Repair Versacamm SP-540V that won't turn on

[edugimeno]

Hi everyone! Hopefully someone can give a hint on this issue.
Trying to help my cousin who is a designer and is completly grounded since this machine stopped working

This is a large size plotter. He said he never turns it off, until one day he had to. When he tried to turn it back on, nothing happened....There is one LED in the MAIN board that's on all the time, and also the Ethernet board seems to be alive as it does detect the presence of the wire and flashes green and orange correspondingly

There is a PS board, pretty simple, only provides +41v, which is fed to the SERVO board, and then this one feeds MAIN.

Something I realized is that when I connect the PS socket to the servo board, I get a pretty big spark, like something in that board is taking a lot of current. I checked all Q's and D and found Q1 in Servo Board (P-Mosfet) to be shorted.

Took this Q out of the board and checked that D-G-S pads on the board were not showing the short anymore with the component out. This mosfet drives the Heater in the machine and I thought that it was the reason I was getting a high current spark. But NO, I assembled it all back on with the mosfet OUT of the board (can't find a replacement part yet) and still get a large spark and "POWER" pushbutton on the pannel does nothing

I removed EVERY connection to and from the servo board, everything but PS socket. I still get a spark as I plug it on so it's not a external module or printing head, its the board itself

I measure resistance between + and - inputs to servo board and its in the order of Megaohms...So why does it make such a large spark? Capacitors I though but I can plug it in and out constantly without waiting and I always get a spark, like it shouldn't have had time to discharge right?

I measure the next transistor Q2, which drives the POWER_ON signal, and I get 41 in S and G, but nothing in Drain, like it's not even trying to power on...

I also checked F1 and BR1 and thay show continuity.

What a challenge! These boards have been obsolete for many many years and if I find one online at the other side of the planet they want to charge $1700 for it...

Any, Any hint, would be appreciated!!

Im attaching photos of board (without mosfet installed) and the service manual. Servo board related to this mosfet is on page 36

Thanks

[R_J]

Re: Repair Versacamm SP-540V that won't turn on

Check the voltage on Q5 & Q6, are they being turned ON?
The spark when you connect the plug to the power supply is caused by the 41v capacitor being charged and without anything connected it will remain charged until something discharges it. You should be discharging (with a resistor), the capacitor before connecting the plug.
IC9 supplies VCC, make sure you have this voltage, if you do, check IC13 VCC3 (3.3v), this supplies the main board micro etc.

[edugimeno]

Re: Repair Versacamm SP-540V that won't turn on

Check the voltage on Q5 & Q6, are they being turned ON?
The spark when you connect the plug to the power supply is caused by the 41v capacitor being charged and without anything connected it will remain charged until something discharges it. You should be discharging (with a resistor), the capacitor before connecting the plug.
IC9 supplies VCC, make sure you have this voltage, if you do, check IC13 VCC3 (3.3v), this supplies the main board micro etc.

Really good tips here. Ok I will check VCC from IC9 and 3.3V from IC13. I see the poweron signal comes directly from the uProcessor, and drives Q5&Q6 so hopefully between those stages I should find something.
Unfortunately Q5&Q6 are on the back side so it will be hard to check those while it's all connected but I will see what I can get
Thanks a lot!

Regarding the spark I would expect a spark that charges the capacitors, but if I unplug the PS and plug it back in within 1 second, I still get another spark and my understanding is that during that time the caps woulnd't have had time to discharge, right?

Thanks again

[R_J]

Re: Repair Versacamm SP-540V that won't turn on

Regarding the spark, try not to do that too often, you can damage other parts.
as for the 3.3v vcc3, just find a spot on the main board where you can check to see if it is there,

[edugimeno]

Re: Repair Versacamm SP-540V that won't turn on

Ok, I've just spent a couple hours at mi cousins shop and made...ZERO progress. And now Im seriously stuck!

I put the servo board back in place, still without the mosfet that controls the heater, but that shoudn't affect the rest of the machine. It should still power on and light up the display, etc...

With all in place I measured all VCC's. They are all good. Both in servo board (VCC3 and +27) and Main Board (Vcc, VCC3, VCC1.5, VCC2.5) at their respective IC's (IC44-45-46-47) checking both their input pin and output pin. All were showing perfect values. Also D9 (LED) on main board lights up all the time on stadby indicanting presecen of Vcc (5v)

Also all fuses on both boards are fine, both SMD and glass ones

Suspecting a bad flex cable from MAIN to the PANEL I measured Vcc at the panel on StandBy and I got VCC (5v)

Despite my initial find of a shorted mosfet at the servo board, I don't think the servo board is involved in the basic power-up of the machine. The MAIN board gets the power pushbutton signal from the PANEL, this is driven into the main processor, which in turn will send some initialization signals to other boards, light up the BL from the LCD, show texts, etc....

Is there any ideas anyone can suggest? I already had to tell my cousin that it looks like unfortunetly we may not end up fixing this machine...


Thanks!

[R_J]

Re: Repair Versacamm SP-540V that won't turn on

If the unit is apart, check if there is a safety switch (ie front cover) that is not being activated and the printer is being shut down. It may be that the +41 volts is needed to supply the vhv0, vhv1 supplies that then send an ok to the micro?

This is from the operator manual

Important Note on Switching Off the Power
Never switch off the main power or unplug the power cord suddenly while operation is in progress. Doing so may
damage the print heads. Be sure to first switch off the sub power.
If the main power is accidental switched off, immediately turn the power back on, and then switch off the sub
power.
➀ Main power switch
Turn this switch on after
closing the front cover. To
turn it off, hold down the
switch for one second or
longer.
➁ Sub power switch
Keep this lever raised when the machine is not in use

[edugimeno]

Re: Repair Versacamm SP-540V that won't turn on

There IS a latch in the front that lifts the button panel so you can access the ink tanks and other stuff, and if its opened during operation, it would stop the heads immediatly, but it woulnd't turn the whole machine off and the display would keep on. Anyway we tested to press the power button with the latch door closed.
I will trace the VHV0/1 signals to see what they do, thanks

[edugimeno]

Re: Repair Versacamm SP-540V that won't turn on

This is from the operator manual

Sorry I didn't see this second part (maybe you editted it later?)
I will ask my cousin to see if he turned it off while working but I don't know what "sub power" is. Does it refer to using the front panel "POWER" pushbutton instead of the machanical switch?

Regarding VHV0-1 I found all instances of these signals and they only power the HEAD0 and HEAD1 mechanics behind a motor driver, I don't see any possible feedback from this signal to the processor. Also before I removed the shorted Q1 from the servo board, it was 100% shorted so this 41V would be getting to the VHV0-1 signals and therefore to the printing heads so if it was needed it would be working at that time

Thanks!!