Question about Audio & Video Receivers
Posted by zatman on Nov 27, 2008
MyDenon avr 2106 goes into protect mode in less than 10 sec (immediately after"Receiver" comes up on display during startup). Tried all the normaluser resets. If I disconnect the 15 pin connector (cn559) between theinput board and cnt unit and restart the receiver will come upcompletely without going into protect mode but does not output to headphones or speakers.Display works properly with all functions. I'm a hobbiest with someequip and would like a recommendation on possible components to check.Have unit schematics. Thanks. Comment posted on Nov 28, 2008 The cnt board is the connect board that bridges between the cpu board and the main board. No inputs are connected to the input board so no short there. No speakers were connected only head phones so
thespeaker short is eliminated. I pulled the input board out completelyand with the rest of the receiver in its normal condition the unitstarts completely as demonstrated by the response from the displayalthough no sound is coming from the headphones. The speaker switchesare in the headphone only mode.
Is there a way to troubleshoot the input board or are there known issues with this board such asa tendency for certain components (ex. caps or relays to fail? Wouldprefer replacing components rather than complete board.
Comment posted on Nov 29, 2008 More info. The 15 pin connector between the CPU board and Connector (cnt) board is labeled;
FR,Gnd,FL,Gnd, SR,Gnd, SL, Gnd, SBR, GND, SBL, Gnd, SW, GND, C for the various speakers.
When all of the ground (Gnd) points (7 total) are disconnected, the remaining points FR through C,
connectedand in their normal positions the receiver starts, does not go intoprotect mode and the display shows correctly. When ANY one of the Gndpoints alone is connected in the circuit the receiver goes onto protectmode after startup. Obviously when all Gnd points are connect as is innormal operation the unit goes into protect mode.
Comment posted on Nov 30, 2008Checkedconnect board for shorts and continuity as well as connecting ribbons.Continuity checked out and no shorts between ground and non-groundconnections were found. Also, checked continuity and ground from themain board, through the connect board through the input board. Again noshorts to ground or shorts between on grounded connections were foundwith the unit off. If there were shorts I would think the unit wouldshut down immediately rather than go through the startup for almost 10seconds with power on. From physical examination none of the capacitorson the input board appear blown. If you have some other ideas pleaseadvise.
Additional: With the unit ON I checked DC voltages between the 15 pin connector at the input board and the chassis (ground). The black connector ground wires all measured about 6v dc. The red and white wires measure about 5.7v dc. The connector was obviously disconnected from the input board to avoid having the unit shut down. Seemed strange to be getting a voltage potential between the blackconnector ground wires and unit chassis ground .
I will will help you with this, but you must follow my instructions. These are not easy unit to repair, and your troubleshooting technic may have even caused more problems. You should never power on a receiver with connectors unplugged. Since the 15 pin connector is used for the audio signals only (CN559) you may be OK, but please do not do this anymore unless you are willing to create a lot of smoke.
Since this unit does turn on without that one connector plugged in, I will assume that you do not have a blown channel even though it is the most common reason for these to go into "Protect Mode" which is what yours is doing. They go into protect mode to keep the receiver from causing more damage to the circuits and to prevent fires.
I think the most likely reason your unit is going into protect mode is because the negative 15 volt regulator on the main board is bad. This regulator is located by ref # IC102 and is on a small heat sink in the power supply area of the main amp board. Since you have the manual for this unit you should be able to find the part number and location very easy.
The second most likely reason for your problem is a resistor, ref # R184, it is a 10 ohm 1 watt resistor and it is right next to the pre-amp board on the main board. It is near CP501 but on the other side of the pre-amp board towards the output transistors a little. Check this resistor first with an ohm meter, see if it is at 10 ohms. If not, get a 10 ohm 1 watt flameproof resistor and replace it. Then make sure everything is plugged in right and try it again.
If the resistor is good, then go to the voltage regulator, you can check it by measuring the voltage at resistors R145 and R146. If you look at the schematic for that area, you will see that those resistors are connected to both the positive 15 regulator and the negative 15 volt regulator. One side of R146 should measure -15 volts and the other side of R146 should be at 0 volts. Then measure R145. You should have +15 volts on one side and 0 volts on the other side. If the voltage you measure there is not within a couple of tenths of a volt either way, change the voltage regulator that is bad. If all you get is positive voltage on R146 and no negative voltage, then IC102.
Now you are probably wondering, how can you check those voltage if the unit is shutting off right away. Here is how. Have you meter probes in place before turn the unit on, watch the meter while is is turning on. You only need a few seconds to check each one. Check R146 first, then after the unit shuts off, check R145 when you turn it back on again. This is much safer than unplugging connectors and letting the amp idle with unbalanced voltages which could cause an extreme current draw if left on too long.
If you can not verify any problems with those two things above, then you really do need to check the amp circuits. You can do this with no power connected, but you must take out the main board with the big heat sink. Once you get it out, check the output transistors and start with the pair that is located at the inner most spot of the heat sink. The area close to the display and CNT board. That is the most common channel to go bad. If either one of those transistors mounted on the big heat sink measures shorted of very low in ohms, that is the bad channel. If you have a bad channel, there will be many more parts to replace, I will let you knwo what those are if you find any shorted output transistors. You can not check the amp circuit any other way, you will only be getting a reading across the relays if you try to check it at the speaker outputs. The speaker relays never open unless the unit comes out of protect mode first.
Let me know if I have explained this good enough for you, if not I will give it another try.
Posted on Dec 02, 2008
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