Infamous? 'Congo'

[sparkythepinmonkey]

An increasing number of people have been asking me about this repair.

The thread actually started in the auction section (http://www.aussiearcade.com/showthread.php?t=14025)

& since I finally found some time to devote to this poor litttle board, I decided to post a repair log here.

 

PCB is currently 1/2 stripped of parts & has had the corrosion treated.

The L/hand switch matrix area was the better of the corroded areas and as such, was rebuilt first.

ATM, I'm 'stitching' the bad tracks together & re-establishing the 'thru-hole' connections with strands of fine copper wire.

 

Pics:

1. PCB, before I got carried away stripping it.

2. Corrosion being treated.

3. Treated PCB after thru-holes had been 'reamed' with a PCB drill.

(this is to remove any oxides & crud from the holes)

4. After rebuilding the affected switch-matrix section (inside red line).

5. Treated & tinned PCB. Purple dots show where thru-holes are failing/non-existent, or I cant quite trust them.

6. An example of some of the 'stitching' of the thru-holes & tracks.

Edited October 28, 2008 by sparkythepinmonkey

[sparkythepinmonkey]

Pics are up peoples! :cool:

[hamish_nz]

WOW I admire you persistence

[stuba]

wow. i'd put you at odds on at the moment. awesome stuff! :)

[drudess]

at least you can rework this board and the componants are normal sized not surface mount 1/2 sized surface mount even 1/3 rd size surface mount .I long for the day for normal sized componants

[AskJacob]

Looks like a thorough and tidy job there. I bet you have to pick away at the job bits at a time to keep sane :D

 

Just a quick question - how come you didn't use machine sockets? I find they make it easier to solder both top and bottom so you don't need to feed wire through the holes to repair and through the hole plating for the ICs.

 

I reckon you'll have this one kicking soon! Good luck with it!

 

Cheers

Jacob

[stuba]

do you mind going into a bit of detail as to how you repair a trace. I'm cool with the stiches for double plated holes and understand what you've done with these, from what you said you are using thin(bare?) copper to do a trace? some detailed pics would be good? think of it as showcasing your skills as well as providing a guide for those to follow....:cool:

 

I have seen solder pens (that are like a liquid paper pen) that apply liquid silver that then 'sets' and provides a new trace. I have also seen 'trace' kits that provide a 'cutout' new trace that is epoxied over the old trace and then soldered at the joins. are you simply using a copper strand from a wire or something else?

 

thanks

Edited October 28, 2008 by stuba

[Darksoul]

Holy crap Batman! that's some serious repair work there.

 

Well done!

 

:o

[johnwartjr]

Got more patience than I do. I've returned better boards as not economical to repair :)

 

Good luck!

[sparkythepinmonkey]

Looks like a thorough and tidy job there. I bet you have to pick away at the job bits at a time to keep sane :D

Yes, I do 'pick' at it. It DOES drive you nuts after a few hours!:120:

 

Just a quick question - how come you didn't use machine sockets? I find they make it easier to solder both top and bottom so you don't need to feed wire through the holes to repair and through the hole plating for the ICs.

Yes, they are a 'quick' solution to connect one side of the PCB to the other, but....

they do introduce problems of their own.

1. Soldering one side of a pin, then the other, can lead to track lifting.

This is due to the expansion & contraction of the opposing joints.

If the thru-hole was sound, this wouldn't happen, as the heat would pass through the entire join

 

2. Machine socket bodies do not rest on the PCB itself, transferring ALL insertion pressure to the pins.

This can lift bad tracks after the first insertion!

It may not be obvious when you first do the repair, but when you hit it with the ol' soldering iron next time 'round,

you'll be saying F@*%! :evil

 

3. Machine socket pins fill the pcb holes quite well & they dissipate heat reasonably well too. So, when desoldering, you are placing quite a lot of heat against the wall of the thru-hole. This either melts the adhesive that holds it in place, or corrupts the substrate the PCB is made of & allows the thru-hole to simply fall out. 'IF' you have continuing problems with the board, regular IC sockets can be removed/ destroyed with much more ease, if the need arises. (with hopefully minimal damage to the PCB) :cool:

 

do you mind going into a bit of detail as to how you repair a trace. I'm cool with the stiches for double plated holes and understand what you've done with these, from what you said you are using thin(bare?) copper to do a trace? some detailed pics would be good? think of it as showcasing your skills as well as providing a guide for those to follow....:cool:

 

I have seen solder pens (that are like a liquid paper pen) that apply liquid silver that then 'sets' and provides a new trace. I have also seen 'trace' kits that provide a 'cutout' new trace that is epoxied over the old trace and then soldered at the joins. are you simply using a copper strand from a wire or something else?

 

thanks

 

Yes, I'm using 'bare' 0.19mm copper strands.

I aquire them by gutting old pieces of CMA 0.75mm 3-core cable. :cool:

(all those short pieces of LAI mains harnesses aren't that useless afterall, hey?)

 

As for detailed shots, I'm getting as detailed a shot as my camera will allow me.

I would LOVE someting with more zoom! :(