My Integra DTM-5.3 receiver is showing "Protect". I have 4 speakers and 2 just purchased. Except for taking the cover off and checking inside the receiver I have done everything I can think of.

you most likely have a blown main output transistor or a shorted speaker. first get a mutimeter and set to lowest ohms setting and check for 4-8 ohms ( CHECK IMPEDENCE rating on back of speaker) at the speaker terminal of the speaker. if this checks out then you take the meter and set to DC and place the + / - terminals to the speaker connection on back of receiver then turn on the receiver . notice if you have any dc voltage at any sp terminal, if dc is present you have a blown output transistor. If you are not an electronic tech please refer your unit to a qualified service tech. I hope this helps.

Sounds like a speaker going bad or being over-driven.

Check to make sure that NONE of your speaker wires on the outputs are touching each other or that there is anything obstructing any the output terminals. Also since this a 5.3 model check all the SUB outputs for the same condition (although probably not as much an issue since they are line level outputs) as well as the condition of all interconnects and speaker cables. After that check all the physical connections at every speaker to make sure you haven't shorted out an output at that location.

Protect means that a fault was detected, disconnect all the speakers

and connect one at a time to find the cause.

If symptoms persist , it needs repair, output stage or power supply

circuits should be the preliminary things to check.

Do more triage first.

Generally speaking, an amp attempts to protect itself from heat, shorts, overloads and operator exuberance by refusing to turn on or stay on.

Overloads can be from excessive periods of high output or marginally low impedance loading by the speakers; and shorts would be wiring issues or a speaker blowing up.

You should be able to feel if it's hot. WHY is it overheating? Make sure it has sufficient ventilation on all sides and that vent holes are not blocked by dust balls. Ensure the fan (if equipped) is running as designed (some only operate on demand). Clean dust and debris from it.

If the amp comes back on after cooling, you're lucky. They only have so many self-protection cycles in their lives so continuously resetting or cycling their power without addressing the cause can do more harm than good.

If it protects immediately on a cool power up you should disconnect the speaker connections and try it 'naked'. If it comes up then diagnose which lead(s) are shorted. If it does not come up the problem is internal and should be left to an experienced and competent hands-on tech.

Check for loose speaker connections at the speaker as a possible root cause for intermittent shutdown.

Generally speaking, an amp protects itself from heat, shorts, overloads and operator exuberance by refusing to turn on or stay on.

Overloads can be from excessive periods of high output or marginally low impedance loading by the speakers; and shorts would be wiring issues or a speaker blowing up.

You should be able to feel if it's hot. WHY is it overheating? Make sure it has sufficient ventilation on all sides and that vent holes are not blocked by dust balls. Ensure the fan (if equipped) is running as designed (some only operate on demand). Clean dust and debris from it.

If the amp comes back on after cooling, you're lucky. They only have so many self-protection cycles in their lives so continuously resetting or cycling their power without addressing the cause can do more harm than good.

If it protects immediately on a cool power up you should disconnect the speaker connections and try it 'naked'. If it comes up then diagnose which lead(s) are shorted. If it does not come up the problem is internal and should be left to an experienced and competent hands-on tech.

HAve you check the cables that are connected in speakers B connectors? This is a common problem for short circuit cables (or speakers). Try to inter-change speakers A with speakers B in order to estimate the problem. Also you can fully disconnect the speakers B (from the speakers side) isolate the cable ends and check. If the problem is not existing then you have to check the speakers themselves. You could also use (if available) a multimeter to check each speaker (cable and speaker).

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Yes, you can do this easily.
Perform the following steps
(1)Plug your amp to AC outlet.
(2)Switch it on.
(3)observe time taken for switching off.
(4)immediate to shut down over current protect(5)3 seconds to shut down DC protect.
If over-current protect do the
following steps
(O)unplug the amp.
(1)download NR806 service manual.
(2)open the amp metal cover.
(3)measure 7 large white resistors resistance loacated next to power transistors mounted on a large heat sink with black probe touching the middle pin and red probe to first/left or third/right pin.
(4)If this 3 Pins large white colour 0.22ohm x 2 resistor is open with infinity ohms ,
(5)replace it and jot down this channel for example left surround faulty. Usually only 1 channel went faulty.
(6)the two large power transistors next to this white resistor 0.22 ohms x2 should also be replaced.
(7)plug the amp
(8)switch it on
(9)if ok, troubleshooting get done
(10)if not ok
(11)replace ALL the components of this power amp channel.
(12)pre-amp section no need to check.

There is a short on one of the speakers cables or the speakers themselves. Test all of them with an ohmmeter.

disconnect all speakers. do this with the power cord unplugged from wall. then re-try without speakers. if still in protect --shorted channel-which is repair/parts will be needed.