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The 5A fuse directly blows when I plug in this board in.

Gwedo

Sep 28, 2021
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I am restoring a DMX Scanner light and the fuse keeps blowing.
The 5A fuse (F2 top right) directly blows when I plug in this board in,
how do I trace the source of this?

Thanks in advance!WhatsApp Image 2021-09-28 at 18.38.05.jpeg WhatsApp Image 2021-09-28 at 18.38.05 (1).jpeg
 

Alec_t

Jul 7, 2015
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Jul 7, 2015
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3,242
Welcome to EP!
I'd start by checking the diodes inside the bridge rectifier to the right of F1.
Look for any signs of overheating/scorching of any other component or the pcb.
Check components mounted on heatsinks.
 

Gwedo

Sep 28, 2021
9
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Welcome to EP!
I'd start by checking the diodes inside the bridge rectifier to the right of F1.
Look for any signs of overheating/scorching of any other component or the pcb.
Check components mounted on heatsinks.
I checked for overheating, also tried without the chips, still blows
 

Gwedo

Sep 28, 2021
9
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Sep 28, 2021
Messages
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checked the diode bridge, also working
Welcome to EP!
I'd start by checking the diodes inside the bridge rectifier to the right of F1.
Look for any signs of overheating/scorching of any other component or the pcb.
Check components mounted on heatsinks.
 

73's de Edd

Aug 21, 2015
3,433
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Messages
3,433
Sir Gwedo . . . . .

The available viewing limitations wouldn't let me make out all of the components assignments, so I just assigned sequential new numbers to them.
Also check my connections. Confirm, for us, that a fuse is being in series to each input of the FWB AC power input, as I can't ascertain that from the photo.( Double sided board----hidden tracks by components covering their views)
What I see there is a separate moderate power level AC supply coming in at the screw terminals that passes down to a FWB block rectifier . . . .needing some heat sinking dissipation assistance.
Its developed DC supply voltage then feeds the main filter cap for that supply at C1 E-cap . . . .it also appears that foil busses also extend on down to parallel in C2 and C3 E-caps.
These apparently compose the MAIN supply to feed the HEATSINKED Power LED /?/ Laser I.C. Drivers U3-6.
Look down to the right bottom corner and see the units secondary minor power supply that uses a pulsed Q5 transistor to drive L1 inductor that rings to each pulse and the recovered back EMF power is harvested by Schottky diode SD1 and the developed power is amassed / filtered in C4 E-cap. Be sure that your short is not being in that transistor or diode . . .possibly even the cap.
But the usual failure mode of that pulse driven E-cap is its gradual transition into a declined state of electrical / capacitive atrophy.

If my analysis to make, I would have both fuses pulled, no power even being involved, and then do a LOW ohms test to confirm that there is no short across the C1 C2 C3 cluster. Then test across C4 for a short on that separate supply, with considerations that SD1 or Q5 switching transistor could be shorted. This lower voltage minor supply is taking care of all of the I.C. circuitry to the left . . . and possibly, a LV portion of the I.C. DRIVERS.

I also see a sprinkling of a few tantalum drop E-capacitors . . . . . that could have gone dead short - bad.

Plus one / all of the earlier mentioned U3-6 power I.C.s could be that short . . . .or its driven device.
On the right photo I have marked up the + terminal of C2 E-cap and its foil goes directly up to the power input pin (8 ? )of U5 so that appears to be the power input pin and the one to watch for a short on the other companion drivers.

Come back with all of the capacitance and voltage ratings of the involved E-caps . . . . . . Q5's identification and any comments / further info..

YOUR REFERENCE . . . . MARK-UP . . . . .

LIGHT-SHOW-CIRCUIT-BOARD.png


https://i.postimg.cc/YM7W9Mkb/LIGHT-SHOW-CIRCUIT-BOARD.png

73's de Edd . . . . .



By your working faithfully eight hours a day you may eventually find yourself working twelve hours a day.

.
 
Last edited:

Gwedo

Sep 28, 2021
9
Joined
Sep 28, 2021
Messages
9
Sir Gwedo . . . . .

The available viewing limitations wouldn't let me make out all of the components assignments, so I just assigned sequential new numbers to them.
Also check my connections. Confirm, for us, that a fuse is being in series to each input of the FWB AC power input, as I can't ascertain that from the photo.( Double sided board----hidden tracks by components covering their views)
What I see there is a separate moderate power level AC supply coming in at the screw terminals that passes down to a FWB block rectifier . . . .needing some heat sinking dissipation assistance.
Its developed DC supply voltage then feeds the main filter cap for that supply at C1 E-cap . . . .it also appears that foil busses also extend on down to parallel in C2 and C3 E-caps.
These apparently compose the MAIN supply to feed the HEATSINKED Power LED /?/ Laser I.C. Drivers U3-6.
Look down to the right bottom corner and see the units secondary minor power supply that uses a pulsed Q5 transistor to drive L1 inductor that rings to each pulse and the recovered back EMF power is harvested by Schottky diode SD1 and the developed power is amassed / filtered in C4 E-cap. Be sure that your short is not being in that transistor or diode . . .possibly even the cap.
But the usual failure mode of that pulse driven E-cap is its gradual transition into a declined state of electrical / capacitive atrophy.

If my analysis to make, I would have both fuses pulled, no power even being involved, and then do a LOW ohms test to confirm that there is no short across the C1 C2 C3 cluster. Then test across C4 for a short on that separate supply, with considerations that SD1 or Q5 switching transistor could be shorted. This lower voltage minor supply is taking care of all of the I.C. circuitry to the left . . . and possibly, a LV portion of the I.C. DRIVERS.

I also see a sprinkling of a few tantalum drop E-capacitors . . . . . that could have gone dead short - bad.

Plus one / all of the earlier mentioned U3-6 power I.C.s could be that short . . . .or its driven device.
On the right photo I have marked up the + terminal of C2 E-cap and its foil goes directly up to the power input pin (8 ? )of U5 so that appears to be the power input pin and the one to watch for a short on the other companion drivers.

Come back with all of the capacitance and voltage ratings of the involved E-caps . . . . . . Q5's identification and any comments / further info..

YOUR REFERENCE . . . . MARK-UP . . . . .

LIGHT-SHOW-CIRCUIT-BOARD.png


https://i.postimg.cc/YM7W9Mkb/LIGHT-SHOW-CIRCUIT-BOARD.png

73's de Edd . . . . .



By your working faithfully eight hours a day you may eventually find yourself working twelve hours a day.

.
So we traced the route of the input and we thought it was weird, so we both plugged the wires in the most right two inserts. Now the fuses dont blow and the LED in the middle starts working. BUT nothing else works on the board....
 

73's de Edd

Aug 21, 2015
3,433
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Aug 21, 2015
Messages
3,433
Gwedo . . . . . still want to work on this ?

Come back with all of the capacitance and voltage ratings of the involved E-caps . . . . . . Q5's identification and any comments / further info..

Since I have received "nuttin" of that nature of info back from you .
 
Last edited:

Gwedo

Sep 28, 2021
9
Joined
Sep 28, 2021
Messages
9
Gwedo . . . . . still want to work on this ?

Come back with all of the capacitance and voltage ratings of the involved E-caps . . . . . . Q5's identification and any comments / further info..

Since I have received "nuttin" of that nature of info back from you .
So we rewired the inputs as a friend of mine said the way its wired now doesnt make sense, now the fuse doesnt blow but nothing works. We put the two cables in the most right two inputs. Is this correct or just totally wrong?
 

Harald Kapp

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Nov 17, 2011
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12,737
Is this correct or just totally wrong?
Sounds correct. I borrowed from 73's Ed and modified the image:
upload_2021-10-15_10-13-5.png
Without power attached, check the connections along the red lines I marked. Are they continuous?
Also without power attached, check the rectifier (the black 4-pin device to the right). Using a multimeter with diode range, there should be these reaings:
"AC" -> "-" : conducting if "-" is on "AC", non-conducting if "+" is on "AC" (conducting usually indicated by a display of 600 ... 700 counts)
"AC" -> "+" : conducting if "+" is on "AC", non-conducting if "-" is on "AC"

If these readings are o.k., proceed by attaching power as indicated. Measure from "+" to "-". DC level should be VDC ~ 1.4 × VAC (provided no fuse blows.
Also check the capacitor labeled C1 in post #5. From the photo it cannot be seen whether it is o.k. To check the capacitor, remove it from the PCB and measure between the capacitor pins. If your meter can measure capacitance, use this function. If not use a high Ohm range, e.g. 20 kΩ. Observe the polarity! "-" is indicated on the capacitor by the white bar which usually also contains the text "-" (in reverse polarity your measurement is not meaningful). The resistance indicated by your meter should rise until the meter displays overload. If it doesn't, the capacitor's leakage current is way too high.
When re-inserting the capacitor (the original or a replacement) also take care to observe the correct polarity.

If the readings on the rectifier are not o.k. especially if one reading is noticeably lower than 600 counts replace the rectifier.

If these measures do not help, the issue is further inward of the circuit and requires more in depth analysis. Hard on a remote basis :(
 

Gwedo

Sep 28, 2021
9
Joined
Sep 28, 2021
Messages
9
Sounds correct. I borrowed from 73's Ed and modified the image:
View attachment 53021
Without power attached, check the connections along the red lines I marked. Are they continuous?
Also without power attached, check the rectifier (the black 4-pin device to the right). Using a multimeter with diode range, there should be these reaings:
"AC" -> "-" : conducting if "-" is on "AC", non-conducting if "+" is on "AC" (conducting usually indicated by a display of 600 ... 700 counts)
"AC" -> "+" : conducting if "+" is on "AC", non-conducting if "-" is on "AC"

If these readings are o.k., proceed by attaching power as indicated. Measure from "+" to "-". DC level should be VDC ~ 1.4 × VAC (provided no fuse blows.
Also check the capacitor labeled C1 in post #5. From the photo it cannot be seen whether it is o.k. To check the capacitor, remove it from the PCB and measure between the capacitor pins. If your meter can measure capacitance, use this function. If not use a high Ohm range, e.g. 20 kΩ. Observe the polarity! "-" is indicated on the capacitor by the white bar which usually also contains the text "-" (in reverse polarity your measurement is not meaningful). The resistance indicated by your meter should rise until the meter displays overload. If it doesn't, the capacitor's leakage current is way too high.
When re-inserting the capacitor (the original or a replacement) also take care to observe the correct polarity.

If the readings on the rectifier are not o.k. especially if one reading is noticeably lower than 600 counts replace the rectifier.

If these measures do not help, the issue is further inward of the circuit and requires more in depth analysis. Hard on a remote basis :(
The red lines are continuous. The rectifier gives numbers in the 600 and when measured across 1600. Also when I meassure from - to + on the rectifier when its powered I get 15.4V. also the LED in the middle of the board works but when I attach the display or a stepper motor it doesnt. I cant remove C1 at the moment since my desoldering iron is broken.
 

73's de Edd

Aug 21, 2015
3,433
Joined
Aug 21, 2015
Messages
3,433
What I was wanting was my marked E-caps capacitance and voltage ratings.
The components cover up and hide the top of the boards foil traces at some places.
You can see that there are two BLUE connector sets and the far right set would be taking AC input and I also visualize the now drawn in and added heavy RED connections as being correct AC power in..
Look at your F2 fuse that was blowing and see its path going over to one of the AC inputs on the FWB rectifier block.
And the F1 fuse would take the other AC power lead and feed to the other AC inputs on the FWB rectifier block.

CONSULT PRIOR POST # 5's PHOTO BELOW . . . . .
LIGHT-SHOW-CIRCUIT-BOARD.png



NOW . . . when you had one of those BROWN AC power leads going to that THIRD terminal of the BLUE blocks,that put AC power into the top of F2 fuse and out of it into the top AC input terminal of the heavy duty FWB rectifier block.
Now we need to look at the foil paths of the right photo. Top left corner we have a HOLE in the board to refer to 5 HEAVY solder blobs on the board to the right. In accounting for that 1st solder blob, look at the top of the board photo and you can just see its silver half peeking out from the right edge of those BLUE connectors, I don't think that it is even connected to anything on board topside . . . BUT . . . look at it as the first big solder blob on the bottoms foil side and can I see it as connecting to wide ground foil connections with a left branches initial connection to the - terminal of the FWB block. . . . for being power supply - / ground.
Continuing on the foil bottom side with solder blob #2 and I think that we agreed that its connection is on the component side as connecting to top clip of Fuse 1.
Solder blob #3 I see as taking a foil side path down to the top clip of fuse #2 . . . . "The Blower".
Solder blob # 4 is not seen to have any connection on the foil side of the board . . . . YOU will have to confirm for us, on the component side.
Solder blob #5, and it being the critical one, on the component side, I am seeing a heavy foil path coming down and connecting to assigned C1 E-caps negative ground lead .
Now check the foil side of the board for that #5 blob and all we can see is reflected light . . .drats . . . but I will bet that our earlier mentioned heavy / wide ground buss travels all across the top of that board, almost to the end where it crooks down. With it making one intermediate drop down to connect into that #5 blob .

NOW . . . WHAT HAPPENED ! . . . .

Well, when you had the AC input BROWN wires connected with one going to the 3rd BLUE terminal over, it passed AC to the #2 fuse and on to one AC terminal of the FWB block.
BUT . . . . Shame . . .shame . . .shame . . . . . when you had the other AC BROWN power wire connected to the innermost BLUE connectors terminals, you connected into ground.
Then when you powered up:
AC into solder blob #3 to pass thru F2 fuse and out into AC input of FWB and then one polarity of the AC voltage will alternatively HEAVY conduct thru the FWB to the GROUNDED other AC power lead . . . . . . F2 fuse pops.
BUT . . . . with that FWB being so hefty, it seems that it evaded damage on your few, quick fuse blowing attempted power ups.

TESTING . . . .
Do a power disconnected test of all of my marked /assigned C1 C2 C3 E-caps negative terminals to confirm direct interconnects . . .little C4 sub power supply cap also.
C1 seems to be the main E-cap . . . . but the foil . . . seems to travel down and also connect C2 and C3 in parallel with it . . .confirm if so.

Since you have correct AC input into the unit and now have the central RED LED lighting, I expect it to be fed by the supply voltage level of the C1-2-3 cluster.
Now go down to C4 and see if and what lower voltage is being developed across it.

Standing by

ATTENTION:
On posting, I am now seeing your add on and the difference in the FWB + and - terminals . . . but causing a like effect in the fuse blowing escapade when the one BROWN wire was miswired into the BLUE connectors terminal .
Might I assume that the C1-2-3 supply voltage is going to be 12 VDC ?

Still need the sub supply C4 voltage presence and value..

73's de Edd . . . . .

EatingPopcorn.jpg

.
 
Last edited:

Gwedo

Sep 28, 2021
9
Joined
Sep 28, 2021
Messages
9
What I was wanting was my marked E-caps capacitance and voltage ratings.
The components cover up and hide the top of the boards foil traces at some places.
You can see that there are two BLUE connector sets and the far right set would be taking AC input and I also visualize the now drawn in and added heavy RED connections as being correct AC power in..
Look at your F2 fuse that was blowing and see its path going over to one of the AC inputs on the FWB rectifier block.
And the F1 fuse would take the other AC power lead and feed to the other AC inputs on the FWB rectifier block.

CONSULT PRIOR POST # 5's PHOTO BELOW . . . . .
LIGHT-SHOW-CIRCUIT-BOARD.png



NOW . . . when you had one of those BROWN AC power leads going to that THIRD terminal of the BLUE blocks,that put AC power into the top of F2 fuse and out of it into the top AC input terminal of the heavy duty FWB rectifier block.
Now we need to look at the foil paths of the right photo. Top left corner we have a HOLE in the board to refer to 5 HEAVY solder blobs on the board to the right. In accounting for that 1st solder blob, look at the top of the board photo and you can just see its silver half peeking out from the right edge of those BLUE connectors, I don't think that it is even connected to anything on board topside . . . BUT . . . look at it as the first big solder blob on the bottoms foil side and can I see it as connecting to wide ground foil connections with a left branches initial connection to the - terminal of the FWB block. . . . for being power supply - / ground.
Continuing on the foil bottom side with solder blob #2 and I think that we agreed that its connection is on the component side as connecting to top clip of Fuse 1.
Solder blob #3 I see as taking a foil side path down to the top clip of fuse #2 . . . . "The Blower".
Solder blob # 4 is not seen to have any connection on the foil side of the board . . . . YOU will have to confirm for us, on the component side.
Solder blob #5, and it being the critical one, on the component side, I am seeing a heavy foil path coming down and connecting to assigned C1 E-caps negative ground lead .
Now check the foil side of the board for that #5 blob and all we can see is reflected light . . .drats . . . but I will bet that our earlier mentioned heavy / wide ground buss travels all across the top of that board, almost to the end where it crooks down. With it making one intermediate drop down to connect into that #5 blob .

NOW . . . WHAT HAPPENED ! . . . .

Well, when you had the AC input BROWN wires connected with one going to the 3rd BLUE terminal over, it passed AC to the #2 fuse and on to one AC terminal of the FWB block.
BUT . . . . Shame . . .shame . . .shame . . . . . when you had the other AC BROWN power wire connected to the innermost BLUE connectors terminals, you connected into ground.
Then when you powered up:
AC into solder blob #3 to pass thru F2 fuse and out into AC input of FWB and then one polarity of the AC voltage will alternatively HEAVY conduct thru the FWB to the GROUNDED other AC power lead . . . . . . F2 fuse pops.
BUT . . . . with that FWB being so hefty, it seems that it evaded damage on your few, quick fuse blowing attempted power ups.

TESTING . . . .
Do a power disconnected test of all of my marked /assigned C1 C2 C3 E-caps negative terminals to confirm direct interconnects . . .little C4 sub power supply cap also.
C1 seems to be the main E-cap . . . . but the foil . . . seems to travel down and also connect C2 and C3 in parallel with it . . .confirm if so.

Since you have correct AC input into the unit and now have the central RED LED lighting, I expect it to be fed by the supply voltage level of the C1-2-3 cluster.
Now go down to C4 and see if and what lower voltage is being developed across it.

Standing by

ATTENTION:
On posting, I am now seeing your add on and the difference in the FWB + and - terminals . . . but causing a like effect in the fuse blowing escapade when the one BROWN wire was miswired into the BLUE connectors terminal .
Might I assume that the C1-2-3 supply voltage is going to be 12 VDC ?

Still need the sub supply C4 voltage presence and value..

73's de Edd . . . . .

EatingPopcorn.jpg

.

I measured C1-C4 using the 200K-ohm setting and C1-C3 gave a number around 77, and C4 around 4. Also C2 and C3 are linked up to C1 as you stated. After hooking it to the power and measuring the C4 using AC I got about 4.8V out of it while C1-C3 give me 15.5V each.
 

Gwedo

Sep 28, 2021
9
Joined
Sep 28, 2021
Messages
9
What I was wanting was my marked E-caps capacitance and voltage ratings.
The components cover up and hide the top of the boards foil traces at some places.
You can see that there are two BLUE connector sets and the far right set would be taking AC input and I also visualize the now drawn in and added heavy RED connections as being correct AC power in..
Look at your F2 fuse that was blowing and see its path going over to one of the AC inputs on the FWB rectifier block.
And the F1 fuse would take the other AC power lead and feed to the other AC inputs on the FWB rectifier block.

CONSULT PRIOR POST # 5's PHOTO BELOW . . . . .
LIGHT-SHOW-CIRCUIT-BOARD.png



NOW . . . when you had one of those BROWN AC power leads going to that THIRD terminal of the BLUE blocks,that put AC power into the top of F2 fuse and out of it into the top AC input terminal of the heavy duty FWB rectifier block.
Now we need to look at the foil paths of the right photo. Top left corner we have a HOLE in the board to refer to 5 HEAVY solder blobs on the board to the right. In accounting for that 1st solder blob, look at the top of the board photo and you can just see its silver half peeking out from the right edge of those BLUE connectors, I don't think that it is even connected to anything on board topside . . . BUT . . . look at it as the first big solder blob on the bottoms foil side and can I see it as connecting to wide ground foil connections with a left branches initial connection to the - terminal of the FWB block. . . . for being power supply - / ground.
Continuing on the foil bottom side with solder blob #2 and I think that we agreed that its connection is on the component side as connecting to top clip of Fuse 1.
Solder blob #3 I see as taking a foil side path down to the top clip of fuse #2 . . . . "The Blower".
Solder blob # 4 is not seen to have any connection on the foil side of the board . . . . YOU will have to confirm for us, on the component side.
Solder blob #5, and it being the critical one, on the component side, I am seeing a heavy foil path coming down and connecting to assigned C1 E-caps negative ground lead .
Now check the foil side of the board for that #5 blob and all we can see is reflected light . . .drats . . . but I will bet that our earlier mentioned heavy / wide ground buss travels all across the top of that board, almost to the end where it crooks down. With it making one intermediate drop down to connect into that #5 blob .

NOW . . . WHAT HAPPENED ! . . . .

Well, when you had the AC input BROWN wires connected with one going to the 3rd BLUE terminal over, it passed AC to the #2 fuse and on to one AC terminal of the FWB block.
BUT . . . . Shame . . .shame . . .shame . . . . . when you had the other AC BROWN power wire connected to the innermost BLUE connectors terminals, you connected into ground.
Then when you powered up:
AC into solder blob #3 to pass thru F2 fuse and out into AC input of FWB and then one polarity of the AC voltage will alternatively HEAVY conduct thru the FWB to the GROUNDED other AC power lead . . . . . . F2 fuse pops.
BUT . . . . with that FWB being so hefty, it seems that it evaded damage on your few, quick fuse blowing attempted power ups.

TESTING . . . .
Do a power disconnected test of all of my marked /assigned C1 C2 C3 E-caps negative terminals to confirm direct interconnects . . .little C4 sub power supply cap also.
C1 seems to be the main E-cap . . . . but the foil . . . seems to travel down and also connect C2 and C3 in parallel with it . . .confirm if so.

Since you have correct AC input into the unit and now have the central RED LED lighting, I expect it to be fed by the supply voltage level of the C1-2-3 cluster.
Now go down to C4 and see if and what lower voltage is being developed across it.

Standing by

ATTENTION:
On posting, I am now seeing your add on and the difference in the FWB + and - terminals . . . but causing a like effect in the fuse blowing escapade when the one BROWN wire was miswired into the BLUE connectors terminal .
Might I assume that the C1-2-3 supply voltage is going to be 12 VDC ?

Still need the sub supply C4 voltage presence and value..

73's de Edd . . . . .

EatingPopcorn.jpg

.
So Ive done that, is there anything I can get out of that?
 
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