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hpr4222 :: Replacing backup batteries in my Kenwood TS940S HF Radio Part 5

Part 5 deals with the removal of the original 40 year old PLL backup battery.

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Hosted by MrX on 2024-10-08 is flagged as Explicit and is released under a CC-BY-SA license.
Amateur, Radio, DIY, repair, electronics, soldering. 2.
The show is available on the Internet Archive at: https://archive.org/details/hpr4222

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Duration: 00:16:09

HAM radio.

A series about all things Amateur Radio/HAM Radio.

Picture 1
Shows the EPROM (Erasable Programmable Read Only Memory) fitted with a label marked JAF7. EPROM's can be erased by removing the sticker and exposing the device to strong ultraviolet light. I incorrectly refer to it as a PROM (Programmable Read Only Memory. Below it is the old leaking PLL backup battery.
Shows the EPROM (Erasable Programmable Read Only Memory) fitted with a label marked JAF7. EPROM's can be erased by removing the sticker and exposing the device to strong ultraviolet light. I incorrectly refer to it as a PROM (Programmable Read Only Memory. Below it is the old leaking PLL backup battery.

Wikipedia article about EPROM’s (Erasable Programmable Read Only Memory)

Link / example of a Fluke 77 DMM (Digital Multi Meter) I mention that I used it to check the battery voltage of the original PLL backup battery which I think was manufactured around 1984. I was very surprised to find that the battery which is likely 40 years old had a battery voltage of 3.2V which is a healthy voltage. The battery still needed changed due to liquid (probably acid) which can be seen in picture 1 being present on the top surface of the battery.

Picture 2
Shows me extending the new battery terminal using the leg of a 1.8 kilo ohm resistor. Note that the resistor leg is shiny because this time I scraped away the surface oxidation using pliers prior to soldering it in place. This improves the final solder joint.
Shows me extending the new battery terminal using the leg of a 1.8 kilo ohm resistor. Note that the resistor leg is shiny because this time I scraped away the surface oxidation using pliers prior to soldering it in place. This improves the final solder joint.

I mention I have an EC2000 Weller Electronically controlled soldering station. Here is a link to an example I found

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Comment #1 posted on 2024-10-08 22:41:21 by Beeza

Old Batteries

Hi Mr X.

I have an analogue multimeter that I inherited from my dad. He bought it in 1983 and it still works fine with the original battery. Contrast that with modern batteries that can be dead when you take them out of the packaging if they are more than a year two old.

Comment #2 posted on 2024-10-10 16:11:43 by MrX

Re Old Batteries

Hi Beeza,
Thanks for the nice comment. How true everything these days is made cheaper; It’s a race to the bottom. My old trusty Fluke 77 DVM had a very old PP3 battery in it that finally failed though I doubt it was as old as 1983! Not only do the batteries not last as long I suspect they are also more likely to leak so it’s probably even more important to check these modern ones more frequently. I hope you have many more faithful years use from your dad’s analogue meter. For a lot of jobs they can’t be beaten.

MrX

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