Hi. New to this great website and new to audio electronics.
I have a Denon DRA 685 receiver that won't get out of protection mode. After I push the power switch, the protection light blinks 8 times and then stays on. I also hear a click which I believer is the power relay. Thats it - no display, no sound,nothing.
Following the recommendation of another website Denon DRA-685, I replaced 2 resistors on the main board (R105 & R106), but that didn't solve the problem.
I am not getting the required "+15V" and "-15V" at test point CN1. I am getting .137V and .567V respectively. This is the same reading I am getting at the power regulator transistors IC1 and IC2.
I am getting the required 6 volts at IC 4.
To make matters worse, the service manual schematics that I downloaded from HiFi Engine are very blurry, thus I can't read the required voltages at different test points.
I am stumped.
Any help would be much appreciated.
Thanks
I have a Denon DRA 685 receiver that won't get out of protection mode. After I push the power switch, the protection light blinks 8 times and then stays on. I also hear a click which I believer is the power relay. Thats it - no display, no sound,nothing.
Following the recommendation of another website Denon DRA-685, I replaced 2 resistors on the main board (R105 & R106), but that didn't solve the problem.
I am not getting the required "+15V" and "-15V" at test point CN1. I am getting .137V and .567V respectively. This is the same reading I am getting at the power regulator transistors IC1 and IC2.
I am getting the required 6 volts at IC 4.
To make matters worse, the service manual schematics that I downloaded from HiFi Engine are very blurry, thus I can't read the required voltages at different test points.
I am stumped.
Any help would be much appreciated.
Thanks
In the related circuitry, check:
both AC windings from transformer at CN3.
resistors in series with each winding.
the four 1N4004 diodes.
resistors in series with each regulator input.
the DCV at each regulator input.
You may need to do this after the repair.
How to Reset the Protection in a Denon DRA 685 | It Still Works
both AC windings from transformer at CN3.
resistors in series with each winding.
the four 1N4004 diodes.
resistors in series with each regulator input.
the DCV at each regulator input.
You may need to do this after the repair.
How to Reset the Protection in a Denon DRA 685 | It Still Works
Something like 18VAC on each winding, or 36VAC across the two in series.
Just the DC voltage at each regulator input pin (around 25VDC) will tell the story.
If those are instead very low, then the fault is between the windings and the regulators.
If the input voltages are normal, there could be excessive loading on the regulator(s),
causing them to fold-back current limit.
Just the DC voltage at each regulator input pin (around 25VDC) will tell the story.
If those are instead very low, then the fault is between the windings and the regulators.
If the input voltages are normal, there could be excessive loading on the regulator(s),
causing them to fold-back current limit.
Thanks again.
The readings at the regulators input pin is very low - less than a volt, so the fault is between the winding and the regulators. Without a good service manual, I don't really know how to proceed?
I downloaded my blurry copy from HiFi Engine. Could you recommend another source for a clearer Service Manual for the DRA 685?
The readings at the regulators input pin is very low - less than a volt, so the fault is between the winding and the regulators. Without a good service manual, I don't really know how to proceed?
I downloaded my blurry copy from HiFi Engine. Could you recommend another source for a clearer Service Manual for the DRA 685?
Carefully measure the AC voltages at each winding. There is a connector from the transformer.
Those will very likely be ok, each roughly 18VAC. Don't short the probes together accidentally.
If both AC windings are ok, with power off and AC unplugged, test each part. Start with the resistors.
I think the problem will be open resistors. Then diode test the bridge rectifier if resistors are ok.
No other schematic seems available.
Those will very likely be ok, each roughly 18VAC. Don't short the probes together accidentally.
If both AC windings are ok, with power off and AC unplugged, test each part. Start with the resistors.
I think the problem will be open resistors. Then diode test the bridge rectifier if resistors are ok.
No other schematic seems available.
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Believe it's CN3, but trace back from the four diodes to find the connector.
It's hard to read the part numbers.
However, first turn off the power and ohm R105 and R106, 1 ohm each.
If those are good, then ohm R71 and R73, 4.7 ohms each.
These resistors are most likely the problem, and several may be open circuit.
It's hard to read the part numbers.
However, first turn off the power and ohm R105 and R106, 1 ohm each.
If those are good, then ohm R71 and R73, 4.7 ohms each.
These resistors are most likely the problem, and several may be open circuit.
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The transformer powering the +/- 15VDC supplies is off the board.
That small transformer is for the standby/protection circuit instead.
You may be looking at the wrong four diodes. The right ones are D7,8,9, and 10.
I would test the four resistors for resistance first, with no AC power applied.
That small transformer is for the standby/protection circuit instead.
You may be looking at the wrong four diodes. The right ones are D7,8,9, and 10.
I would test the four resistors for resistance first, with no AC power applied.
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