Need Help ROLAND SP-540V SERVO BOARD REPAIRING

[conan981]

Hello , i hope someone can help me into repairing this sp-540v servo board. i have a short to the ground on the output of IC13 ( voltage regulator) but i cannot understand what this 3v goes in to power.. Can someone with more experience in this stuff give me an hint?
will happily pay for any help
thanks

 

[damonCA21]

I'm not sure what you mean, but have you removed and tested C29 and C71? If either has failed it could be causing the ground at the output. Other than that the regulator could have failed internally, in which case just replace it.

VCC3 is not powering anything on the regulator, that is the regulated voltage coming out of the regulator

 

[damonCA21]

I'm not sure without looking at the whole circuit, but when you measure between OUT and GND on the regulator you should see a small voltage there, probably around 5V

 

[netsol]

you need to systematically remove loads and find the shorted component/board

order a service manual
or
choose a company to send the board to for repair

(1) inkjet performance in georgia

(2) search for roland circuit board on ebay. find someone offering repair services or selling a fair number of boards WITH GOOD FEEDBACK
use "ask seller a question" and see they want to work on your board.

for what it's worth, to me a 3v dead short strongly suggests a shorted cpu or other major chip.

i am not familiar ENOUGH to tell you whether there are major revisions on these boards that have to match (and it is too late to check your
old board. perhaps solventinkjet or one of the other techs with more experience on these machines can post

you might also try to find someone with a HUNTRON TRACKER an old piece of technology but one of the few instruments that can
identify which component on a source is shorted. a great piece of technology to troubleshoot this type of problem without desoldering,
cutting and resoldering foils & generally make a mess of your board

the problem is THE CLOCK IS YOUR ENEMY. all of this takes time, and unless you are really meticulous about keeping the captops wet, you will probably destroy your head.

 

[damonCA21]

Agreed Netsol.
The other quick and dirty method ( if you are experienced in soldering ) is to replace all the components directly connected to the regulator and the regulator itself. This can sometimes work if you don't have test equipment just by trial and error.

I would be definitely looking at C29 as most faults on boards are caused by electrolytic caps going bad.
The other bad news apart from the head drying out as Netsol mentioned, is that any faults with the main chips are not repairable as you can't get them, so you would need to replace the board.

Often it can be cheaper to buy a used board rather than using a repair company ( I know the one that advertises on Ebay charge around £500 inc shipping for a repair, and used servo board is normally £350 - £400 )

 

[conan981]

thanks to all for the answers.this regulator take in input 5v and should give 3v output (called VCC3 into service manual) (that doesn't give power cause the short).

indeed I didn't tell you all the tests I had done. once I found the short on the output of the voltage regulator, I obviously desoldered the regulator and tested on the board whether the short circuit to ground remained (and I tested the regulator on the bench alone, and it works correctly). Then obviously I removed the capacitor C29 (tested and ok, the C71 and also the resistor R127 but they are all working... the short is not in those components,if i check on the board with those components removed , short to ground is always there.I wanted to find which integrated circuit was powered by that 3V output voltage from the regulator.
i have the service manual for this board, but I honestly haven't been able to understand the answer to the previous question yet

to me a 3v dead short strongly suggests a shorted cpu or other major chip.

i suspected broken IC11.. but i would check without desoldering/resoldering it if possible.

the problem is THE CLOCK IS YOUR ENEMY. all of this takes time, and unless you are really meticulous about keeping the captops wet, you will probably destroy your head.

i have not this problem. since i make all the tries only with electronic board.. and even turned off I can see if the short circuit disappears

thanks to all for the hints , i hope someone else too can give his contribution to help me
of course, maybe in the end i will have to replace the board or send it to china service for repair, but since i have no problem in soldering/desoldering/checking electronic components maybe i can learn something new.

 

[damonCA21]

The service manual should have the schematic in it so you can check from there where the output goes to.
p.s. don't send it to china to get it repaired !

 

[netsol]

p.s. don't send it to china to get it repaired !

Oh, God no!

 

[damonCA21]

The next step I would take is to follow the schematic and find out where VCC3 goes to, and what else is connected to it. As all the components you have checked so far are on the same node ( the output of the regulator ) where you are seeing the short, then the short must be being caused by something further along the path

 

[netsol]

many of the medium sized computer depot repair facilities have hot air stations for repairing these boards
(a few years ago, NVIDIA had a huge problem and 500,000 laptops with their chipsets needed to be flow soldered,
creating a new industry!)

you may be able to find someone "local" to change that ic, without the proper equipment it would be very difficult

 

[damonCA21]

Having a quick look at the schematic VCC3 feeds a lot on the board as it is the main supply voltage for the ICs

 

[conan981]

ok, after some measurements and a bit of reasoning, I desoldered the IC11 chip, and voilà the short circuit disappeared, the absorption dropped a lot (and obviously the same error still remains ) I don't want to be wrong but that integrated circuit is programmable, so now the hopes of being able to repair the board are considerably lower. I wrote this to close the topic (for the moment) and still thank everyone who responded and helped me

 

[damonCA21]

Well done for finding it, but yes, you won't be able to get a replacement chip for that as it would be custom made for Roland and they have never sold them seperately. The best option now would be to look for a working used board instead

 

[netsol]

i will reach out on monday with some of the companies i have gotten used boards from

i still say ebay>ask seller a question will be your best bet

that almost always works for me

everyone who does this has a substantial junk pile