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My power supply has a constant 23 AMPS 13V the 1550 has a internal switch for actavating lights, horns ect. this is rated at 1 amp, how do I drop the amps so not to fry something? Thanks for your help

Put a 1A (or less) fuse in-line with the switched power line.

Your 23 Amp capable power supply can furnish UP TO 23 Amps if called on to do so. How much of that is actually called for is determined by the requirements of the equipment connected to the supply. So, if you radio draws 10 Amps, and the siren/lights
setup draws another 3 Amps, the system will be drawing about 13 Amps, which literally means you can put more equipment on the
power supply without any problem, up to around 20 or 21 Amps.

Another factor you must consider is whether that 23 Amp. figure is for intermittent or continuous duty. Also, that 10 Amp. figure I
used as an example on the radio's current requirement would probably apply only when transmitting because the receiver part of the
radio will only draw 1 or 2 Amps (probably less) when receiving.

engine110 wrote:My power supply has a constant 23 AMPS 13V the 1550 has a internal switch for actavating lights, horns ect. this is rated at 1 amp, how do I drop the amps so not to fry something? Thanks for your help

Typically these outputs are meant to drive external devices, such as a relay coil or small indicator lamps. If your worried about these outputs, you can always fuse them with a 1 amp fuse. Measure the current the external device uses before connecting the radio input/output lines. While some outputs *may* source voltage with a very limited output current, many outputs are actually an open transistor collector lead (or FET) to pull the line to ground. This is ideal to activate a relay coil, which typically is much less than 1 amp (for small relays - not starter selonoids). Let the relay contacts do the heavy current work and save your radio! Also when working with external relay coils, its best to add a diode across the relay coil, to keep the EMF pulse from your radio when the relay de-energizes. The "band" marking on the diode goes towards +12V.

It doesn't matter how many amps the power supply is capable of delivering. The radio will only take what it needs. As long as it doesn't need more than 20 amps or so, everything will be fine. Here I am presently using a Samlex 23 amp power supply with a Kenwood TK 840 which draws 7 amps on tx, but 99.9 % of the time the radio is just sitting idle, & barely drawing 1 amp. That's fine. The only time you would have a problem would be if you connected a device that drew more than the 23 amps the supply is capable of supplying. GARY N4KVE

You will need a relay to switch anything greater than one amp. Better yet always use a relay on the radio for external switching, saves repairing the radio.