Message 29069 in TECH.WW
From: G8MNY
Date: Sun, 30 Aug 26 21:19:00 Z
Newsgroups: TECH.WW
Subject: Pac-Comm Tiny2 Battery Tale
Message-ID: <3722_GB7CIP>
Path: N2MH4|VE3KPG|GB7CIP
R:260830/2120Z 36349@N2MH4.#SENC.NC.USA.NOAM LinBPQ6.0.24
R:260830/2120Z 104@VE3KPG.#ECON.ON.CAN.NOAM BPQ6.0.25
R:260830/2119Z @:GB7CIP.#32.GBR.EURO #:3722 [Caterham Surrey GBR] $:3722_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Jan 08)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I have been looking at the disastrous results of adding external backup
battery connection to a tiny2, as the small rare soldered in Li battery had
died.
The external batteries outside the metal case had been wired from the anode of
low voltage drop D5 to JPB 2 battery 1k earth jumper link.
_ _ _ _ _ _ _ _ _ _ _ _ _
D5 | |
1u === 1k
As you see from the circuit there is very little other than the 1uF protecting
the static sensitive memory IC from external electrical shock (static & HF).
The Li battery current limiting 1k earth resistor left in the external battery
system only making matters worse!
THE DAMAGE
In the end the TNC packed up with a blown up memory 62256 IC & a Z80 S10/0 IC
Which handles the data bus to the memory & Z80 CPU. This was found by swapping
ICs to another TINY2, luckily all in sockets. The logic IC U4 a 78HC132 took
the Zapp OK!
MY SOLUTION
After replacing the ICs, I unsoldered the Li battery & wired the battery
connections to 2x AAA Alkaline cells (soldered to batts with special solder or
file ends) all tapped up (parcel tape) to provide insulation & some battery
leakage protection to the PCB & double side taped the bundle to the PCB where
the 82C88 IC hole space is.
I expect the 2 AAAs should last as long as the original Li?
I hope this tale stops anyone else from zapping their TNC.
P.S. don't forget to backup your TNC EPROM if you can, as EPROMS only have a 7
year G'tee image lifetime!
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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