repair plc and pcb

hy all
I repair plc and pcb in in an electronics workshop most of the pcb
are ralated to many types of plc most of them are with no circut diagram i hope to upgrade my skill in this field.
I will be greatfull to see any notes or websites that help me in my job.
thanks

I think it will be tough to get schematics for PLCs. There was a somewhat similar question in THIS thread...

You may want to PM Kaz and ask if he has found anything. He'd probably be willing to share any info, as you aren't close enough to be stealing any of his business...

beerchug

-Eric

I have never been able to get schematics for modules. But then I have trouble finding stuph on Google. I have come to rely on Eric for "links"

I am not sure if the PLC repair depots have schematics, or if they reverse engineer the modules and PLC's.

When I was doing work for General Electric, I was told it was not possible to get them, or to even see them in when in the factory.

When I worked on two-way radios, we often didn't have schematics available, often the manufacturers were out of business. But we always seemed to get by.

Most manufactures probably feel that if they gave out their schematics, that someone would make them in their basement and sell them real cheap.

Would you pay $100.00 for a new "AB" I/O card ??? when factory price is considerably !!! more.

I spent several years at a diesel-electric traction drive minig truck manufacturer, and a couple of more at a locomotive builder. They would get large complex wiring harnesses back for warranty, only to find that someone else had made them and sold them as factory original at a considerably cheaper price. (They cost several thousand dollars each)

Anyway, I think you are just going to have to fly by the seat of your pants.

regards......casey

PCB repairs

Juad
I have spent my first 3 years of working in repairing control PCB's ,motor drives ,Process controllers....etc
Most of this were coming without schematic diagrams and i usually using the traditional measuring methods dor electronic component such as diodes ,transistors,Scr and using digital voltameter.
Regarding IC's i was have three devices for testing
1-IC testing system(I don't remember it's name now)but the new
version of it is "SYSTEM 8" by ABI for testing IC's in board.
Sometimes the result was not accurate because to test IC on boared
you must generate a high impedence around it to be isolted from the
rest of the circuit hence the testing result will br for the IC not
the Thevinen equivelent.
2-Digital IC tester BY ABI ,testing difital IC's out board.
3-Analog IC tester BY ABI ,testing Analog IC's out boared.
These 2 methods were taking alot of time in desoldring and
soldring the IC,s from PCB beside you have to draw the layout of
the PCB to know exactly the location and direction of each IC when
you resolder the IC's.you must be profissional in slodring and desoldring in order to remove the IC's without any damage to the PCB tracks or the IC it self.

4-I-V curve comparator by Huntron and you must have a good PCb to compare with in this case.

Any how this field is vanishing know in Egypt due to the newest technology in PCB's and IC's like multilayer PCB's and Surface mount technology in IC's.
Regarding repairing PLC cards usually as i mentioned above i got the cards without any schematics,when i got a failed power supply module it's easy to repair and i do it many times ,when you get I/o Modules it's easy to repair when the fault in the ISolation stage usually Opto coupler or in the output stage(Output module)to replacea malfunction relay or transistor or whatever.
I alawys refuse to recieve CPU modules for repair and i apologize for the client that we can't repair this type of cards(Multi layer PCb,ASIC IC's not commercial one,and others)
I hope that this information could help you.
Good luck

ERIC,KC9IH,HESHAM
thank you very much for your notes ,it is really good .
I still work with ABI SYSTEM 8 in circut ic testr and leap
programmer and depend on my experence to expect the fault item.
in incircut ic tester i allays desolder the crystel oscillator , reset any processor and any signal generator (timer multivibrator,..)
it help some thing but still some test is failed.if the PAL is under
security fuse i do nothing to check it because it seems like blank one). and so many problems that limit the ability to repair the PCB.
thanks again

Like most electronic devices today, the labor required to troubleshoot and repair a PLC often winds up more costing more than a new replacment. IMO, anything beyond renewing fuses and replacing I/O components is just not worth the effort. I'm sure the majority of your work involves doing exactly this, as the I/O is the most susceptible to damage.

Best of luck in your endeavor!...

beerchug

-Eric

Like most electronic devices today, the labor required to troubleshoot and repair a PLC often winds up more costing more than a new replacment.

Click to expand...

I have repaired many a PLC (usually output transistor gone or output relay failed) where replacing the plc is not a cost effective solution.

Reason; no programming software for that brand of plc.

Plus I have seen people charge unbelievable fees for uploading and downloading a program from a bad PLC to a good one.

ERIC, GOODY
thank you very much
In my country the price of PLC and I/O is very very high with respect to the price of repairing pcb, replacing fuses and I/O is done in the factory fields i just recive the faulted (cards) . some times it is easy and other we cannot repair it.
in genareal I would like to point down the problems that face
me when repairing plc:
1- you cannot be sure that the I/O is good unless you be sure that it
communacite with plc through rack that mean you must collect all types of racks ,soft ware and communaction cabels.
2- I cannot find the pin configration for some components .
3-some times we did not find the checksome of the eprom fixed in the label so we cannot be sure that the program have no change.
4- as I said before the PAL is putting under security fuse.
5- I dont know if there is any limits that prevent using ICBASE.

thanks to all..... I am very greatfull