STEREO POWER AMPLIFIER RB-981
Bridged Mono Operation | Troubleshooting |
[See Figure 3 for bridged operation jumper setting and connec- tion illustration.]
The two channels of the RB-981 can be “bridged”. In this configu- ration the single channel produces a massive 390 watts! This fea- ture allows you to increase the overall power output of your system by bridging the RB-981 and adding a second bridged RB-
981.Or the RB-981 is bridged to drive a monophonic subwoofer. Note however that when the RB-981 is bridged the speaker con- nected to it must have an impedance of 8 ohms or more.
In order to use the RB-981 in bridged mode, three “jumper” con- nectors inside the amplifier must be moved from one set of pins to another. This task should be done by a qualified technicain. See your Rotel audio retailer. In addition the RB-981 is connected to the other components in a different way. When the RB-981 is setup for bridged operation the Bridged Mono indicator light 4 on the front panel will light.
Most difficulties in audio systems are the result of poor or wrong connections, or improper control settings. If you encounter prob- lems, isolate the area of the difficulty, check the control settings, determine the cause of the fault and make the necessary changes. If you are unable to get sound from the RB-981, refer to the suggestions for the following conditions:
Front Panel Power Indicator Is Not Lit
No main power to the RB-981. Check the front panel power switch. Make sure that it is set to the on position. Check AC power connections at the amplifier and the AC outlet.
Fuse Replacement
If everything checks out correctly and you still cannot get the am- plifier to turn on, the internal power fuse may have blown. If you believe this has happened, contact your Rotel dealer for informa- tion on where to take your amplifier to get the fuse replaced.
Resetting Jumpers
Before opening the RB-981 cabinet to reset the jumpers, the power cord must be unplugged from the wall. DO NOT OPEN THE CABINET OF THE RB-981 BEFORE THE POWER CORD HAS BEEN UNPLUGGED FROM THE WALL. FAILURE TO DO SO WILL EXPOSE YOU TO HAZARDOUS VOLTAGES.
After the power cord has been unplugged, remove the screws that hold the cabinet cover in place and slide the cover off the amplifier. Locate the three jumper pin blocks labeled S 601, S 602 and S 603. The factory standard (stereo) position of the jumpers is on pins 1 and 2 of each block. There is a * mark on the circuit board next to this position. To convert the RB-981 to bridged mono move all three jumpers so they are on pins 2 and 3 of each jumper pin block. Replace the cover of the cabinet. Do not plug the RB- 981 power cord back into the wall outlet until the cabinet cover has been replaced.
No Sound
If the amp is getting AC power, but is producing no sound, check the Protection indicator on the front panel. If it is lit, see below. If not, check all of your connections and control settings on associ- ated components.
Protection Indicator Is Lit
The front panel indicator lights when the RB-981 protection cir- cuits have shut off the amplifier. Typically, this occurs only when the ventilation openings are blocked, when there is faulty speaker wiring, or after a period of extreme use. Turn off the system and wait for the amp to cool. Then push the front panel power switch in and out to reset the protection devices. If the problem is not corrected or reoccurs, there is a problem with the system or the amplifier itself.
Input Connection
When using the RB-981 in bridged mono mode, connect the cable from the preamplifier output to the left input. No connection is made to the right input.
Bridged Speaker Connection
When using the RB-981 in bridged mono mode, the wire to the speakers is connected to the positve terminals of the left and right channels. Connect the wire that goes to the postive terminal of the speaker to the positve terminal of the left channel of the RB-
981.Connect the wire that goes to the negative terminal of the speaker to the positve terminal of the right channel of the RB-981. No connections are made to the negative terminals of the RB-981.
