Knoll systems ma 1250 owners manual

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Knoll Systems service information The MA 1250 ampl ifier does not contai n any user servi ceabl e parts inside. I f yo u suspect a problem t hat ma y r equire servicing, contact us at www.knollsystems.com/contact.html , or by phone at 800 566-5579. Troubleshooting If a problem is encountered with the MA1250, the most expedient procedure is to loca te the problem and if possible repair it before requesting serv ice. Be sure to carefully check other system components such as controllers, CD players, volume controls, wiring, speakers , etc. that may be at faul t. Problem Action Power LED does 1. Check that the MA1250 is plugged in. not l ight - no sound 2. Test the AC outl et wi th a l amp. 3. If remote on/off i s used, check that the tri gger vol tage i s at 12 VDC. 4. Check MA1250 power button on (in). Sound cuts out 1. Verify speaker impedance is 4-16 ohms. Changi ng speakers may be requi red. 2. Check if the MA1250 feels hot. If it's hot increase cooling - see Installation . Sound is distorted 1. Turn the volume down. 2. C heck speakers for damage. 3. C heck in pu ts for proper lev els. MA1250 gain and source output level may have to be adjusted. 4. Speakers may be less than 4 ohms. MA1250 does 1. Push MA1250 power switch off (out) not turn off 2. If tri gge r is being used, power switch needs to be set to off (out) posi tion or amp i s on al l the ti me. 3. Try disconnecting trigger jack. Trigger does not 1. Measure trigger v oltage w ith a v olt work meter. It needs to be 11-15 vol ts DC to work (current i s 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 termi nal. Suggest 2k0 1/4 w. Discharges speaker internal cap. Installation Installing the MA1250 should be re latively easy. With a bit of planning, the MA1250 will give tr ouble free service for years. 1. The most important consideration when installing the MA1250 is cooling. The MA1250 has a lot of power packed into a small ch assis siz e. Wh en in stallin g it in an equ ipmen t st ack , it shoul d be the top component. It needs at least 3"-5" of space abov e t he amplif ier t o allow for adequ ate con vect ion coolin g. 2. When installing the MA1250 in a rack, we suggest adding a 3-1/2" blank above and below the MA1250. In multiple MA1250 installations, plan for a 3-1/2" blank (double) between each MA1250 and a 3-1/2" blank on th e top and bottom. Amplifiers should always be the top components in a rack system. 3. If MA1250 channels frequently shutdown due to overheating, install a fan directed up from the MA1250 bottom center. 4. Never operate the MA1250 on its side, as the cooling pot ential drops sign ifican tly w hen operat ed on the side. 5. Connect the MA1250 inputs to the source component outputs with good quality, short as po ssible RCA jack cables. Connect each ch an nel in div idu ally . 6. Connect the MA1250 speaker outputs to speakers using good qual ity speaker wi re. Mi nimu m 16 gauge copper wire is recommended with 14 gauge minimu m for runs over 30' (10m). Note: Ideally the MA1250 likes 6- 8 ohm loads. Connecting to 4 ohm loads won't hurt the MA1250 but those channels connected to 4 ohm loads may occasionally shutdown due to overloading. Never connect the MA1250 to less than 4 ohms. 8. In div idu ally adju st the ch an nel gain s as requ ired. Ideally , all gain s are f ully on (fully clock wise) . 9. Make sure the speakers in each room are connected in phase wi th the ampl ifier + goi ng to the speaker + . Out of phase speakers gi ve unstabl e i mag ing and poor bass response.