Best way to repair 7800 board?

[FrumpleOrz]

I was having issues with my 7800 power button so I desoldered it to replace it and I noticed that the copper pad underneath is lifting off the board. I've taken a picture of it and bent the copper a bit so it's more obvious what is happening. What is the best way to repair this so it makes connections with the button switch?

 

[+-^CrossBow^-]

Easiest way is to put the new switch in. And when soldering it back in on the bottom, Add trace wire between the points to make up for the missing traces. You could also use really thing 30ga kynar between those, but since the pads are missing it would be best to repair from the bottom of the PCB.

 

Now that I look at it closer, the power switch might only require the connections on the right side next to that small cap, resistor and LED. The other connection to the left were just additional anchors most likely.

 

Also I'm not sure what iron you are using for this, but my guess is that it is too hot and cooking the traces and pads off the board.

Edited April 4, 2019 by -^Cro§Bow^-

[FrumpleOrz]

Easiest way is to put the new switch in. And when soldering it back in on the bottom, Add trace wire between the points to make up for the missing traces. You could also use really thing 30ga kynar between those, but since the pads are missing it would be best to repair from the bottom of the PCB.

 

Now that I look at it closer, the power switch might only require the connections on the right side next to that small cap, resistor and LED. The other connection to the left were just additional anchors most likely.

 

Also I'm not sure what iron you are using for this, but my guess is that it is too hot and cooking the traces and pads off the board.

Thanks for the quick response!

 

I'll completely admit to being a super novice solderer and haven't done much besides replacing batteries in game cartridges so I probably am setting it way too high. What is the appropriate temperature for something like this? When I add trace wire, it would just be recreating the bent traces on the bottom of the board, correct? Should I completely remove the damaged copper parts on the top of the board afterward to be on the safe side?

[+-^CrossBow^-]

I tend to keep my iron no hotter than about 350c and that is still on the getting close to too warm for most work. Now if I'm dealing with stuff on a large ground plane, then my iron will get cranked to some very high heat!

 

You might not actually need trace wire at all. In looking at your pic, you still have some copper left on the right hand pads and that is what I think directly ties to the neighboring components. I haven't a 7800 board in front of me, but if the pads on the bottom are still good, then soldering to those should be okay. So you actually just need to make sure you have connections on the bottom for the left side of the switch and have it soldered down on the top for the right hand side of the switch. I can look at one of my parts boards when I get home from work and verify this for you if you can wait until later this evening?

Edited April 4, 2019 by -^Cro§Bow^-

[FrumpleOrz]

I tend to keep my iron no hotter than about 350c and that is still on the getting close to too warm for most work. Now if I'm dealing with stuff on a large ground plane, then my iron will get cranked to some very high heat!

 

You might not actually need trace wire at all. In looking at your pic, you still have some copper left on the right hand pads and that is what I think directly ties to the neighboring components. I haven't a 7800 board in front of me, but if the pads on the bottom are still good, then soldering to those should be okay. So you actually just need to make sure you have connections on the bottom for the left side of the switch and have it soldered down on the top for the right hand side of the switch. I can look at one of my parts boards when I get home from work and verify this for you if you can wait until later this evening?

I am in no rush at all and if you're willing to look at your board, I'd be very appreciative! Thank you so much for all of your help so far.

[+-^CrossBow^-]

Its no problem. I've got 2 parts donor 7800 boards at the ready on my worktable I can refer to to confirm the traces for the switch.

[CPUWIZ]

Now that I look at it closer, the power switch might only require the connections on the right side next to that small cap, resistor and LED. The other connection to the left were just additional anchors most likely.

 

That is correct, only the 2 pins on the right need to be connected, to turn the unit on.

 

I know this, because I just built an Alexa device, to control all 4 buttons.

[ChildOfCv]

The other big killer of circuit boards is what I might call the "melt and pull" method. When removing a component, you really should use solder wick to remove as much of the solder as possible before even placing any force on the connection. Wick from both sides of the board. Then use a small screwdriver to break the legs loose from whatever traces of solder remain. Only then do you lift the component. Requires patience, but is far less likely to require trace repair.

[DrVenkman]

The other big killer of circuit boards is what I might call the "melt and pull" method. When removing a component, you really should use solder wick to remove as much of the solder as possible before even placing any force on the connection. Wick from both sides of the board. Then use a small screwdriver to break the legs loose from whatever traces of solder remain. Only then do you lift the component. Requires patience, but is far less likely to require trace repair.

 

In my experience, this is a big no-no. That last trace of remaining solder is just as likely to take a pad or adjacent trace right off the board if you just break it loose by main force. In my personal experience - your mileage may vary - I'll heat the leg with the iron directly to melt that tiny bit of remaining solder, and only when it can be moved away from the wall of the through-hole with essentially no force is it safe to remove from the board entirely.

[CPUWIZ]

I agree, but I just use a FR-300.

[ChildOfCv]

 

In my experience, this is a big no-no. That last trace of remaining solder is just as likely to take a pad or adjacent trace right off the board if you just break it loose by main force. In my personal experience - your mileage may vary - I'll heat the leg with the iron directly to melt that tiny bit of remaining solder, and only when it can be moved away from the wall of the through-hole with essentially no force is it safe to remove from the board entirely.

True. You should only need a tiny amount of force to break the leg loose. A tiny jeweler's screwdriver would minimize the chance of overdoing it. If it takes a pry tool, you still have more solder to remove. And if the pad breaks loose anyway, that probably indicates it was already lifted. Being gentle could still have salvaged it, but the longer you hold the heat, the more you risk delaminating it. I guess this a case of "pick your poison and pray you chose correctly"

 

But yeah, the main thing is, don't just try to pull the component simply by melting its solder and wrestling it out. Especially if it has too many pins to heat all at once.

 

And also, I'd love to justify getting a FR-300 or similar.

[DrVenkman]

I agree, but I just use a FR-300.

 

Word.

 

True. You should only need a tiny amount of force to break the leg loose. A tiny jeweler's screwdriver would minimize the chance of overdoing it. If it takes a pry tool, you still have more solder to remove. And if the pad breaks loose anyway, that probably indicates it was already lifted. Being gentle could still have salvaged it, but the longer you hold the heat, the more you risk delaminating it. I guess this a case of "pick your poison and pray you chose correctly"

 

But yeah, the main thing is, don't just try to pull the component simply by melting its solder and wrestling it out. Especially if it has too many pins to heat all at once.

 

And also, I'd love to justify getting a FR-300 or similar.

 

I bought an FR301 (current very slightly updated model) for my birthday last July. It wasn't cheap but after several years of doing increasingly more in-depth repairs, bigger fixes, and building ever more complex stuff, it was well worth it. It's like freaking magic.

[CPUWIZ]

I know, magic, used 808's for over a decade, before the FR-300. What did they upgrade on the 301?

[DrVenkman]

I know, magic, used 808's for over a decade, before the FR-300. What did they upgrade on the 301?

 

I think the only significant change beside the name was they made the thing compatible with their N61 series nozzles, whereas the FR300 uses N50 nozzles. I guess there's a wider variety of sizes and styles in the N61 line. The Amazon description also says the filter compartment is the same as the FR-401 soldering station which supposedly makes it easier to clean than the prior version. I dunno know - I have the 301, a friend has the 300 but we've never compared them side by side.

[Jinks]

I cut legs and heat and pull. Then repair traces..

[CPUWIZ]

 

I think the only significant change beside the name was they made the thing compatible with their N61 series nozzles, whereas the FR300 uses N50 nozzles. I guess there's a wider variety of sizes and styles in the N61 line. The Amazon description also says the filter compartment is the same as the FR-401 soldering station which supposedly makes it easier to clean than the prior version. I dunno know - I have the 301, a friend has the 300 but we've never compared them side by side.

 

That makes sense, why they only upped the number by 1, I was hoping for motor control or something like that. I'd love to have the thing have a sensor in it, when it is on, so if it doesn't move for 2 hours, it shuts itself off.