Blackmagic Mini Pro LCD Monitor "checkerboard"

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SuperCinema

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Blackmagic Mini Pro LCD Monitor "checkerboard"

PostTue Nov 02, 2021 11:44 pm

Hello, I just purchased a Blackmagic Ursa Mini Pro 4.6k (G1) used. The seller described some intermittent issues with the camera, but because of price I decided to take a chance on it:

The seller described this issue as LCD monitor "cross-hatching"; I turned the camera on, opened the LCD monitor and was changing the settings. After moving the LCD to face up, the LCD monitor displayed a clear checkerboard pattern when not in the menu, and when I switched to RAW the whole thing turned red. I decided to close the LCD for a few minutes and when I opened it back up, the pattern was gone. Nothing I did with the settings could replicate the issue, I tried moving the LCD, tried leaving it open for 10 minutes and it still wouldn't replicate the issue. It's definitely not FPN, these were clear "boxes" about 1/2cm wide.

I'm just curious if anyone's experienced this before. I thought because it happened after I moved the LCD that one of the cables inside the joint could be loose, but it may not be an issue at all because it didn't bake into footage and still hasn't happened again.
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Uli Plank

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Re: Blackmagic Mini Pro LCD Monitor "checkerboard"

PostThu Nov 04, 2021 7:52 am

It could be one of those very hard to find electronic problems with a badly soldered joint, which may even be invisible to the eye on inspection. Nevertheless, you may take the LCD apart and try to touch the cables and connectors and see what you get. Such problems can be triggered by vibration as much as by temperature.

If it's not baked in and the price was really good, try to get a good price for the excellent EVF too and live with it. The outside LCD will give you the most important info when shooting.
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SuperCinema

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Re: Blackmagic Mini Pro LCD Monitor "checkerboard"

PostThu Nov 04, 2021 1:03 pm

Uli Plank wrote:It could be one of those very hard to find electronic problems with a badly soldered joint, which may even be invisible to the eye on inspection. Nevertheless, you may take the LCD apart and try to touch the cables and connectors and see what you get. Such problems can be triggered by vibration as much as by temperature.

If it's not baked in and the price was really good, try to get a good price for the excellent EVF too and live with it. The outside LCD will give you the most important info when shooting.


Thank you for the info! After reading what you have stated and also that it could just be a faulty screen, I will live with it. The seller's description said it is baked into the footage and visible in this photo, but all I saw was FPN from it being underexposed (this is not the same thing I am describing, and I do not see this when I light/expose properly)
blackmagic_ursa_fpn.jpg
blackmagic_ursa_fpn.jpg (130.35 KiB) Viewed 805 times


The 2nd thing seller said is that a few of his files were corrupted. I am not really concerned by this because I won't be using it for paid work. For 1200USD, a completely working Ursa Pro with some occasional glitches, I think is a pretty good deal.
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robert Hart

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Re: Blackmagic Mini Pro LCD Monitor "checkerboard"

PostThu Nov 04, 2021 7:13 pm

If this was the camera listed on eBay, I nearly went for it myself as I have another dead Ursa Mini Pro.

If you are getting clean recordings, I concur with Uli. If it is not entirely broke, I would not try to fix it. From memory, there are some small white plugs inside the screen's case so there are possibilities of dry joints within it, which movements of the cable inside the case could provoke.

Inside the right cover of the main camera body, at the front low corner on the main board, there is a strip connector which connects a cable from the LCD. It is retained by a small plate. I doubt this connection has been disturbed as it is held secure.
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SuperCinema

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Re: Blackmagic Mini Pro LCD Monitor "checkerboard"

PostMon Jan 24, 2022 3:43 am

I've been running some tests with the camera and unfortunately the problem seems to be present on the footage most of the time. I have attached screenshots, these are all taken in a studio setting with a properly exposed scene, 422 HQ and ISO 500. There's weird green and purple lines in a couple, definite checkerboard, and almost a "solarization" effect it seems like (as seen predominantly in the out of focus shot). But here's where it gets weirder. All the "bad" screenshots are either taken from footage recorded internally at 4k, or with the camera set to 1080p and recording externally to an Atomos Shogun Inferno (I don't know why this works, but I accidentally pressed record on the Shogun Inferno and it recorded to the SSD). The "good" screenshot (the last one, that has no visual issues) is with the camera set to 4k and then the Shogun Inferno compressing the footage to 1080p (again, I don't know why this worked, I thought you needed a Cfast to SSD adapter for this camera).
bad_screenshot.jpg
bad_screenshot.jpg (446.34 KiB) Viewed 598 times

bad_screenshot_2.jpg
bad_screenshot_2.jpg (432.98 KiB) Viewed 598 times

bad_screenshot_3.jpg
bad_screenshot_3.jpg (348.04 KiB) Viewed 598 times
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SuperCinema

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Re: Blackmagic Mini Pro LCD Monitor "checkerboard"

PostMon Jan 24, 2022 3:44 am

Fourth picture (good footage)
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good_screenshot.jpg
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robert Hart

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Re: Blackmagic Mini Pro LCD Monitor "checkerboard"

PostMon Jan 24, 2022 6:32 pm

There may be some "crosstalk" happening between circuits if something is not quite connected and a signal is finding its way home by alternative routes. There may be an interfering signal being generated occasionally by a circuit not behaving itself.

The banding might be caused by a LED light somewhere. If the is no LED light source anywhere near, then there might be interference coming from one of the two LCD displays.


As a wildcard :-

When next the artifact occurs, if either internal or external microphone is selected and no phantom powered microphone is connected, check if phantom has been left selected "on".

Try deselecting phantom power without powering the camera down to see if the artifact goes away.

If your camera has the EF-Mount fitted and you are using EF-Mount lenses, try changing lenses. I would normally counsel against hot-swapping electronically controlled lenses but is said to be a harmless practice by many.

A hot swap of lenses may either provoke the artifact or make it go away if there is something going across from the lens control circuit.

On the Mini Pro, the small lens control ribbon cable travels from the lens mount to the mainboard and connects via a strip connect which is of the less robust style. On the Ursa Mini 4.6K this cable travels from the lens mount to the sensor PCB.

In either camera, the cable passes close enough to the general area of the sensor that something might go across if something in the lens control circuit is weirding out.

Ribbon cables for the media slots, audio switching and audio level pots are routed to the left side in relay via another small PCB, from a rear PCB which is permanently part of the mainboard/processor assembly via a broad ribbon cable. This connects via other ribbon cables.

Those are secured by wedge style retainers, tiny fiddly small things which may have been disturbed and the conductors under less direct pressure might have developed a dry or resistive joint.

The LCD display screen itself connects via a bound cable across to the lower front of the mainboard via a strip connector which is positively retained by a small plate. I doubt if the connector itself is faulty but it could be.

If the artifact seems to be provoked by the lens control circuit, you might try unfastening the lens mount, not by the little screws around the ring but the piece which attaches to the front of the case which has I understand been called the interchangeable mount.

There are some small pins, similar to the exposed pins in the bottom of the EF-Mount which are covered by the interchangeable mount. They press upon conductive pads in the back of the interchangeable mount.

Another Mini Pro user discovered that some strange behavour was caused by poor connection of those other internal pins. Disturbance and gentle cleaning of the conductive pads made the problem go away. He had observed that disturbance of the EF-Mount lens made the problem come and go.

Please await the more sensible comments from people who are more in the know than myself. I am no engineer but somebody who has fairly good fine dextoral motor skills and sometimes some luck.

Other explorations by yourself into the camera main body would be best left to a Blackmagic authorised repairer. Gaining access to those connectors is a deeper mining exercise, a tricky task requiring fine dextoral motor skills and great care as essential parts which cannot be repaired can be damaged.
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SuperCinema

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Re: Blackmagic Mini Pro LCD Monitor "checkerboard"

PostFri Jan 28, 2022 7:31 pm

Thank you for all the information!
I was using LED cob lights for the tests. I will switch to halogen/shoot some outdoor shots and see if it makes a difference. I don't have electronic lenses, however I was swapping out lenses and different dumb adapters on the EF mount, so I'll try your lens mount trick too.

I'll also try updating or downgrading firmware, because when switching formats the camera straight up freezes and doesn't restart. Waiting 5+ minutes, then unplugging everything, turning on again, waiting and it powers on but still frozen. That and it takes a solid 1-3 minutes to power on. Just annoying :p, I would not take this on a job any time soon. My URSA is going on 8 years old and no glitches ever.
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robert Hart

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Re: Blackmagic Mini Pro LCD Monitor "checkerboard"

PostSat Jan 29, 2022 6:32 pm

It you are using dumb adaptors it may be worth cutting strip of thin brown parcel tape just wide enough to cover the lens pins and placing that strip across the pins so that there is no possible electrical contact with the dumb adaptor. Be sure to tamp any overhanging end down over the ends of the pin row or a high end may pick up on the rear face of the dumb adaptor and roll across. I doubt that the dumb adaptor will be your problem but who knows? Be aware that gum from the sticky face of the tape may eventually cause a pin to become stuck down, so change the tape every few weeks or more often if you use the camera in hot environments.

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