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Lifted pads and other butchery

Subtox

Mar 8, 2016
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Mar 8, 2016
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I am replacing most or all of the capacitors on the mainboard of my old Roland XP-50 synthesizer (my original thread is here, not that it’s necessary for context). I have replaced several successfully, but in my inexperience along with my horribly cheap tools and likely cheap/expired adhesive on the board I have managed to snap off a few surface-mount pads. I did try watching videos and reading threads and articles for advice but nothing seems to apply to the particular situation I’m having.

Be forewarned, these photos are probably cringe-worthy for the more seasoned guys here haha, but I don’t have the budget or desire to outsource this and I had already written off this unit at the outset, so there's nothing to lose by getting my hands dirty and using this as a learning experience.

So here is the first of the two trouble spots. These are composite images because I was using a macro lens that can only focus on a small area. I drew a red line where I believe the pad connects to the trace and where it ends.

Vksa7E2.jpg


How would you recommend I fix this? I want it to be secure but it doesn’t necessarily have to be pretty. Could I, for example, run a wire from the leg of the capacitor straight to resistor R18 (with the code 222)?

Note that I'm replacing the surface mount capacitors with through-hole capacitors by bending feet and soldering them to the pads, if that makes a difference in how to best go about this. (I went with these because they looked easier to solder with the equipment I have, they were cheaper, and the vendor didn't seem to have the same size SMD's as the originals so I was worried they wouldn't fit.)

YEmNmtz.jpg


Here is the other spot, which looks trickier to me:

ahWzz2U.jpg


In this case both pads are missing. The negative pad on the left looks like it goes into the hole diagonally next to it. The positive pad goes over to the hole at the right. Can I solder wires directly from the feet of the capacitor to these holes? If so, this area is insanely tiny so I’m not sure how to best solder the wires there with the cheap soldering iron I have. Any advice on that would be helpful. Also I would need a way to physically secure the capacitor if both legs are solely connected to wires rather than mounted on the board. I'd rather not have it rattling around in there...

Or, is there a whole other way you would recommend going about these repairs?

Again, sorry for the cringey photos and just know that I’m fully aware how bad I’ve butchered this. (In my defense I did about six other capacitors without a hitch, maybe not the cleanest work but I’m getting better as I go!) I’m going to invest in a soldering station with a heat gun and better precision tips since the iron I have now is one of those bottom-of-the-barrel $7 abominations -- e.g. the point of the tip doesn’t get as hot as the sides so I have to lay it down across any joints I’m soldering (maybe just a tip issue?). Anyway I’m sure a replacement is a good first step. Any recommendations on which tools and accessories to buy or techniques I can employ for the issues above is very much appreciated!

EDIT: I still have the three pads that fell off, they're just a bit bent up. I could flatten them and reglue them to the board, and somehow reconnect them to their respective traces if that's possible. I'm just not sure of how to best do that, especially reconnecting them to the traces.
 
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davenn

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Sep 5, 2009
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Or, is there a whole other way you would recommend going about these repairs?

OK you need to do a good cleanup of the board for a start. There appears to be lots of gunk that needs cleaned away

cotton buds and isopropyl alcohol would be a good start

How would you recommend I fix this? I want it to be secure but it doesn’t necessarily have to be pretty. Could I, for example, run a wire from the leg of the capacitor straight to resistor R18 (with the code 222)?

yup, that would do ..... supaglue the capacitor on it's side after soldering the leg to the good pad ( first pic) do you know which way around it goes (polarity)?

CLEAN up around that area first, as advised it's a mess

In this case both pads are missing. The negative pad on the left looks like it goes into the hole diagonally next to it. The positive pad goes over to the hole at the right. Can I solder wires directly from the feet of the capacitor to these holes?

again I would glue the replacement cap on its side to the board, after soldering the negative pin down into the board through hole
Then just extend the cap's positive leg out, using some fine insulated wire, to the other through hole and solder it in

again, clean up all that mess before you start



finally show some pic's of your repair :)


Dave
 

Subtox

Mar 8, 2016
10
Joined
Mar 8, 2016
Messages
10
Well, that went better and worse than I could've expected... I fixed the problem spots and went on to replace all of the capacitors on the board. In the process, two more pads broke off so I fixed those as well. Some of it I can attribute to my lack of experience but I wonder how much of it is the old adhesive and possibly shoddy construction (someone commented on another thread that the original capacitors were about the worst ones you can use so I wouldn't be surprised if other corners were cut...not to shift the blame haha).

After finishing I turned on the unit and it worked! It booted up to the main menu and all looked fine. But when I played some keys there was absolutely no sound at all. Even before I got a whooshing sound and very little audio, but now it's completely silent. I opened it back up and found that one capacitor was in backward, although it seemed ok so I corrected it. It wasn't part of the audio path anyway so I'd expect it wouldn't make a difference to the sound. Anyway I turned it back on and still nothing. Now I'm just scratching my head.

Here are photos of the two capacitors I fixed. Sorry, I don't have closeups of the other two that broke later.

D1iUSwi.jpg

Notice I used two twisted strands from a scrap wire. Is this acceptable?

Ur51Qau.jpg

This one I wired directly through holes that the traces went to. The solder seems to be in contact with the copper around the top of the holes so I think I'm good but I'm not entirely sure. I removed and resoldered it to be sure but it didn't change anything.

And below is a photo of the whole board. I circled the capacitors whose pads I had to fix.

aYKgDdh.jpg


Any thoughts on the above and whether my "fixes" need fixing, or ideas for what I can check next? I'm happy to post any other pictures or info if needed.

Side note on the capacitor I soldered in backward: This is part of the LCD control, which worked fine before and after I corrected the capacitor, so I'm guessing it is OK, and in any case not worth replacing to try to fix the audio. For reference, the capacitor in question is the yellow one in the far lower-left of the board picture above (C932).

Side side note: I made sure all ribbon cables were plugged in correctly, I tried new cables, using headphones and a mixer, multiple plugs on the mixer, and any other combination of troubleshooting to narrow it down to the board itself. I know the keyboard works because I recorded some notes on the built-in sequencer and the notes are coming in. It's down to the audio path on the board at this point, as far as I can tell.
 
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