I have a jbl mr-4 that will not turn on, I have checked for power and ground on both sides of the connection plugs also I have reset the button behind the take off face plate and it will not come on. It just stopped working one day, no water issues etc. This unit seems to be discontinued, is the jbl mr-6 a replacement and will the wiring harness conections the same so that I can just exchange units. Thanks Brian

Question edited for clarity, proper 'make model (what it is)'.

I can't find a manual, but they have a common theme. Remove the faceplate and press the Reset Button, then clean the contacts both sides with electrical switch cleaner or Isopropyl Alcohol.

https://www.premiumleisure.com/Manuals/nov07/Hydro_Spa_JBL_Stereo.pdf

https://www.rocktheboatmarinestereo.com/specs/MR18.pdf

https://www.google.com/search?q=JBL+marine+MR-15b+manual

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It sounds like the internal battery has failed. Try and claim on the warranty or ask for a repair.

JBL Support - Returns & Warranty

JBL https://ca.jbl.com > support-returns-and-warranty
If you believe your product is malfunctioning during the warranty period, we can help!

Warranty

JBL https://ca.jbl.com > warranty
Unless a different warranty period is stated in the Warranty Card provided with your JBL product, JBL warrants for a period of 1 year (5 years for any non- ...

Troubleshooting help

https://www.ifixit.com/Wiki/JBL_Charge_4_Troubleshooting

JBL Charge 4 TroubleshootingiFixithttps://www.ifixit.com > Wiki > JBL_Charge_4_Troub...Make sure the charging light on the base of the device is blinking. If it is fully charged and still not turning on, the power button may be worn out or broken. ‎The Speaker Will Not Power... · ‎The Device Won't Connect to.....

Try doing default factory settings.
Step 1. Press the "Power" button located on the top center part of your JBL Charge 4 Bluetooth speaker. The speaker will be powered on when the LED backlight under the Power button is lit.
Step 2. Hold down the "Bluetooth" and "Volume Up" buttons at the same time for roughly three seconds. The Volume Up button looks like a plus sign. Additionally, it's important to hold down the "Bluetooth" button in the center of the device next to the Power button, as it's easier to hold down. After three seconds, the LED ring around the Power and Bluetooth buttons will briefly light up before the JBL Charge 4 powers down.
Step 3. Press the "Power" button again to turn the JBL Charge 4 Bluetooth speaker back on. The Charge 4 will instantly turn on in Discovery mode, with the Bluetooth LED blinking on and off, and the speaker making a pinging sound. This confirms that you've successfully reset your JBL Charge 4 to its default factory settings. You'll need to pair or re-pair any devices you want to play audio through the JBL Charge 4 speakers with the device.

Check the fuse if the fuse is good check if you have pluged the face well

The connections are pretty straight forward, but it will depend on what amplifier you're driving them with. Normally, I'd connect the two TR to one side of a stereo PA amp and the two MR to the other side. All four cabinets are rated at 8 ohms, so running tow parallel per side would give you a 4 ohm load on each channel which would be a common load for most stereo PA amps.
However all this would depend on your gear and what you need to accomplish. If what your question really meant is how do you connect all 4 to one channel, you can't as in most cases the total impedance would be too low and you'll fry your amp.
If you can be more specific about your system we could be more helpful.

Press and hold power button while trying to connect to new device to reset conmection

#1. Disconnect the main power to the JBL box.#2. Check the DB9 cable connections, spray with Contact Cleaner (Techspray T8-162210S) in the male & female terminals.#3 Use a toothpick to press a reset button located top left close to the DB9 socket on the JBL box. #4 Reconnect power a& test operation. Good Luck! : ) : ) : )#5 843-849-9037 Ask about warranty or Technical support.
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Because of that moisture it may have fired the lighting connection inside the unit, does it produce and sound?

Will a REM 25 remote work with the MR 15 JBL radio?

Hi,

Initially, have you tried a full hard reset? The reset button is at the panel at the back of the faceplate, bottom left side. Of course doing so will also erase all presets and user settings & configurations.

Additionally, pls verify that the multiple contacts pins are clean, free of corrosion and makes a positive contact with its mate at the rear of the faceplate. If the unit is used in a salty environment, it may be necessary to manually scrape of whatever blue green build up develops between the connector pins and the plastic insulator. You can try using an old toothbrush and WD40.

Further to check are:
1. the red, yellow and black wire are tightly connected where they are supposed to be connected. If the unit is used onboard, it might be to your advantage to likewise check the grounding system;
2. one of the rear connector is for a remote, pls likewise check that none of the pins are shorting and no presence of any corrosion.

If problem persists, it may be necessary to seek the services of a qualified professional as this involves opening the unit up and tracing the circuitry of the logic/controller circuit.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

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