Gathering the parts

The parts you'll need to modify the converter box include:

• 4-pin header (standard 100-mil spaced)
• 12V cigarette lighter jack with cable
• various sizes of heat-shrink tubing

The 4-pin header should be bent so the outer two pins are touching and the inner two pins are touching as shown.  

For a 12V cigarette lighter jack I chose the MPD ZA5077 available from Digi-Key for $3.74/each.  The Digi-Key part number is ZA5077-ND.  

Removing the power supply

Removing the power supply is quite easy.  First, be sure the unit is unplugged.  Both the motherboard and the power supply have about four screws holding them to the plastic chassis.  Once these screws are removed, the boards can be lifted and separated from each other. 

The power cord going to the power supply can be removed by squeezing the white tab the locks the connector in place.  Here's what it looks like when you're done taking it apart.  

Now we're ready to remove the power cord.  While there may be a more elegant way of doing this, I chose to take a more brute force approach.  I simply took a pair of wire cutters and cut a notch in the plastic chassis to remove the power cord without destroying the cord.  The image below shows the notch having been cut out.

With the notch in place simply slide out the power cord and keep it in case you want to undo the modifications.

The Power Connector

The next step was to figure out the power connector pinout.  Using a voltmeter, it the connector pinout quickly became apparent.  Nothing could be easier.  Power is delivered using a standard 100-mil 4-pin header.  The outer two pins are ground and the center two pins carry 12V DC as shown below.

RCA DTA800 in hand

I just got my hands on an RCA DTA800 converter box.  So the next step is to crack it open.  But first I made make sure the unit is unplugged before attempting to open the lid.  Otherwise, there is a risk of serious injury or death from electrocution.  

After removing all the small screws visible from the outside of the box and gently prying open the lid I got to see the inside.   The first thing I noticed is how integrated everything is.  All there is besides the power supply is a Broadcom chip, an SDRAM, a Thomson tuner and some discrete components.  

Not only is the RCA DT800 a great performer, it turns out it will be really easy to hack.  This is because the box natively runs on a single 12V power supply.  

The only thing that needs to be hacked is to replace the power supply with a direct connection to the car's 12V power.  Basically, there's no need for a power supply at all!

Choosing a converter box

After receiving the $40 coupon in the mail the next step was to choose a converter box.   The best performing unit available is the RCA DTA800.

The RCA DTA800 is based on the Broadcom BCM3543 single chip ATSC receiver.  The guys at Broadcom and RCA did a great job on this one.  The box consumes little power so it's gentle on the car battery and the receiver performance is top notch at pulling in those weaker channels.  

While I'm not a fan of Walmart, they do have it in stock (link) for $49.87.   With the coupon you end up spending something close to $14 after tax.  They don't sell it online, so you'll have to drop in to get your box and hand them your $40 coupon card.  If you don't like Walmart you can try one of the other retailers listed on the letter you receive with your coupon.

$40 Off Coupon

In order to help folks with old analog TVs be able to watch TV beyond the analog TV cutoff, the government is offering $40 coupons.   These coupons can be used towards the purchase of eligible digital TV converter boxes.

You can sign up for your coupon by going to:

www.DTV2009.gov