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Louie
Louie, Technician
Category: Home Theater-Stereo
Satisfied Customers: 11427
Experience:  Have been in the business 25+ yrs., down to component level.
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I have a denon receiver that doesn't power up. All it does

Customer Question

I have a denon receiver that doesn't power up. All it does is clicks constantly.
Submitted: 1 year ago.
Category: Home Theater-Stereo
Expert:  info tech replied 1 year ago.
Hello
Welcome
Thanks for the Question

Has this happened on its own you have not moved or interfered with any wiring particular speaker wiring ?

How old is the unit please?

Is the power-light lit ?or is it just the clicking you hear?

Anthony
Customer: replied 1 year ago.

the power led comes on and clicks in standby. when I push the power button the led flashes green and unit starts clicking. I want to do a component level repair on this. I have a service manual if you need it.

Expert:  info tech replied 1 year ago.
Mike to save me going over old ground exactly what have everything you done so far?

Anthony
Customer: replied 1 year ago.

not much really. The original problem was no power. I found shorted and blown parts and replaced them. The unit powered up after. I then was told to check the idle current and forgot to set the volume to low so as soon as I turned the power on, there was smoke and then now clicking. Checked parts i replaced and they are all good. It has to be something in the power supply.

Expert:  Louie replied 1 year ago.
Hi again Mike and welcome back to JustAnswer,Initially, have you checked all the output transistor pairs of Q101 & Q102 out-of-circuit?
Customer: replied 1 year ago.

I found a transistor Q504FR on the pre amp board which is part number KSC1845F. It measured bad in and out of circuit .I was getting readings both ways and tested against a good one and it is probably defective. All of the output transistors measured good.

Expert:  Louie replied 1 year ago.
That would be for the front right channel; an equivalent of the 2SC1845 family.Have you likewise checked resistor R511FR / 47Ω?
Customer: replied 1 year ago.

yes I measured R511FR and it is open, so I think I found the problem with the power relay clicking. I will order the parts and update you.

Expert:  Louie replied 1 year ago.
Nice find!Appreciate the update Mike now and again later when able.Cheers.
Customer: replied 1 year ago.

I also found R110FR and R111FR both open.

Expert:  Louie replied 1 year ago.
If both R110FR and R111FR are open, then the output transistor Q102FR would be highly suspect as it is a Darlington pair. Similarly, check its pair, Q101FR as well as its driver Q103FR and its peripheral resistors.
Customer: replied 1 year ago.

I tested all of them and they are good.

Expert:  Louie replied 1 year ago.
If the output transistors tested good and are confirmed, then replacing the resistors + the KSC1845F would be the next step.
Customer: replied 1 year ago.

I replaced the parts and the unit still clicks.

Expert:  Louie replied 1 year ago.

Then it is still kicking in auto-protect mode due to another fault.

What are the voltages of pins 1 and 2 of connector CP502 of the Main Board please?

...and have you re-checkled all the output voltages of the power supply ?

Customer: replied 1 year ago.

I was able to get the voltages from the p/s, the 5,15 and -15v and they were all good. At CP502 the voltages jump around since the ps keeps going into protective mode. For some reason the display now stays on, the power LED is solid green and the clicking stopped, but when I try and take voltage readings they drop as soon as I touch my probe.

Expert:  Louie replied 1 year ago.
With the unit unplugged, what is the resistance to ground of the emitter leg of each of the output transistor?

By chance would you have an analog multimeter?
Customer: replied 1 year ago.

Yes I have an analog meter.

Expert:  Louie replied 1 year ago.
Proposed test # *****:
  • • meter set to X 1, black probe to chassis ground;
  • • check/list resistance to ground of all emitter legs;
  • • meter set to X 1K, still black probe to chassis ground;
  • • check/list resistance to ground of all emitter legs;
  • • repeat above 2 test series with red probe to chassis ground.

Please post back results / observations of the above once tried.

Customer: replied 1 year ago.

what will these tests check for. I also noticed that when testing voltages they jump around a even show a negative voltages even though the circuit i tested doesn't have negative voltages.

Customer: replied 1 year ago.

I posted a video on youtube so you can see what I am seeing with the receiver.

https://youtu.be/-Iz0Xh8pBkg

Expert:  Louie replied 1 year ago.
The above test would comparatively show the status of each channel/amp. This is to determine if any of the amp is trigerring the protect circuits.

On the video and as earlier proposed, have you re-checked the consistency of the standby voltage? CPU +5.6V and relay ~12V
Customer: replied 1 year ago.

ok I am not getting anything consistent for either, voltage drops when I measure.

Here is another video

https://youtu.be/JzKpJogSOLk

Expert:  Louie replied 1 year ago.
The display appears to be consistent.

Please check the ground connections of each board (trace and connector) to the chassis ground (even if just for the purpose of eliminating it as a suspect).
Customer: replied 1 year ago.

ok found something else. When I measured from chassis ground to the pre amp board, when I measured from chassis ground to ground, I got no resistance. I don't have any of the screws in place on the receiver, just sitting loose. When I connected chassis ground to a ground pin on the pre amp board, the power now stays on and I get all the voltages. Not sure what is missing for the ground to be gone.

Expert:  Louie replied 1 year ago.
Mike,

It would be to your advantage to consider / use alligator clips with wires; double the ground. A number of models even of other brands uses the back plate as a common ground path. If have not been tried, please click HERE.
Customer: replied 1 year ago.

Ok I got everything connected properly so I can do voltage tests now. It still keeps clicking.

Expert:  Louie replied 1 year ago.
The clicking can possibly be the result of:• weak RLY106 relay coil (least likely);• low/inconsistent standby/CPU +5.6V from IC103 and/or relay RLY106 ~12V (likely);• erratic RLY_POWER trigger on pin 14 of connector CP555 of the main Board from the CNT Board and/or failing Q116 or Q117 or D157(most likely). Please post back results / observations of the above once the voltages are checked.
Customer: replied 1 year ago.
Thanks Louie. I will check these tomorrow. Thanks
Expert:  Louie replied 1 year ago.

Appreciate the update now and again later when able.

Cheers.

Customer: replied 1 year ago.

ok I found that if I turn the power on and don't have any outputs selected, the power stays on. Once I turn on speaker a or b, or surround, the power keeps turning off and on. On connector CP557, there is a DC protect, over protect that is normally 0v. When I turn on the output, the voltage jumps up to 0.7v,then to 0v.

Expert:  Louie replied 1 year ago.
Hi again Mike, That the protect lines are triggered would indicate a fault at the speaker terminals / output transistor pairs. Bear with me and if have not been done, test the output transistors out-of-circuit or better yet since these are Darlington pairs, test for their hFE.