This is the 12th in a series of articles about my recent quest to replace a broken VCR in this era of DVDs, DVRs, and other newfangled gadgets. Click here for the beginning of the series.
Here is a photograph of the first TV remote control that we wired with the switches. It was a remote for a 13 inch Magnavox stereo color TV. It had only four switches. One was for power. Another was for channel up and the last two were for volume up and down. Although this TV was cable ready, at the time there were only about 30 channels on our cable system so it didn’t really take very long to go around the dial to get to the channel you wanted. I limited it to four switches to keep it simple and because I was concerned that I would have difficulty handling more than four switches at a time.
In those days they didn’t have universal remotes. You had a dedicated remote for every device and that was it. If you had to replace a remote you had to write to the manufacturer so it was risky to take it apart and wire buttons into it. Fortunately our rewiring job didn’t damage the remote. In fact I’m still using that television today a good 15 or 20 years later. The TV is mounted on the wall in our bedroom at the Lake.
By the time I was ready to replace that television, it was possible to purchase universal remotes inexpensively. So rather than risk damaging the remote that came with the television, I purchased an inexpensive RCA universal remote and we wired it for use with my next television in the bedroom. That same rewired remote served me just fine until just a few months ago. It originally had a record five micro switches! I finally decided that in addition to power, volume up, volume down buttons, I would splurge and have both a channel up and a channel down button. Those are the five switches shown at the bottom of the cluster in the image below.
I think it was only three or four years ago that I decided to expand that remote. I added four more buttons for a VCR. These four additional buttons in the middle row control stop, play, fast-forward, and remind. Then a little over a year ago when I got my first HDTV for my bedroom I need two additional buttons. Those are the buttons shown at the top. One of them controls the zoom feature so that I can switch between the 4:3 at 16:9 aspect ratios. The other one toggles between component inputs and composite inputs. Component inputs are connected directly to the cable box for HD viewing. The composite inputs are for the VCR. If you watch through the VCR you don’t get high definition so I needed an extra button to toggle back and forth. Since the zoom and input toggle features were not available on my old RCA universal remote I had to purchase a second “learning” remote to get these two additional features. A learning remote allows you to copy any function from another remote by pointing the two remotes together at capturing the signal.
As you can see from this image, three sets of wires connecting the buttons to two different remotes is quite a mess. That mess, combined with the fact that I knew someday I might have a device that the old RCA remote would not control, had led me to decide to rewire the entire thing from scratch. It was such a big job to rewire it I hadn’t done it but now that “someday” was today and the old RCA remote wouldn’t work the new Sony VCR/DVD we were going to have to go ahead and do it now. It turns out that the Sony device used DVD codes and the old remote predated DVDs!
I had already purchased a new Zenith ZEN-760 learning remote to replace the old mess. I ordered a new batch of micro switches from RadioShack.com. Because I was going to need 11 of them I didn’t think I could find that many in stock in a local store.
Here’s what the inside of the Zenith remote looks like inside and out.
The image was created by placing the circuit board on my scanner. The light green areas are silver circuit board traces covered in a layer of green protective coating. The wide black lines are another layer of electrical traces. The large black lump middle left hides the chip that controls everything.
In this close-up the green S-shaped areas created by the little black interlacing fingers are where the actual keys go. A metallic contact on the back of the rubber keyboard membrane makes contact with the little interlocking fingers. That completes the circuit and the chip figures out what to do from there. You can’t solder onto the black traces… only the green ones. So you have to figure out where the alternate sides of the little black fingers connect to green traces. Then you can solder wires onto the green traces. The round “connection dots” on either side of these interlaced fingers are the locations where the black traces connect to the pale green traces. The image shows a couple of places where it would be good to solder wires for the button location created by the little fingers on the right.
As you can see, the two sets of fingers creating S-curve locations on the left side of the above image share a common trace with the one on the right. That is because you don’t have two unique wires running to every button on the keyboard. If you did, it would take 22 wires to connect my 11 micro switches. If you were to draw a schematic you would see that the keys are actually arranged in a series of rows and columns. The chip in the remote sends a signal down each of the column traces one at a time, many times a second. If a key is being pressed, the signal will come back in one of the row wires. This way the chip knows that the button at that particular row and column is being pushed.
In earlier remotes, I had to use the actual button locations for volume up, volume down, channel up, channel down etc. Sometimes those particular buttons didn’t have easily reachable places to solder wires. In a learning remote you can put any function in any key location. That was going to make the wiring a lot easier. It would also allow me to exploit the row and column arrangement. I could choose buttons that shared common rows and columns and it meant I could run fewer wires to my micro switches.
The first few times I did one of these rewiring jobs I simply had to sit and stare at the circuit board for long periods of time trying to follow the traces with my bare eyes. Fortunately I figured out that if I put it in the scanner and created a digital image, I co
uld blow it up big and use a paint program to label the solder points so that dad could figure out where to put the wires. Also if you used the “color fill” tool on the paint program you can colorize the little green traces in multiple colors and keep track of where they go a lot easier. In the image on the above left I have labeled the locations of the “6”, “9”, & “TV/VCR” buttons as well as colorizing some of the traces so they are easier to follow.
I spent about a day working with this remote and creating a wiring diagram for dad to follow. He wired up 11 micro switches for all of the functions I talked about earlier. Then we tried to get the remote to learn all of the functions that we needed.
It didn’t work!
Although you can put any function you want into a button, somehow this remote “knew” whether or not a particular function belonged to a TV, VCR, etc. It wouldn’t let you mix codes from different devices. It assumed you were going to put all of your TV codes under one device, VCR codes under another device, cable box under another device etc. It didn’t really care if you put TV codes in a VCR slot or VCR codes in a cable slot. But it would only let you put one kind of device codes in each device slot. That meant I would’ve had to wire more micro switches into the CBL, TV, & VCR device select buttons. The bottom line was we had completely rewired this new phenomenal remote and it was totally useless!
In our next installment we start from scratch with a Sony remote.