G8MNY > TECH 24.11.23 08:13z 68 Lines 2546 Bytes #16 (0) @ WW
BID : 60926_GB7CIP
Subj: Pac-Comm Tiny2 Battery Tale
Sent: 231124/0806Z @:GB7CIP.#32.GBR.EURO #:60926 [Caterham Surrey GBR]
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
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 | |
³ _³_ Replacement
ÃÄ´<ÃÄoVCC Ü Li 2x AA in
³ D4 ³ battery Holder
³ 1 o |
³ JPB 2 oÄ¿- - - - - - - - Ù
³ 3 o ³
ÄÄÁÂÄÄÄÄÄÄÄÄÄÄÄÁÄ)ÄÄÂÄÄÄoVBB to Ram Memory
³+ ³ ÀÄÄÄoBACKUP to IC U4
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!
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!
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.
³12V (~~~~~~~~) DD SW ³
³ ( 2x AAA ) 45 [Li] ³
³RIG ~~~~~~~~ ³
³DIN ÚÄÄÄ¿ ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ L³
³sw ³ ³ ³ ³³EP ³³RAM³ ³
³ ³Z80³ ³Z80³³ROM³³MEM³ E³
³ ³S10³ ³CPU³³ ³³ ³ ³
³2 ³ ³ ³ ³ÀÄÄÄÙÀÄÄÄÙ D³
³3 ÀÄÄÄÙ ÀÄÄÄÙ ³
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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