[Kenwood] TS-850 Battery Replacement

[Paul Pagel]

Having purchased a used TS-850SAT last year and reading many posts about =
the rig, I decided to replace the memory back-up battery in my 12- or =
14-year-old TS-850SAT (its age depending on which formula you use). The =
battery hadn't leaked, but I wasn't going to wait until something went =
awry and I wound up with more than a battery replacement on my hands. I =
suspect the battery might have been running low because I noticed that =
it took several seconds before the display would come to life after the =
transceiver had been unused for a few days; this may or may not be true.

I basically followed the instructions given by Bill Smith, KO4NR (see  =
http://www.jzap.com/n6tr/850repair.html). At first I thought I was =
lucky: It appeared that the battery in my TS-850SAT was in a coin-cell =
holder! Indeed it was, but unfortunately the holder is spot-welded to =
the battery, so the holder/battery combination must be unsoldered from =
the digital PC board (X46-3080). G-r-r-r-r!

Much to my dismay, I discovered that RadioShack no longer stocks any =
coin-cell holders and I couldn't locate them anywhere locally. Although =
Newark stocks CR-2430 and CR-2032 holders and batteries, I decided I =
didn't want to pay $5 for not meeting Newark's minimum order requirement =
($25). Besides, from what I could see of the pictures of the Keystone =
holders, I wasn't sure the CR-2430 holder would exactly match the holes =
in the PC board. Then I got a tip from a guy at a local RadioShack =
service center. He suggested I try to find an old computer motherboard =
and scrounge the holder from it. Most motherboards (if not all) use =
CR-2032 coin cells in holders for CMOS memory backup. My first call to a =
local computer store netted me a pair of old motherboards from which I =
took the batteries and holders.

After removing the coin cell/holder from the computer motherboard, I =
attached a pair of color-coded wires (cut from ribbon cable) to the =
now-empty holes on the TS-850's digital circuit board. I suggest you use =
color-coded wires to ensure you wind up with the correct polarity: The =
battery's negative pin is at the top and the two positive pins are near =
the middle of the board; both positive-pin holes are connected by a =
PC-board trace.

I secured the scrounged CR-2032 holder to a small piece of perfboard =
(roughly 2x2 inches) using hot-melt glue and connected the free ends of =
the wires from the TS-850 battery location to the holder pins; again, =
ensure proper polarity. Using double-stick pads I attached the perfboard =
to the left-hand face of the left wall separating the fan/final assembly =
and RF unit (X44-3120), placing the perfboard within the RF-unit =
compartment. In this position there's easy access to the battery-holder =
clip and it's simple to pop out the old battery and insert a new one.=20

During disassembly of the front panel and digital PC board, I was able =
to access the bottom of the board after removing only three cables: one =
above the battery and two near the upper-left of the board. But after I =
reattached the board and front panel, some of the front-panel key =
functions didn't work. Anxious? Scared I'd done something wrong? You =
bet! But I discovered the problem to be a disconnected cable near the =
bottom of the front panel. This short, flat multiconductor cable =
interconnects the front panel and the digital PC board and is located =
(as viewed from the top of the transceiver) below and to the left of the =
VFO knob. So be careful when moving/positioning the front panel. Having =
another inch or two of cable there would've been nice (as would an =
easily removable memory back-up battery).

Nevertheless, the TS-850's a fine rig. Imagine how large it would have =
to be if it were built when only vacuum tubes were available! My first =
rig, a Heathkit DX-40 -- without the companion VF-1 VFO -- was half the =
size of the TS-850 and ran only CW and grid-modulated AM!  My =
Hallicrafters SX-101 receiver alone was easily the size of the TS-850 =
and weighed in at about 75 pounds.=20

Paul / N1FB




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