Author Topic: Help reading PCB layout from service manual  (Read 1287 times)

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Offline nixfu

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Help reading PCB layout from service manual
« on: May 20, 2015, 03:34:11 pm »
Ok. I am not a PCB layout pro, so I don't totally follow the masks etc and the way it looks when you print it out on paper.  I assume these are basically just printouts of the gerbers or something from the copper layer maybe.

I am trying to repair this thing, and I had to replace a very small g5v-1 relay, and in the process of unsoldering it, and removing it from the board, I noticed what looks like the top pad, and via was still stuck on the leads of two pins when it came out.

It was the two pins highlighted in yellow.

What I need help with is, do these pins connect to anything on the top, so I need to reconstruct a pad there on the top, when I put the replacement relay in, or can I just solder them on the bottom layer and be ok?

What I am asking I guess is, when looking at a PCB layout like this from a service manual from the manufacturer, do the pins with the white circle totally around them, show small pads on top that are not actually connected to anything? 

That would mean that of these two pins, which are common, only one of them is connected and only on the bottom if I am reading this diagram correctly, so I am ok with not worring about the pads and vias that came off and just making sure I get a good connection soldering the one pad on the bottom.

Any advice is appreciated.

Thanks!


Bonus Q:  Does the filled in vs unfilled arrow on the relay contacts in the diagram, denote which is the off/default state?
« Last Edit: May 20, 2015, 03:37:09 pm by nixfu »
 

Offline AlfBaz

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Re: Help reading PCB layout from service manual
« Reply #1 on: May 20, 2015, 03:46:08 pm »
That would mean that of these two pins, which are common, only one of them is connected and only on the bottom if I am reading this diagram correctly, so I am ok with not worring about the pads and vias that came off and just making sure I get a good connection soldering the one pad on the bottom.
In a word, yes.

Quote
Bonus Q:  Does the filled in vs unfilled arrow on the relay contacts in the diagram, denote which is the off/default state?
relays a normally drawn in their default off state, so it appears they are only using the normally closed contacts
 

Offline Asmyldof

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Re: Help reading PCB layout from service manual
« Reply #2 on: May 20, 2015, 03:54:35 pm »
Since the yes has already been given...

The filled in arrow in the relay contact drawing can sometimes mean a different contact rating, but it is used for different reasons by different engineers at different companies. But mostly just not at all.
What often happens is that the contact the spring pulls towards (default on contact) has a slightly higher switching current, because of the contact force. And sometimes one of the two contact is actually better reinforced with harder types of metals, or metals that don't spark, etc.

So it CAN mean that. But it might not.
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