Problems with panasonic dmr ex75 HDD recorder

Deano 19690

Novice Member
Hi All,
I'm new to the forums and in need of some advice/help.
Having owned several panasonic hdd/DVD recorders over the years I know all to well the problems of the U81 and No freeview tuner problems.
Steve on ebay has fixed a few for me in the past.
Now when one of our machines just died the other day with the missus dvd disc inside. I opened it up to see the power board looking a bit worse for wear.
So then I purchased another machine off EBay , real cheap with a U81 fault and removed the power board to use as a donor for the faulty one....
It worked, i released the disc, dvd and hard drive still working as before.
All good so far.

However, me being a nosey sod then decided to swap over the HDD drives to see what was on the donor machine.
After turning the power on it greeted me with a 'Format HDD ' screen and No other options.
Not knowing what state the donor hdd was in, I did so. It formatted ok and I recorded on to it.
The problem came when reinstalling our original hdd back in, again i am greeted with a 'format HDD' screen.,
no other options...
Now we had recordings of the kids/holidays etc on there that I really don't want to lose.
I thought it would be a simple plug and play hdd like the external hard drive we connect to our laptops .

If anyone can advise me how to reconnect and save our recordings I'd be grateful


Active Member
Without a tremendous amount of work your recordings are lost.
There is a requirement imposed by the tv and film industry, that hdd recordings are tied to the recorder and can not be copied or played on other machines. This is acheived by tying the hdd to the recorder. Panasonic tie the hdd to the power board, hence it demanding a format, to effectively delete all recordings.

You will likely be able to recover snippets of recordings but with no recording names and no idea which snippets belong to which and no idea of the order is either, you would face a tremendous challenge.


Standard Member
The problem your describing makes perfect sense, based on the order of events.

Panasonic recorders after the 85H model here in the United States began including a "transaction number" that rolls forward after each change to the hard disk and storing that in the non-volatile memory on the mainboard and the hard drive itself.

On power up the recorder compares the "last transaction number" held in NVRAM to the value stored on the hard disk. This is used to detect corruption or differences on the hard drive.

When they don't match the recorder goes into auto-repair mode and attempts to "fix" the hard drive by suggesting it be re-initialized, wiping the hard drive of its recordings.

I believe its called a "uformat fault". If it succeeds then the drive is reset and allows you to continue making new recordings.. but the old "transaction number is wiped or lost" so putting the old hard drive back into the recorder will result in a new "mismatch" and it will suggest re-initializing it, also wiping it of its recordings.

The solution depends on whether you allowed it to "re-initialize" or wipe the original hard drive.

Basically I can describe what needs to be done to save the recordings and to restore the hard drive so that it matches the recorder again.. but neither will seem easy.. and require technical skill.

The fairly good news, is Isobuster can probably read and copy the recordings from the original hard drive and put them on a PC. (If the hard drive hasn't been wiped).

The software costs money to actually copy the recordings, but you can run it in demo mode to see if the recordings are still there.

Now as to re-synchronizing the "transaction number".. I have not worked out a minute carefully scripted procedure.. but it goes roughly like this:

The transaction number is stored in the area of the hard disk "before" the recordings index on the drive. To learn this I have to use a hex editor and scan for a few keywords in one of the recordings title. The areas of the hard disk are separated by gaps of empty space.. so once you know where the recordings index table is.. you can back up until you find yourself in an empty area of the disc.. usually filled with zeros.

So now that you know how many bytes for this particular model you need, you can use a different hard disk to wipe and initialize in the recorder.. copy just that number of bytes from the newly initialized hard drive and put those on the old hard drive.. with the new "transaction number" that is currently in the recorder.. with luck.. when it powers up they will match.. and your recordings will show up again and can be played.

Any previous scheduling or electronic program guide information will be gone.. so if you had a season pass.. or a schedule to record upcoming broadcasts.. those will all be gone.. since the initialization did not carry over from the old drive to the new drive.

This procedure could be vastly refined and formalized.. but the Panasonic repair depots never offered a service to recover user recordings or perform service on customer hard drives.. the standing procedure was to wipe the drive, or replace it and tell the customer it was not possible to recover old recordings. -- there are myriad reasons for this, from protecting the customers privacy, to avoiding copyright claim entanglements.. and downright costs associated with recovery time.. and customer dissatisfaction if the repair did not go right.

The most important thing you should do however is safe guard the original hard drive and make sure its labeled with a sticky note or something so it doesn't get used for something else, or accidentally get wiped. The next thing is a technical person should make a backup of it using a raw disk imaging tool like Hdd Raw Copy Tool 1.10, or Isobuster (it has an image backup feature).

Then you can feel safe going about the task of recovering the recordings to a PC, and or re-synchronizing the original drive to the NVRAM so you can use it as before.

My experience is people tend to get very emotional and keep trying things until they damage the situation beyond hope.. and or wipe the drive and then there is nothing you can do.. you could then "try" to see if something like Isobuster can scan the entire hard disk and try to pull off videos.. but its much less likely to work. The recorder index table contains information that tells Isobuster where recordings begin and end and how long they are in logical blocks.. which enables it to be much more precise.

I went into a lot of detail not knowing where you are at in the process at the moment.. because other people might get into the same situation and think it was hopeless.. in the beginning.. before thrashing back and forth and doing desperate things.. it really isn't.. but after a few hours or days.. it tends to become hopeless.

Back tracking a bit.

An event that updates the "transaction number" by rolling it forward includes many possibilities, it can be a new recording being made, changing a setting in the recorder menus with the remote or buttons on the front of the recorder.. or a simple update of the electronic program data with a new scheduled program to record. Any of these can cause the "transaction number" to update.

The non-volatile memory and the hard drive aren't normally updated simply by inserting a different hard drive into the recorder and powering up.. it was that "format" that was performed in the attempt to see if anything was on the other recorders hard drive that did the trick. That's what rolled the "transaction number" forwards.

I don't know what Panasonic officially calls it, I call it the "transaction number" simply because it reminds me of the transaction log of a database, or at least that is how it behaves.

Now something else you should be wary of is after CPRM, the hard drive serial number was used to create an encryption key when it was initialized and stored on the hard drive as well.. specifically so that you "could not" play back recordings marked by the broadcaster on any other recorder.. this was due to a requirement to satisfy Copyright Laws. Not all broadcasts carry the CGMS flag that tells the recorder to encrypt.. but the encryption key is generated and it can only be decrypted from the hard drive with the original serial number.

So cloning the drive and restoring the transaction log will play back all un-encrypted recordings.. which if they are all personal camcorder footage they should be un-flagged and thus un-encrypted.. but I bring it up, because after being burned by previous events.. people sometimes try to safeguard by only working with a cloned hard drive.. and the serial numbers won't match up.

This also leads to any DVDs burned of "flagged" recordings also being encrypted and "tied to the recorder" so that they will only playback on the original recorder that made the original recordings.. all kinds of surprising Copyright inventions show up when you least expect them.. the thought process there being most people won't try to playback recordings on other DVD players.. and any video given to relatives on DVD should be personal camcorder footage which isn't encrypted. People only notice when the recorder dies.. and assume the DVD has gone bad since it won't play back on the new DVD recorder they bought.

To be sure.. you ("should") make a full raw disk image backup of the hard drive on another hard drive to work from.. and keep it safe. Isobuster can work with a raw disk image in fact... and need never touch the original hard drive.

But when it comes to trying to re-sychronize the hard drive with mainboard memory, its best to work with the original hard drive.

And its best to be very aware of how your Panasonic indicates to you that a recordings has been Copy Protected.. with an icon, or CP or some other indicator in the title menus.. so you know those are at risk.. and any DVD's made of those.. will be tied to the life time of the hard drive they came from.. and possibly the recorder if the hard drive dies with it.
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Deano 19690

Novice Member
Thanks for your input , that's far more then a layman like me can comprehend.
But someone has previously mentioned to me..
"it can be done by using a clone disc or drive but it's complicated"
So I know we're on the right track here.

So you say, unplugging the hard drive and reconnecting it didn't cause the problem.
The problem was caused by reformatted another hard drive on the same machine?
Is that right ?

I'll have to ponder the rest of the info...

Thanks for your input though, its very appreciated 😀

I never got notification of your reply other wise I woukd have been back here sooner

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