MINI PRO G1.

The place for questions about shooting with Blackmagic Cameras.
  • Author
  • Message
Offline

robert Hart

  • Posts: 692
  • Joined: Mon Jul 28, 2014 3:16 pm

MINI PRO G1.

PostThu Dec 01, 2022 1:05 pm

Here is a bit of a weird one. One of my faults has been to buy in deceased cameras in the eventual hope of finding enough functional bits and pieces to heal together a whole camera.

It is a similar probability to locking a herd of monkeys in a room with a bunch of typewriters and eventually getting a viable film script out of the process.

Most moribund G1s are beyond redemption but the most recent one is a curiosity. There is a soft fixed position banding artifact in the image. The pitch of the banding changes with changes in the area of the sensor scanned.

The interesting part is that the bare metal closest to the selection switch for phantom power gives the finger a very faint electrocution like a mobile phone burn. However I am not tempted to stick my tongue on it to investigate further.

Inserting a media card into the slot, then starting the camera again made the banding artifact issue go away.

It may well come back again when the camera cools down.

If any electronic wizards are tempted to come up with an explananation do not feel bashful. I am all ears.
Offline

Howard Roll

  • Posts: 1914
  • Joined: Fri Jun 03, 2016 7:50 am

Re: MINI PRO G1.

PostThu Dec 01, 2022 6:04 pm

Strange that you can feel anything for sure. Place both hands on a car battery's terminal and you'll feel nothing because 12V doesn't provide enough current to make skin a decent conductor, despite the amperage.

Maybe it's related to the phantom circuit as that is 48v, but then again the current is so low. Maybe a diode has failed, or something has shorted. Probably best to remove the switch and give it a physical inspection first. If that doesn't reveal anything it's time to pull out the meter.

Good Luck
Offline

robert Hart

  • Posts: 692
  • Joined: Mon Jul 28, 2014 3:16 pm

Re: MINI PRO G1.

PostThu Dec 01, 2022 6:20 pm

The first cab off the rank will be to check the left side cover and its connections to the main system by the two strip connectors.

Phantom power going where it shouldn't and creating RF interference within the shielding of the metal casework might be enough to set off soft banding in the image.

RF and audio frequency interference used to do some weird things to analogue video cameras. Some early Sony PD150s had an interference issue in the audio circuits.

The camera also does not switch to playback and the artefact's disappearance after a media card is inserted hints that something is being disturbed by slight movement or vibration from the media card holder.

The issue might chance to be limited to the side cover assembly but the LCD screen's signal itself is supplied from the front of the mainboard.

If only life could be so easy. I have a spare side cover assembly. If the mainboard is faulty then I have a good one to replace it with. The sensor itself could be faulty in which case all bets are off. It is a lottery.

The sensor board associated with that good mainboard was also good electronically but the mezzanine connector's solder joints or traces they solder to were faulty and not repairable.

There is a guy in the east of Australia who is examining a possible repair scheme.
Offline

robert Hart

  • Posts: 692
  • Joined: Mon Jul 28, 2014 3:16 pm

Re: MINI PRO G1.

PostFri Dec 02, 2022 6:01 pm

The postscript to the story is that the camera appears to have experienced a tripod fall to the left front onto a rough paved or gravelly surface. Otherwise the camera seemed to have been well looked after.

With soft fixed bars and fixed pattern noise which seemed to improve with changes of recording options and three boot ups, my thoughts were that maybe the sensor had taken a hit.

The same chafe damage caused to the mainboard's rear flexible circuit ribbon by pressure against the rear SDI outlet assembly was seen again. This may not have caused the problem but who knows? I am not clever enough to chase it down.

A change of left side cover assembly did not make it go away. Nor did disturbance of the mezzanine connection between the mainboard and the sensor assembly.

A change of the mainboard to a known good one seems to have fixed it ---- for now. The rest of the peripherals have to be reassembled and things yet could go awry.
Offline

Steve Fishwick

  • Posts: 956
  • Joined: Wed Mar 11, 2015 11:35 am
  • Location: United Kingdom

Re: MINI PRO G1.

PostFri Dec 02, 2022 9:09 pm

Have you got pictures Robert of this open-heart surgery? I'm a fan of your posts, for one.
Offline

robert Hart

  • Posts: 692
  • Joined: Mon Jul 28, 2014 3:16 pm

Re: MINI PRO G1.

PostSat Dec 03, 2022 2:45 am

Steve Fishwick.

Organisational discipline when pulling stuff apart is not my strong suite. The plastic cell packaging is a cheap backroom table working surface which helps to avoid things getting injured.

For sensitive electronics it really should be a conductive surface. I get by with boiling a kettle to put some steam into the environment.

When one pulls a camera apart and finds things inside like tiny prairie grass lint, a signature colour of dust on the fan blades and cooling fins, a well burnished lens mount face, it is evidence of more than a few casual hours up and adventures somewhere.

One wonders what the operator of that camera saw in the LCD screen of viewfinder and what was made with it. It had been taken care of with little weather covers on the SDI ports.

The current one has little sharp indentations on the edges of the left front side cover. My guess is that it may have taken a tumble with the operator onto rocky ground whilst handheld, versus a tripod fall. Those sudden impacts to the sides seem to be what do the mainboards in.
Attachments
HEALING URSA.jpg
HEALING URSA.jpg (316.21 KiB) Viewed 755 times
Offline

robert Hart

  • Posts: 692
  • Joined: Mon Jul 28, 2014 3:16 pm

Re: MINI PRO G1.

PostSat Dec 03, 2022 2:36 pm

The rescue Mini Pro is now all carefully buttoned up and tidy. No spare parts left or any rattles inside either. The final outcome has been a positive one although of course the effluxion of time will tell if the melding of two principle wrecks endures.

I had hoped to try it successfully in time to go buy a lotto ticket on the basis of an improved trend. However, I left my run a bit late so the prize I was going to win flew away into the sunset.

When first observing and checking, I observed that when given time to exhibit its true nature, the apparently faulty motherboard was reducing the soft banding and replacing this with a fixed pattern artefact like a sensor which has not had blacks set.

This changed to a slightly less obvious pattern but when gained up, it was very much there in the image.

As this occurred, there developed a slight magenta hue in hot zones on a plain wall, almost like clipping of the green channel on the SI2K in 12 bit linear uncompressed before the later revisions of the operating system.

That got me to thinking about the main processor board and that it might be doing deleterious downstream things to an otherwise good image and prompted me to try the mainboard swap which seems to have worked.

The playback failure continued on with the replacement good mainboard so it was apparent that the uncontrollable agency, the human hand of the operator was at fault. It confounded me for a while.

The penny finally dropped after several back and forths of CF2 cards between machines. The Ursa Mini 4.6K has cDNG and ProRes. The new rescue camera does not have cDNG. Instead it has Blackmagic Raw.

That is something new I shall have to learn to use but so far the recordings seem to be fine.
Offline

Steve Fishwick

  • Posts: 956
  • Joined: Wed Mar 11, 2015 11:35 am
  • Location: United Kingdom

Re: MINI PRO G1.

PostSun Dec 04, 2022 2:15 pm

Thanks Robert. Didn't you once resurrect an old JVC HD101, that had a fallen apart prism? You have a saintly aura to save cameras, that have met a violent end, my friend! Does the Mini Pro G1, now work OK?
Offline

robert Hart

  • Posts: 692
  • Joined: Mon Jul 28, 2014 3:16 pm

Re: MINI PRO G1.

PostSun Dec 04, 2022 5:25 pm

It seems to work fine. I only had about two minutes of uncommitted CF2 card to test it with so it has not had a long session yet. The BM SSD dock is on the other rescue camera. Folk on eBay seem to be hanging onto them.

As well as the CF2 card slots, there seem to be two SIM card slots as well. That threw me for a few minutes. Nothing happened initially because there is a selector switch. I have to read up on whether those are for firmware updates or actual recording media.

I devised a repair scheme for detached blue channel sensors for the JVCs but by then ProHD cams were already feather dusters.

I was awfully tempted to have a go at the $1,000 worth of five Arri Alexas on auction a while ago but chickened out. The guy who eventually bought them got one working pretty much straight away after melding some bits. I think there were two goers in the end. He has published his adventure on youtube.

I have been tempted to do a meme photo by taking the ruined Ursas out into the yard, parking them in the grass to image them in forced perspective to look like a car wrecker's yard but that would not be kindly towards Blackmagic.

In fairness it should be said that three out of the seven dud cams I have bought in had experienced some degree of trauma and another one was comprehensively crunched. The good ones usually have dead sensors and the ones with skin and hair off them yield good sensors.
Attachments
HEALING URSA 2.jpg
HEALING URSA 2.jpg (311.87 KiB) Viewed 566 times
Offline

Steve Fishwick

  • Posts: 956
  • Joined: Wed Mar 11, 2015 11:35 am
  • Location: United Kingdom

Re: MINI PRO G1.

PostTue Dec 06, 2022 8:38 am

robert Hart wrote:As well as the CF2 card slots, there seem to be two SIM card slots as well. That threw me for a few minutes. Nothing happened initially because there is a selector switch. I have to read up on whether those are for firmware updates or actual recording media.


They are either/or and is for actual recording. I switched to CF cards recently on my UBG2, from SD and I initially forgot that. Is that a Moviestuff Super 8 (or 16mm) telecine rig in the background, Robert?

I saw that YT video, where the kid bought the 5 Alexa Classics. Still great cameras if they have all the upgrades, but mighty heavy beasts.
Offline

robert Hart

  • Posts: 692
  • Joined: Mon Jul 28, 2014 3:16 pm

Re: MINI PRO G1.

PostTue Dec 06, 2022 9:28 am

Steve Fishwick.


Thanks for that. I had not got around to reading up on the G1.

Yes. That is a Moviestuff Mark II with 8mm and 16mm guides.

I have an archive to preserve before the vinegar finishes it off. Afterwards, if there are enough folk wanting transfers done, I will see if it can earn its way, otherwise I will resell it.

I have been doing a few mods to draw closer to the newest version with its better illuminator and camera. So there is a new LED lamp and separate power in it, plus a 5 micron groundglass-finished piece of microscope slide for a diffuser versus the original lucite panel.

There is a BM Ursa camera IR filter disk to deal with what seems to be an IR influence which is skewing the colour rendition in the blacks to a stronger blue when neg is inverted. Any benefit may be imagination on my part but there seems to be a cleaner effect when it is in the optical path.

It is to be used for scanning negatives. That learning curve has been a bit of a struggle. Inversion of neg without increasing lots of film grain and imaging camera sensor noise is a craft well worth my learning.

I am getting there slowly. This practice piece was scanned off film which had been stored before recent use since 1994. The jitter is the unavoidable side-harvest of scanning old film, not due to the camera which is rock steady.

Stabilising it will be a challenge as the CP16R gate is not in focus as the film rides on two rows of chrome balls. The frame line therefore is not sharp.

Offline

Steve Fishwick

  • Posts: 956
  • Joined: Wed Mar 11, 2015 11:35 am
  • Location: United Kingdom

Re: MINI PRO G1.

PostTue Dec 06, 2022 9:49 am

My very first job, in the industry, some time in the 80s, was in sound transfer. One of my tasks was to record 16mm optical sound tracks, on high contrast orthochromatic film, for later lab printing to the married print. In fact, I was one of the very last people in the UK to do this work, mostly Rank if I recall. You had to load the 'camera', in dark room conditions. I would have to perform X-modulation transfer curve tests to determine exposure and focus, first. The exposing light was UV, so as to avoid halation and focus only on the very surface of the stock. The rolls were 2400' and would be stored flat. Due to contraction and settle, they would bow and sometimes around 1200' or so of recording, it would snap, ruining the whole recording and wasting the very expensive stock. Since the storage was to blame, over which I had no control, I thought it very unfair that my boss would ball me out, then. But such were the times.

The step printers used for contact printing and some telecines, I believe, used a 'wet gate', where liquid with the same refractive index, as the film base, was used to fill in the scratches and tramlines, before the days of digital restoration. I wonder why they don't still? Except they would be even more expensive now, I suppose.
Offline

robert Hart

  • Posts: 692
  • Joined: Mon Jul 28, 2014 3:16 pm

Re: MINI PRO G1.

PostWed Dec 07, 2022 10:34 am

Steve Fishwick.

I saw a wetgate printer being used at a lab before it closed. It was fascinating watching that fluid gurgling around behind the glass and yet not spilling out everywhere. With electricity, light and heat close and friendly, use of flammable fluids would be fraught with all manner of possibilities.

Some folk are apparently using a total loss method of wetting the film with a suitable solution with soaked pads just before it goes through the scan aperture. It has also mentioned that the presence of the fluid in sprocket hole edges upsets laser-type edge detection systems with more frame jitter being the result.

A misting method with a shield/mask over the sprocket holes might be a workaround.

Modern high-end scanners apparently still have a recurculiting wetgate process as an option. Alas it is way out of my league.

Return to Cinematography

Who is online

Users browsing this forum: Bing [Bot], Jeffrey D Mathias and 11 guests