Denon AVR-X1000 MCU Shorted

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

The pots are all set to minimum, or all the way counter-clockwise. However turning the pots in either direction has no effect on the readings at CN5x05.

I redid those readings with another meter and they are pretty well spot on with the addendum that SL and SR peak higher at about 1.1v where the rest peak below that, around 0.6-0.8v, but all still fluctuating up to about 200mV each.

[R_J]

Re: Denon AVR-X1000 MCU Shorted

L5101-5501 all hover around 0.8v but go as low as 0.5 and as high as 1.1v on all channels.

The measurements were the same at the emitter resistors so I turned all pots down to minimum but the readings didn't change.

Also when the relays cut out and the unit goes to protection the readings at the emitter resistors jumps to positive rail voltage and begins to dissipate quickly but maybe that's normal ?

If the voltages are changing " too rapidly" How did you adjust the pots to minimum voltage?

I see the board has a lot of jumper wires for the B+ and B- , It could be that one of them (B-) has an intermittent connection.

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

See post #14 for those readings.

[R_J]

Re: Denon AVR-X1000 MCU Shorted

Yes you can use your scope, But the dc offset voltage should not be changing that much, unless you have an auto ranging meter and it starts a low mv range. If this is the case, lock the meter to a higher voltage range.

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

My meter doesn't have a Max function and the values are changing too rapidly to nail it down. Can I hook up my scope to chassis ground and probe pin2 without blowing it up ?

[R_J]

Re: Denon AVR-X1000 MCU Shorted

The B+ and B- for the amp are not that critical voltage wise, they can be slightly different and that will not effect the dc offset, The Dc protection is activated because it sees a high DC voltage (likely over 1~2 volts) on the output of one of the amp sections. You need to monitor the voltage on pin2 of CN5x0 on each channel one at a time from when the amp is turned on. One of them must be going higher than (+-) 1 volt and activating the DC protection circuit

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

I wonder why the speaker relays click on but there is still nothing from the speakers or headphones before the protection turns everything off ? Could the HDMI board be causing this issue somehow ?

Not very technical but I'm tempted to disable the protection circuitry in the hopes that something smokes.

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

Ya colour me confused. It seems to be affecting all channels. What was the problem in the Crown amp ?

[budwich]

Re: Denon AVR-X1000 MCU Shorted

not sure whether you can... but in the DC detect / protect /activate circuit at the bottom of the main board diagram, there is a jumper (j5675)... which appears to bond the surrounds detection to the front detection. I am wondering if removing that jumper will allow you to determine if indeed both are having an issue or only one.... although you seem to indicate that you see DC on all outputs which then means it is further back in the circuitry.

sorry just throwing out ideas... I know from my crown endeavor, I was looking at the negative side of the amp because of high negative values but it turned out that the positive side had the issue is that design.

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

That part is referring to the bridge rectifier making the B+ and B- rails. Could be leaking somewhat will give it a diode check.

[budwich]

Re: Denon AVR-X1000 MCU Shorted

have you checked the diodes in the connection jumper "pack" d5701 at the power input area. Perhaps the +B is shorted, resulted in a higher incoming +B causing a "differential".

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

Are you sure you are not loosing the -B+ to the channels?

I don't know what you mean by that ?

Yes I have the 12v line and PRE B- getting to the preamp. And yes I agree it's common to all channels.

As stated earlier my B+ and B- rails are off by roughly the amount of the emitter voltage. Is that normal and/or ok ?

B+ = 57.5v
B- = -56.6v

[R_J]

Re: Denon AVR-X1000 MCU Shorted

If ALL channel offset voltages (emitter resistor voltage) jump to positive, it must be something common to ALL channels. Are you sure you are not loosing the -B+ to the channels?
Do you have +12 volts and Pre-B getting to the preamp section?

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

L5101-5501 all hover around 0.8v but go as low as 0.5 and as high as 1.1v on all channels.

The measurements were the same at the emitter resistors so I turned all pots down to minimum but the readings didn't change.

Also when the relays cut out and the unit goes to protection the readings at the emitter resistors jumps to positive rail voltage and begins to dissipate quickly but maybe that's normal ?

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

I have here a similar, possibly the same main board from an AVR-E300. There are no #18 wires as stated in the schematic there are only traces bottom side of board which lead to the collectors of the output transistors for the negative rail. There are three jumpers used to get there all the same size from what I can tell. If one had no continuity I would not be reading anything at all the collectors.

I feel compelled to redo some of my voltage readings but cannot do so until later today.

Thanks for helping out, btw.

EDIT: I have tried using this main board in place of the one at issue but this board shuts off before the relays kick in IIRC.

[budwich]

Re: Denon AVR-X1000 MCU Shorted

OK... I see the "soft start" function for the pre-amp that RJ is alluding to... :-)
maybe doing some simple resistance tests at each amp (strategic / accessible points) and compare the results to see if anything jumps out.

missed your post... sorry but I agree with your statement.

are you able to get at / check the wiring options around the -B area... there are some jumpers near that area along with something like the "#18" which seems like potentially some form of "fuse link" maybe.

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

I can't get to that connector during operation but you'll notice the schematic says both the Main B+/- run direct to the collectors of the output transistors with nothing in between (except for jumpers, maybe) so the readings should be identical.

[budwich]

Re: Denon AVR-X1000 MCU Shorted

can you also check the input powers at cn503... just for comparison sake at the "source". I still think your "negative observation" is a good clue.

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

I measured B+ and B- at the collector of each output transistor.

I think RJ means Q5702 only conducts after C5708 is charged up (?) so that PRE B- line starts up AFTER the main B+/- rails are fully powered.

Still trying to find out why the rails are not exact inverse of each other...

RJ,

Yes the speaker relays click on. The amp stays on for up to a minute at most (usually much shorter) before clicking off with the infamous fast flashing power light. Going into diagnostic mode afterwards shows DC Protection was triggered.

There is no sound from the Tuner at all during that time.

I will measure at the inductors soon.

[budwich]

Re: Denon AVR-X1000 MCU Shorted

One question, where did you measure the +B / -B values that you reported? I am not sure I understand RJ's comment about the q5702... if I read the schematic right, it is dealing with the -B side of things and not +B... but then again, I did say I have only limited experience on this.

As for the differences in voltage, I would expect them to be close / very close. I don't believe its an "adjustment" (although could be) but more of something not right / happening.... almost like a diode / transistor difference somewhere... hence the previous question.