Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Equipment Usage, Soldering, Techniques, and Reviews
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools
Old 03-07-2022, 05:30 PM   #1
Forumzboard899
New Member
 
Join Date: Mar 2022
City & State: nj
My Country: usa
I'm a: Knowledge Seeker
Posts: 5
Default PAD repair? What are pads?

Hello,

This is a Roland MC-505 synthesizer I bought used years ago and 1 of the knobs was bent.

Eventually it started 'ghost editing' by changing the parameter of this knob on its own.

I resoldered the 5 pins on this knob (the two larger solder spots above these 3 smaller ones is for the same knob).

Then it started happening again, or maybe the knob stopped working totally (I set it aside months ago and forgot about it).

I bought a replacement knob/Potentiometer but when I recently opened it up, it seems the previous repair I did didn't 'stick' and wasn't making good contact. So I'm trying to use the same Potentiometer.



The previous repair was atrocious. I used a $5.50 harbor freight 30W non-adjustable pen-style iron and it was tricky to get the 3 small prongs soldered, I'm surprised it even worked and didn't short from solder touching eachother.

I got decent at soldering recently repaired headphones and learned I was doing it wrong before by trying to basically transfer globs of solder from the iron to the work instead of heating the work for a couple seconds and touching solder to it. I also didn't use flux or anything before. I'm using a digital ~$14 80W Chinese eBay pen-style iron with various tips and it seems to be ok.





I just did the 2 larger solder spots and then noticed the circle pads on 2 of the 3 smaller pins are detached!, and one seems to have vanished but I think it was working like that. I guess I added too much heat previously or that there was some wobble from using the knob on the synthesizer.



The pic with the screwdriver is spare parts of a stereo I took from the curb to practice on so maybe I can use something from that? The circle pads are really tiny like 2mm diameter.

What do these pads even do? They transfer electricity to the darker green lines/tracks on the board? The solder is supposed to touch the dark green surrounding tracks, or no? I don't get why these pads are even there, are they supposed to insulate/isolate electricity from the board (light green).



any help greatly appreciated. thank you
Attached Images
File Type: jpg IMG_0002.JPG (673.3 KB, 28 views)
File Type: jpg IMG_0003.JPG (794.3 KB, 21 views)
File Type: jpg IMG_0007.JPG (780.6 KB, 19 views)
File Type: jpg IMG_0009.JPG (570.8 KB, 17 views)
File Type: jpg IMG_0010.JPG (1.34 MB, 15 views)
Forumzboard899 is offline   Reply With Quote
Old 03-07-2022, 05:49 PM   #2
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,990
Default Re: PAD repair? What are pads?

The component has been ripped away from the circuit traces (solder pads)
Carefully scrape the green paint from the places I indicated in blue, then tin the copper with new solder and solder the component leads to the trace (or solder pad)

You can remove the leftover solder pad from the components lead, then bend the lead so it comes in close contact to the circuit trace, then solder the lead to the trace.
Attached Images
File Type: jpg IMG_0002.JPG (672.7 KB, 16 views)
File Type: jpg IMG_0002-1.jpg (671.5 KB, 19 views)

Last edited by R_J; 03-07-2022 at 06:10 PM..
R_J is offline   Reply With Quote
Old 03-08-2022, 01:08 PM   #3
Forumzboard899
New Member
 
Join Date: Mar 2022
City & State: nj
My Country: usa
I'm a: Knowledge Seeker
Posts: 5
Default Re: PAD repair? What are pads?

AH ok, I think I get it,

The dark green lines on a circuit board aren't what carries the electricity like I thought, the entire lighter green part DOES.

For this 3 pin example the pin to the right I guess is grounded or something because it conducts to the entire board which many other pins also connect to the same copper, but the two on the left are meant to only conduct to whatever is surrounded by darker green isolating lines, in this case they conduct to the light green circle that someone pointed out this is a double sided board and the green circle 'feed throughs' go to components on the other side.

I still don't understand pads though, why don't they just omit pads and keep that spot bare copper? That'd cause too much risk of something metal like a loose screw shorting it out?

Pads are paper thin, so the paper thin edge is the only thing transferring electricity to the thin copper layer.

Also, thanks so much for the replies this should be easier than I thought.
Forumzboard899 is offline   Reply With Quote
Old 03-08-2022, 01:54 PM   #4
ReeceyBurger123
Never Give Up !
 
ReeceyBurger123's Avatar
 
Join Date: May 2014
City & State: Telford
My Country: Britain
Line Voltage: 240 VAC 50Hz
I'm a: Student Tech
Posts: 7,232
Default Re: PAD repair? What are pads?

Iíve got a nice one I did for you. Xbox one S hdmi pads.
__________________
Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

https://www.facebook.com/Telford-Tel...7894576335359/
ReeceyBurger123 is offline   Reply With Quote
Old 03-08-2022, 06:28 PM   #5
Forumzboard899
New Member
 
Join Date: Mar 2022
City & State: nj
My Country: usa
I'm a: Knowledge Seeker
Posts: 5
Default Re: PAD repair? What are pads?

I scraped the areas to clean copper and bent the pins down but I'm hesitant to solder.

The left pin, right below where the pin comes through the hole, there looks to be some exposed copper.

When I solder the middle pin I'm afraid the solder might contact the left pin's zone, keep in mind this is a really small repair and the dark green non-copper isolation lines are like only 1mm thick, so everything is super close.

Is there some sort of non conductive heat resistant epoxy or something I can put over the area right below where the left pin sticks out?

I have superglue but think that'll melt from soldering. Unsure if I want to buy and wait for a special product but definitely will if bridging these two zones as an error would destroy the whole board or something.
Forumzboard899 is offline   Reply With Quote
Old 03-08-2022, 06:41 PM   #6
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 7,990
Default Re: PAD repair? What are pads?

Just be careful and don't put a big blob of solder. An alternative is to solder one end of a thin wire to the center lead, and the other end to the solder point just below the feedthrough.

If you get any glue on the copper trace the solder won't stick.
Attached Images
File Type: jpg solder wire.jpg (204.0 KB, 19 views)

Last edited by R_J; 03-08-2022 at 06:46 PM..
R_J is offline   Reply With Quote
Old 03-09-2022, 02:19 AM   #7
macattack600
Member
 
Join Date: Aug 2011
City & State: N/A
My Country: USA
I'm a: Knowledge Seeker
Posts: 97
Default Re: PAD repair? What are pads?

is the pin in the far right able to use the area scraped above it ? Looks like the far right 3rd is to a ground plane just solder that one up , middle pin down ?

Last edited by macattack600; 03-09-2022 at 02:46 AM..
macattack600 is offline   Reply With Quote
Old 03-09-2022, 11:30 AM   #8
Forumzboard899
New Member
 
Join Date: Mar 2022
City & State: nj
My Country: usa
I'm a: Knowledge Seeker
Posts: 5
Default Re: PAD repair? What are pads?

Mission accomplished! Everything fixed now. Thanks again!

I didn't branch a wire for the center pin, it ended working out and not touching the pin to the left of it.
Forumzboard899 is offline   Reply With Quote
Old 03-09-2022, 08:43 PM   #9
macattack600
Member
 
Join Date: Aug 2011
City & State: N/A
My Country: USA
I'm a: Knowledge Seeker
Posts: 97
Default Re: PAD repair? What are pads?

I figured it would , just have to have a little guts huh , lol .

Good Job , I actually enjoy reworking broken traces
macattack600 is offline   Reply With Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums © 2003 - 2022
Powered by vBulletin ®
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 08:28 AM.
Did you find this forum helpful?