I have yo repair a 1-474-012-11 lamp driver, the R1 resistor is broken and I can't measure it. It doesn't have a standard code resistor.
Could somebody tell me the value of that resistor? Who has this board please measure it.
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Resistors R1, R2, R3, and R4 are arranged in a circuit as shown in the figure above. The direction of positive currents I1, I2, I3, and I4 through the resistors are shown. (i.e., negative current values correspond to currents in the opposite direction to that shown above). The values for the resistors and the batteries in the circuit are: R1 = 100 ?, R2 = 200 ?, R3 = 30 ?, R4 = 400 ?, V1 = 4 V, and V2 = 12 V.
R1 is probably different for different models of the timer.
Normally if R1 is burned... look carefully and other nearby parts have signs of burning also.
R1 is the first place you see the overheat problem,,, and that's true with the older and newer models in the GM and Woods series timers, including defrost series. http://waterheatertimer.org/images/Defrost-timer-burned-part.jpg
Contact Intermatic.com and see if they offer a schematic and replacement parts sheet... but I've not seen a parts sheet.
The timer is usually taken out of service and replaced once R1 is burned.
Frequently these timers with burned R1 are sold on ebay after they have been removed from service... simply because the timer looks good or repair seems simple.
Let us use a bit of logic to resolve this... I have an Axiom but it would be a lot of screws to take out to get to the part... so let us think about this. The resistor value starts with a "1" and we know it is 5% tolerance (gold). we know the resistor burnt up with likely 5 volts on it... Value could be 1000 ohms, however the voltages present (12 volts max) would NOT have burned up a resistor of 1000 ohms. The USB area is mostly 5 volts and across 100 ohms is only a quarter watt... not enough to really burn up a resistor... First thing is to MEASURE that the resistor s open... in spite of being burned, it MAY still be OK... these resistors now usually either open or remain close to their value. The resistor ALSO may be a fusible resistor intended to act as a fuse... Is the resistor open or not? is it near a resistance with a "1" as the first digit? If it is not open I suspect it is not all of the problem. In that case, look for a burned circuit trace on the board. If it is open, then MEASURE the voltage across the resistor with the power applied. If you find 5 volts, then it MIGHT be a 10 ohm used to limit the USB current to 500ma. Get back to me with your findings... I have unraveled many of these things...
The dial could have a desoldered pin or oxydized slider contacts. Try to resolder the pins, but if that doesn't solve it then you would need to disassemble and clean the internal slide contacts on the dial which can be a bit difficult, so the alternative is to replace the dial if you can find a spare one.
To bypass the dial (with fixed resistances) you need to know the resistance at each side of the dial when it is in the position that suits your needs (connect the snare to a working input, set the sensitivity as needed, mark the position of the dial).
The resistance can be measured with an ohm meter.
To be sure that the measuring will be accurate, it is ok to remove the dial from the circuit board (adjacent components may affect the measured value).
You should do the measuring on a dial that is good.
After you've removed the dial, set it to the position that you marked previously.
Measure the resistance between left and middle pin of the dial - this will be the value of the fixed resistor which you need to connect to the left and middle hole on the circuit board.
Now measure the resistance between middle and right pin on the dial - this will be the value of the fixed resistor which will be connected to the middle and right hole on the circuit board.
Now you need to get resistors which have the values that you've measured and solder them in place of a bad dial.
It is likely that the measured value will differ from the standard fixed resistor values. To achieve the exact measured value, you can connect two or more fixed resistors in series, just make sure that the added value of the fixed resistors for each side is the same as the measured value on each side of the dial.
Now you need to solder the fixed resistors to the circuit board and the modification is complete.
If you actually decide to do this modification and you're unsure about anything, just post me some feedback, i'll be glad to help.
Anyway, hopefully it is just a desoldered pin that you need to reflux.
Try finding out the nominal voltage for the original lamps (or the replacement you want to use) and then measure the voltage on your unit's display lamp socket (or wires).
Seems like the lamp supply voltage is slightly higher than normal and with each power on/off it will spike a little, eventually burning out the lamp in time.
You can try to connect a resistor in series with the lamp. Measure the lamp's resistance - if you add a resistor of the same value, the lamp will then have only about one half of the voltage across it. You can then decrease the value of the resistor until the voltage across the lamp is about the nominal lamp voltage, maybe a tiny bit lower, the rest of it will drop across the resistor. You may have to experiment a bit to find out the correct resistor value.
Be sure to use a resistor that has at least the same power rating (wattage) as the lamp, or it may heat up or burn out.
The part that you speak of is called the emitterstabilizer resistor. It is common to the output pair on one channel. You will find that the large "output" transistors mounted to the heat sink either side of this resistor will most probably be faulty.
Best not to run the amp at all whilst in this condition.
To be sure that you have an effective repair, you will need to change both these parts, and also the "driver" transistors that connect to the outputs. They too are in symmetrical positions close to the the output transistors. You should also check that the 3 legged resistor you mentioned is measuring its correct value, and check all other low value resistors in the output stage area to that channel.
If you are not familiar with repairing this sort of equipment, perhaps you can find a repair guy with some experience on audio equipment, then this work should be all he needs to do to repair the amp. I would also ask him to "blanket resolder" the output/bias stages and power regulator stages in the amp as problems with heat stressed cracked/failed soldering and dry joints often cause these amps to blow the output transistors.
BE SURE THAT THE CORRECT PARTS ONLY are used for the repairs. Different transistors could cause future problems with the amp. The parts can be obtained relatively easily from a marantz distributor(we can find one in a country near to you). OR if you can give me the markings to each of the parts you need, I can provide you with an international source to get them from.
The amp is decent HiFi, and worth repair. Happy to provide you any assitance I can, Good Luck