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G8MNY > TECH 21.06.25 07:12l 68 Lines 2546 Bytes #0 (0) @ WW
BID : 35149_GB7CIP
Read: GUEST
Subj: Pac-Comm Tiny2 Battery Tale
Path: JH4XSY<N3HYM<K5DAT<W0ARP<VK2RZ<GB7CIP
Sent: 250620/2202Z @:GB7CIP.#32.GBR.EURO #:35149 [Caterham Surrey GBR]
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 | |
ﾚﾄｴ<ﾃﾄﾄﾄﾄﾄﾄﾄﾄｿ+3.6V External
ｳ _ｳ_ Replacement
ﾃﾄｴ<ﾃﾄoVCC ﾜ Li 2x AA in
ｳ D4 ｳ battery Holder
ｳ 1 o |
ｳ JPB 2 oﾄｿ- - - - - - - - ﾙ
ｳ 3 o ｳ
ﾄﾄﾁﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾁﾄ)ﾄﾄﾂﾄﾄﾄoVBB to Ram Memory
ｳ+ ｳ ﾀﾄﾄﾄoBACKUP to IC U4
1u === 1k
ﾁﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾁﾄﾄﾄ0V
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.
ﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｿ
ｳ12V (~~~~~~~~) DD SW ｳ
ｳ ( 2x AAA ) 45 [Li] ｳ
ｳRIG ~~~~~~~~ ｳ
ｳDIN ﾚﾄﾄﾄｿ ﾚﾄﾄﾄｿﾚﾄﾄﾄｿﾚﾄﾄﾄｿ Lｳ
ｳsw ｳ ｳ ｳ ｳｳEP ｳｳRAMｳ ｳ
ｳ ｳZ80ｳ ｳZ80ｳｳROMｳｳMEMｳ Eｳ
ｳ ｳS10ｳ ｳCPUｳｳ ｳｳ ｳ ｳ
ｳ2 ｳ ｳ ｳ ｳﾀﾄﾄﾄﾙﾀﾄﾄﾄﾙ Dｳ
ｳ3 ﾀﾄﾄﾄﾙ ﾀﾄﾄﾄﾙ ｳ
ｳ2 Sｳ
ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾙ
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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