13 Aug
2002
13 Aug
'02
11:20 a.m.
Fair enough ....
That would still leave about 8 volts after double-phase
rectification to charge the nicads with. (thru a 4.7ohm
internal resistor)
Never operate the TI59 without the nicads! when
the machine is turned on the excess voltage
will be dumpt into them so the -vbat will be kept at
-3.7 Volts! To operate it without nicads might
toast the machine !!!!
Sipke de Wal
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http://xgistor.ath.cx
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----- Original Message -----
From: "Carlos Murillo" <carlos_murillo(a)epm.net.co>
To: <cctalk(a)classiccmp.org>
Sent: Tuesday, August 13, 2002 6:35 AM
Subject: Re: TI-59 question
At 06:54 PM 8/12/02 +0100, you wrote:
Failing that, if you can find the right connector
(possibly from another
TI calc PSU) the TI-59 requires 6.2V 200mA AC.
I always wanted a TI-59, but I have to make do with a -58...
You can probably build something with epoxy/rubber and a couple
of pins off a female DB-25 connector..
A word of caution: if you are going to build a charger with a 6.3V
transformer, keep in mind that the chargers that TI provided
for this and other calculators had very high secondary winding
resistances; I just measured mine, and it is 16 ohms. I have
no idea about the reactance, though.
The high resistance in effect limits the maximum current across
the rectifier diodes and battery. I suspect that if you connect
a < 3ohm transformer something might burn.
carlos.
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Carlos E. Murillo-Sanchez carlos_murillo(a)nospammers.ieee.org