Manual Online.
Just asking if anyone has the manual or knows what size it might be .
Heres a photo
Its on the leg of a 7815 Voltage Regulator.


Thanks.

[R_J]

Re: Help identity blown part in Alesis Mixer PS

It's likely a .33µf, if on the input or .1µf if on the output

[Carm99]

Re: Help identity blown part in Alesis Mixer PS

Thanks Man.
I'll check...
Its between the middle leg ,Ground ,and the Input ,from a 2200uf 35 volt cap.
There was a big flame when it blew.
Do you think the cap might have been bad to cause it to happen.?
Cheers.

[stj]

Re: Help identity blown part in Alesis Mixer PS

ceramic caps randomly fail, and go short circuit.
surfacemount ones can also fail from flexing - like if the board is dropped or bent.

where in London are you??

[Carm99]

Re: Help identity blown part in Alesis Mixer PS

I replaced 7815 and 7915 prior to it blowing as they were bad.
I thought that was it. It worked ok but no output on the master as if the channels outputs weren't getting sent or not being recieved.
Im a novice really but if i can test individual parts that are bad I can change em out.
Im repairing it to sell. Its in bits at the moment.Im cleaning it up a bit.
Im in NW London.

[R_J]

Re: Help identity blown part in Alesis Mixer PS

The cap value in this case is not that critical, It is mainly there to prevent high frequency noise and prevent the ic itself from self oscillating.
If you don't want to order one, or don't have a cap meter to check values, check scrap boards and find one that is close to the size of the old one and it should work just fine.

[Carm99]

Re: Help identity blown part in Alesis Mixer PS

Ive got a meter but the cap is blown so cant be measured.
I was thinking it might be the same as the other one on the 7915.

[R_J]

Re: Help identity blown part in Alesis Mixer PS

PC20 & PC30 should be the same value (input to ic)

[sam_sam_sam]

Re: Help identity blown part in Alesis Mixer PS

Can you please post a photo of the front of board

[Carm99]

Re: Help identity blown part in Alesis Mixer PS

[sam_sam_sam]

Re: Help identity blown part in Alesis Mixer PS

This should fairly easy to fix as far as I can see from what I can see from the the photo that you have provided

I would check all the surface mount caps for shorts and check all of diodes for open or for shorts

I would also check all other caps for there ESR value if you have that type meter you can also check the surface mount caps as well

What are the parts number that are NOT LM7815 or LM2575
there is another part that starts with LM25–>something

What is the part number of PQ1

I hope this will help

[Carm99]

Re: Help identity blown part in Alesis Mixer PS

There are 2 LM2575's.
The PQ1 is BD239C.

[sam_sam_sam]

Re: Help identity blown part in Alesis Mixer PS

Please post your results of what you find wrong with this power supply

[R_J]

Re: Help identity blown part in Alesis Mixer PS

Are you still having problems with the mixer after repairiing the power supply? or are you still missing voltages?
It looks like they are just using .1µf caps on both the input and outputs of the regulators

[Carm99]

Re: Help identity blown part in Alesis Mixer PS

The 2200 big cap on the board is testing 0.00Ω esr.

[R_J]

Re: Help identity blown part in Alesis Mixer PS

Are you saying the 2200µf is shorted? are you checking the esr out of circuit?

[Carm99]

Re: Help identity blown part in Alesis Mixer PS

I used a MK-328 to test it and thats what it said i even reversed the leads and tested it the other way.Same thing

[Carm99]

Re: Help identity blown part in Alesis Mixer PS

Yeah.Out of circuit.

[R_J]

Re: Help identity blown part in Alesis Mixer PS

Is the power supply working or not? As long as the cap is not shorted (check it with your multimeter (ohms) I suspect it is ok

[Carm99]

Re: Help identity blown part in Alesis Mixer PS

Nope.No Resistance on the multimeter.