Anyone had this Problem
 

I just checked the tapes that I had been shooting for the past 3 days. This was a large production with many crew members. We also used a mini 35 system so when I found that I had lost the first 8 minutes of one of of the 3 tapes I checked I was completely devastated.
This is what happened: we shot during the day on tape 1 and we started the night shoot on tape 2. I reset the time code to start at 2:00:00:00, the TC generator was set on record. We shot about 8 mins then I changed the battery. We went on to shoot another 30 mins.
When I got home I found the first 8 minutes before I changed the battery was completely blank and 8 minutes into the tape the time code started reading 2 hours 8 minutes.
I did not clean the heads, all I did was change the battery at the 8 minute mark. I have no idea what coud have caused this to happen. I was shooting HDV24P. I cannot trust this camera until I know for sure, so I have been using the other camera.
It's too much of a coincidence to think it was dirty heads when all of a sudden it cleared up the same time I changed the battery.
Does anybody have any clues what could have caused this to happen?

Thanks in advance,

Richard

Richard, is your camera an "A" version? You can check by looking at the serial number on the bottom of the camera, under the shoulder pad. Is there a little "A" sticker near the serial number? If not, then you need to send in the camera to the Cypress, CA service center and get the "A" upgrade done. Here is a link that has all of the information:

http://pro.jvc.com/pro/special/HD100...00upgrade.html

Also, if you are shooting something critical, and you want to verifiy the recording after each take, use the review button on the top of the lens grip.

Yes I had the upgrade done
On the Mini 35 there is no review button

Are you sure that you did not double clutch? Meaning hit the record trigger twice.

No if I had done that there would not be 8mins of blank tape and in that 8mins I shot 2 scenes each with at leats 3 takes each so I was stopping and starting alot.

Also the 20min or so after that time look just fine.
Thanks for your help

It could have been a clog in the heads that I guess just cleared itself, or maybe just became dislodged after the first 8 minutes you shot. Either way it sucks, and I'm sorry that happened to you. Sorry that I can't be of more help.

There's no way this was a clogged head.

i know exactly what happened to you.

I know exactly what happened to you. It's happened to me too.

When you changed the battery, did the camera simply die mid record or did you unhook the battery mid record?

When either of these scenarios happen the computer in the camera loses its timecode on the tape and whilst it all says its recording, u will note that the timecode doesnt actually move, The red lights are on but Mr JVC aint writing anything down.

I got caught out once. Losta 30 min timelapse of the city i was doing as a big storm approached. Spewing i lost it but better i lost that than the i/v with a big CEO straight after.

The solution. TRY TO NEVER LET THE CAMERA RUN FLAT WHILST RECORDING. IF IT DOES, EJECT THE TAPE AND START UP FROM SCRATCH AGAIN HIT THE RETURN BUTTON AND DO A LITTLE RECORD TEST.

Why does it do this? My battery set up is home made using idx batteries and an idx v lock plate with a 7.2v and 14.4 v otuput. The 7.2v output is hooked into the camera through a modified DC in cable.
There is no option for a battery warning time on the camera , only on the side of the batts.
I havent tried it but i wonder what happens when you "run flat" the supplied battery. Does it give an on camera warning?

Prick of a problem , i know. But it will only get you once!

Craig - I question whether this is necessairily the cause of the problem, simply because at least twice I've had the camera stop in the middle of a shot when I ran out of battery power, and in both cases I didn't lose any footage (replaced the battery and continued with the documentary shoot). I have the AB adapter, running Dionics 90.

If you're using the AB adaptor kit and/or have an upgrade, the camera tells you when voltage is low, no? Maybe the "A" software upgrade realises this problem occuring and saves a tiny bit of power to keep the timecode up .....or something. (We dont get the A upgrade in Australia)

In my case, i know this was definitely the cause of the problem. Its not the battery but the way the voltage is regulated in the camera.

No the camera didn't die from low battery everything seemed normal in the first 8 mins I was shooting lots of short takes stopping and starting every min or so. The IDX battery got low and I turned the camera off and changed it after that time the camera worked flawlessly. When I got home there was nothing on the tape for the first 8 mins and the timecode also started at 2:08:00:00 as At the start of the tape I set the timecode to 2 hours and recorded 30 secs of bars and tone. I feel that the camera thought it was recording and continued to count timecode and it wasn't until I reset the camera by turning it off and changing the battery that it actually started working correctly. This camera has had the A upgrade and only has 45 hours on it. I only use the JVC HD Pro tapes. I have 2 of these cameras but I can never trust this camera until I know for sure what happened.
So I really appreciate this input Thanks
Richard

Sounds like we had the same problems....but under slightly different circumstances. however, i reckon it's a safe bet that the reason this happens is to do with voltage in the camera.
The camera doesnt seem to be able to find time code again after a sudden power loss or perhaps, in your case, a battery change at prolonged low voltage?

Whatever the problem it seems jvc have fixed it with the inclusion of AB battery systems and software upgrades. Short of that there is no solution other than to keep the batts topped up.....

Still be interesting to see what happens with the supplied battery when it is run flat during record........

Craig - I'm confused. Why would the battery dying at the 8 minute mark affect footage prior to that? It's the first 8 minutes that is missing.
I've had one of my batts die in the middle of a shot with no adverse effects. I am using the AB mount, but not an AB battery so I get no warning in the viewfinder.

I think this is more likely the tape change that caused this but as to why - maybe low battery, maybe bad alignment on the HDV side (I know HDV is more finicky than recording DV on the same transport). I also know that if the main board has been replaced at all (eg blown firewire chip) then the tape transport needs re-alignment.

Either way it seems we need some way of monitoring signal being written to tape and a warning if nothing is going down. At the moment we call that review :)

BTW - Seems a shame you can't remap the lens return to a user button. Perhaps you could hook up a zoom remote with lens return directly to the camera body when using a mini35?