Denon AVR-589 ASO / DC Protection Mode - No blown channels?

[Dirus]

I have a Denon AVR-589 that is going into protect mode that I've been trying to diagnose but so far have hit a wall.

I followed what unclejed613 had posted in this thread about testing to see which channel is blown and was unable to find one that is actually blown. None of the 10 pairs of transistors are shorted out.

There is mention of a protection trigger transistor however I've been unable to locate the correct one in the schematic. The only "DC Protect" circuit I can find is for the higher end 1709 on the 2CH Board. Which I'm assuming is the separate board for the 2CH "Zone 2" option that they had.

Any suggestions on where to go from here?

I picked this unit up used a couple weeks ago with no WAF. Now that it's busted it has an even lower WAF..

 

[Nigel Goodwin]

You don't randomly check output transistors to see if they are S/C, you need to measure the voltage on the output of each amplifier - these should both be very low (well under 1V).

 

[Dirus]

Wait? Under 1v?

That conflicts with info I've found else where while searching for info on faults in these Denon receivers. Where the output voltage should be -/+35-55v. (This was posted by unclejed613 on another forum.)

All the Transistors measure between 47.2v and 50v with the exception of the center channel which is 39.9v to 42.9v.

Q101FR 49.4v, Q103FR 50.1v, Q103FR 49.5v, Q101SR 47.8v, Q103SR 48.7v, Q102SR 47.2v, Q101C 39.9v, Q103C 42.9v, Q102C 40.7v, Q101SL 49.3v, Q103SL 49.3v, Q102SL 48.9v, Q101FL 49.5v, Q103FL 50.0v, Q102FL 49.5v.

Other info is that the voltages at CN511 are all correct as well. The -15v is -14.94, the +15v is +15v, the +24v is 23.9v, and the +5.6v is +5.73v.

I finally found the DC protect circuit/resistors (r115xx) which I'm about to test now, however I have a feeling they're all going to check out fine as well.

 

[Nigel Goodwin]

Wait? Under 1v?

That conflicts with info I've found else where while searching for info on faults in these Denon receivers. Where the output voltage should be -/+35-55v. (This was posted by unclejed613 on another forum.)

Do you have a circuit for the amplifier?.

The output should (and MUST!) be very low, as I said well under 1V - it's this not been zero that triggers the DC protection (to save the speakers from been killed).

I would suggest the +/-35V is the peak to peak signal level ouput of a fully driven amplifier shown on a scope - and NOT a DC voltage measurement.

 

[Dirus]

Ok, lets see if I can get on the same page as you here as we seem to be looking at different things and I'm somewhat confused. I'm not an absolute beginner with electronics, however this is the first time I've tried to troubleshoot an amplifier and I do want to learn how it's done.

The +/- 35V that I was checking for was said to be a DC voltage level.

actually the easiest thing to check are the DC voltages on the output transistors. check the voltages on the metal tabs of the output transistors. the transistors with part numbers beginning with A or B should have a negative voltage on them of 35 to 55. the transistors with part numbers beginning with C or D should have a positive voltage on them approximately numerically identical (except it's positive, not negative). if one or both of those voltages is missing, you have a problem with the amp supply.

When you asked if I had a circuit for the amplifier, are you asking if I have the schematic/wiring diagram? Then yes I do. I also have a diagram that shows the path of the analog signal thru the circuit. I've attached a pdf of the diagrams I'm working with.

I've been basically trying to rule out the common issues that people have posted on the web and so far have done so.

However, when you say the output voltages should be under 1v where am I supposed to be measuring this at?

 

[Nigel Goodwin]

Ok, lets see if I can get on the same page as you here as we seem to be looking at different things and I'm somewhat confused. I'm not an absolute beginner with electronics, however this is the first time I've tried to troubleshoot an amplifier and I do want to learn how it's done.

The +/- 35V that I was checking for was said to be a DC voltage level.



When you asked if I had a circuit for the amplifier, are you asking if I have the schematic/wiring diagram? Then yes I do. I also have a diagram that shows the path of the analog signal thru the circuit. I've attached a pdf of the diagrams I'm working with.

I've been basically trying to rule out the common issues that people have posted on the web and so far have done so.

However, when you say the output voltages should be under 1v where am I supposed to be measuring this at?

The emitters of the output transistors, or preferably the junction of the emitter resistors (test point TP101/3 on the top amp). This point is the actual output of each amplifier, and it's this point that is monitored for the DC protection.

All you're checking measuring the collectors is the HT rails.

 

[Dirus]

I think I've been getting stuck in the "test known issues only" area and i need to kick myself out of that habit. I will admit I skipped over checking the values at the Test Points due to the Service manual mentioning they needed to be adjust at the 2min & 10min mark, and I can't get it to stay powered for more then 5 seconds.

However I checked them and they test as follows. TP101 = 2.6mv, TP102 = 2.8mv, TP103 = 2.4mv, TP104 = 2.6mv, TP105 = 3.1mv. All well under 1v.

I do not know at which voltage the DC protect kicks in for these circuits however I do know in the service manual they're supposed to be set to 2mv after 12mins. So I'm going to try turning them all the way down and see if that does anything. If not then worse case scenario that I can think of as a result is that I have to do the adjustment procedure when I get it working again.

Edit: They're all reading around 0.9mv now, still going into Protect. Alright, time to start somewhere else.

 

[Nigel Goodwin]

Are you measuring the voltage from chassis? - don't measure across the test points like the manual says to, that's just for monitoring the current through the output stages (not what we're wanting to do).

 

[leal]

denon

If you don't have any bad outputs or unbalance circuit output, then go to protection circuit itself. I had problem very close to what you have and found this is the cause. Also the dolby circuit could cause the circuit to trip in protect mode. follow the protect circuit all the way up.

 

[Dirus]

That was across the test points. I just measured across the chassis, and all but the Center Channel TP103 do eventually stabilize(somewhat) below 1v.

The center channel seems to be the culprit. I did a few tests on it. The resting voltage is -46mv with the power switch off, turn it on standby and it rests at -44mv. When you turn the unit on it climbs to 4.02v by the time the protection kicks in and shuts it down, at which point it receives a 32v spike and any attempts to cycle it again right after shows that it still draining the residual of that 32v spike till shut down. It usually gets down to about 9v the next time protect kicks in. Which of course gives it another 32v spike.. rinse.. repeat..

 

[Dirus]

Fiddling around with it some more, it seems like R117C is open as it's values don't reach as high as the other R117x's. Checking the voltages on either side of R117C compared to the other 4 channel's R117x and it's out of whack. Which I'm assuming means that the incorrect ohm reading I was getting from it is via other components in the circuit. I'm still checking other areas to see if I can find some more issues before I start de-soldering parts to properly test them.

Side note tho, this Denon service manual seems to be somewhat out of whack. They list R117 & R118 as the same part # yet they're not even the same type of resistor :/

Took out R117C and checked it out of circuit. It's working correctly.. Back to the drawings, to figure out where it's mesed up.

 

[Nigel Goodwin]

R117 is nothing to do with it - it's just part of the protection circuitry.

The fault is in the amplifier, the centre one from what you've said.

Check the exact voltages on all pins of the two output transistors and post them here - measured from chassis of course.

If R117C is removed it probably won't display 'protect' then, but don't connect a speaker to the centre channel.

 

[Dirus]

B-2390: B = climbs to 5.8v slowly, C = 53v, E = Climbs to 4.4v slowly
B-1560: B = climbs to 4.1v slowly, C = -53v, E = Climbs to 4.8v slowly

 

[KeepItSimpleStupid]

OK, my turn. The offsets that everyone is speaking of is the voltage at the speaker before the protection relay. Bridged amps (-) speaker not connected to ground would be a little more difficult.

 

[Dirus]

The voltage at the protection resistor (R117x) on the rail side is 0.66v, which matches the other channels. On the Amp side it's trying to reach 5.6ish volts. This is the same goal that both the Base and Emitters on the B-2390 & B-1560 are trying to accomplish. This same behavior is also measurable at jumper's 297, 298, 299. The voltage is also the same at the speaker output which is to be expected considering jumper 298 is what feeds it plus the obvious issues with the channel it's self.

Currently I've moved out of the Amp section and I'm looking at the pre-amp section to see if it stems from there or not since jumpers 297 & 299 are the feeds from there. It's a little more tricky tho since I'm working underneath the rest of the components and through a narrow opening.

 

[Nigel Goodwin]

The voltage at the protection resistor (R117x) on the rail side is 0.66v, which matches the other channels. On the Amp side it's trying to reach 5.6ish volts. This is the same goal that both the Base and Emitters on the B-2390 & B-1560 are trying to accomplish. This same behavior is also measurable at jumper's 297, 298, 299. The voltage is also the same at the speaker output which is to be expected considering jumper 298 is what feeds it plus the obvious issues with the channel it's self.

As I've said all along, the DC protection is triggered by a DC voltage at the output of one of the amplifiers, you've now identified which one.

Currently I've moved out of the Amp section and I'm looking at the pre-amp section to see if it stems from there or not since jumpers 297 & 299 are the feeds from there. It's a little more tricky tho since I'm working underneath the rest of the components and through a narrow opening.

It can't be in the preamp, as the preamp isn't DC coupled to the power amp.

The power amp consists of Q101, 102, 103, 106, 107 and 108.

 

[Dirus]

The Transistors Q101, 102, 103, 104, 106, 107, 108 Are all testing as ok.

So are R101, 103-115, 118, & 119 122-127, 128(diagram says 470ohm, but a 220ohm is installed this is the same in all channels), 129-132, 135.

And D101, 102, 105 & ZD101, 102.

 

[Nigel Goodwin]

Randomly checking components with a meter isn't the way to fault find, and it's only a very crude and poor test anyway.

You need to fault find using the meter on volts, and find out why the voltages are wrong.

 

[Dirus]

That is what I was attempting to do. Basically I spent a lot of my time comparing one section of the channel to two of the other working channels to narrow down problem areas and go from there. However due to the design of the Receiver I can't access the lower half of the circuit to test it with it powered up as it's underneath 4 other circuit boards. Hence why I switched and tested all the components individually.

i.e. Q134 isn't shown on the schematic diagram as being in the "Analog Audio SIGNAL LINE" in the schematics diagrams (1/20). However I tested it out anyway since it is center channel specific and on initial tests it looked like 5.6v was being leaked into the circuit since that was where it seemed to be trying to climb to, and following the MC_+5.6v trace leads right to it. From there it feeds into JP132 to JP232 to R121C (Center Channel). I've since ruled that out however as switching it with Q135 didn't move it from the Center Channel to the Surround Right & Left channels.

My line of thinking at that time was that if the transistor or diode worked properly individually then they couldn't be the issue it's self without something "bad" feeding the the wrong voltage. After all would ruling out the fact that all the components in the channel are working properly not mean that the issue is a channel specific circuit outside of the main amp circuit that is feeding in the wrong voltage?

I did pull R117 so that protection wouldn't kick in to see where things end up after the circuit settles down and the output on the center channel finally rests at 3.69v. It doesn't cycle thru various voltage levels every 250-500ms then drop to 1mv like the other 4 channels. It just steadily climbs in voltage.

 

[Nigel Goodwin]

Do you understand how the amplifier works?, and what each section of the power amplifier does?.