Circuit Board repair

[n2ize]

While working on the inner guys of my yaesu FT-470 I noticed a section of the IF connector board that seems to have taken a bit of heat (not from my soldering iron but perhaps a momentary short at some point) which has caused one of the traces on the board to peel from the board and break.

I am wondering if anyone can recommend a fix. I was considering trying one of those silver conductive pens but I am not sure if it can produce a narrow enough trace. real estate is tight on these boards, they are assembled by robots, and traces are very narrow. Another possibility might be to bridge it with a very thin piece of hookup wire running from just before the point where the break starts to a suitable solder connection point on the circuit board itself. I am inclined to try this second method as the silver pen might be too messy on such a narrow trace and might end up bridging components that I don't want bridged. The narrow gauge hookup wire might be better as it is insulated and can be easily removed if it don't wuyk.

Of course any other suggestions of clever ideas are appreciated. :-D

[PA5COR]

I'll go for the (isolated) hookup wire.
If needed glue in place, i have some teflon coated hookup wire just for that.

[n2ize]

I'll go for the (isolated) hookup wire.
If needed glue in place, i have some teflon coated hookup wire just for that.

Yeah, I think I'm going to opt for the hookup wire as well.

[K7SGJ]

I did rework for over 40 years, and I have found that, as noted above, small hook-up is the best bet. I had all kinds of machines, cameras, reflow, etc. and have found a small bridge across the trace is likely to fail. Follow the trace and try to connect the hook-up wire to solid solder pads on both ends. Scratching the "green" mask off and soldering there makes for a lousy connection. Good luck.

[N5RLR]

I'll echo what others have said; go for the wire method. I've literally "stitched" broken PC boards back together this way -- simple solder bridges would have failed in short order.

Do this repair while rested and alert, and doublecheck your work before applying power to the board. :yes:

[N8YX]

Another "aye" for the wire.

[kb2vxa]

I used to do board work for a living and we never used insulated wire except where it crossed traces, then we used Teflon tubing. In a cramped space a thin soldering pencil and needle nose tweezers come in handy when you bridge the space with small gauge bus wire. If you clean the ends of the burned trace with the tweezers and apply a drop of liquid flux first, then a dab of solder from the pencil iron while holding the pre-cut bus wire in place with the tweezers you won't have to worry about a poor joint. Oh and BTW, cutting the trace back with the point of an Exacto hobby knife to where it's firmly attached sure helps keeping it from peeling off.

Yup, aye for wire, you'll make a helluva mess with solder blobs.

[n2ize]

Well, in my case with limited soldering equipment and a ultra cramped circuit board and poor eyesight and considering that a fairly long stretch of the trace has dissolved I think the wire would be the best and least damaging of my options. Even then I still have to figure out why the board took enough heat to peel away and break the trace. In short I have to check some nearby components for shorts and test it very carefully when i apply voltage to it.

In any event I'll be buying a new HT so in the event this one turns out to be a total loss at least I'll have another working radio. Besides, this FT470 has been problematic since i bought it. During the days I had it in operation I had to open it and repair it several times and even had to send it back to Yaesu on one occaision. Nonetheless, i'd like to get it working again. This radio does have some sentimental value to me.

[kb2vxa]

"...a ultra cramped circuit board and poor eyesight...
Maybe that's why I no longer do board work? (;->) I hope your vision didn't go to the middle distance like mine did so maybe a lighted bench magnifier would help. Yeah for sure, SOMETHING fried the trace so should the problem remain after the "fuse" is replaced with wire something's gonna give big time. Remember the precious smoke, you can't put the genie back in the bottle.

[KA5PIU]

Hello.

I remember when some old telephone man was complaining about the "tiny wires" inside a 500 series telephone. ;)
But, yes, teflon magnet wire if need be.
I have soldered quite a few hearing aids in my day but now it is all in the ear, very little soldering, the parts are actually held together to work.
Some radios are better than others.
My current ham talkies, the TH-f6a, and VX-3R and VX-7R, have proven themselves over again.
For commercial service we have all gone away from Motorola back to GE, now Harris, and have been tickled pink.
Pull apart any of the ham talkies, the boards are connected with ribbon cable that makes servicing (modding) very easy.

[n2ize]

"...a ultra cramped circuit board and poor eyesight...
Maybe that's why I no longer do board work? (;->) I hope your vision didn't go to the middle distance like mine did so maybe a lighted bench magnifier would help. Yeah for sure, SOMETHING fried the trace so should the problem remain after the "fuse" is replaced with wire something's gonna give big time. Remember the precious smoke, you can't put the genie back in the bottle.

Great News. I fixed the circuit trace by jumpering the gap with some very thin enameled wire. Rudy's suggestion of teflon wire made me think of the fine enameled magnet wire. A short stretch of wire, some very careful soldering and some scotch tape, to fix the loose parts of the trace to the board and to hold the wire in place and insulate. Then i put a meter across it and it showed no sign of any shorts. So I decided to go for it. I reattached the various boards that wed to one another and...knock on wood... very carefully applied power... just a little at first then I cranked it up to 7-12 bolds DC in and VIOLA'... the display came on !!! So, thus far it looks like my FT-470 still lives !!

There is still plenty of "fuse" left should anything short again. But I don't expect that to happen.

[N5RLR]

And that, is the thrill of victory. :monkeydance:

[n2ize]

And that, is the thrill of victory. :monkeydance:

Unfortunately I'm not out of the woods yet. I powered it up but i don;t have full functionality. So i did some more careful probing around the circuit boards... magnifier in hand, and I noticed a problem with a short length of flat flexible cable (that ribbon like cable with numerous multiconductors running in parallel) that interconnects between the control unit board and the IF unit on this particular radio. . It appear with all the moving and flexing from repairs past and present. a few of the conductors have torn loose. That could easily explain the loss of some functionality. In any event it's an easy fix provided I can replace that cable. It looks like standard "flat flexible cable". Hopefully I can track some down online of through an electronics distributor, i.e. DigiKey, etc.

of course any help or suggestions are welcome.

[KC2UGV]

Unfortunately I'm not out of the woods yet. I powered it up but i don;t have full functionality. So i did some more careful probing around the circuit boards... magnifier in hand, and I noticed a problem with a short length of flat flexible cable (that ribbon like cable with numerous multiconductors running in parallel) that interconnects between the control unit board and the IF unit on this particular radio. . It appear with all the moving and flexing from repairs past and present. a few of the conductors have torn loose. That could easily explain the loss of some functionality. In any event it's an easy fix provided I can replace that cable. It looks like standard "flat flexible cable". Hopefully I can track some down online of through an electronics distributor, i.e. DigiKey, etc.

of course any help or suggestions are welcome.

How many conductors? Less than 36 and you can just strip off needed lengths from a EIDE cable.

[n2ize]

How many conductors? Less than 36 and you can just strip off needed lengths from a EIDE cable.

I think there is something on the order of 16 conductors. But I don't know if IDE cable will work. Not sure if its the correct pitch. It's about 16 conductors in a 1 inch wide narrow film strip. IDE cable the conductors may not line up with the connectors on the PC board and it might be too thick to sandwich nicely between the very narrow space between the two boards. IDE cable is more along the lines of ribbon cable. This FFC cable. However I'll give it a try and see if it works.

This is along the lines of what I need.

http://www.wavelinkcable.com

[KG4CGC]

Is it flat like flexible traces? The TS 570 has flat connectors that resemble flexible, coated traces with gold plated ends.

[n2ize]

Is it flat like flexible traces? The TS 570 has flat connectors that resemble flexible, coated traces with gold plated ends.

The conductors (there are 20 of them in my case) are very thin traces embedded in a very thin flexible yet semi rigid cellophane like film. At each end of the flat cable a tiny bit of the conductor is exposed so that each conductor can line up with the connectors on the pc board. Yes, I know the type connectors you are speaking of in the TS-570. Thats an example of flat flex cable. You also see it used in printers to electrically connect the moving print head to the electronic circuitry of the printer. It's more desirable than ordinary parallel ribbon cable because it's semi rigid yet flexible nature enables it to hold it's position without flopping as the head moves and its flexibility allows the head to move repeatedly thousands upon thousands of times without the conductors breaking (provided it is not flexing on a very sharp bend.). Sometimes they may be gold. The one in the Yaesu I'm repairing is silver.

There is a possibility I might be able to salvage this cable if I can carefully cut away enough of the film to expose 1-2mm of the end of each conductor. Since I;ve never done that with flat flex cable this will be a first time for me. I just want to be ready to get more if I need it.

[KG4CGC]

Any hamfests happening anytime soon?
I looked for the right picture on the web but obviously I'm not entering the correct search terms.

[NQ6U]

That stuff is a beach to work with, John, I've never had any luck with trying to scrape it clean enough make good contact. Some sort of chemical treatment might work, though, possibly acetone but of course it would be good idea to have some sort of backup just in case of disaster.

[n2ize]

I think I may have found what I need. I need to measure mine to make sure.

http://www.alancomputech.com/ffc-20p-40mm.html

Update... this cable doesn't have the right pitch to mate with the conductors of the connectors on my boards. DigiKey has the stuff I need but unfortunately it's not a regular stock item and I'd have to order in bulk. I might try and contact Yaesu and see if anyone there can help me. They probably use the same stuff in some of their other radios. All I need is one piece. There is a company that makes up this type of connector to order and they provide samples but to get a sample I'd have to tell them that I'm planning on ordering in bulk in the future. It is also possible I might be able to find a wider cable and cut it to size... if it has the correct pitch. I'll check out al possibilities.

[KC2UGV]

Check at Mouser. I was just browsing their flat cables, and they have a metric fuck ton of varieties.

[NQ6U]

Check at Mouser. I was just browsing their flat cables, and they have a metric fuck ton of varieties.

How many metric assloads in a metric fuck ton?

[n2ize]

Check at Mouser. I was just browsing their flat cables, and they have a metric fuck ton of varieties.

Tnx.... I'll; give them Mouses a look.

[n2ize]

I think I finally found what I need. Allied has FFC with 20 conductors at 1mm pitch. I need to check a few other specs but so far it looks good. Price is good also.

[KG4CGC]

How many metric assloads in a metric fuck ton?
If a single metric assload is given a factor of 1, a metric fuck ton has a factor of 1.3.

[NQ6U]

If a single metric assload is given a factor of 1, a metric fuck ton has a factor of 1.3.

Thank you for clarifying that.

[KG4CGC]

Thank you for clarifying that.
I'm just happy to be of service :)

[K7SGJ]

The OI812 unscientific calculator will do those conversions with a single key stroke.

[NQ6U]

The OI812 unscientific calculator will do those conversions with a single key stroke.

Good to know, thanks.

[KG4CGC]

Good to know, thanks.
He was just happy to be of service.

[NQ6U]

He was just happy to be of service.

1.3 Metric Assloads of gratitude to you both.

[KG4CGC]

1.3 OM!