From the looks of the attached PCB image, it's obvious that the PCB is bad.

But, I can't seem to find what caused this issue with the PCB ?

 

What the image shows appears to be some surface contamination on a printed circuit board. That is not an adequate reason to call the PCB "bad". A fair guess is that the material came from that capacitor located near the center of the contaminated area. BUT that is only a guess, based on having no other information provided.
That contamination may also have arrived from some source external to what we see.
What is the complaint relative to that PCB??
Of course, given that we get only a small view, and no hint as to the context, there may be another source of the problem.

Requesting a useful response without any adequate context of the situation is seldom likely to obtain a useful answer.

 

Looks like an explosion of something, maybe the capacitor or some silicon device. What is the pcb for?

 

Looks like dust, dirt, and water contamination.
First thing is don’t attempt to power it up.
Clean it with isopropyl alcohol and a soft bristle brush.

 

1. The PCB is for Samsung Laser printer - ML 1640
2. I too thought it was a capacitor leak. But, this black stuff appears in contact points ( much far away from the area where there is more black stuff ).
3. Can the SMD capacitor leak ? And can it go in between PCB layers and appear in random contact points ?

 

If it is not some discharge from the bottom of a failed capacitor, then it may be the condensed vapor from some arc (spark discharge) incident. Arc Flash can also happen in much less exciting instances than what we see in the training films.

 

I suspect a nearby lightning hit got into it (EMP). Just one more possibility…
Or, something dripped onto the board from elsewhere.

 

Clean it with isopropyl alcohol and a soft bristle brush.

Yep, you have to start somewhere and that is a good start point. Wash it off and see what you have.

Ron

 

Toner leakage?

 

Printer was not working initially. But, after I cleaned the PCB with IPA 3 weeks ago, it started working.

But, the issue is sometimes it randomly stops working and sometimes it works. The USB cable is fine. The moment the PCB starts working, my computer gives an alert ( new USB device detected ).

Attached is the current full PCB image with the power supply ( Note the arrow mark for physical orientation ). With this orientation if you compare the original image, most of the guesses ( Capacitor leakage / Toner Leakage / Fire etc ) will be ruled out due to reasons like gravity ( for direction of leak spread ), physical protection ( toner cartridge is exposed to the rear side of the PCB which is totally clean ), Fire ( black stuff is not uniform, as the black stuff appears in random soldering contact points ). I've checked the power supply voltages from the power supply board to the PCB 3 weeks ago, and all voltages were fine.

The spread pattern of the black stuff is very specific and gives a lot of clues, but I cannot guess what it means.

One thing was that the printer was not used very frequently, and sometimes not used for months together. It was in a good storage location ( not in a basement with any leaks / pests etc ).

I can probably get a new printer formatter board, but I wanted to be sure that the issue is with the PCB before throwing it out. Because when it works, it works 100% fine continuously. But, if I try next day it stops working. I don't want to get a new PCB only to get the same printer red LED blink errors.

Thanks!

 

Printer was not working initially. But, after I cleaned the PCB with IPA 3 weeks ago, it started working.

But, the issue is sometimes it randomly stops working and sometimes it works. The USB cable is fine. The moment the PCB starts working, my computer gives an alert ( new USB device detected ).

Attached is the current full PCB image with the power supply ( Note the arrow mark for physical orientation ). With this orientation if you compare the original image, most of the guesses ( Capacitor leakage / Toner Leakage / Fire etc ) will be ruled out due to reasons like gravity ( for direction of leak spread ), physical protection ( toner cartridge is exposed to the rear side of the PCB which is totally clean ), Fire ( black stuff is not uniform, as the black stuff appears in random soldering contact points ). I've checked the power supply voltages from the power supply board to the PCB 3 weeks ago, and all voltages were fine.

The spread pattern of the black stuff is very specific and gives a lot of clues, but I cannot guess what it means.

One thing was that the printer was not used very frequently, and sometimes not used for months together. It was in a good storage location ( not in a basement with any leaks / pests etc ).

I can probably get a new printer formatter board, but I wanted to be sure that the issue is with the PCB before throwing it out. Because when it works, it works 100% fine continuously. But, if I try next day it stops working. I don't want to get a new PCB only to get the same printer red LED blink errors.

Thanks!

My bet is that the electrolytic capacitor at the center of the mess is guilty. If it is a surface mount device it should be fairly simple to replace. A two terminal device should not be terribly hard to unsolder, and installing a replacement capacitor should restor the functionality. Also, that part is not terribly expensive. But be sure to clean that black stuff off while you can do it conveniently. Alcohol may be an adequate solvent to remove it.

 

Toner leakage?

I don't own a laser printer, but that was my first guess, initially, it looks more like ink 'spillage' than a Cap blowing over that area?

 

I don't own a laser printer, but that was my first guess, initially, it looks more like ink 'spillage' than a Cap blowing over that area?

Good point. I would be looking for another reason for the intermittent operation, for example, a heat stress test.

 

My bet is that the electrolytic capacitor at the center of the mess is guilty. If it is a surface mount device it should be fairly simple to replace. A two terminal device should not be terribly hard to unsolder, and installing a replacement capacitor should restor the functionality. Also, that part is not terribly expensive. But be sure to clean that black stuff off while you can do it conveniently. Alcohol may be an adequate solvent to remove it.

Did you get a chance to look at the second image ( today's image of the PCB ) attached ? ( as I have already cleaned the PCB with IPA ( iso propyl alcohol 99.9 % ) 3 weeks ago ). The original bad PCB image was 3 weeks ago.

 

I don't own a laser printer, but that was my first guess, initially, it looks more like ink 'spillage' than a Cap blowing over that area?

1. As already mentioned, only the rear side of the PCB is facing the printer ink section. Read side of the PCB is 100% clean.

2. Even If it's any kind of spillage, how come the black stuff is in some remote place particularly surrounding contact / solder points and not evenly distributed ?

 

My bet is that the electrolytic capacitor at the center of the mess is guilty.

If you compare the 2 images ( bad and cleaned PCB ) with the direction orientation ( pink arrow ), it would be obvious that this leak has happened in lots of places in the board, particularly around solder / contact points. If it was 1-2 capacitor leaking, it should be around and below those capacitors ( due to gravity and the physical fitting of the PCB to the printer ). But, the black stuff is there in places far away from any capacitor.

 

What I see is liquid damage. Coffee cups and soda cans do not belong on top of printers (or copiers) or "accidents" happen. "Black Stuff" is probably toner since it is a laser printer. Cartridges tend to leak sometimes, especially when changing, and toner gets into everything. Liquid damage is not easy to fix and toner dust while not electrically conductive, can cause problems for electrically sensitive devices due to static buildup. They make a special vacuum for toner cleanup that uses a "grounded" hose and HEPA filter as toner can go through a standard vacuum filter due to its small diameter.

 

OK, I saw that the board was cleaner, but the complaint could have been related to a failed capacitor. That part might be innocent, or it might not. Probably all of the connectors could stand a bit of contact cleaner spray, and being un-mated and then reconnected. That plus the cleaner has solved problems many times for me. Simple, cheap, and easy.

 

Printer was not working initially. But, after I cleaned the PCB with IPA 3 weeks ago, it started working.

But, the issue is sometimes it randomly stops working and sometimes it works. The USB cable is fine. The moment the PCB starts working, my computer gives an alert ( new USB device detected ).

Attached is the current full PCB image with the power supply ( Note the arrow mark for physical orientation ). With this orientation if you compare the original image, most of the guesses ( Capacitor leakage / Toner Leakage / Fire etc ) will be ruled out due to reasons like gravity ( for direction of leak spread ), physical protection ( toner cartridge is exposed to the rear side of the PCB which is totally clean ), Fire ( black stuff is not uniform, as the black stuff appears in random soldering contact points ). I've checked the power supply voltages from the power supply board to the PCB 3 weeks ago, and all voltages were fine.

The spread pattern of the black stuff is very specific and gives a lot of clues, but I cannot guess what it means.

One thing was that the printer was not used very frequently, and sometimes not used for months together. It was in a good storage location ( not in a basement with any leaks / pests etc ).

I can probably get a new printer formatter board, but I wanted to be sure that the issue is with the PCB before throwing it out. Because when it works, it works 100% fine continuously. But, if I try next day it stops working. I don't want to get a new PCB only to get the same printer red LED blink errors.

Thanks!

I don't know if it's just a trick of the light, but does the small electrolytic cap below and to the left of C105 on the PSU board look to be bulging slightly. It doesn't have the crossed top style, so may not have built up enough pressure to have popped it's bottom plug yet.
Just a suggestion.

 

If the complaint is an intermittent malfunction, I still suggest cleaning the connectors and possibly additional cleaning of the PCB. Simply cleaning does solve enough intermittent problems to make it worth the effort. Also it is cheap and easy.