Monday, 23 December 2019

Realistic DX394 RAM Memory Back Up Battery Replacement


The DX394 has a small rechargeable battery soldered onto a totally inaccessible place in the front of the radio, and when the battery failed on my radio, I was faced with a row of irritating flashing zeros on the clock, a display that reverted to 150khz, and blank memories, each time I returned from a holiday or weekend away and the power to the shack had been shut down. Eventually I put the radio in my cupboard and stopped using it. Then I discovered someone called Dino from the DX394 io group had discovered a possible way of bypassing the very complicated disassembly of the front panel (which requires manufacturing your own tool to remove the tuning knob). It is shown above in my slightly edited photo to aid clarification to complete beginners like myself. 

I was a bit reluctant to take my soldering iron (and craft knife for severing the PCB trace) to my beloved radio, but it didn't look like rocket science and I figured I'd give it a try. 

I have already done a couple of radio mods, easy ones. Like the Uniden 9000XLT discriminator tap and the PRO2005 EL backlight replacement. I'm a rubbish solderer, I have shaky hands, but I'm careful and methodical and down-to-earth about the idea that if I damage the radios beyond repair they are not so expensive they can't be replaced one day. I| might even use the opportunity of their demise to try a different radio. So with this mentality you can't go wrong. 
I am so glad I tried all of these mods and would not hesitate to try them again if the need arose. They are not too hard and really help boost your confidence. 

Firstyl, you have to buy a Panasonic VL2020 battery from ebay (about £8).

When you have removed the top panel of the DX394 if you look inside at the back of the front panel you will easily find D206 in the diagram.

To sever the trace to its left where shown you need a sharp knife. I practiced a bit on an old, broken radio, to figure out the pressure needed to break the copper. It did need pressure, a steady hand, and using your other hand as a brake in case you slip. But afrer a few firm scroes across the trace and lots of inspections with a jewellers loupe (an ordinary magnifying glass was useless) it was clear when the copper had been cut completely. A useful tip: after each scoring across the trace, I wiped the debris with a small cotton bud dipped in surgical spirit to more easily see the result of the cut.

Soldering a small piece of insulated wire from pin 1 of D206 I firstly tinned the tip of the wire and dipped it in flux before carefully soldering it in place. That would be soldered to the positive terminal of the battery. I did the same thing with the negative lead, soldering it to the big blob of solder shown on the diagram.

The result:

I then put the battery inside a small memory card folder and neatened thing up a bit.

Although the battery read 3V when I inserted it, after just half an hour it had gone down to 2.8V and after a 30min power down, the memories were empty again. So I left the DX394 connected to a 13.8V power supply overnight for two consecutive night, to fully charge the new battery and since then everything is working splendidly.

I can't tell you what a joy it is to have the memory working again. The radio has been reborn. To switch on in the morning and see the right time, no flashing, and my last used frequency, with all the memories intact is indescribable joy! I must be a true radio geek!

Had it not worked, I would have bought another DX394 cheaply and tried again, as I have always loved this radio. The MW and maritime MF bands are incredibly sensitive. HF sensitivity is excellent. The memories are quick and easy to use and program and change and delete. The display is large and pleasing to look at.
Sadly AM broadcast listening is fatiguing. Most people agree here. But I use a DX400 for broadcast stuff nowadays, and with its excellent murata filters and audio quality use the 394 for aero/utility monitoring, MW and maritime MF.

I'm a big aero fan, and always monitor Stockholm radio and Shanwick. The DX394 is perfect for this.

Anyway, message me if you need an advice via the comments or QRZ (M6RDP). I just wanted to show you this excellent mod here on my blog.

Bye. 73