Re: TI-H: TI-86 Slowdown with EL backlight
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Re: TI-H: TI-86 Slowdown with EL backlight
Well, it sounds like the inverter is injecting noise into the power
lines. Depending on the circuit and chip the calc uses, it may be that
the processor uses the frequency of the inverter instead of its own
oscillator. You should put a filter capacitor in parallel with the
inverter, close to it. You may even need a choke in the line as well.
Try another inverter, if you have one.
-Adam
David Knaack wrote:
>
> Alright, I installed a backlight in an 86 for the first time,
> and I've run into the slowdown problem. The calc works fine
> if the backlight is off, but as soon as I turn on the inverter
> the calc drops to a much slower speed. This is happening with
> new or old batteries, and does not appear to be effected by a
> series resistor, which seemed to fix the problem in other 86s.
>
> I have tried several series resistances in the inverter supply
> line, including 10, 22, 32 and 47 ohms. The slowdown is not
> effected at 32 ohms, and at 47 ohms the inverter does not come
> on.
>
> I rigged up a seperate battery supply and powered the inverter
> from that, with the calc running from its own battery supply
> and every thing worked as normal. Linking the grounds of the
> two supplies immediatly slowed the calc.
>
> The only thing I can think of as a cause is noise that the
> inverter is causing in the power supply. Bybass caps of
> 100uf, 50pf and 2pf across the battery supply had no effect
> on the problem.
>
> I will attempt to get a 'scope in here so I can check things
> in more detail sometime this week, but in the meantime, can
> anyone suggest some more diagnostic procedures, or suggest
> some possable solutions?
>
> Thanks
> DK
>
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