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AXBB charge pump fault
I wired my machine to use the charge pump output so that the relay would only activate the motor psu if the software was active and not in a reset/error state. This has worked perfectly while testing until I tried it a couple of days ago. When I apply power the relay and therefore the motor Psu all spring to life. I checked all wiring and even stripped it all back to the bare minimum and tested again with the same issue. I have checked the charge pump isolated output and it appears to always be active even if the indicator LED is off? I have checked that the option to always enable charge pump isn't active and am now wondering whether it's faulty...does anyone have any other ideas?
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Re: AXBB charge pump fault
Does the other outputs work as expected ?
Assuming the output transtor is open drain and grounds the relay coil terminal to switch the relay on
With the power off you can use a multimeter to check the resistance between the negative supply terminal and each isolated output
in the manual
http://www.cncdrive.com/downloads/AXBB_E_manual.pdf
see diagram 9.1.2 .Connecting a solid state relay (SSR)
test between 24V0 and Ox
You should find they are all open circuit unless the transistor controlling the relay is short circuited
John
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Re: AXBB charge pump fault
Cheers John, I'll check the resistance tomorrow but one more thing I remembered. I also tried output 2 of the isolated outputs and that one does read the voltage change if I set that as the charge pump output however that one doesn't activate the relay? The manual states that the isolated outputs can drive upto 500mA so I'm assuming it's not enough power to drive the relay and the output 1 is different. [emoji848]
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Re: AXBB charge pump fault
what relay are you using ?
any idea what the coil resistance is ?
This one from RS Components has a coil resistance of 650 ohms
https://docs-emea.rs-online.com/webd...6b815856e9.pdf
If the RS StockNo:450-0425 relay was used with the AXBB and its 24V DC supply only 37 mA would flow via the AXBB output
John
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Re: AXBB charge pump fault
It's like the one below
https://rover.ebay.com/rover/0/0/0?m...2F283248324744
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1 Attachment(s)
Re: AXBB charge pump fault
going by this data sheet
Attachment 26191
your relay also has a resistance of 650 ohms
page 4
Non-latching – DC
rated voltage = 24V
rated current = 36.90 mA
coil resistance = 650 ohms
John
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Re: AXBB charge pump fault
Forgive my ignorance but does that mean the other isolated outputs are all capable of driving the relay? I did check that and thought so but its been a while since I DoD electronics!
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Re: AXBB charge pump fault
Quote:
Originally Posted by
john swift
With the power off you can use a multimeter to check the resistance between the negative supply terminal and each isolated output
in the manual
http://www.cncdrive.com/downloads/AXBB_E_manual.pdf
see diagram 9.1.2 .Connecting a solid state relay (SSR)
test between 24V0 and Ox
You should find they are all open circuit unless the transistor controlling the relay is short circuited
John
It looks like I'm getting approximately 100 ohms on output 1 to ground, all other outputs are open.
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Re: AXBB charge pump fault
The reference to " other isolated outputs are all capable of driving the relay "
differentiates the outputs from the 5V logic level outputs that you connect to other logic gates or the stepper driver step & direction inputs
from the open drain outputs designed to switch inductive loads like the relays
As an example
Going back to equipment I used and maintained in the eighties
all the logic was built from 7400 series TTL logic
Typical gate inputs passed 1.6 mA when an input a input was grounded
and the outputs could sink 16 mA
so you could only connect 10 inputs to the output of an IC
unless you used a buffer that could pass more current
To connect to other devices like tally lights for the control panel switches
A lamp “driver” / BCD decoder like the 7445 switched 28v bulbs ( run off a 24V supply ) by grounding the other end of the bulbs filament
The 74141 being another version with high voltage outputs for driving Nixie tubes
(which is basically a neon with an anode connected to 180V DC via a resistor and 10 cathodes shaped in the form of the digits 0 to 9 that glows when grounded )
These days you would use a 7447 BCD to 7 segment decoder driver connected to a 7 segment LED display or LCD
John
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Re: AXBB charge pump fault
It looks like the FET for output 1 has short circuited
I would check you don't have a wiring problem that could connect the 24V DC to the AXBB output
Did you check the relays coil resistance is 650 ohms as expected
less than 48 ohms would pass more than the 500mA limit for the output
John
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Re: AXBB charge pump fault
The coil is reporting around 600ohms with my voltmeter but the battery is about dead so I'm not sure how accurate it is atm. No other isolated outputs are being used on the AXBB at the minute. I have proximity switches on the isolated inputs and a cheap 5 axis Bob for the control panel wiring. I'm wondering if I could use the 5 axis bobs relay as a charge pump to control the safety relay...i can assign it in uccnc but I think I read it can only be used by powering the 5v off usb rather than the boards 5v input.
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1 Attachment(s)
Re: AXBB charge pump fault
I having read the manual again I see the charge pump controls the damaged output 1
Not all outputs as I thought last night !
which breakout board are you thinking of using ?
To add another charge pump you need to use a breakout board with a built in charge pump circuit or
something like cnc4pc's C4
https://www.cnc4pc.com/c4-safety-charge-pump.html
the detector circuit is hidden under the board !
You need the circuit that controls the relay to ignore static logic levels
and only detect the 10Khz charge pump signal
older version
https://www.cnc4pc.com/pub/media/pro...ser_manual.pdf
Attachment 26196
John
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Re: AXBB charge pump fault
In the ucnc software I can configure which outputs to use for the charge pump so I was planning on setting it to the output 17 in the bob which is for the relay or forward reverse control but it isn't switching the relay which is why I think I need to power it from the ish rather than the on-board 5v connectors. I've included the pdf for the bob
I appreciate the help John [emoji4]
Edit.
I should probably add that the bob is connected to port 3 of the AXBB and not to the pc parallel port.
https://uploads.tapatalk-cdn.com/201...ed549cf2be.jpghttp://cloud.tapatalk.com/s/5d514e97...%20%281%29.pdf
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2 Attachment(s)
Re: AXBB charge pump fault
The BOB you have linked to does not have the charge pump / watchdog circuit needed
Attachment 26197
pin 17 just switches the relay on when the pin is taken high ( +5V )
one DIY circuit from Geckodrive.com
Attachment 26198
John
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Re: AXBB charge pump fault
Quote:
Originally Posted by
john swift
The BOB you have linked to does not have the charge pump / watchdog circuit needed
Attachment 26197
pin 17 just switches the relay on when the pin is taken high ( +5V )
one DIY circuit from Geckodrive.com
Attachment 26198
John
Oh...my understanding was that the AXBB watched for the signal from the pc and then activates a chosen output for the charge pump. In my case it would be pin 17 controlled through the AXBB's 26pin idc to the bob which would then switch the onboard relay on to complete the circuit to power my safety relay for the drives.
Am I understanding it wrong? There should be no random outputs on the AXBBs port 3 lile would be on a pc's parallel port on start up or at least that's what I assumed.
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Re: AXBB charge pump fault
last night I expected the AXBB to work as you described but after downloading the manual
at the bottom of page 19
8.1.1 .Digital isolated ports.
Port#1 pins 2. to 8. are isolated outputs. These outputs contain high speed 10Mbit/sec
optocouplers and an N-channel Mosfet transistors.
The outputs can drive upto 500mAmps of current upto 24Volts voltage levels.
The high current capability of the output transistors makes these outputs ideal to drive
relays, solid state relays and other signals which require isolation.
19/29
on page 21
8.3 .Charge pump safety circuit port
There is one charge pump safety circuit integrated on the board in port#1 O1 CHP output.
The charge pump circuit senses the charge pump pulse stream signal from the controller and
if the signal exists then the output is switched on and if it cuts then the output switches off.
The charge pump can be used to control a safety relay to cut power when the software is not running on the computer.
Unless I have missed it
I have not seen an explicit ref to all output being switched off as I would of expected
My be another AXBB user can confirm
John
PS
have you contacted the manufactures ?
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Re: AXBB charge pump fault
Quote:
Originally Posted by
john swift
last night I expected the AXBB to work as you described but after downloading the manual
at the bottom of page 19
8.1.1 .Digital isolated ports.
Port#1 pins 2. to 8. are isolated outputs. These outputs contain high speed 10Mbit/sec
optocouplers and an N-channel Mosfet transistors.
The outputs can drive upto 500mAmps of current upto 24Volts voltage levels.
The high current capability of the output transistors makes these outputs ideal to drive
relays, solid state relays and other signals which require isolation.
19/29
on page 21
8.3 .Charge pump safety circuit port
There is one charge pump safety circuit integrated on the board in port#1 O1 CHP output.
The charge pump circuit senses the charge pump pulse stream signal from the controller and
if the signal exists then the output is switched on and if it cuts then the output switches off.
The charge pump can be used to control a safety relay to cut power when the software is not running on the computer.
Unless I have missed it
I have not seen an explicit ref to all output being switched off as I would of expected
My be another AXBB user can confirm
John
PS
have you contacted the manufactures ?
I think I will have to, I just wanted to check I hadn't missed anything. It was working fine and I'm not sure when it turned faulty but noticed a few days ago that it started straight away[emoji848] it seems strange that the software will allow me to choose any output for the charge pump though.
Cheers for the help[emoji16]
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Re: AXBB charge pump fault
So I got a response that it could be the input transistor. I have asked whether it is covered under warranty but haven't had a response yet however I decided to check the values myself and the resistors seen in the pic below should be....
30B=2k
221=220ohm
01C=10k
All the values are correct other than the one circled which gives more like 1k value so in your opinion is it blown or do you think there is a path from elsewhere?
Edit
How easy is it to replace a faulty smd and what would be an acceptable cost at an electronica shop? I'm just wondering if the cost will be cheaper than shipping back to CNCDrive.[emoji848]
https://uploads.tapatalk-cdn.com/201...cc1e064a54.jpg
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Re: AXBB charge pump fault
I've seen people replace them with a thin tip soldering iron, a pair of tweezers, a steady hand and a magnifying glass. Read a tip in the UB1 manual today that said disconnect your iron from the mains and then ground it once it's at temperature. I'm sure you'll find examples on the old YouTube.
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Re: AXBB charge pump fault
The smt resistor coding used is this -
https://www.hobby-hour.com/electroni...-resistors.php
So far I have not found the transistor marked A66
I thought it would be something like a high current version of a 2N7002
https://uk.farnell.com/search?st=2n7002
http://www.farnell.com/datasheets/22...4aAiVAEALw_wcB
may be a
FDN337N - MOSFET Transistor, N Channel, 2.2 A, 30 V, 0.065 ohm, 4.5 V, 700 mV
is closer to what we are looking for
https://uk.farnell.com/on-semiconduc...-23/dp/9845356
could you post some wider pictures to see more of the circuit connections
to see what its connected to
usually I expect resistors to go high resistance when overloaded and semiconductors to go short circuit
John
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Re: AXBB charge pump fault
Here's a pic of the full board, there looked like a lot of dust on it so I've brushed it all off but it's still reading the same resistance. So are you thinking its the transistor and no the resistor? I had a look at the back of the board and it looked like a short from the pin of the led but it brushed off so maybe it just looked worse[emoji848]https://uploads.tapatalk-cdn.com/201...9dfec1ec3e.jpghttps://uploads.tapatalk-cdn.com/201...d23aa5e2b5.jpg
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2 Attachment(s)
Re: AXBB charge pump fault
the board is very much what I expected
basically an all in one UC300 and opto isolated breakout board from what I can see
looking at your photo
the 10K resistor is in parallel with
the 200 ohm resistor that's in series with the FETs gate & drain connections
your probably seeing the 220 ohms in series with the short circuited FET gate & source
Attachment 26205 Attachment 26206
I expect the 2K resistor is probably limiting the indicator LED current
whats the 14 pin IC number that you can just see 7 of its pins ?
John
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Re: AXBB charge pump fault
This one says HC14
It's hard to take decent photos!https://uploads.tapatalk-cdn.com/201...9da885f704.jpg
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2 Attachment(s)
Re: AXBB charge pump fault
that makes sence
it will be a 74HC14 which is a hex inverter very often used on breakout boards
Attachment 26207
I think this shows output 1 is fixed for use as the charge pump output
Attachment 26208
John
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Re: AXBB charge pump fault
Whatever file you posted I can't see it on my phone? So in your opinion do you think it's the transistor with the AA6 that's faulty? And what physically makes that port different? I mean how is that port able to provide enough current to power the solenoid when the others can't? Sorry for all the questions!
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2 Attachment(s)
Re: AXBB charge pump fault
yes , I think the AA6 is faulty
the first file is just a PDF copy of the 74HC14 data sheet
As the same AA6 transistor is used for all 8 opto-isolated outputs
the only obvious differance I can see is the charge pump has control of output 1
and you via mach 3/4 control of the other 7 outputs
any output should be able to control a relay
John
PS
looking back at an earlier post
Attachment 26209
I would of thought you should be able to change port 1's charge pump to another pin
for example to pin 2
Attachment 26210
John
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Re: AXBB charge pump fault
That's what I thought too but when I tried it didn't work[emoji848]....
I will have another go tomorrow and report back my findings.
We have a localish electronics shop so I might give them a ring about replacing the smd.. my hands are way too shaky and my eyes are not much better[emoji23]
Thanks again for the help
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Re: AXBB charge pump fault
its the sort of thing you need to have some practice before you try to repair a valuable board
I found scrap PC boards are good to practice on
the last board I worked on was this XMT-2360 speed control board
the 14 pin IC , a transistor and a few diodes had been damaged by a short circuit to the speed control potentiometer
Attachment 26211
I guess the main issue is finding the new AA6 transistors
John
PS
have you checked the relay is OK
does it work when its connected directly to the 24V DC supply ?
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Re: AXBB charge pump fault
I've been following this thread with some interest. Personally I'd RMA the board for replacement/repair, however, if that's not an option...
From the photo of the board it's feasible that some of the analogues to the left of the transistors are involved with the charge-pump - it's not clear but if I squint hard enough I can believe it. At this time I'd give-up looking for a "AA6-j" marked device - it isn't present in the top-hits of SMD-marking google hits. but the purpose of the device is clear - a logic-level N-channel MOSFET with a working voltage in excess of 24V with a commutating diode to avoid problems with back-EMF from the relay (this was one area that concerned me originally when considering this device could be a BJT). This would support the traces to OP1 being the only charge-pump output. That, in itself, is somewhat peculiar as I understand that the micro controller on the AXBB generates the charge-pump output to itself - so I'm not entirely sure of the logic behind this decision - the integrity of this safety feature is then at the lowest integrity of the board - likely the program running on the micro controller... but I digress.
In a bind, I'd look to sweat-off the MOSFET for OP1, and the three resistors for OP2, then haywire the gate signal from the landing pad from OP1 to OP2. This would transfer the charge-pump output to OP2. Or, you could carefully (without overheating) sweat off the MOSFETs for both OP1/2 and swap them - assuming that you don't require the OP2 output. It looks as though any/all of the OP1-8 have the same circuitry/options, with just OP1/2 shifted on the board to avoid the stand-off pillar.
Or replace the MOSFET with a generic with the same SOT-23 packaging and pinout - there's nothing special about it's function that requires it to be matched to the original. John's mention of the 2n7002 is a suitable device in SMD packaging.
John's analysis of the failed MOSFET is, I believe, the most likely scenario here. There is a question as to why this failed, but sometimes s**t happens. It would be worth, if possible, diagnosing this more completely before attempting a repair. OP has a meter, it would be sensible to measure the voltage at the "IC" side of the 220R resistor with the output OFF/ON (0V, 5V respectively) and at the transistor side of the 220R resistor (similarly, 0V, 5V respectively). That he mentions the LED turns on/off, however, it a pretty good indicator that this should be working.
OP asks about a sensible price for a repair shop to perform this - a blind replacement (they won't be able to easily test without a licensed UCCNC installation) would be 5 minutes work and 10 pence of component, but they run a business and have to cover their operating overheads. On a good day - price of a pint, however, if the boss is around I'd expect £30 upwards.
If the OP was closer I'd offer to help - but it's not really viable (100 miles). But if he wants to play with a hot-air rework setup with stereo microscope then the offer is there.
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4 Attachment(s)
Re: AXBB charge pump fault
Its a pity they had not used a DIL (dual in line ) octal transistor array like the ULN2803
or a new FET array
like the Toshiba TB D62381A series DMOS transistor array
that would enable the user to plug in a replacement
Attachment 26218
Attachment 26219
If the AXBB controller was mine I would remove the AA6 FET
To prove the 74HC14 and resistors that drive the FET are OK
then either replace the AA6 FET with a
Vishay Si2306DS if it has the same footprint
Attachment 26220
John
plan B could be link the Gate & Drain PCB pads
that would enable the use of a relay and an external relay driver
for example
Attachment 26221
after checking the boards details
https://www.ebay.co.uk/itm/24V-TOP-A...592caec3ec0e9d
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Re: AXBB charge pump fault
Charlie
have you had a quote from CNCdrive what they charge for the repair of the AXBB controller ?
John
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Re: AXBB charge pump fault
I have been in contact with Balazs from CNCDrive and unfortunately it seems it won't be covered...
No, this kind of problem is not covered by warranty, because the transistor can be damaged only with overstressing the output e.g. with misconnecting the output, e.g. connecting a low resistance like a direct connection to the +24Volts.
Or if the issue is something else like a soldering error then we repair in warranty for 12months from purchase (shipping) date.
I haven't asked for a cost of repair but I did ask for the data sheet for the mosfet....
The transistor this one: https://www.digikey.com/products/en?keywords=NTR5198NL
It is not hard to remove and replace this kind of component, I mean it looks harder than it actually is.
You just need a tweezers and a soldering iron.
I haven't had chance to try another output as the charge pump yet but I'll try later. The Relay switches on and off fine when I connect it up to 24v.
I will also check the voltages as suggested but my local electronics shop may still be cheaper than shipping to Hungary and back. I am wondering though what could of caused it and will it happen again[emoji848]
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Re: AXBB charge pump fault
knowing the part number is a great help
( the Vishay Si2306DS from post 30 looks similar )
if you melt the solder on all 3 legs by adding fresh solder
a Desoldering Pump may well pick it up as well as the solder !
https://uk.farnell.com/duratool/908-...tic/dp/3125646
Attachment 26222
once repaired I would be inclined to use a relay with its own driver !
John
PS
Farnell have the NTR5198NLT1G FET
https://uk.farnell.com/on-semiconduc...ngdom%2Fsearch
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Re: AXBB charge pump fault
<deleted - just really agreeing with John>
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Re: AXBB charge pump fault
Hi Doddy
I see you changed your mind
dont worry
your original reply just pointed out we use the technique that we are happy with
I have to admit unless I am under instructions to maintain a lead free status
I use 60/40 solder and add some rework flux
If lead tin solder is good enough for use in pacemakers and other mission-critical equipment
its good enough for me :welcoming:
John
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2 Attachment(s)
Re: AXBB charge pump fault
Quote:
Originally Posted by
john swift
If lead tin solder is good enough for use in pacemakers and other mission-critical equipment
its good enough for me :welcoming:
John
Similarly, gifted with an industry that embraces the old 60/40.
Right, just tried a quick experiment - I have some 2N7002's in the shed so hooked one up to a signal generator set to 1Hz (though I ramped up to 35Hz out of boredom).
Basic circuit...
Attachment 26226
...using a practice board for SMDs as a breadboard...
Attachment 26227
So, this ran for 5 minutes without fail.
I then cut the diode (observed in image) to see if the back EMF would pop the transistor. I ran that for 5 minutes at upto 35Hz, with no failure.
Out of interest, I wet my fingers and placed across the relay coil - this calibrated method of measuring EMF confirmed that there was OUCH! volts of back-emf. Recovering the diode did quench the back emf, as expected.
I had expected the 2n7002 to fail due to the excessive VDS, but for the duration that I ran this it did not. The OUCH! test did confirm the expected high EMF present on the drain of the transistor.
So, CharlieRAM - you asked what could cause this to happen again... although inconclusive I'd recommend placing a diode, e.g. 1n4004 across the relay coil, cathode to +24V, anode to the AXBB board output. If you want a couple of diodes and a couple of 2n7002s thrown into the post let me know.
I'd recommend this for any output driving a relay or other inductive load.
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Re: AXBB charge pump fault
I think I have some of those diodes lying around from a previous project, I'm all for belt and braces approach [emoji16] I've contacted my local shop regarding the repair so I'll wait for a response.
Just a thought....my machine is in a log cabin at the bottom of the garden connected by an RCD in the house so if I leave anything on in there and then decide not to go back down I just trip the RCD. Would that likely cause an issue? It's just easier than going back down to turn it all off![emoji87]
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Re: AXBB charge pump fault
Quote:
Originally Posted by
CharlieRam
if I leave anything on in there and then decide not to go back down I just trip the RCD. Would that likely cause an issue? It's just easier than going back down to turn it all off!
I don't see anything wrong with that approach.
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1 Attachment(s)
Re: AXBB charge pump fault
The belt and braces approach of adding a diode across the relay coil works for me
( As long as you have it the correct way round )
Attachment 26228
I would look for a wiring problem that could of shorted the +24V to the AXBB output
As semiconductors fuse faster than expensive fuses thats supposed to protect them
you could try adding a 22 ohm 1/4W resistor in series with the relay coil
( the resistor should only fail if the relay coil is shorted )
The only issue I would expect with tripping the RCD will be corrupting the PC hard drive
If you have not shut the PC down
John
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1 Attachment(s)
Re: AXBB charge pump fault
Another diagram to expand on the one in post 39
Attachment 26320
John