Need help! Wer hat Erfahrung mit der Umpolung eines großen elektrischen Drehzahlmessers von "negeativ auf positiv ground". Ein Schaltplan oder eine Anleitung wäre nicht schlecht.
gruß hb
Drehzahlmesser Umpolung
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Anbei ein Auszug aus John Twists (University Motors, Ada, Michigan) Anleitung zum Umpolen von POSITIVE auf NEGATIVE ground - hier muß dann SINNGEMÄSS GEÄNDERT werden. Sorry, mehr hab ich auf die shcnelle nicht, hope it helps:
9) Tachometer. If the car is fitted with a mechanical rev counter, then obviously this section will not apply. The RVI tach is labeled on its face whether it is positive or negative earth. It is driven by a pulse from
the hot side of the coil. Modern tachometers are driven by the pulse from the distributor side of the coil, and are much improved over the older RVI units. Two changes are necessary to make the tach work: a) the wires
must be reversed at the "white wire loop" at the back of the unit; and b) the power and earth connections must be reversed on the inside of the unit.
a) The wire in the "white wire loop" comes from the key switch and travels to the hot side of the coil. Select one of the wires and tag it with two pieces of tape for identification. Then cut the wire between the pieces of tape, and cut the other wire to the same length. Reverse the connections (now there is one piece of tape on each wire), and solder them (remember-- this is the power lead for the coil and is unfused). Tape up the connections carefully, When later replacing the plastic block on the back of the tach, ensure that the metal band around the block is carefully positioned. This is a necessary half of the electromagnetic pickup.
b) To reverse the power wire and earth wire on the inside of the unit, it is necessary to remove the chrome ring, the glass face, and the glare shroud. The chrome ring is usually removed with great difficulty by prying at it with a small screwdriver at the tabs. Then, remove the two screws on the back of the unit that hold the internals to the case, and allow those internal to drop carefully into your hand. DON'T BEND THE NEEDLE! The spade terminal which carried the green or white wire is the power lead. Just next to this is the earth connection. One of the two leads is a resistor. Unsolder the wires and resistor from their positions and reverse them, resoldering the connections. Reassemble the unit after cleaning the glass.
9) Tachometer. If the car is fitted with a mechanical rev counter, then obviously this section will not apply. The RVI tach is labeled on its face whether it is positive or negative earth. It is driven by a pulse from
the hot side of the coil. Modern tachometers are driven by the pulse from the distributor side of the coil, and are much improved over the older RVI units. Two changes are necessary to make the tach work: a) the wires
must be reversed at the "white wire loop" at the back of the unit; and b) the power and earth connections must be reversed on the inside of the unit.
a) The wire in the "white wire loop" comes from the key switch and travels to the hot side of the coil. Select one of the wires and tag it with two pieces of tape for identification. Then cut the wire between the pieces of tape, and cut the other wire to the same length. Reverse the connections (now there is one piece of tape on each wire), and solder them (remember-- this is the power lead for the coil and is unfused). Tape up the connections carefully, When later replacing the plastic block on the back of the tach, ensure that the metal band around the block is carefully positioned. This is a necessary half of the electromagnetic pickup.
b) To reverse the power wire and earth wire on the inside of the unit, it is necessary to remove the chrome ring, the glass face, and the glare shroud. The chrome ring is usually removed with great difficulty by prying at it with a small screwdriver at the tabs. Then, remove the two screws on the back of the unit that hold the internals to the case, and allow those internal to drop carefully into your hand. DON'T BEND THE NEEDLE! The spade terminal which carried the green or white wire is the power lead. Just next to this is the earth connection. One of the two leads is a resistor. Unsolder the wires and resistor from their positions and reverse them, resoldering the connections. Reassemble the unit after cleaning the glass.