Hello people

Anything at least distantly related to MegaDrum

Re: Hello people

Postby Goldie » Fri Nov 16, 2007 7:20 pm

Better picture posted (old removed)
Last edited by Goldie on Sat Nov 17, 2007 1:06 am, edited 1 time in total.
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Re: Hello people

Postby baguette » Fri Nov 16, 2007 8:12 pm

Goldie wrote:
This is best, unfortunately component side is not so good. I'll try another one

that would be good, because bottom side without component side does not give a lot ;)
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Re: Hello people

Postby Goldie » Fri Nov 16, 2007 10:26 pm

Better picture posted (old deleted)
Last edited by Goldie on Sat Nov 17, 2007 1:08 am, edited 1 time in total.
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Re: Hello people

Postby Goldie » Fri Nov 16, 2007 10:50 pm

alesisd4-1.jpg


Ok i managed to make better one. Anyway nice feature beeing able to upload pictures directly to server.
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Re: Hello people

Postby Goldie » Fri Nov 16, 2007 11:23 pm

alesisd4-2.jpg


And here is new bottom one.
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how to debug some alesis gear...

Postby baguette » Sat Nov 17, 2007 1:11 am

Ok, so let's start with the power supply - the new pictures are really better but unfortunately missing the important part :)
I hope the images work...

The power regulation part is in the lower left corner of the component side (old pics).
You could check if the capacitors leak or look somewhat stoned - however i doubt that because in this case the sound would most propably be with a buzz like a ground loop, and not 10 min delayed.
The caps are these:

Image

The next thing to check are the voltage regulators:
Image

they should have a number like 7805 , 05 being the output voltage.
The pinout is usually input - ground - output, from left to right (seen from the front, the pins downwards).

1. Start with the upper one: check immediatly after plugging the voltage between in vs ground and out vs ground.
BE CAREFUL not to shortcut the pins, otherwise you are almost sure to burn a fuse inside the power supply unit! (or damage it otherwise)
Consider not to touch their pins directly but just follow the copper leads on the board to more distant areas.

2.repeat the mesurements once the board has auto-circuit-bent (ACB) :)


Now there are 3 cases:

1-input voltage is about the 11 volt you measured at the supply unit, output voltage is as expected (^= conforming the part number) BOTH before and after ACB
-> no problem at power supply

2-input voltage is always the 11 volt, output voltage drops after ACB
-> change the voltage regulator

3-input voltage is the 11 volt before ACB but drops after ACB, output voltage drops too
-> check the diodes that are before the regulators!



the diodes are these:

Image

you can check the voltage between the both ends of the diodes (after ACB). It should be less than 1V. However i doubt that they would take more than an hour to "recreate", and it would be a strange diode defect however.
If the diodes are ok and you were in case 3 above, it means that the supply unit has a problem - its voltage goes down after ACB.
Inside the unit there will be 4 diodes (or one component that comprises them). We will check it if this is the case.
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Re: Hello people

Postby Goldie » Sat Nov 17, 2007 1:21 am

Thanks man.

I see what is missing, and i am gonna scan it now. Yes you heard me , scan :D . Real DIY spirit. I see you are concentrated around power . I dont know very much about electronics, just thought it would be easy to pinpoint because of nature of failure. As i said before same thing happened to Alesis HR16, maybe Alesis decease.
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Re: Hello people

Postby Goldie » Sat Nov 17, 2007 1:28 am

alesisd4-3.jpg


Missing part.
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Re: Hello people

Postby Goldie » Sat Nov 17, 2007 4:44 am

7805 (Positive Output Voltage Regulator) = Input, ground, output
7905 (Negative Output Voltage Regulator) = Ground, input, output

I dont get any reading using pin shematic on 7905, so i use same as 7805

Power on :
7805 - 24,5v - 10,3v
7905 - 28,8v - 17,6v

I waited 4 hours for crash, and it didnt :D . I'll try again tommorow.
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Re: Hello people

Postby baguette » Sat Nov 17, 2007 12:01 pm

Goldie wrote:I dont get any reading using pin shematic on 7905, so i use same as 7805

what do you mean?

Power on :
7805 - 24,5v - 10,3v
7905 - 28,8v - 17,6v

where did you measure these?
can you measure the power supply unit voltage in AC mode of your mulitmeter?

I waited 4 hours for crash, and it didnt :D . I'll try again tommorow.

propably it does not overheat anymore because the heat dissipates better without the case.
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