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Quote:
My HP28s is dead. There are a few discrete components on the main board. A resistor marked 102K, is that a 100k resistor? Next to that a capacitor or resistor. It is 0 ohms. Next a glass circular component, possibly a diode. Then a three terminal device with two ports joined, probably a diode. A tantalum capacitor then a 1000uF electro.
Can someone verify these observations.
The case was easy to open and then repair if you have the right tools.
102K is 1Kohm, the "2" means "2 zero's".
That zero ohm component is probably an inductor. If it does not look like the other resistor and it's not marked then it's more likely an inductor than a shorted capacitor.
The three terminal device is most likely a diode.
Glass circular components are almost always diodes.
I have never opened my 28S, so this is only an educated guess from an electronics designer.
Dave.
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Quote:
The case was easy to open and then repair if you have the right tools.
Really?! What tools? I've taken one apart, but how do you get it back together?
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The 1000uf cap is the supply bypass/memory backup.
102k is a capacitor, the component next to it, an inductor. Those two form the clock tank circuit. The others are part of a voltage doubler for the LCD display driver.
The usual failure is not electrical but rather mechanical in nature - a loss in contact between the logic board and keyboard due to failed heat stakes around the keyboard connector area.
Quote:
The case was easy to open and then repair if you have the right tools.
What tools would those be?