Re: 82002A Question (nothing to do with that auction website) Message #9 Posted by Randy on 19 Feb 2007, 11:51 p.m., in response to message #8 by Mad Dog ebaycalcnut
If the display flashes or otherwise acts weird, it is usually the capacitor. A 470 uf, 25 volt radial lead aluminum electrolytic is a good replacement as 400 uf is not a common value. Tolerances on this type of cap can be as wide as +80/-20% so the value change is not an issue.
The brown area is usually near the 470 ohm resistor* that supplies base current to the pass regulator. They can go high or even open due to the heat. Measure it, replace if necessary.
*=yellow-violet-brown-silver color bands. That's if it isn't toasted.
PS: The easiest way to test a 82002 is with a voltmeter. Assuming a digital type, set the meter to a ~20 volt DC range, you don't want it auto-ranging. Stick the negative lead in the center hole of the charger plug, calculator end. With the lead at the bottom, put the plus lead in the right hole. The DC voltage should be around 4.5-5.0 vdc. If you don't read anything, wiggle the wire at the plug end and see if voltage appears. If the voltage is intermittent, the problem is usually fractured wires right where they enter the strain relief of the plug.
If it's good, move the plus lead to the left hole, it should measure about 16 volts. If good, set the meter to read ~20 volts AC. With the probe still in the left side, check the AC voltage. It should be below 0.2-0.3 volts AC. If it's any higher than that, the 400uf cap is bad.
|