Knoll Systems service information

The MR1250f amplifier does not contain any user serviceable parts inside. If you suspect a problem that may require servicing, contact us at www.knollsystems.com/contact.html, or by phone at 800 566-5579.

Troubleshooting

If a problem is encountered with the MR1250f, the most expedient procedure is to locate the problem and if possible repair it before requesting service. Be sure to carefully check other system components such as controllers, CD players, volume controls, wiring, speakers, etc. that may be at fault.

Problem	Action
Power LED does	1.	Check that the MR1250f is plugged in.
not light - no sound	2.	Test the AC outlet with a lamp.
	3.	If remote on/off is used, check that
		the trigger voltage is at 12 VDC.
	4.	Check MR1250f power button on (in).
Sound cuts out	1. Verify speaker impedance is 4-16 ohms.
		Changing speakers may be required.
	2.	Check if the MR1250f feels hot. If it's
		hot increase cooling - see Installation.
Sound is distorted	1.	Turn the volume down.
	2.	Check speakers for damage.
	3.	Check inputs for proper levels.
		MR1250f gain and source output level
		may have to be adjusted.
	4.	Speakers may be less than 4 ohms.
MA1250 does	1.	Push MR1250f power switch off (out)
not turn off	2.	If trigger is being used, power switch
		needs to be set to off (out) position
		or amp is on all the time.
	3.	Try disconnecting trigger jack.
Trigger does not	1.	Measure trigger voltage with a volt
work		meter. It needs to be 11-15 volts DC
		to work (current is about 35mA total
		per amp). See page 5 for details.
Speaker pops when	1.	Speaker may need resistor placed
amp turned on or off		across terminal. Suggest 2k0 1/4 w.
		Discharges speaker internal cap.

Installation

Installing the MR1250f should be relatively easy. With a bit of planning, the MR1250f will give trouble free service for years.

1.The most important consideration when installing the MR1250f is cooling. The MR1250f has a lot of power packed into a small chassis size. When installing it in an equipment stack, it should be the top component. It needs at least 3"-5" of space above the amplifier to allow for adequate convection cooling.

2.Amplifiers should always be the top components in system.

3.If MR1250f channels frequently shutdown due to overheating, install a fan directed up from the MR1250f bottom center.

4.Never operate the MR1250f on its side, as the cooling potential drops significantly when operated on the side.

5.Connect the MR1250f inputs to the source component outputs with good quality, short as possible RCA jack cables. Connect each channel individually.

6.Connect the MR1250f speaker outputs to speakers using good quality speaker wire. Minimum 16 gauge copper wire is recommended with 14 gauge minimum for runs over 30' (10m).

Note: Ideally the MR1250f likes 6-8 ohm loads. Connecting to 4 ohm loads won't hurt the MR1250f but those channels connected to 4 ohm loads may occasionally shutdown due to overloading. Never connect the MR1250f to less than 4 ohms.

7.Individually adjust the channel gains as required. Ideally, all gains are fully on (fully clockwise).

8.Make sure the speakers in each room are connected in phase with the amplifier + going to the speaker + . Out of phase speakers give unstable imaging and poor bass response.

9.Connect trigger if being used to a 12 VDC source (about 35mA) using a 3.5mm mono jack. 5 VDC triggers will not work.