please,i need to repair a circular PCB board inside the rotating camera head of a robot,a small tractor for sewage inspection.The brand is Pearpoint,model 494/04,part of S.C.S Ex94C1001 & 1002
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An internal short circuit,probably due to iron dust,generated heat,enough
to burn away the golden plated track and carbonize the PCB
Repairing it requires to redraw and rebuild the PCB,it would be good if someone has the spare part,or the service manual,because i could do errors in redraw the burned tracks and vias
Repairing that would be problematic, because it looks like it serves as a r otating slip ring with multiple connections. You might repair the traces bu t it could not be smooth, the connections thru the brushes or contacts woul d not be steady or reliable as it rotates. A replacement is your only real option.
Yes,exactly.A correspondig PCB mounts some spring loaded spheric contacts(i think they are also called pogo pins),sliding on the circular tracks.
no spare parts availabile,product out of production since long time,but i
admit that i still have to ask to their support about the drawings
I completely agree,i dont know any product that i could paint even on a perfectly flat surface,hard enough to withstand the friction Furthermore the burned PCB could have lost insulation.
I started drawing an identical PCB some days ago The problem is to get the right distances and positions of tracks and vias,and some of them almost disappeared ,despite their function looks trivial(unless strange crossings). The most precise method i found was doing an accurate photo,and using the
pixel meter of a free image editor as GIMP to get the distances. Once drawn,i will print it on a transparent sheet to check it versus the real one
Ask them for the Gerber files. Then you can send them out to be reproduced. It will be expensive because you need the "hard gold" surface finish (not ENIG) on the entire board. This is usually only used on edge connectors and is almost obsolete.
Can you post a picture of the other side of the board?
The best way would be to copy the PCB photographically, and make a new PCB. However, if you want to try repair, find some thin sheet copper. Draw the missing traces on the copper sheet. Cut out the semi circular sections with an Xacto knife. Glue to the existing PCB. If you overlap the new copper to the existing gold traces, you should have a sufficiently good connection without soldering. Stained glass copper tape should work.
You can also do this with aluminum foil duct tape, but will need to do something to improve conductivity and prevent electrolysis. For dry (no DC) connections, I dope the sticky glue back of the tape with graphite powder.
Another approach would be to totally replace the PCB with a ribbon cable. It appears to simply provide the ability to do multiple 360 degree rotations without binding. That's a useful feature, but probably not a necessity for sewer inspections. Build an umbilical cable between the electronics and the camera head that replaces the function of the board. Either provide a mechanical stop that provides over-rotation protection or just be careful when rotating. Hopefully, you have room inside for the umbilical.
Good luck.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
No Jeff, that's nonsense. Copper tape or aluminum foil tape will not hold u p to the pogo pins rubbing on them. It'll last a few rotations before it we ars thru, or folds up the tape, or pushes it off the substrate, likely crea ting another short.
I do like the slip ring idea if there is room and a way to secure it.
Otherwise, get the original gerbers, or recreate the gerbers in a PCB cad p rogram, Eagle would do this easily. Then consult with a domestic PCB house on how to specify the copper thickness and hard gold plating. Doing it by d esign rather than some photocopy process would insure correct alignment wit h the pogo pins.
A "dry" connection does not imply no DC, by the way, it implies very low cu rrent.
I'll admit that I haven't tried it with a similar device, but it worked well enough on an HP8640B signal generator switch that was somehow mangled. I don't have a photo of the repair, but this is the switch type: I used 3 mil copper shielding tape without soldering. Something like this: The contacts are made from beryllium spring stock and do not apply much pressure. There was a slight groove in the copper tape, but no rips or tears. As far as I know, the generator is still functioning about 10 years after the repair.
However, you might be right. The signal generator switch has much less pressure, movement, and use than the robot head. However, there's nothing lost (except time) in attempting to repair the original with copper foil or tape. If the heads on the pogo pins are wide and rounded enough, such a repair might hold together long enough for the PCB to be cloned and replaced.
Agreed. Seems like a better idea than to patch together the existing slip ring assembly. It might fit better if the it more closely resembled the original: Maybe something like this one:
Or, go back to the dark ages and make a "tape up" of the board on mylar film, probably using a drafting pen and India ink. When done, photograph and reduce the photos to film which would be sent to the PCB fab house. I'm not sure they know how to handle such dark ages technology, but it's worth a try.
Nostalgia:
Sigh. I stand corrected: However, on a slip ring device, the contact spring pressure is sufficient to break through any oxidation. Therefore, there's no need to rely on DC current to break through it.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
That in fact is correct -- hence better quality dry circuit switches are implemented with a wiping action set of contacts AND a low-reactivity contact material such as gold.
Good idea. However, I wouldn't do it just in the damaged area. With a thicker piece of PCB material, one could mill concentric slots (probably on a lathe or drill press). A copper or brass strip could be inserted in the slot and glued in place. Bending the rectangular strip would only work for a mounting it on edge, which might be a problem making contact with the Pogo contacts. Flat would be better, but that would require machining the circular contacts.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
In data aprile 2018 alle ore 18:38:13, ha scritto:
Thanks, i tried to simulate with a plastic spare part that i roughly filed to the
eight of one of the slip rings in the datasheet,but it looks too thick,even removing the board with circular tracks,that could be substituted by the slip ring.
That's too bad. It's always nice to be able to use stock parts. Since the housing comes apart would it be possible to have a machine shop make up a spacer so you would have a little more room to work with? I don't know what your robot head looks like so I really don't know what you are working with. But since I own a machine shop I tend to see machining answers to problems. Could you post a link to a picture of the robot head? I'm curious about it. Eric
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