Repairing pc traces on a multi-layered board.

[David Farber]

The pc board is from a Korg piano. The model number is C-56M. Schematic is
here.
http://www.synfo.nl/servicemanuals/Korg/CONCERT-26-56M_SERVICE_MANUAL.pdf

The relevant pages of the service manual are page 30 for the pc board view
and page 121 for the schematic.

Photo of the board I'm fixing is here.
http://webpages.charter.net/mrfixiter/images/Electronics/Korg/KLM-1653-pc-board.jpg

The problem is that all of the 10uF 10v caps are bad. I've removed them and
replaced them with through-hole capacitors. Due to the damage caused by the
leaking electrolyte, I was forced to be creative in finding working paths in
the circuit that were still usable. There is one spot I got stuck. Looking
at the photo, you will see a 5 pin connector which connects the volume
control on the top of the piano to this circuit board. There is no
continuity between the left and right output caps to the connector. I've
made a trail of red dots in the photo where the connections are supposed to
be. The dots do not represent a specific physical path but are there for
clarity. The way the signal path connects to the two pins are from the
negative sides of C116 and C117. (page 121 in the service manual) and then
through the two through-hole connections adjacent to the capacitors. Is it
possible to solder jumper wires from the capacitors to the through-hole
connectors (highlighted by arrows)?

Thanks for your reply.
--
David Farber
Los Osos, CA

[mike]

Why can't you just run the wire from the cap to the connector?

[David Farber]

Hi Mike,

I wanted to avoid running wires from the top of the board to the bottom. If
you meant running wires directly to the connector, those terminals are used
when the cable from the volume control gets plugged in. If you meant
anything else, I'm not sure what you meant. :-)

[N_Cook]

so drill a hole through a blank part of the pcb to pass the jumper wire

[Gareth Magennis]

"David Farber" wrote in message news:mlnqes$ph8$1...@dont-email.me...

You could prize off the plastic connector housing off the pins, and solder
thin wires from that to the capacitors, then put it back again.




Gareth.

[David Farber]

You could prize off the plastic connector housing off the pins, and solder
thin wires from that to the capacitors, then put it back again.

Gareth.

Hi Gareth,

Good suggestion but I was still wondering if a wire can be soldered to those
circular through-hole connectors.

[Gareth Magennis]

"David Farber" wrote in message news:mlpbu6$vq9$1...@dont-email.me...

Dunno, sometimes these vias are very small, and/or covered in solder resist.
You could always drill them a bit bigger, bearing in mind they will no
longer connect both sides.


Gareth.

[John Robertson]

On 06/16/2015 12:03 AM, N_Cook wrote:
> On 16/06/2015 05:55, David Farber wrote:
>> mike wrote:
>>> On 6/15/2015 5:27 PM, David Farber wrote:
>>>> The pc board is from a Korg piano. The model number is C-56M.
>>>> Schematic is here.
>>>> http://www.synfo.nl/servicemanuals/Korg/CONCERT-26-56M_SERVICE_MANUAL.pdf
>>>>
>>>>
>>>> The relevant pages of the service manual are page 30 for the pc
>>>> board view and page 121 for the schematic.
>>>>
>>>> Photo of the board I'm fixing is here.
>>>> http://webpages.charter.net/mrfixiter/images/Electronics/Korg/KLM-1653-pc-board.jpg
>>>>
>>>>
>>>> The problem is that all of the 10uF 10v caps are bad. I've removed
>>>> them and replaced them with through-hole capacitors. Due to the
>>>> damage caused by the leaking electrolyte, I was forced to be
>>>> creative in finding working paths in the circuit that were still
>>>> usable. There is one spot I got stuck. Looking at the photo, you

... Is it possible to solder jumper wires from the

>>>> capacitors to the through-hole connectors (highlighted by arrows)?
>>>> Thanks
>>>> for your reply.
>>>>
>>> Why can't you just run the wire from the cap to the connector?
>>
>> Hi Mike,
>>
>> I wanted to avoid running wires from the top of the board to the
>> bottom. If
>> you meant running wires directly to the connector, those terminals are
>> used
>> when the cable from the volume control gets plugged in. If you meant
>> anything else, I'm not sure what you meant. :-)
>>
>> Thanks for your reply.
>>
>
> so drill a hole through a blank part of the pcb to pass the jumper wire

Multi-layer board - you have no idea where the traces are running so
drilling a hole is not be a good idea, unless the board is translucent
enough that you can see the inner layers that is.

John :-#(#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

[John Robertson]

Multilayer board, vias may connect to other traces in other layers that
the top and bottom alone.

Mind you if it is just a four layer board then the two middle layers are
typically power and common (but not always).

[Gareth Magennis]

"John Robertson" wrote in message
news:DKadnQB4qfud_x3I...@giganews.com...

I suspect this is a dual layer PCB.



Gareth.

[mike]

My Bad.
When you said thru-hole caps, I made the wrong assumption.
There's no reason you can't solder to the feedthrus.
Be aware that they're not very robust.
If the hole is big enough, stick a tiny wire thru for the
connection. I use solid wire-wrap wire for such things, but
a strand from a stranded wire can work.

If there are only 2 layers, you could ream the hole if necessary
If there are inner layers, you will break some other internal
connection.

Another issue is that if the corrosive stuff from the caps
ate the connection, there may be other issues to follow.

I fixed a TEK scope once where the cap goo ate feedthrus for
some distance around the caps. Finding where to bridge the gaps
was challenging without schematics.

The goo is difficult to clean off, but if you don't do it
thoroughly, you'll be fixing it again later. It gets under
the SMT chips.
Alternating simple-green and alcohol and a toothbrush
a few times should take care of it.

I'm far too lazy to decipher the manual. If the caps go other places,
you can bridge to there instead of the connector.

[John-Del]

On Wednesday, June 17, 2015 at 5:03:14 AM UTC-4, mike wrote:

> If the hole is big enough, stick a tiny wire thru for the
> connection. I use solid wire-wrap wire for such things, but
> a strand from a stranded wire can work.

I just repaired a Snap-On Modis OBDII scanner in this manner. This is a multi-layer board, but fortunately the liquid damage was limited to a top to bottom connection, not an internal one.

Years ago I was given a roll of transformer wire, which is very thin and lacquer coated. This will snake into very small plated through holes and it did perfectly in the scanner. If the scanner were a double layer board, it would have been simple enough to drill a small hole next to the dead feed through, but on a multi layer, that's out of the question. Transformer wire is ideal for pushing through a blackened feed through. Single strands from stranded wire is certainly thin enough, but it won't have the stiffness to push through most plated through holes.

[David Farber]

I decided to take some fine gauge wires and run them around the side of the
board to get to the other side. It wasn't the most elegant fix but it
corrected the problem.