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help in identifying component

rjenkinsgb

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Most Helpful Member
OK, there is something drastically wrong with the basic power circuit then...

Can you take a few more photos of the circuit board - each side as three or four overlapping parts and try to get the detail sharp enough to read the numbers on the resistors etc?

I'm going to try to draw out part of the circuit to figure out how it should work, if I can see the components clearly enough.
 
ok, i will do it, i really appreciate a lot your help, i will upload the picture tomorrow, today its a little late here in germany, and all the stuff are in the basement, and now its to cold to go there today.
 
pls sorry if i brake some rule but i need to upload many picure
 

Attachments

i hope all this picture work
 

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rjenkinsgb

Well-Known Member
Most Helpful Member
I think that covers it for photo detail!

What voltages do you get on the three square gold pads in a group between the XLR wires and IC? They are test points in the power circuit.
 

rjenkinsgb

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Most Helpful Member
OK; remove the large electrolytic cap from the other side of the board, the same size as the one behind those gold pads but higher up - then re-check the voltages?

There is a short circuit to ground somewhere in that area.
 

rjenkinsgb

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Most Helpful Member
The capacitor is still in place in that photo?
If you have removed it, please take a photo of the topside of the PCB, centred on where it was; there are through VIA holes underneath it.
 

rjenkinsgb

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Most Helpful Member
Sorry, wrong cap - I intended for you to remove the other large one..

Leave that one out as well though, for now.
 

rjenkinsgb

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Most Helpful Member
OK, it looks like the connection from the positive of that cap goes up the topside and out between the other two caps.
It then continues up the edge of the board & under the black stuff, with a branch.

See the yellow arrows on this photo. Check the voltage on that resistor.


However, looking at the earlier photo with voltages marked, I just noticed the one for the IC pin 14, which is the lowest of all. :banghead:
That may mean it is the cap or device next to it, possibly a zener in a three terminal package?

The Y4W marking seems to make it a 15V zener, such as this:

Without connecting to power, check resistance from pin 14 to pin 7 - then remove that Y4W device and check again?
If it's then not shorted, fit a new 15V zener!

If the short is still present it must be the IC or capacitor, from what I can see..


IMG_6924-min.JPG
 
resistance 7 and 14 it's 5.004Mohm that its without taking out any components, can you pls show me wicht component i have to take out
 

rjenkinsgb

Well-Known Member
Most Helpful Member
OK, that's a false lead then... It must be fed via a transistor or diode and there is just not enough voltage present for that to conduct

It does appear to be a short somewhere around the area that had the black coating, as the voltages there are very low, lower than anywhere else that has a power connection.

Can you confirm that the yellow marked trace does connect through to the centre of the group of three gold pads? That's where I think it feeds from, but it's better to confirm it.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Another suggestion - try scrubbing the entire board with a small stiff brush - eg. an old toothbrush - and isopropyl alcohol.
There is a lot of flux residue around some components and I can see fragments of loose solder in some photos.
 

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