Denon AVR-1603 power rail question (B+, B-)

[guizmo1967]

Hello,

This is my first post on this forum !

I'm trying to repair this Denon receiver and made a mistake while doing so. I accidently while probing the collector of Q101FL, to measure B+, touch the heatsink and made a spark.

This is the original problem before my mistake:
Stuck on standby mode, did the reset thing with A + B buttons, display flashing, release buttons A + B, display show SPEAKER OFF with all lights on but every buttons, knobs are frozen, they don't
do nothing at all !!!!

After my mistake, I remove the board, check for shorted components but did not find one. I unsoldered E B C of Q101FL, put everything back together, turn on the receiver (reset procedure) and started measuring some voltages.
This is what I find:

B+ is now at +56V and B- at -41V, before my mistake everything was fine at +48V and -48V ?
Ground of IC103 (7805) is 8.25V ?

Where should I start looking ??

Thank you for your help !!

[David_AVD]

Sounds like you now have a burnt (open circuit) trace to do with the power supply area? You'll need to remove the board set and inspect the bottom on the PSU / amp board.

[guizmo1967]

Thank you David_AVD, I did inspect top and bottom of PSU, pre-amp and power board but did not find anything burnt, no trace or component !! I just unsoldered the transistor that I shorted to ground accidently, to make sure it was not the problem.

How can a power rail not be equal, what can cause it ??

[Thunderer]

Can you post here a screenshot of the schematic around power supply and one of the PCB? Of course, you'll need the service manual. Probably available on Hifiengine.

In the meantime, isolate completelly the power supply from the rest of the receiver, to avoid other defects.

[guizmo1967]

Look at the end of my first post, You can download the schematic ....

The main power is not applied, when you plug the receiver AC only goes through the sub transformer to get the standby voltage (IC103, 5V). To have main power, relay106 must be engage and in my case
it is not. This relay only engage if I do the reset thing with speaker button A + B !

Like I said in my first post, I measure +8.25V at the ground pin of voltage regulator IC103, that's not normal .....

[Martin72]

Hi,

IC 103:

Check input and outputvoltage against ground(anode D153).
Check diode D160.

B+,B- :

Should be only avaible when relay is switching:

B+ is now at +56V and B- at -41V, before my mistake everything was fine at +48V and -48V

When did you measure it?
Unbalanced voltage could have several reasons:
One faulty Cap (unlikely)
One sided load
Faulty rectifier bridge ( watch with scope)
Or the main circuit already had no voltage and the electrolytic capacitors are discharged differently.

[guizmo1967]

B+,B- :

Should be only avaible when relay is switching:

B+ is now at +56V and B- at -41V, before my mistake everything was fine at +48V and -48V

When did you measure it?

When I simply plug in the receiver, I'm stuck on standby mode. This is what I do to have the power relay (RLY106) on:
     - Unplug the receiver
     - Push speaker buttons A and B simultaneously
     - Plug in the receiver, the display flashes
     - Release speaker buttons A and B
 Then RLY106 is energize and I have voltage everywhere !!!

Hi,

IC 103:

Check input and output voltage against ground(anode D153).
Check diode D160.

I'm gonna do that tomorrow ......

And one more question, what is IC105(ICP-N15) just before the input of IC103 I don't know that symbol, is this a fuse

[Thunderer]

B+ is now at +56V and B- at -41V, before my mistake everything was fine at +48V and -48V ?
Ground of IC103 (7805) is 8.25V ?

Where should I start looking ??

Thank you for your help !!

First, the ground pin (central one) of IC103 should not have but around 0.7V potential to the ground, and this because of the D160/1N4148 diode.

Its output should not be 5V, but around 5.7V, because of the same D160.

I'start by disconnecting all loads and measure all voltages, from all power and control rails. Before returning all voltages to the normal values (as per the 100 pages service manual) I would not power anything in that enclosure. Higher control voltages would fry the processor, if not already dead.

Read all service manual, then measure the voltages. Do not re-power anything before all is good.

[Audiorepair]

[/quote]

And one more question, what is IC105(ICP-N15) just before the input of IC103 I don't know that symbol, is this a fuse
[/quote]


Yes it is a fuse.  Also known as "IC protector"

[Thunderer]

Unfortunately, the OP will only damage more the unit. I asked him to look into the complete service manual. Such questions as the 0.6A IC protector are indicated in the manual.

A lot of electronics enthusiasts try to fix (or even worse, attempt to improve) apparatus they have no qualification whatsoever to do it. The case of a healthy unit becoming defective is so typical for this forums.

There is no issue with the IC105, as the ICP-N15 is a kind of reversible fuse, so it can be triggered multiple times. Plus, it is normal to kind of warmish (if question comes), as the IC protector has an internal resistance, so it will dissipate some heat depending on the current passing through.

[Audiorepair]

There is no issue with the IC105, as the ICP-N15 is a kind of reversible fuse, so it can be triggered multiple times. Plus, it is normal to kind of warmish (if question comes), as the IC protector has an internal resistance, so it will dissipate some heat depending on the current passing through.

I don't think these fuses are resettable. 
Pioneer use loads of them in their mixers etc, and I have replaced many that went Open Circuit.
Akai samplers also used them on the SCSI socket, these would commonly blow if the SCSI drive was hot swapped.

[Thunderer]

The datasheet says:

[Audiorepair]

The datasheet says:

Where in the datasheet is any data on how many times this fuse can be reset?

"Cutoff is sharp and repeatable" is too ambiguous.

Seeing lots of blown ones is IMHO more reliable data.

[Thunderer]

I give it to you that the datasheet is not saying much. Looks like they are obsolete products, so the info is scarce and limited to what we'd found already.

[guizmo1967]

Hello again,

*** If my english written is not so good, it's because my first language is French ***

I attached a pdf file with all my reading so you can have a look !! On my scope, the signal that goes to the cathode of D154 is not perfect so I think I'm gonna change C157 because the one that goes
to the IN of IC103 is almost perfect !!

I have one question, resistor R160 and R159 act as a voltage divider for the base of Q151, so if +7V goes through r160 and 0V through R159, according to my calculation, the base should be at +4.66V ?? I measure 0V at the base of Q151 ? Do you think the base to emitter or the collector to emitter are shorted, that's why I have -0.6V to PWR_DOWN pin ?

 

[Martin72]

Which reference did you use for your measures ?
If it´s the point I´ve marked (and should used) it´s hard to believe you´ve measured -0.6V on the diode to IC103..

[Thunderer]

Hello again,

*** If my english written is not so good, it's because my first language is French ***

I attached a pdf file with all my reading so you can have a look !! On my scope, the signal that goes to the cathode of D154 is not perfect so I think I'm gonna change C157 because the one that goes
to the IN of IC103 is almost perfect !!

I have one question, resistor R160 and R159 act as a voltage divider for the base of Q151, so if +7V goes through r160 and 0V through R159, according to my calculation, the base should be at +4.66V ?? I measure 0V at the base of Q151 ?

You did not measure correctly. Use the real ground, not what you believe is the ground. Plus, I already told you about the real ground of 7805.

1. The 0V is not at the middle pin of the LM7805. But at the K of the D160. So the 0.6V is at the middle pin of 7805. Which makes 5,6V at the output of 7805.
2. D154 is a 8.2V zener, so if at its K you have 14V, at its A you should have (14-8.2)V. Well, the 8.2 varies between 7.8 to 8.2. So no way you have 7V there. Again, wrong ground used.
3. The Vb of Q151 cannot be 0V, it should be 0,6-0,7V, but given the wrong measurement reference...



I am from MTL, So french is my language too. We can communicate via phone if you want help.

[Martin72]

LOL, two minds same thoughts..

[guizmo1967]

Ok my bad, I use a ground screw on the main board ! I'm gonna redo my readings with anode of D153.

But even then, it's not gonna change why I have 0V at the out of R158

[Thunderer]

But even then, it's not gonna change why I have 0V at the out of R158

You know why you have less than 1V at the left side of the R158? Because the Q151 is conducting, so you see Vce there.

[guizmo1967]

Ok, the voltage divider from R160 and R159 send +4.66V to the base of Q151 so it's on, like you said, that's why I have 0V left side of R158.
My question is, what voltage should PWR_DOWN received for the AVR to turn on ? OV or 5V ?

According to the schematic, Q151 will always be on ?

[Thunderer]

Can you please check IC105? Is it 0V (or close to 0V) across the IC105? Should be, because there is 5,6V at the output of IC103.

The PWR_DOWN is not explicitly defined in the service manual, but as it is represented with a line atop the text, it means it is active when 0V. 

A visual explanation:


PS: a cap forgotten...

[guizmo1967]

Just to let you know, I change my ground reference and all voltage have gone up by 0.6V !

Yes it's 0V across IC105

So everything is fine, the receiver should power on but it does not ......

[Martin72]

The relais will switch on, when....

...Q116 is conducting...
...Q117 is NOT conducting...
...RLY_POWER signal is high.(CP555, pin13)
Check the state of the PROTECT signal (CP555, pin7)

[Thunderer]

The Q117 drives the Q116 which gives power to main transformer. But, previously, it was said that the power rails were ON, not with the good voltages though.

When exactly the PWR_DOWN comes high? When IC105 goes OFF, you lose the power rails, because the relay RLY106 turns OFF.

What are the voltages on these connectors?