file Frage Dead 420 Help please!

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14 Jan 2017 14:26 #42505 von Garth15
Dead 420 Help please! wurde erstellt von Garth15
After almost 2 years of excellent service, my 420v2 has given up the ghost. When I went to use it this morning, everything seemed to fire up ok but when I came to nudge the spindle - nothing moved! After checking at the back of the machine the little power light does not come on. I have checked the power supply output and am getting the requisite 30V so it appears that the main board has died for some reason.

My question is, is anyone aware of anything I can check / replace on the main board? Or is it a question of obtaining a complete replacement board?

Also, does anyone have a circuit diagram of the board? Even if I have to replace the complete board I would like to understand what element on the board has failed after just 2 years for future reference.

Thanks for any help.

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14 Jan 2017 14:41 #42507 von MagIO2
MagIO2 antwortete auf Dead 420 Help please!
Have a look here , the part which has F4A written on it is a fuse. Very likely it`s gone.

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14 Jan 2017 15:31 #42509 von Garth15
Garth15 antwortete auf Dead 420 Help please!
Have just checked and fuse appears to be fine. Thanks for the suggestion.

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14 Jan 2017 16:15 #42513 von peterg1000
peterg1000 antwortete auf Dead 420 Help please!
Garth,

Have you measured voltage at PSU plug when disconnected or actually on the board itself at the back of the power socket.

I've just recovered from a PSU failure where volts were fine on the plug, but dropped to virtually nothing (<1.5V ) when connected. The control board was fully functional with a new PSU.

Peter.

SC 420/2, Industrial VFD spindle from StoneyCNC
UC100 + UCCNC
Cut2D, Autosketch10, Draftsight, Eagle 9.5.1


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15 Jan 2017 13:43 #42556 von CNCMiller
CNCMiller antwortete auf Dead 420 Help please!
Did you check your crash-stop button.

could accidentally been triggered?

SC 1/420 + Gantry extension, Kress 1050 FME-P, NeJe 20W Laser, WinPC-NC USB v4.00, Vectric Aspire 9, SolidWorks 2021

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15 Jan 2017 14:05 #42557 von MagIO2
MagIO2 antwortete auf Dead 420 Help please!

CNCMiller schrieb: Did you check your crash-stop button.

could accidentally been triggered?


Unlikely because of: "power light does not come on"

SC 420 mit DIY parallel + Proxxon mit Mod + HF500 + SprintLayout + LibreCAD/QCAD + FreeCAD +WinPC starter/USB->EstlCAM + EstlCAM LPTAdapter + EstlCAM Handrad + DIY Vakuumtisch

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15 Jan 2017 18:48 #42577 von Garth15
Garth15 antwortete auf Dead 420 Help please!
Thanks for the input guys,

CNCmiller - As Andreas points out, no power so can't be the switch. But I tried it anyway, just for completeness ! Unfortunately no effect.

Peter - If I measure the voltage on pin 5 of IC5 (LM2574 step down voltage regulator) I get 30V. When I measure the output on pin 7 I am getting nothing. I am not an electronics expert but this suggests to me that this voltage regulator is deceased. Looks too tricky to replace so have ordered another board from Rory at StoneyCNC.

I don't know why this chip should fail (if I am correct in my assumption that this is the culprit!) but will continue to investigate further down the circuit and report back anything I find. Might be useful for others as future reference.

Thanks again for all of your input. Any other thoughts would be be gratefully received!

Garth

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15 Jan 2017 21:48 #42582 von peterg1000
peterg1000 antwortete auf Dead 420 Help please!
Hi Garth,

It sounds as though your diagnosis is correct - a dead LM2574N-5. However it might be that there is a short between +5V and ground, it's worth checking just to eliminate the obvious.

If the IC is dead, then as it's a standard DIP8 dual in line package with 0.1" pin spacing it should be relatively easy to replace. The trick is not to try to unsolder everything at the same time, just cut off each pin close to the IC and then remove each one individually using a fine tipped soldering iron (2mm tip or thereabouts) on the non component (solder) side of the board

The through holes would need to be cleared before inserting a replacement part. Use a solder sucker if you have one, or failing that, sharpen a cocktail stick and gently push that into each hole when the solder is melted. This should allow the new part to be inserted easily - dont force it just in case you damage any of the through hole plating.

Resolder the new part taking care not to overheat or use excess solder. The LM2574N-5 can be bought on eBay for around £5 or so in UK.

Good luck if you try this.

Peter

SC 420/2, Industrial VFD spindle from StoneyCNC
UC100 + UCCNC
Cut2D, Autosketch10, Draftsight, Eagle 9.5.1


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16 Jan 2017 11:29 #42602 von Garth15
Garth15 antwortete auf Dead 420 Help please!
Thanks Peter,

Little bit clumsy when it comes to soldering so plan is :-

New board is ordered and should be with me tomorrow (Tuesday). I will install and hopefully all should be OK and I can get on with current project.

However, I have also ordered a couple of LM2574N-5 (£4 on eBay) and when they arrive on Thursday I will have a go at replacing the dud (assumed) and will test the renewed board without reinstalling into Stepcraft.

If successful I will end up with a spare board. Expensive exercise but at least will have got to the bottom of the issue (at least the what, not the why!)

Again if successful, may be useful to others if they have a similar problem - £4 for new chip rather than £120 for new board.

Will report back later in the week on my soldering efforts!!

Many thanks,
Garfth

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20 Jan 2017 11:41 #42835 von Garth15
Garth15 antwortete auf Dead 420 Help please!
Good news is that new board installed and I am up and running again!

Bad news is that I have replaced the assumed culprit voltage regulator on the old board to no effect. Bit of a b****r to remove the old one but followed Peters advice and finally got there. Started using my fine point 12W iron but not up to the job so had to file down the bit on my 25W iron to get the job done.

Measuring the voltage at the JP5 pads, I don't get any voltage. Leaving the common probe on the GND tab and touching the +ve probe either side of the fuse F1 I get 30V so fuse is ok. Touching on pin 5 of the voltage regulator I get 30V (my soldering worked!). On pin 7 I get nothing.

I am at a loss to know how or where to look next. Also not sure I could replace any of those miniature surface mount components anyway without totalling the board.

So it looks like the end of the road for this thread, unless anybody can come up with a magic silver bullet?

Thanks for all your help and input.

Garth.

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20 Jan 2017 12:42 #42848 von peterg1000
peterg1000 antwortete auf Dead 420 Help please!
Hi Garth,

Glad you are up and running again, pity the replacement chip didn't solve the problem.

If you are willing, just throw the old board in my direction - I've done some SMD device work so I might be able to resurrect it.

The regulator circuit is bog standard and simple (straight out of the IC data sheet), so probably there is either an O/C inductor or a short circuit on the 5V logic supply (capacitor or diode on regulator posssibly).

Regards,

Peter

SC 420/2, Industrial VFD spindle from StoneyCNC
UC100 + UCCNC
Cut2D, Autosketch10, Draftsight, Eagle 9.5.1


There is no problem, however simple, that cannot be made more complicated by thinking about it.

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20 Jan 2017 13:38 #42854 von DocBrown
DocBrown antwortete auf Dead 420 Help please!
As Peter says there could be a short on the out-pin to ground or the diode is dead. So it seems that the root cause is still there somewhere.
Also it is important that PIN 3 has contact to ground otherwise the regulator is shut down.

If you want to check if the regulator is working you should think about to interupt the PCB track on it's way from PIN 7 to anywhere and then to check the output voltage. But after that you have to remove the paint on the track to get it resoldered.

Maybe there is a tiny tiny metal chip (aluminium) somewhere causing a short ... ???

Good luck!

Viele Grüße

Hartmut
V2/420 China 800W wassergekühlt
UCCNC & ARDUINO ESTLCAM Controller
ESTLCAM & QCAD
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20 Jan 2017 15:43 - 20 Jan 2017 15:44 #42863 von peterg1000
peterg1000 antwortete auf Dead 420 Help please!
Hartmut,

The board has worked reliably for a couple of years or so, and there is plenty of solder resist over the tracks, so I think a metal sliver is probably the least likely.

If there is no short on the logic supply, then it has to be one of the three output components (schottky diode, inductor or capacitor) - assuming the LM2574 in still good, connected and enabled.

If there is a short, then a low voltage ( < 2V or so ) current limited power supply fed onto Vcc and ground will, with care, reveal the culprit as the current is increased (slowly!!). A hot component or even smoke is a good sign. :woohoo:

Sounds as though hours of fun can be had Garth!!

I'm a very good catcher!!

Peter

SC 420/2, Industrial VFD spindle from StoneyCNC
UC100 + UCCNC
Cut2D, Autosketch10, Draftsight, Eagle 9.5.1


There is no problem, however simple, that cannot be made more complicated by thinking about it.
Letzte Änderung: 20 Jan 2017 15:44 von peterg1000. Grund: Typo corrections

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26 Jan 2017 10:49 #43220 von Garth15
Garth15 antwortete auf Dead 420 Help please!
Apologies for slow response gentlemen. Too busy chipping!

Ummm, my electronics goes back to the Neolithic period so a little out of my depth here. Have made an attempt to sketch out the front end of the power supply area. As Peter says, it looks very similar to the data sheet for the LM2574. However, I don't have the skill or wherewithal to play with SMD components and my understanding is that you can't check things like Schotkky diodes 'in circuit', they need to be demounted.

So, Peter, if you are still up for it, I am happy to donate the boards body to science! Still determined to understand what has failed for future reference (and feedback to Stepcraft).

If you could let me have your address I will ship it off early next week. (Not sure how to do private messaging on this forum).

Thanks again for the input and look forward to getting to the bottom of this.

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26 Jan 2017 11:20 #43222 von peterg1000
peterg1000 antwortete auf Dead 420 Help please!
Hi Garth,

Address sent via a private message to your good self - click on "Private Messages" on this page header to access your mail.

Peter.

SC 420/2, Industrial VFD spindle from StoneyCNC
UC100 + UCCNC
Cut2D, Autosketch10, Draftsight, Eagle 9.5.1


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01 Feb 2017 13:45 #43587 von peterg1000
peterg1000 antwortete auf Dead 420 Help please!
Hi Garth,

Thanks for sending your defunct control board in my direction for disposal. :evil:

I thought to put my electrical/electronics so called expertise to the test so as to diagnose the problem(s). A quick check revealed almost a dead short (approx 0.9ohms) between logic 5V and ground.

Fortunately I have a lab power supply on which I can set both output voltage and current limit. So working on the principle that if the supply was set to a couple of volts, and the current to 1amp, whatever was causing the short would get hot when the supply was connected to the board without risking further damage!! And so it did (get hot that is)!!!

The circuitry around the power converter chip is identical to that published in the LM2574N data sheet, and the culprit proved to be a schottky clamping diode which had morphed into a very good 0.5 ohm resistor. Garth had already replace the converter chip, so it was no surprise that when the offending diode was replaced the power converter came to life again with a good solid 5v supply drawing around 150mA.

Of course swapping out SMD components is quite tricky and one needs to be careful not to fry the replacement with enthusiastic soldering, but it worked ok in this case.

Since the design of the converter follows the chip manufacturers recommendations, there are two possible reasons for failure. Firstly it may just be a simple "infant mortality" failure or, secondly, a malfunction of the stepper driver chips which overloaded the 5V logic supply. I wasn't able to check the second possibility without swapping out on my own machine - needless to say that I didn't pursue that one. "If it ain't broke, don't fix it!!"

Peter

SC 420/2, Industrial VFD spindle from StoneyCNC
UC100 + UCCNC
Cut2D, Autosketch10, Draftsight, Eagle 9.5.1


There is no problem, however simple, that cannot be made more complicated by thinking about it.
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01 Feb 2017 14:21 #43590 von Owen Sparks
Owen Sparks antwortete auf Dead 420 Help please!
Nice work Sir.

Owen S.

Production Engineer
HWM-Water Ltd.

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01 Feb 2017 14:53 #43592 von Garth15
Garth15 antwortete auf Dead 420 Help please!
Excellent piece of detective work Peter !! I look forward to the first episode of CSI : Stepcraft !!

Thanks for all of your effeorts on behalf of myself and the rest of the Stepcraft community. I know exactly where to come in future for any related electronic stuff. ;)

Cheers,
Garth

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16 Nov 2017 07:26 #51212 von Zizza
Zizza antwortete auf Dead 420 Help please!
Hi guys, i did a mistake on the board and the fuse F4A is broken, i see on some website there is different models of that fuse so i would like to know the spec of that fuse to replace it by myself

thanks
Mirco

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16 Nov 2017 12:22 #51216 von MikeRD03
MikeRD03 antwortete auf Dead 420 Help please!
The fuse says its specs :) F4A = (F)use 4A(mps) OK?

SC M.500 | 2,2kW Spindel G-Penny | Mach4 über Ethernet Smoothstepper

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