PCB Repair

I hesitate to start with the questions, but I have a few minutes.

What makes you think you have an electrical problem?

Can you trouble shoot PCB's down to component level?

Can you solder?

Can you read resister codes?

The list goes on and on............................

If it was easy, everybody'd be doing it.

Is this something you would personally do? You have to take into account the time needed to affect the repair. If you would hire someone to do it, the cost may be more than the cost of the replacement. Only a time/motion study will reveal which course is the most cost effective.

You should start by taking a class on basic electronics at a local college. This will give you a better basis to understand if the root of your problem is the circuit board or which component on the circuit board is your problem. Once you have a better understanding on how to troubleshoot electronics you can now identify if the electronics is stopping the process or if the mechanics is stopping the process and possibly the electronics is preventing you from wasting more product. Now you could consider hiring one of the many underemployed electronic technicians out there to occasionally refurbish a batch of spare electronics boards that you could keep as spare parts. But I suspect that unless the design of the electronics is flawed in the first place, the root of your problem is not the electronics.

So, how about I just buy the entire borad? Is that possible?

The best thing to ask the manufacturer for repair and let him to tell you about the repair cost in advance, otherwise buy a new machine.

Maybe, but you might have to also buy a programmer for the microcontroller or whatever software that's embedded on that board too. If the board does anything but the most rudimentary logic function (OR AND NOT NOR NAND) then it likely has a microcontroller that needs to be programmed.

You see, there's a reason that so many electronic technicians are out of work today. It is rarely worth anyones time to fix an electronic part today, particularly an old electronic part. Now there are some rare fields that downtime and system failures will be a greater expense than keeping a full time electronics technician on staff. Most of these technicians keep a batch of spares on hand to permit quick downtime recovery. The failed components are then repaired or replaced once the system is returned to operation.

Well, but from where to get the original soft ware program of the microcontroller to re-program it ?

It is only on the hand of the manufacturer and will not give it to any one ?

Today's electronic devices are not repairable, if it fails throw it away and buy new one or send it back to the manufacturer.

My Magic Jack has a problem in its PCB ,I believe it has a cold solder ,can you help me how to fix it ?

And multilayered.

My brother and me ware electronic technicians, after the appearance of Surface Mount Technology (SMT) , both of changed career, me to electrician and he to Auto mechanics.

Sir, you and your brother missed the target, 'Cooling and Heating' is the best choice this time !

Repairing PCBs is not something you should attempt unless you know what you are doing. Modern, multi-layer PCBs have tiny, surface mount components on copper tracks which are very thin and flimsy. Even if you are able to identify and remove the defective component there is a good chance you will damage the track or overheat the new component. You must use lead-free solder which is not easy to rework. This all assumes you have good test equipment and the knowledge to find the cause of the defect. The fault could also be in the software or even off the PCB altogether. How much downtime can you take on your business? How much is your personal time worth compared with the hours you will spend on trying to repair this item? How reliable will the repaired board be and what collateral damage will it cause if it fails?

I started repairing electronic units 54 years ago, including avionics and advanced weapon systems ending up running a Company with a £5M turnover. Now in retirement I am still doing electronic repairs and mostly enjoying the time doing something useful for small independent service engineers around the UK. I use the best soldering equipment and still get into trouble sometimes so you are on a very expensive learning curve. My advice would be to buy a repacement PCB and look through your local area for a repair workshop - there is always a guy like me working away on a home bench near you. He will repair your board and you will have it ready to use next time the fault occurs.

Good luck

This is major draw back of PCB system. If any one of tiny part goes you need to replace whole card, which is expensive also other good parts go as waste.

I do it for a living, over 40 years, consumer and industrial, DIY repair to a component level (involving embedded systems)? - forget it..

But, but most of the problems, and the one you're describing, is most likely caused but other hardware problems, i.e. defective switch, dirty optical sensor, jammed mechanizm, mechanical misalignment, etc.

I'm big on Do It 'Yourselvsism', and with a flood of info available at you keyboard & screen, search the web for tips, there is million websites that may give you a sound advise (caveat: many are unsound) and in some case you may find a solution.

Good luck.

I believe that the old style PCB's with conventional discrete components are much more reliable than the new ones based on microcontroller.

Most PCBs, old and new, are reliable until the batteries leak, the software gets updated and someone who should know better tries to do a repair!

Old PCB's work on 12V supply and the new one's on 5V or less ,12V supply gives much more immunity against noise effect

I am agree with AfricanGiraffe that the old style boards are more reliable but the cost is much more higher.

Now I'm quit sure that mr.Mekhemer is a spiritual and technical expert at the same time.

http://cr4.globalspec.com/thread/58951/Whale-Suicide-Phenomenon

1) Check for bad solder joints; 2) Check for fried components; 3) Check to see if the board itself is broken; 4) Check all power supply voltages; 5) Check to see if clock is running; 6) Check bias of all transistors; 7) Check the remaining electronics.

As mentioned by others, it depends on what technology the board is. If this is an older single or 2-layer PCB it is easier to repair. Otherwise, modern PCBs are designed to be throw-away, except for sophisticated instruments and hardware. Even boards in PCs are mostly throw-away if they go bad. Most technicians and field engineers in today's world do NOT troubleshoot to the component level. They diagnose and replace bad boards/modules. Another subject is the sometimes poor manufacturing quality of stuff being built in China or other Asian facilities. Not all are bad, but enough -- especially in consumer type electronics.

Like tom (post #12) I've worked in electronics for many years (38) and surface-mount technology has changed the skills needed for repair. The proper equipment is necessary, also. Otherwise you might seriously damage an otherwise usable board.

My point is that when one of the component of PCB is busted why all other components should be replaced. It is expensive process.

Well you're overlooking a few critical ideas. First, the other parts on the PCB are just as old as the part that wore out. Second, when the part that wore out dies, it likely stressed if not damaged the other parts on the PCB. Lastly, the process of electronic diagnosis and repair takes a considerable amount of time. This is particularly true when one does not repair that particular system regularly. So when one does a simple cost benefit comparison of the cost of a spare board with new parts and repairing a board while your system is down, most of the time it is less expensive to just install the new spare board. Now once the system is up and running, the technician may test the failed board on a test jig and decide if this PCB is worth repairing. But soon one realizes that it is a rarity that PCB repairs are worth the effort and keeping the infrastructure and knowledge base to do effective repairs are cost prohibitive on anything but the most expensive systems. I doubt that the OP printing operations meet this criteria.

I've just re-read your original question and think you are talking about the guillotine blade on a cash register?

Before you start repairing/replacing the PCB check that the blade moves freely - the dust and ink from the paper can form a ridge on the blade which eventually makes it stick. Then check the resistance across the solenoid coil - it should be a few ohms. If the coil is open or short circuit that is bad. If you fit a new PCB with a defective solenoid you will probably blow that up too! With this type of fault the PCB will likely show signs of a burnt component, if you know the value and have the right part to replace it with then always chop the old component out leaving just the pins which are much easier to unsolder and less likely to damage the PCB tracks. Remember to make a quick sketch of the connectors positions to help you reassemble it all

Other things to check on printers - always use good quality ink ribbons as the ink contains a lubricant for the print head needles. Check the edge of the cutter blade(s)the cashier might have dropped a coin into the slot - happens more often than people imagine especially on a counter where the cash passes back and forward over the top of the register.

I'm sure you will know to take the usual safety precautions and good luck with the repair.

Apologies Tom - Just caught your post. GA.

More likely the solenoid return spring or a sticky mechanical thing.

There will be an interlock on the board and a sensor to detect the blade is at 'home', to prevent paper feed it it's not, as that = massive tangle and choke

That it is 'shutting down' indicates the problem is not electronic.