Resurrect the MiniDV Camcorder

So many old video tapes, and no way to watch them. I think we got our first camcorder in ’88, it was a Sony Video8 (not Hi8 or Digital8, as those had not yet been invented). It was impressive, too — stereo audio, autofocus, and about 1/3 the size of the VHS camcorders that were the norm those days (yes, you had to physically place a VHS tape in a device, put it on your shoulder and record….. good times). There are a dozen or so Video8 tapes kicking about, although I had the foresight to transfer them to Beta, and later to VHS. But more about Video8 later.

Fast forward (see what I did there?) 11 years, the expensive stereo Video8 camcorder had been sitting in a closet for years with a tape in it, and it was just completely hosed. I discovered this the day before a big family vacation, and used it as an excuse to run out and buy a state-of-the-art MiniDV digital camcorder, the JVC DVM50.

Impressive machine for it’s time. Maybe 1.5 times the size of my fist, 32- or 48-khz audio sampling, it took digital stills (yes, my first digital camera) and had a firewire port to connect to a PC. Lots of captured memories – a few even sent back to the computer – and another dozen or so tapes hanging around the house. The batteries (yes, they were LiOn batteries – definitely state-of-the-art) have long since died, and the charger/ac adapter was lost years ago. So, how can I get my videos?

Well, time to make a new ac adapter. Let’s start with the 17-yr-old original battery.

Those warnings weren’t meant for me, were they? 🙂  Note the +, T and – marking on the battery terminals. The “T” stands for “thermistor,” which is a safety measure intended to tell chargers to stop charging if the battery pack gets too hot – that’s pretty cool, but for our purposes totally irrelevant. Note also the voltage output rating (7.2v). A quick search indicates that a 7.2v Lithium ion battery pack will normally vary between about 8.4v (100% charged) to somewhere in the mid-6-volt range fully depleted. So we are going to shoot for reaplacing this with something in the 7.5-8v range.

The first step is to carefully pry open the battery pack plastic – it’s not easy, and it requires some care to not demolish the plastic. No need to be real neat about it, though, we just need enough of the original shape so the camcorder thinks it has a battery installed. After opening the case, cut out the leads going to the battery cells and pry out the batteries (in this case they were glued in).

Here’s where it’s good that we made note of the + and – terminals. The next step is to find a suitable ac/dc adapter. I have a shoe box full of old adapters from long-discarded devices, after digging around I found some candidates. I also decided to test them before letting them power the camcorder, so I brought out the trusty voltmeter, plugged ’em in and measured. Hmmm, the most promising adapter, marked 7.5v/1a, was putting out 10.52v. That ain’t right, is it?

Luckily, I know how to use a search engine. Searching for “voltage divider calculator” gave me a nice cookbook on how to use 2 resistors to reduce that 10.5v down to my desired range. And I happen to have a bunch of resistors around, so this was easy enough to try. Before soldering everything up, I tested it again and got…. huh. 3.2v. That ain’t right either, is it? I fussed with the resistor values a bit, and got similar results. Then I thought it through. With no load, the adapter was putting out 10.5v. Add a load, it drops. At 1A, it’s rated at 7.5v.  A little more searching, and a little more experimenting, and I confirmed it (more or less, I measured it at 7.63, but who is counting, right?).  So, all that remained was soldering the wires from the adapter to the terminals of our disassembled battery pack.

Re-assemble, using some hot glue as strain relief, then re-test to the terminals. And… working camcorder, ready to transfer my old tapes to the cloud.

As with any of my posts, try this at home (or anywhere else) at your own risk.