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Noob Help, Power Board Problems, Parts Advice

Tyler Durdem

Nov 16, 2014
7
Joined
Nov 16, 2014
Messages
7
Hello Everybody,
This is my first post, I'm looking for a long term place to lurk so I am glad to find this site. I'm getting into small electronic projects but this time I have a stressful repair for myself that popped up and need some help.

I have an industrial printer, I went to turn it on and there was no power at all. I replaced the main fuse cause it was burnt out and then the power resister fried as soon as I plugged it in.

I need to get this thing back up and running, so I can work.

The other problem I found with my meter was a bad transistor. I don't know what caused the problem but I suspect the printer turned on for a self cleaning over night and it is possible a servo motor was stuck and blew something. That's all I can think could of happened, because it worked perfect the day before.

Anyhow, Im trying to replace parts and fix this thing.
My questions are, what is the best replacement for the burnt resistor. I can't find an exact, See pic, I don't want to cause more damage.

The transistor pictured is hard to come by, what would be a good replacement spec wise? What else should I check for, I'm very worried other parts are fried or when I put it back in It could break again or damage another board. This printer has like 5 circuit boards. Its a large roland 545ex.

I'm not good at testing, I just happen to be lucky to find the bad transistor when compared the the same one next to it. This is the power board for the printer.

Any help or suggestions welcome. I tried to find a local tech but all that you can find now are ipod repair places.

Thank YOu
Capture 2.JPG Capture 1.JPG3.JPG
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
Hi Tyler and welcome to Electronics Point.

1) Can you tell us how you determined that the transistor had failed and what you replaced it with? (BTW, it's a 2SK2915)

2) Also can you tell us what the rating and type of the fuse was that you replaced and the type and rating of the one you replaced it with? (is it the 6.3A 250V fuse visible in the bottom image?

Power supplies can fail when switched on, so it may just have failed at that time.

3) It appears from the last image that you have removed two transistors. Are they the same type? (OK, these would be the two you compared?)

4) Do you have access to a circuit diagram of this power supply?

5) can you take a picture of the other side of the board?

The failed resistor is 10Ω like the replacement one on the left. Note that the original is radial, the replacements are axial. If you replace the radial resistor with an axial one you need to insulate the lead that will be bent down from the top. It may be at mains potential and (in any case) you don't want it shorting against anything.

You also need to be aware that when connected to the power this board can kill you. The large green capacitor will hold a charge from anything from seconds to hours after power has been removed. It can give you one hell of a belt, and is also potentially waiting to kill you. Be careful.

6) Your desoldering looks pretty good on that mosfet, how much experience do you have and do you have a multimeter?

Please try to address all of these questions so we can all the information we need before we continue. :)
 

Tyler Durdem

Nov 16, 2014
7
Joined
Nov 16, 2014
Messages
7
Wow thanks for the reply.

The original fuse was 6.3a 250v I replaced it with 5a 250v, all I could find at the time and I figured less A would not hurt anything. I was surprised the 5a did not blow when replaced even when the resistor was burning up. It happened so quick I could not do much but stare into the glow.

I did remove the two transistors to test and confirm that one was bad,
They are the same so it was easy to test with my MM. I removed both because I was unsure if other components could fault the testing.
I ordered some replacements

I have a decent MM and look to Youtube for how to test components. I had a similar problem before on a head board where I was able to fix it with the replacement of one transistor and a micro fuse.
These boards cost 1k plus and take time to arrive. I use the printer to make money so I'm out of work until I get it running.

The printer turns itself on overnight and does a 3min cleaning, which include running 3-4 stepper motors to turn the ink pumps. I know one has been jamming up which leads me to suspect that may have caused the original board failure.

I will take better pics and look for a schematic.

Thanks so much, I really appreciate the community's help.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
They are the same so it was easy to test with my MM.

OK, but because they are mosfets it is possible that they could be in a different state due to a static charge on the gate.

It's quite possible that one of the mosfets is dead, but you need to check correctly. For example, you should connect the gate to the source, then check the resistance both ways. You should see a diode. If you see conductance both or neither way then the mosfet is toast. If you do see diode action then it *may* be OK.

So presumably you ordered and installed some 2SK2915's?

I'll wait for the photos and to see if you turn up a schematic
 

Tyler Durdem

Nov 16, 2014
7
Joined
Nov 16, 2014
Messages
7
I cannot locate a schematic, but here are a few more photos.
New part number is 1000007552.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
Can you point me to a link showing the specs of this "1000007552" device?
 

Tyler Durdem

Nov 16, 2014
7
Joined
Nov 16, 2014
Messages
7
Hi Steve,
I wish I could, this thing is harder to find than big foot.
I found a service manual and it has diagrams for the other boards but not this power supply.
I see It's made by Nichicon with an internal part number of K-F01-027-A11, I cant find info on that as well.
I am going to call Roland tomorrow and see if I can get any info or parts from them.
 

Tyler Durdem

Nov 16, 2014
7
Joined
Nov 16, 2014
Messages
7
Thanks all for the help,
I ended up getting a new board an it all is working fine now. I am going to work on getting the old one repaired.
 
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