Posted on June 26th, 2011 6 comments
We got a set of 4 Panasonic DECT-6 wireless phones (Models KX-TGA931T) a few years ago and they worked beautifully at first. But after a while, the phones began to exhibit an annoying behavior when we attempted to answer a ringing phone where it would display a message that it lost its connection to the base after a single ring, making it impossible to pick up the call. The other phones continued to ring normally. Sometimes repeatedly pressing on the ‘Talk’ key would get it to answer the call, but it became are real annoyance because it always seemed to happen to the phone that was the closest to answer.
Upon searching the Internet, I found many people complaining about the same issue. I read through a number of forums and found that although it was a rather common problem, there was not a consistent sure-fire solution. One solution suggested unplugging the power to the base unit temporarily, but that didn’t fix the issue, at least in my case. Even the Panasonic website was of no help despite having numerous complaints of the problem in its reviews. I had tried replacing the batteries in one of the phones, but even the one with fresh batteries would still misbehave. However, I had used a cheap set of NiMH batteries from Harbor Freight that were a few years old, and so maybe I exchanged one bad set of batteries for another. The amount of talk time available when the phone worked didn’t seem to indicate the batteries were worn out. Sometimes one of the handsets would not charge fully, and it would be warm to the touch when taken out of the cradle. But then later, it appeared to charge to full capacity according to the battery icon.
Eventually, I grew so tired of the problem that I ordered fresh batteries for all 4 phones. I got them from Batteries America, by ordering the high capacity Sanyo AAA NiMH batteries (P/N HR-4U-1000). I’ve had good luck dealing with Batteries America, especially for things like rechargeable batteries for older ham radio and aviation hand held transceivers. They also carry custom rechargeable batteries for equipment that is no longer available even from the original manufacturer of the product.
I am happy to report that by changing all of the batteries, the problem has gone away. Better yet, the new batteries have 50% more capacity than the original Panasonic 650 mah batteries and will last many hours between charges.
These phones have this difficulty when one or both of the batteries wear out, which all rechargeable batteries tend to do after a year or two of use. It’s not unusual for a new rechargeable battery to be weak if it had been on the shelf too long prior to using it so make sure to purchase your batteries from a reliable source only when you need them. The charging circuitry in the phone is not effective at notifying the user of weak batteries. If you experience this issue, I’d recommend getting a new set of high quality NiMH batteries for all of the phones and keeping track of when you replace them, because when they wear out, the phone will not give you any clue about what’s wrong other than this inexplicable problem where its connection to the base becomes flaky along with contradictory evidence that would seem to indicate that the batteries are not the issue.
[UPDATE: 2013-01-20] I just wanted to follow up to say that after nearly two years of using the Sanyo batteries, we still have not experienced a single ‘cannot find base’ issue. So I’m even more confident that this issue was battery-related and compounded by the phone’s battery charge status to properly identify the problem.
Posted on May 18th, 2011 539 comments
One day I returned home only to find that our Sony Wega TV (Model KV34HS420) was no longer working. It would respond to the remote control and begin to start to turn on, but then it would make a clicking sound and turn itself off before a picture appeared on the screen. After that, the standby/timer LED would continue blinking 6 or 7 times. This blinking LED is a diagnostic code, but its description of the potential issue provided little value. After reading a few dozen postings on the issue, a pattern began to emerge that made me hopeful that I could repair it myself.
We purchased this TV in 2005 while the jury was still out about which flat panel TV technology would eventually replace the tried-and-true CRT technology. Back then, the LCD and plasma flat panel displays still had viewing angle and reliability issues and cost 2 or 3 times as much as an equivalent-sized CRT model and so we just decided to replace our 15-year-old Sony CRT TV with a modern HD-capable CRT TV. I was hoping to get 15 years or more out of this $1500 investment before having to send it to the landfill. After all, this was a SONY, not some no-name brand that I’d expect to fail after only a few years. And tube TVs usually last a very long time. I have one in my basement I purchased in 1985 that is still working fine.
This TV has excellent picture quality and no restrictions in viewing angle, and other than its size and weight, I found it much better than what was available with flat panel technologies at the time. Its speakers provide excellent sound quality, much nicer than the tinny sound produced by some of the razor-thin flat panels. It sits in a corner and therefore takes up no more room than an equivalent size flat panel display. So, after only 6 years, I was wondering whether it would need to be replaced or if I could fix it. After a fair amount of forum reading, I found that this 6 or 7 LED blink code was a rather common problem, along with a common solution, namely to replace the MCZ3001DB integrated circuits known as IC8002 and IC6501 on the ‘D’ board. This chip is functionally identical to earlier versions of it known as MCZ3001D or MCZ3001DA. The forums had many people describing their success at making the repair, but pictures of this procedure were non-existent, hence the reason for this blog posting. Also, the level of difficulty and amount of work involved was not clearly described, so I hope to explain and show what I did so the reader can determine whether it is within his or her skill level to attempt this repair.
This TV weighs 200 lbs. I didn’t want to have to move it from its stand. Fortunately, it was possible to remove the entire back shell simply by removing all of its screws and sliding it off. There are a lot of screws, about a dozen around the periphery of the TV along with several more on the back panel, but fortunately, it’s a one-person job although it wouldn’t hurt to have a helper because the shell, although fairly lightweight, is bulky. Removing the shell allows access to the ‘D’ board.
The ‘D’ board is the one shown in the picture below. I should mention that before removing the cover, you must unplug the TV and give it a few hours for the high voltages to dissipate so as to avoid shock hazards. It’s best to unplug it and wait overnight, since if the TV is not working so there’s no need for it to remain connected to power.
It wasn’t clear how to remove the board, or if it would be necessary to undo all of the wiring connections. Some of the connectors were easy to remove, but the 3 high voltage wires that connect to the CRT did not have easy-to-unplug connections. I eventually figured out that I didn’t need to remove those wires at all. There are a number of connectors that need to be flipped upward to disconnect the ‘D’ board from an adjacent board. It wasn’t clear at first how they worked, but if you feel around for a flange you can pull them upward, they’ll unsnap and pivot up 90 degrees like a draw bridge. Two of the connectors had latches on them that require squeezing the lever to unlatch it before they will come out. I unplugged all the other cables I could find, removed about 8 screws, and the board came out far enough to let me rotate it into a position where I could access the bottom of the board. It was necessary to use a stubby screw driver to remove one screw that was far forward, hidden between two connectors, and just under the CRT. To make that easier, you will notice that there are two plastic hooks, one on each side of the tray that the boards are mounted to that you can unlatch which allows all the PC boards to slide back about 4 inches. That makes the front screw easier to access, although you’ll still need that stubby screwdriver. (I’ve since added images of the latch and the board slid back at the end of this article.) After you get all the screws out, the board is still held in by a few plastic clamps on the edge which you can bend back a little to release the board. The board was still tethered by the high voltage connections, but I was able to fix it ‘in place’, by turning it over like shown in the image below.
Unsoldering the two ICs is not difficult if you use a spring loaded solder sucker like the one shown below. Do not waste your time trying to use solder wick or a bulb-type solder sucker for desoldering the chips. Search for YouTube videos with the word ‘desoldering’ if you’ve never desoldered a chip before to see how it works. Also, make sure that the soldering iron is a low-wattage type, and not too hot to avoid lifting the copper traces.
Be aware that each chip has two pins are not soldered to the board. This is normal and so don’t try to solder those pins or the fix will not work. Take note of the orientation of the chips since there is a notch on one end facing the closest edge of the board. You do NOT want to install the chips backwards. Also, don’t solder the new chips in directly to the board. Use sockets in case you ever need to do this repair again, since having to unsolder these chips is most of the work. If they were socketed in the first place, you could replace them without having to solder or even having to remove the D board.
I wasn’t sure of the best way to purchase the ICs, since forum participants mentioned purchasing them on Ebay, where there are several China-based vendors offering MCZ3001DB chips but the shipping times from China vary considerably and can take from 10 days to 3 weeks. The vendor I chose was TriState Module because I wanted a U.S.-based company. They sent me a pair of ICs for around $20 including shipping charges. However, they no longer have these parts in stock and they are getting harder to find. I also needed a pair of 18-pin dip sockets which I found at the local Radio Shack for $.59 each. They look like the parts on the left in the image below:
After replacing the ICs with sockets, you’ll need to install the replacement ICs. Odds are that only one of the chips is bad, but since you won’t know which one, it’s best to just replace them both. It is necessary to squeeze the pins together to get the legs aligned with the holes in the sockets. This style of IC has its legs spread out by default, and so they won’t automatically align unless you pre-bend them inward just a little to align with the holes in the socket. Carefully examine the chips after you install them to make sure all the legs made it into the socket and that the little half-circle notch at the end of the chip is facing toward the near edge of the board as shown in the photo below.
After re-installing the board and attaching all the cables, it would be a good idea to test it to make sure the repair worked before reinstalling the cover. If you unlatched the tray and slid the boards back to make access easier, you’ll need to put them back in position or else the remote control and on/off button won’t reach the board. With luck, your TV will be back up and running, avoiding a premature trip to the landfill. I can’t guarantee this fix will work for you, but the consensus on the forums is that it frequently fixes the 6 or 7 blink code problems on the Sony Wega flat screen CRT models.
I found the repair to be of intermediate difficulty, and the result was very gratifying when the TV turned on again. Our TV has now been working like new for more than 2 years, and if it ever happens again, I could fix it more easily thanks to the sockets that are installed. It felt good to resurrect a TV that has great picture and sound quality and, hopefully, a lot of life left in it.
And, in the event it doesn’t work for you, then maybe getting one of those new and improved flat panel TVs is your best alternative. 🙂
[UPDATE 2013-11-15] I mentioned earlier about the difficulty of finding and removing one of the screws under the CRT. Some of these TVs, including the model I repaired, have a set of latches that allow you to release the board and carrier and slide it back about 4″ to make that screw much easier to access. You can see it in the images below:
Posted on December 31st, 2010 No comments
If you have a 115 piece drill set and have lost the chart that translates the diameter of the drills to a decimal equivalent based on the drill number, letter, or fractional size I have scanned mine, stitched it together and have it available as a jpg or pdf file. When I lost mine, I spent an inordinate amount of time with calipers searching for the right drill diameter. Now that I found it again, I keep it near the drill index and if I ever lose it again, I’ll know where to go to make a new copy of it.
The chart is a real time saver. If you click on the image below, you’ll get the full scale jpg image of it. From there you can right click and ‘Save As’ to have your own copy of the jpg file so that you can print it.
I generally print it to fit to a single page, which shrinks it a little. If you prefer, you can print it full size from the pdf file and then cut and tape it together.
UPDATE: After looking at that image for a while, I decided the chart needed a ‘do over’ and so I put it in a spreadsheet and printed it as a PDF which makes it much more readable. Click on the image below for a PDF file suitable for printing on a single page.
Posted on December 30th, 2010 5 comments
My friend was building a Stirling engine and when he found out that I owned a small lathe, he asked if I’d machine a piston and cylinder for him. Having some materials on hand like copper tubing for the cylinder and some solid aluminum rod for the piston, I agreed to make the parts. Another one of the parts he needed was a 7/16″ bolt with a hole drilled down the center of it. He had tried to make the hole with his drill press, but ran into a problem where the hole he drilled was not centered. This became apparent only after the hole was finished, of course, as it exited the far end of the bolt off center.
I had an idea about a procedure for drilling an accurate center hole in a cylindrical part with a drill press by first aligning a drill vice to hold a drill bit stationary while using the drill chuck to grip and spin the work piece. My drill’s chuck can hold a drill up to 1/2″ in diameter, which would be more than sufficient to grip a 7/16 bolt on its shank. I thought I’d run a quick experiment and document the procedure for anyone else who may want to try using a drill as a lathe for making a center hole in a cylindrical part.
A lathe is most often used to turn a part using a cutter that can either remove material from the diameter or from the part’s face. But it also has a very nice feature when a drill chuck is inserted in the tailstock, and that is to accurately drill a hole precisely down the center of the part. An example of that is shown below.
Normally, you would use something called a center drill to start the hole and then swap it out for the drill of the proper diameter. If the hole is large, you may have to drill with several drill sizes to get it up to the finished diameter. In this case, the hole I wanted to make was just .125″ in diameter so it was possible to do with just a single drill in one step. The procedure I describe below would need to be modified by resetting the alignment for each drill if you need to open the hole up in several steps.
If you didn’t own a lathe but had a drill press and a drill vice, here is a procedure for drilling a center hole in a cylindrical part.
First, you put a drill of the desired diameter in the drill chuck and tighten it. Then gently raise the drill table, clamp the table to set its height, and then and move the drill vise to the bit and clamp the drill vice down on the bit. The drill vice must have a ‘V’ groove one its jaws to align it vertically on the drill bit. This is important for a subsequent step. After everything is aligned, then use a pair of ‘C’ clamps to hold the drill vice to the table so it cannot slide from side-to-side. Then un-clamp the drill bit from the chuck and the drill vice and turn the bit upside down and clamp it in the vice’s V-groove again so that its tip is facing upward. Then clamp the workpiece in the drill chuck. In this case, I’m using a .5″ diameter section of aluminum rod as the workpiece.
Here the drill is clamped in the vice pointing upward and the workpiece is just partly visible and clamped into the drill’s chuck.
Then turn the drill on. Just like on the lathe, the drill bit will be stationary and you can lower the spindle with workpiece and it will drill the hole accurately through the center of the part. Remember to lift up on the spindle periodically to clear out the metal chips. If you got everything aligned correctly, the drill will make the hole directly in the part’s center. In my case, the hole was within .002″ of being concentric with the outside diameter of the part on both ends of the part. That’s about as accurate as you would get with a lathe so the technique works well.
It may not be apparent but the part is spinning, the drill bit is stationary.
Here’s the finished part with the hole perfectly centered.