I’ve got an Amana 93HQ furnace, a Goodman CKL36-1L AC unit, and a Robertshaw (unk model) digital thermostat. All are about 2-3 years old.

Several days ago, we lost power to my house during an electrical storm. The power was off for several hours. Eventually, the utility company replaced the (ancient) transformer and restored power. I do not know what else they may have done, as I was at work when power was restored. I know a loud lightning strike woke me, but I do not see any evidence of an actual strike at the house.

Upon returning home, I found that my DSL modem, my garage door opener motor, and my digital thermostat were not functioning. All other electronic devices seem fine (TV, Wii, etc).

The modem power supply had been humming for a while, and my electrician friend said that garage door motors seem to be sensitive to the surge after a transformer hookup. Particularly if they hooked the house to the transformer, and -then- hooked the transformer to the grid. He said this seems to create issues more often than hooking the transformer to the line, and then the house to the transformer. I have no idea how things were connected, obviously.

Upon looking into the thermostat issue, I found that the 3A fuse on my furnace board was blown. Replace, blows again. With some trial and error, I found that the circuit is -fine- in the heat, or fan-only settings. It’s only when the thermostat tries to activate the AC that an issue occurs. Discussion with an HVAC acquaintance of mine led me to think it may be the contactor.

I pulled the access cover from my AC unit, and manually pushed the contactor…everything seems to work normally. Fan spins, I can hear the compressor fire up, etc. Try to activate from the thermostat, though, and the 3A fuse blows. I also pulled the low-voltage wires at the furnace board (wires which run out to contactor on AC unit). When this is done, the thermostat can be switched to "Cool" without issue. Obviously the AC unit doesn’t engage, but no fuses blow.

Ideas? Could the surge of power (after transformer replacement) have hosed the coil in the contactor? Is there a way to test this, prior to replacing the contactor? Is there a way to get 24V power to the contactor (to see if it engages) without tripping the fuse on the furnace board?

Other thoughs, suggestions, or advice?

Will there be a problem if I plug a window AC unit into the same electrical circuit as electronic equipment such as computers and home AV gear? The closest outlet on another breaker is 20 feet away through a door and this room needs additional cooling in the summer. the unit is rated to only draw 5.3 Amps normally so it shouldn’t blow the fuse, but I don’t know if the compressor surge/voltage drop when it kicks on will harm the other electronics.

I blew a fuse on the air conditioner circuit board (model: 580.74085400). I contacted Sears and the only way to replace it is to replace the entire circuit board. Can anyone help me find the amperage of the fuse so I can buy one on my own? The owners manual says it is a 250V / T2A Fuse. The fuse says 250V / T2L.

looking for the soldered in fuse, in a balboa deluxe 120 circuit board, and where to buy one
still need to know the amperage, the metal caps cover thi info on the fuse

I need a timer circuit that once activated, does nothing for an adjustable amount of time, then allows a separate circuit to complete it’s connection or simply supply power to another circuit.

Basically I know enough about electronics to wire from a diagram, but I don’t know enough to find that diagram. This is for an electronic fuse for a model rocket that I designed. I want to press a button or switch, then be able to walk away before it launches (or worse if I mess something up welding it)

I was wondering, i've seen it before, having a circuit board in between the front seats and it has a master switch, and switchs for the lights individually.
I was wondering how i can hook up my glow lights under my seats, and under the dash to a circuit board with switchs instead of plugging them into a ciggerette lighter. Also, do i run the wire from the board straight from the battery or through a fuse? Thank you

* 12 Volts DC Output at 0-2 Amps
* Fully Adjustable Current Limiting
* Constant Voltage
* Excellent Load and Line Regulation
* Low Ripple & Noise
* Reverse Voltage Protection
* Built-in Short-Circuit and Overload Protection
* Optional 10-turn Current Potentiometer
SPECIFICATIONS: DC Output: 12 volts at 0 to 3.5 amperes, continuously variable. Current Regulation – Load/Line: 0.25% from short-circuit to rated voltage/0.1% from 105 to 125VAC. Ripple & Noise: 500uV RMS. Overload Protection: Load and power supply are protected by an adjustable electronic current limiting circuit. Current limiting is adjustable from less than 1% to 105% of rated output current. AC input is fuse-protected.

wen i fit in a 20A fuse to my amplifier,it jus blow up my fuse…….where could the problem cum from……..if is the transistor in the apm….where should i start……i have sum basic in electronic……i can read circuit diagram…..pls explain in detail…thank you…..

1. If the current through a heater coil is 5 amp and the supply voltage is 120 volts, the coil resistance is
A. 0.04 ohm.
B. 24 ohms.
C. 110 ohms.
D. 575 ohms.

2. The amount of current flowing in a circuit can be measured by
A. an ammeter.
B. a voltmeter.
C. a neon test lamp.
D. an ohmmeter.

3. Which one of the following letters is used in formulas as the symbol for voltage?
A. P
B. W
C. I
D. E

4. The conductors in electrical devices are commonly made of
A. iron.
B. nickel.
C. copper.
D. lead.

5. The energy used by an appliance which operates at 240 volts at 15 amp for 4 hr. is
A. 0.92 kwhr.
B. 3.45 kwhr.
C. 14.4 kwhr.
D. 60.0 kwhr.

6. What is the voltage in a circuit with a resistance of 12 ohms and a current of 20 amp?
A. 0.58 volt
B. 1.74 volts
C. 120 volts
D. 240 volts

7. If an appliance does NOT work at all when you plug it in and turn the switch on, the appliance circuit is
A. shorted.
B. overloaded.
C. leaking.
D. open.

8. To read the line voltage supplied to an appliance, you should connect the voltmeter
A. in series with the power supply.
B. between the grounded wire and the water pipe.
C. across the power supply.
D. between terminals of two adjacent circuit parts.

9. The best method for testing the continuity of each part of an appliance uses
A. a voltmeter.
B. an ammeter.
C. an ohmmeter.
D. a wattmeter.

10. A 2000-watt heater connected to a 120-volt circuit will draw a current of
A. 5.75 amp.
B. 15 amp.
C. 16.67 amp.
D. 23 amp.

11. What type of fault causes an appliance to blow a fuse when the appliance is turned on?
A. An open circuit
B. Too much resistance
C. A short circuit
D. Too high a voltage

12. Which one of the following conditions is unfavorable for the use of an ohmmeter?
A. Voltage is supplied to the appliance
B. The appliance is grounded
C. Moisture is in the insulation
D. The appliance circuit is shorted

13. A series circuit in an appliance consists of
A. several branches carrying independent currents.
B. more than one part connected across the same terminals.
C. several parts connected end to end.
D. more than one path carrying the current.

14. Which one of the following components is used to change an AC voltage to a lower or higher value?
A. Transistor
B. Transformer
C. Capacitor
D. Resistor

15. A full-wave bridge rectifier uses how many diodes?
A. One
B. Two
C. Three
D. Four

16. An NPN transistor is correctly biased and turned on if the
A. base is negative.
B. collector is negative.
C. collector is positive with respect to the emitter and negative with respect to the base.
D. collector is the most positive lead followed by the base.

17. When an SCR turns ON, it acts like a(n)
A. transistor.
B. resistor and capacitor in series.
C. electronic switch and rectifier.
D. bridge rectifier.

18. Which one of the following IC digital gates requires a high on both inputs to output a high?
A. AND
B. OR
C. NAND
D. NOR

19. Which one of the following IC gates will have a low output if either of the inputs are high?
A. Buffer
B. NAND
C. NOR
D. OR

20. A microprocessor runs an internal program called a(n)
A. operating system.
B. scratchpad memory.
C. instruction chain.
D. PAL.

21. A resistor with the color bands brown, red, red and silver will have a resistance of
A. 120 ohms.
B. 1,200 ohms.
C. 2,100 ohms.
D. 6,400 ohms.

22. What type of diagram chart in a service manual can be used to easily service an electronic circuit board with ICs?
A. Exploded
B. Flowchart
C. Assembly
D. Pictorial

23. An LED display device uses how many segments to create the number 8?
A. Three
B. Four
C. Seven
D. Eight

24. When testing transistors, how much minimum voltage difference should be seen across the base-emitter junction?
A. 0.1 VDC
B. 0.4 VDC
C. 0.6 VDC
D. 0.9 VDC

25. When you are forward-bias testing a diode with a digital VOM, the red test lead should be placed on which lead of the diode?
A. Anode
B. Cathode
C. Emitter
D. Drain

I need a page about capacitor, fuse, circuit, electronic, resistance, etc all about electronic. Thnxs