vinyl cutter power supply

[crow11]

hi all another newbie here and just wondering if someone could help me out please
bought a second hand us-cutter mh 1351 vinyl cutter/plotter was working ok when i went to look at it and was working for first 5 minutes when i got home then all of a sudden everything went off no lights no screen,so took the bottom off and came across the power supply i have tested the feed into the supply everything ok checked the onboard fuse its ok, now when i come to test the dc output side there is nothing to any of the contacts its is if the dc side is totally dead in the pic you can see a green led just behind the 18v contact which does not light up either the powerboard to me doesnt look that complex(but im a newbie so it could be lol) and could some please explain why there is a -8v and where to start checking first these are the best pics i could take as its night time here cheers

 

[(*steve*)]

The photographs are too poor to make out much in the way of detail and I can't read your notes on the last one.

However that's a switchmode power supply, and I presume that you have removed several heatsinks to get this board out.

Be aware that the board almost certainly operates with a significant portion at mains potential, and has a capacitor that can store about 300V for long enough to give you a very alarming surprise hours after the power was last applied. With the power connected the surprise may be the last you ever get.

Try to get higher resolution images which allow us to read what is written on the board.

There is a -8V rail because something needs it.

My guess is that something may have jammed in your vinyl cutter and with a motor stalled the power supply could not handle the overload and died. Many common failures will then result in the fuse immediately blowing, so you may have a somewhat atypical fault.

 

[crow11]

updated photos

i have now updated the pics to the best i can get them, yes i took the heatsinks off to get try get better photos, on the last pic there is a row of connectors they are labeled as follows left to right 36v/gnd/18v/-8v/gnd/5v then the mains supply in the ground next to the 5v doesnt get used hope this helps cheers

 

[(*steve*)]

OK, several things...

Since you have removed the heatsinks, you may have to replace the heatsink compound when you put them back on. Also there may have been insulating washers and/or plastic bolts that you will have to put back in the correct places.

Also, you say the fuse is OK. Is this based on examination, or by measuring the resistance across it?

Was there a jam or something in the cutter? Were you cutting something particularly difficult for this machine?

Please see this thread, and assume I've asked you all the questions I asked there. (There's probably some that you have already answered).

 

[crow11]

thanks for the reply i have had my tester on the fuse while powered up and getting 240v to both sides and i have had my tester on the components just after the fuse and getting voltage all the heatsinks had no plastic on them they all connect up with metal bolts, it didnt even get to the stage where it started to cut just loaded the some vinyl and click send on the program to cut but it takes a couple of seconds before anything moves to cut i was stood right at the side of it and noticed it wasnt lit up cheers