Hi all
Wondering if I could get some insight on a Dell U27HM. First turned it on and the image was completely black. I later realised that if I dragged a window from one monitor to (the broken) other one then smeared colors would appear on the bottom 75% of the screen. After being on for several hours the top part of the screen started flickering showing an image (I have a video of this) and then suddenly the image appeared albeit rather fuzzy in the bottom 75% - image attached - and some hour later it now appears normal
I do have two of these monitors so a compare/swap...
cjard
Member
Last Activity: 09-13-2022, 02:14 PM
Joined: 05-03-2014
Location: TN
-
Dell U27HM flickering/quarter image/black with smeared colors
-
Re: A motor controller is a power supply, right?
I was able to resolve this, hopefully; turned out every transistor in the schematic above, was toasted bar one J3Y.. Schematic was right, but the volts I had measured were completely out of whack because of the number of damaged components
Not having enough time to wait for the exact replacements to arrive I raided 3 PC power supplies and was able to cobble together a pair of SC8050 and an A733 for one side, and a pair of 2222As and an A1015 for the other; reshaping the legs suitably so they perch where the SMDs used...Last edited by cjard; 10-16-2020, 07:07 PM. -
Re: A motor controller is a power supply, right?
Yes, it's a different package but I can rearrange the legs so it perches in the right place
So you'd say there's a possibility that some of the J3Y are damaged too? This could explain some things; I've been following "how to test your transistor" guides and I just couldn't get them to match up to how the components behaved. I thought it was just because I was testing them in-circuit (which I understand can't always work out because other components present on the circuit will confuse the readings) but I couldn't...Last edited by cjard; 10-15-2020, 11:36 PM.Leave a comment:
-
Re: A motor controller is a power supply, right?
I don't know where the diode connection goes - it's "the point beyond which the voltages are the same and I stopped measuring"
The schematic is "wrong" in the sense that the colors don't match what I measure - I didn't draw the colors; falstad's circuit simulator does that for me and I can't make the sim match the voltages I measure (dont know how). If I toggle the 5v between 0 and 5v I can see that the output of the NPN-PNP pair whose emitters are linked switches between 0v and 12v when the 5v goes...Last edited by cjard; 10-15-2020, 03:06 PM.Leave a comment:
-
Re: A motor controller is a power supply, right?
Not quite sure I fully understood what was said there, but here's a bit more info (that schematic is what I see when I don't ask the board to do anything i.e. its what I see with it powered up but not activating any motors):
These FETs (IRF3205 NPN are present on either side of the board and they seem to be used to turn the negative on and off to the motor - I say this because there is a large bolt to which the user should connect his battery, labelled N, and this bolt is clamped to a big rail that runs round the board....Last edited by cjard; 10-15-2020, 11:19 AM.Leave a comment:
-
Re: A motor controller is a power supply, right?
hi eccerr0r
Yep, the coloring in reflects the voltages I measured on-board when the board is powered up
It's the right side of the colored-in pic that is faulty, the left side (with 0v between the transistors) works ok/ supplies 12v to the gates of the IRF3205s when the board is powered up..Leave a comment:
-
Re: A motor controller is a power supply, right?
As requested:
Note these images have the MOSFETs removed (except one known good as a test). On the base of the board most of what you see is either negative or positive. This board connects to nothing else except 12v DC In on the middle bolt pair (and 12v DC out on the outer bolt pairs depending on motor direction). The red fly leads go to some devices that are some kind of thermal cutout I believe- glued to the lids of the lower two relays (which are constant energized when power applied). The bit...Last edited by cjard; 10-14-2020, 05:09 PM.Leave a comment:
-
A motor controller is a power supply, right?
Hoping someone here will be able to provide a few pointers with this. I've got a motor controller board for a device that moves a caravan. A DC motor on each wheel is supplied with 12v DC or -12V DC depending on whether the remote control is pushed in "forward" or "backward" mode. The control is arranged by having 2 relays per motor that, at rest, are all connected to the negative.. If the motor is to go forwards, then relay 1 activates meaning the motor sees "positive negative" on its terminals 1 and 2. If the motor is to go backwards then relay 2 activates meaning...Last edited by cjard; 10-14-2020, 01:41 PM. -
Re: Power supply board from a ventilation unit - burnt out something
My neighbor has the same device as I pulled this board from, so I'm gonna take a look at the components and see if I can see anything on them, writing wiseLeave a comment:
-
Power supply board from a ventilation unit - burnt out something
This vent axia ventilation unit stopped working and I pulled the power supply board hoping it was the internal fuse. Seems this other component might be to blame but what is it? It looks like a capacitor to me but next to it on the board is printed RV1 whereas a physically similar component at the other side of the board is labelled C15...
Any ideas guys?...Last edited by cjard; 10-20-2019, 10:57 AM. -
Re: New Members - please post your introductions here
Hello. Joined to get some info on my plasma tv.. But looking at the knowledge here I can foresee getting into all sorts of cool electronics projects
CjLeave a comment:
No activity results to display
Leave a comment: