Vintage Synth Repair

My SH-101 was in worst shape than I thought: broken copper traces near  
one of the keyboard matrix connectors. Reflowing the solder joints  
didn´t do any good as it quickly melted the phenolic (or whatever 
material is the PCB made of) and the traces jumped off. 

As the keyboard contacts are of the conductive rubber type, the copper 
traces lead to what seems like conductive carbon ink pads, so there´s 
nothing solderable to run "oops wires" from. 

One possible solution might be removing the varnish at the connector 
end, exposing enough solderable copper area. What can be used as 
solvent?

There is also one special silver ink pen that I could use to redraw new 
traces directly from the carbon pads, but how well would the ink bond 
to the pads? I coudn´t measure the carbon´s resistance, let alone any 
signs of continuity... 

Do you know of a more conventional way to do the repair?

Any advice would be greatly apreciated.

On Tuesday 10 June 2008 10:16, inocencio66 wrote:
> One possible solution might be removing the varnish at the connector
> end, exposing enough solderable copper area. What can be used as
> solvent?

If you're talking about the solder mask that sits on top of the traces, I use 
an x-acto knife...


-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

--- In vintagesynthrepair@yahoogroups.com, "Roy J. Tellason" 
<rtellason@...> wrote:
>
> On Tuesday 10 June 2008 10:16, inocencio66 wrote:
> > One possible solution might be removing the varnish at the 
connector
> > end, exposing enough solderable copper area. What can be used as
> > solvent?
> 
> If you're talking about the solder mask that sits on top of the 
traces, I use 
> an x-acto knife...
> 
> 
> -- 
> Member of the toughest, meanest, deadliest, most unrelenting -- and
> ablest -- form of life in this section of space,  a critter that can
> be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet 
Masters"
> -
> Information is more dangerous than cannon to a society ruled by 
lies. --James 
> M Dakin
>
Thanks.
Yes, solder mask is how you call it. Sorry I couldn´t remember. Well, 
using a sharp blade seems obvious, but the traces are really thin, 
hence why I thought of dissolving the mask instead of scraping (and 
the traces going with it). 
I´m going to try anyway. There´s enough area for mistakes and I can 
make the bridges with wirewrap wire.

Done. It�s a bit messy but it works :-)
Wouldn�t try without asking the pros first...
Thank you!

Use a minature flat screwdriver, it works very well.

2008/6/10 inocencio66 <paulo.simoes5@...>:
> --- In vintagesynthrepair@yahoogroups.com, "Roy J. Tellason"
> <rtellason@...> wrote:
>>
>> On Tuesday 10 June 2008 10:16, inocencio66 wrote:
>> > One possible solution might be removing the varnish at the
> connector
>> > end, exposing enough solderable copper area. What can be used as
>> > solvent?
>>
>> If you're talking about the solder mask that sits on top of the
> traces, I use
>> an x-acto knife...
>>
>>
>> --
>> Member of the toughest, meanest, deadliest, most unrelenting -- and
>> ablest -- form of life in this section of space,  a critter that can
>> be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet
> Masters"
>> -
>> Information is more dangerous than cannon to a society ruled by
> lies. --James
>> M Dakin
>>
> Thanks.
> Yes, solder mask is how you call it. Sorry I couldn´t remember. Well,
> using a sharp blade seems obvious, but the traces are really thin,
> hence why I thought of dissolving the mask instead of scraping (and
> the traces going with it).
> I´m going to try anyway. There´s enough area for mistakes and I can
> make the bridges with wirewrap wire.
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>



-- 
Antoine Deschênes

--- In vintagesynthrepair@yahoogroups.com, "inocencio66" 
<paulo.simoes5@...> wrote:
>
> My SH-101 was in worst shape than I thought: broken copper traces 
near  
> one of the keyboard matrix connectors. Reflowing the solder joints  
> didn´t do any good as it quickly melted the phenolic (or whatever 
> material is the PCB made of) and the traces jumped off. 
> 
> As the keyboard contacts are of the conductive rubber type, the 
copper 
> traces lead to what seems like conductive carbon ink pads, so 
there´s 
> nothing solderable to run "oops wires" from. 
> 
> One possible solution might be removing the varnish at the 
connector 
> end, exposing enough solderable copper area. What can be used as 
> solvent?
> 
> There is also one special silver ink pen that I could use to redraw 
new 
> traces directly from the carbon pads, but how well would the ink 
bond 
> to the pads? I coudn´t measure the carbon´s resistance, let alone 
any 
> signs of continuity... 
> 
> Do you know of a more conventional way to do the repair?
> 
> Any advice would be greatly apreciated.
>
Just use a sharp X-acto blade a carefully scrape tha solder mask of 
down to the bare copper,then tin the traces.Good old 30 ga.wire wrap 
wire is perfect for trace repair.
                 Jim

--- In vintagesynthrepair@yahoogroups.com, "jahg88" <jahg88@...> wrote:
>
> --- In vintagesynthrepair@yahoogroups.com, "inocencio66" 
> <paulo.simoes5@> wrote:
> >
> > My SH-101 was in worst shape than I thought: broken copper traces 
> near  
> > one of the keyboard matrix connectors. Reflowing the solder joints  
> > didn´t do any good as it quickly melted the phenolic (or whatever 
> > material is the PCB made of) and the traces jumped off. 
> > 
> > As the keyboard contacts are of the conductive rubber type, the 
> copper 
> > traces lead to what seems like conductive carbon ink pads, so 
> there´s 
> > nothing solderable to run "oops wires" from. 
> > 
> > One possible solution might be removing the varnish at the 
> connector 
> > end, exposing enough solderable copper area. What can be used as 
> > solvent?
> > 
> > There is also one special silver ink pen that I could use to redraw 
> new 
> > traces directly from the carbon pads, but how well would the ink 
> bond 
> > to the pads? I coudn´t measure the carbon´s resistance, let alone 
> any 
> > signs of continuity... 
> > 
> > Do you know of a more conventional way to do the repair?
> > 
> > Any advice would be greatly apreciated.


Try a conductive paint pen.
>

The later replies have been apreciated, but the problem is fixed since 
my post #3854. I used a Stanley knife and wirewrap wire. 

The upper tracks (by the carbon pads side) are wider and make the 
soldering much easier. Longer runs of wires are needed and have to be 
arranged so they won�t get in the way of the key contacts. 
Once the keyboard is reassembled the wires stay hidden.

Since there was nothing to hold the connector I superglued it to the 
board.

The synth has been working faultlessly since then. 


An off-topic tip: when calibrating the 101 don�t underestimate the 
service notes where it�s said to tune the VCO to 442 Hz. 
I tuned it to the usual 440 Hz and now have to rotate the pot a bit 
clockwise off-center...