Plotter power supply repair

HI all,

I’m told I should place this post here, so here goes:

I have a vinyl plotter/cutter and seem to have blown the power supply. It is a fairly expensive part to replace ($500-600), plus it would have to be shipped from Japan.
Is there anyone who can test and repair this kind of things?
If you can get me (build?) a reliable alternative, that might work too.
I don’t mind paying for it, but the catch is, I need this within 2 weeks.
Let me know if you can help me out, otherwise I’ll have to go original…

Input: AC 220-240V, 0.6A, 50/60Hz
Output: DC +41V,1A / +5V, 2.5A / -5V, 0.2A
Below is a pic to give you an idea about number of components etc.

Just stating the obvious just in case.
Have you tested the fuse?

Other than that there doesn’t seem (from the photo) to be any burn marks or discoloration where it has gotten overly hot. As such it would be hard to debug and get bits within two weeks.

HI lhovo
sorry, should have mentioned that.
Yes I did check the fuse. It seemed fine, but didn’t have a spare to check so checked with a solid wire for a few seconds. That didn’t make any difference.
There is some burning evident from the back, From memory it was at the spool with the horizontal white block (C-L00-332 or something). I’ll check that when I get home tonight.

didn’t get to it last night, so here it is:
this is the back of the board, which shows a few ‘brown spots’.

The worst is at the bottom right, which is at the component below, and the heatsink mount. (Sorry can’t remember what they are called. Are these MOSFETs, or does that just show how little I know…?)

There is also some minor browning of the board around the large blue resistors below, which is just left of the centre in the first pic.

The mosfet is the most likely cause, though it might be a idea to replace those resistors as well with a equivelent power rating.

After some hunting around I think I found that mosfet.

Plugging in the specks into digikey you get a handful of equivalent parts
The cheapest is FQPF6N90C

Ensure you get one in a molded case to prevent it shorting on the heat sink.

Wow, could it really be as ‘simple’ as that! (It helps if you have someone with some clue help :stuck_out_tongue: )
This looks like something I could even do. I’ll give it a crack. Not too much too lose I guess…

Thanks heaps!

Bring it down on a tuesday evening, we’ve got all the gear to make that a super painless procedure. :smile:

Thanks for the offer Rutger.
I have ordered the components. If they come in today or tomorrow, I will! Should be around 8, since I have a volleyball game till 7:30, or not at all I guess.
If I don’t receive the components by tomorrow I’ll have a crack myself. It is an older board and nothing is too small. Think I should be able to do it… (Famous last words…?)

Came home to a package from Digikey, so will try and pop in tomorrow.
As mentioned before; I really don’t mind paying for your help, so please let me know what is most appreciated (eg cash for personal help/the space, case of beer/softdrink, let me know)


As I said last night, if you feel like driving out to springwood then I can pull those bits off and test them.

A board of that age is likely to have bad electrolytics, and if anything else like the MOSFET is gone it is likely to be an effect rather than a cause.

The browning of the PCB was not from a one off incident. It has taken years to turn that colour, so I would not assume the 2SK1985 died a horrible death and burnt anything.

Though the flux residue around that component indicates it HAS been replaced before, so maybe it is a common fault this that power supply.

Because the supply also is not “smart” or communicates with the plotters main electronics - you should be able to easily replace with 2 seperates PSUs a 41V unit and 5V unit no problems.

thanks Andrew,

I tested the large caps and 3 of the resistors, which all seemed fine. Then I got impatient and decided to just replace the MOSFET and see. When I first hooked up I had 5v and 41v output! Unfortunately, when I lightly hooked it all into the machine to try, nothing… Tested the supply again and nothing.
Since I have an extra MOSFET, I’ll have a drink, replace it again and test all the resistors and caps. If no joy, I’ll drive to Jaycar. Saw they have some supplies there for 5v and 45v (I think).
What is a good way to reduce the 45 to 41? Just resistors is not a very good idea, is it?

each silicon diode you go through will drop some where close to 0.6…0.7v independant of current. So you can wire 6 diodes in series to get in the ballpark of 41v

How did you test the capacitors? Their old age failure mode will not be wrong/low capacitance, but high ESR (magic resistance)

If you are driving to jaycar underwood - I am a kilometer from them.

OH - and if you go the series diode voltage drop. Make sure you don’t exceed the power dissipation the diode is capable of. I can’t remeber the current on that 41v rail.

My ‘multimeter’ is really more a digital AVO meter. I found online a way to test by measuring resistance (suggested climbing resistance means it is good). Is that a dodgy way to tell?
Was going to go to W’gabba or Browns Plains, but just saw on the map that it is much the same distance to Underwood…

climbing resistance on a meter is measuering capacitance not ESR.

Ive sent you a PM with contact detaisl if you want to pop in this way when you are at jaycat

Hi All,
I happened onto this same problem with what looks like the exact same power board. My plotter is a Roland Camm Pro 300cx. I know this conversation was quite a while ago, but did you find a solution to your problem? I would really like to have my power board repaired but am not electronic savvy. Can anyone please help me? Please reply.

Hi dkong

as I had a $1500 job waiting for this to be sorted out I decided to cough up some cash and got a new power supply.
Put me back $450 plus $15 shipping. Got it from DES in Darra; if you are interested.

Hi Patrick,
Thank you for your response. I am reluctant to pluck down 5 big ones for a old model. I have access to other cutters but this one is in my home and is very convenient. I think I’ll try to troubleshoot further and maybe narrow down the bad component. Thanks again for your input.

dkong - as I said earlier in this thread - it is likely to be old electrolytic caps. If you are in Brisbane then I or someone else here can probably help with checking that part.

Hi Andrewm,
Thank you for your input on my dilemma.
Electronics is not in my wheelhouse but from some observation of the power board, I found a mosfet on a heat sink that appeared to have discolored the board. So I ordered one from Digikey. However after soldering the new MOSFET 2SK1985,
it still did now power on :((
Shame to buy a new board when only a component needs to be replaced. I just don’t have the knowledge to do it myself.
A new board is out of my budget, but I would appreciate very much if I could send to you the PCB to check over / repair. Let me know what you would charge for this service. This would be great as there is no place where I can bring this PCB in for service.
Much Appreciated…