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Denon DRA-545RD

Lopo

May 1, 2019
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My old Denon dra-545rd amplified uses up to 3 minutes before it turns on after the power button is pressed, Can there be dehydrated capacitors? Someone who has a service manual for this?
 

Martaine2005

May 12, 2015
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Yes, the capacitors would definitely be a culprit. Have you opened the unit for a visual inspection?.

Martin
 

Ylli

Jun 19, 2018
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Describe what you mean by "3 minutes before it turns on". Do you mean it takes 3 minutes for the display to light up, or that it takes 3 minutes for the speaker protect relay to engage (enables audio output)?
 

Lopo

May 1, 2019
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Describe what you mean by "3 minutes before it turns on". Do you mean it takes 3 minutes for the display to light up, or that it takes 3 minutes for the speaker protect relay to engage (enables audio output)?

The display and loudspeaker relay turn on approximately simultaneously after approx. 3 minutes.
 

Martaine2005

May 12, 2015
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Also, is the 'three minute' wait for 'turn on' from cold?.

Or is this after using the amp for a while?. Possibly a thermal issue and the protection circuitry is resetting after a couple of minutes of cooling.

Martin
 

Lopo

May 1, 2019
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Also, is the 'three minute' wait for 'turn on' from cold?.

Or is this after using the amp for a while?. Possibly a thermal issue and the protection circuitry is resetting after a couple of minutes of cooling.

Martin
Yes it is only when it is cold, if it is hot it starts instantaneously again.
 

Ylli

Jun 19, 2018
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Going to need to get in there with a voltmeter. Being very careful to not short between any components/traces.....
From a cold start, check the voltage at the input of IC605 - should be about +18 volts.
Check voltage at the output of IC605 - should be about +6.0 volts.
Check the rail voltages, + end of C503 should be about +42 volts.
Negative end of C504 should be about -42 volts.
Emitter of TR413/+ end of C407 should be about 16 volts.
Emitter of TR417/- end of C408 should be about -16 volts.

These voltages should be there within a second of switch turn on. Report any discrepancies.
 

Lopo

May 1, 2019
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Going to need to get in there with a voltmeter. Being very careful to not short between any components/traces.....
From a cold start, check the voltage at the input of IC605 - should be about +18 volts.
Check voltage at the output of IC605 - should be about +6.0 volts.
Check the rail voltages, + end of C503 should be about +42 volts.
Negative end of C504 should be about -42 volts.
Emitter of TR413/+ end of C407 should be about 16 volts.
Emitter of TR417/- end of C408 should be about -16 volts.

These voltages should be there within a second of switch turn on. Report any discrepancies.

The voltage at the input of IC605 is +14.26 volts
Output of IC605 is 5,89 volts
+ end of C503 is 50,7 volts
Negative end of C504 is 50,4 volts
Emitter of TR413/+ end of C407 + 0,5 volts when cold, increases to +15.86 when the display comes on
Emitter of TR417/- end of C408 - 0,5 volts when cold, increases to -15.86 when the display comes on
 

Ylli

Jun 19, 2018
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OK, first let's be sure the on/off command is making it to this regulator segment.
Measure the voltage at the base of TR415 - it should be near +0.6 volts immediately when turning unit on.
Collector of TR415 should go to ground when unit is turned on.
Collector of TR416 should go to about +40 volts when unit is turned on.

The negative regulator is also turned on when the collector of TR416 goes high. Since both the regulators stay low until after the three minutes, I suspect the problem is here.
 

Lopo

May 1, 2019
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OK, first let's be sure the on/off command is making it to this regulator segment.
Measure the voltage at the base of TR415 - it should be near +0.6 volts immediately when turning unit on.
Collector of TR415 should go to ground when unit is turned on.
Collector of TR416 should go to about +40 volts when unit is turned on.

The negative regulator is also turned on when the collector of TR416 goes high. Since both the regulators stay low until after the three minutes, I suspect the problem is here.

Base of TR415 is +0.174 volts when cold and increases to +0,6 volts when the display comes on
TR415 Collector ,04 volts (Ground)
TR416 Collector +49 volts
It may look like it's been hot in that area.
 

Ylli

Jun 19, 2018
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TR415 Collector ,04 volts (Ground)
TR416 Collector +49 volts
^^I assume these are after the unit starts working.

Looks like the 'on' command is not being generated or is not making it to the base of TR415. Find the end of R420 that is *not* connected to the TR415 base and measure it's voltage before and after the unit comes on.
 

Lopo

May 1, 2019
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TR415 Collector ,04 volts (Ground)
TR416 Collector +49 volts
^^I assume these are after the unit starts working.

Looks like the 'on' command is not being generated or is not making it to the base of TR415. Find the end of R420 that is *not* connected to the TR415 base and measure it's voltage before and after the unit comes on.

Before it comes on, 0,2 volts, after it has come on 2,5 volts
 

Ylli

Jun 19, 2018
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That P.ON/OFF signal comes from the processor IC701 pin 27. It is likely an open collector output, and it does have a pull up on it. It appears to feed two loads - it turns on the +/- 16 volt regulators, and it turns on power to the receiver circuitry via TR612 & TR611. There are three possibilities that i see at the moment:
1. The processor is bad and not properly asserting the signal.
2. The 10K pull up (part of RA701) is bad
3. Bad load on the line.

Let's concentrate on #3. Lift the base (or totally remove) TR612. The tuners won't work but other functions should. See if the voltage on the input side of R420 now comes up immediately.
 

Lopo

May 1, 2019
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That P.ON/OFF signal comes from the processor IC701 pin 27. It is likely an open collector output, and it does have a pull up on it. It appears to feed two loads - it turns on the +/- 16 volt regulators, and it turns on power to the receiver circuitry via TR612 & TR611. There are three possibilities that i see at the moment:
1. The processor is bad and not properly asserting the signal.
2. The 10K pull up (part of RA701) is bad
3. Bad load on the line.

Let's concentrate on #3. Lift the base (or totally remove) TR612. The tuners won't work but other functions should. See if the voltage on the input side of R420 now comes up immediately.

No, when cold 0 volts and when it turns on 1,4 volts with TR612 removed
 

Ylli

Jun 19, 2018
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Sorry for the delay, dog demanded a walk...

With TR612 installed and the unit operating, you see 2.5 volts on the P.ON/OFF line, and with TR612 removed, you see only 1.4 volts? 2.5 volts is what I would expect. Strange, but let's continue.

Do a good physical inspection of the area around RA701. Looking for any cracked solder connections. The unit obviously is not in front of me, so if any of these suggestions are not physically possible, just let me know. with power off, try to get an ohmmeter reading between the P.ON/OFF line and the +5 volt bus. Should be <10K. (trying to confirm the 10K pull up is not open) You can put TR612 back in now if you haven't already.

I do see a couple of signals coming into the processor that may be causing the issue. I see a 'Hold' and a 'Reset'. It's also possible the internal oscillator in the processor is not running until the processor warms up (3 minutes or whatever). Reset is probably easiest to access at the collector of TR703. What happens there between turn-on/not working and working states?
 

Lopo

May 1, 2019
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Sorry for the delay, dog demanded a walk...

With TR612 installed and the unit operating, you see 2.5 volts on the P.ON/OFF line, and with TR612 removed, you see only 1.4 volts? 2.5 volts is what I would expect. Strange, but let's continue.

Do a good physical inspection of the area around RA701. Looking for any cracked solder connections. The unit obviously is not in front of me, so if any of these suggestions are not physically possible, just let me know. with power off, try to get an ohmmeter reading between the P.ON/OFF line and the +5 volt bus. Should be <10K. (trying to confirm the 10K pull up is not open) You can put TR612 back in now if you haven't already.

I do see a couple of signals coming into the processor that may be causing the issue. I see a 'Hold' and a 'Reset'. It's also possible the internal oscillator in the processor is not running until the processor warms up (3 minutes or whatever). Reset is probably easiest to access at the collector of TR703. What happens there between turn-on/not working and working states?

I've done a physical inspection and can't find anything. But now I see that the service manual does not quite match the amplifier, there is no RA701 on the PCB and the processor IC701 is called IC702 on the PCB. There are also no TR703 and TR704 but TR701 and TR702 are there. So there is obviously a difference between the service manual for Denon DRA 545-R and my DRA 545-RD. It's just to give up, put the amplifier in the trash. Thanks for the incredible helpfulness!
 

Ylli

Jun 19, 2018
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Don't give up! One other technique you can try. I really think the processor is not properly asserting the 'P.ON/OFF' signal and it may be thermally related. Grab a can of freeze spray, and after the unit has been on and working for a bit, try using the freeze spray around the processor and associated circuitry. See if you can get it to quit.

And/or.. From a cold start, turn the unit on and use a hair dryer to blow warm air into the processor area and see if the unit responds quicker than with no external heat.
 
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