Denon AVR-1603 power rail question (B+, B-) - Page 1
Forum section: electronics / repair

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 26, 2022, 02:26:00 am
content: 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'tdo 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 !!

author: David_AVD
author_rank: Super Contributor
timestamp: December 26, 2022, 08:01:38 am
content: 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.

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 26, 2022, 04:59:12 pm
content: 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 ??

author: Thunderer
author_rank: Regular Contributor
timestamp: December 26, 2022, 05:12:18 pm
content: 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.

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 26, 2022, 09:24:42 pm
content: 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 caseit 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 .....

author: Martin72
author_rank: Super Contributor
timestamp: December 26, 2022, 10:37:03 pm
content: Hi,IC 103:Check input and outputvoltage against ground(anode D153).Check diode D160.B+,B- :Should be only avaible when relay is switching:QuoteWhen did you measure it?Unbalanced voltage could have several reasons:One faulty Cap (unlikely)One sided loadFaulty rectifier bridge ( watch with scope)Or the main circuit already had no voltage and the electrolytic capacitors are discharged differently.

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 27, 2022, 01:00:23 am
content: Quote from: Martin72 on December 26, 2022, 10:37:03 pmWhen 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 BThen RLY106 is energize and I have voltage everywhere !!!Quote from: Martin72 on December 26, 2022, 10:37:03 pmI'm gonna do that tomorrow ......And one more question, what is IC105(ICP-N15) just before the input of IC103I don't know that symbol, is this a fuse

author: Thunderer
author_rank: Regular Contributor
timestamp: December 27, 2022, 01:35:51 am
content: Quote from: guizmo1967 on December 26, 2022, 02:26:00 amFirst, 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.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: December 27, 2022, 08:01:10 am
content: And one more question, what is IC105(ICP-N15) just before the input of IC103I don't know that symbol, is this a fuseYes it is a fuse. Also known as "IC protector"

author: Thunderer
author_rank: Regular Contributor
timestamp: December 27, 2022, 06:01:02 pm
content: 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.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: December 27, 2022, 06:34:27 pm
content: Quote from: Thunderer on December 27, 2022, 06:01:02 pmI 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.

author: Thunderer
author_rank: Regular Contributor
timestamp: December 27, 2022, 06:52:47 pm
content: The datasheet says:

author: Audiorepair
author_rank: Frequent Contributor
timestamp: December 27, 2022, 07:06:07 pm
content: Quote from: Thunderer on December 27, 2022, 06:52:47 pmWhere 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.

author: Thunderer
author_rank: Regular Contributor
timestamp: December 27, 2022, 07:18:48 pm
content: 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.

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 27, 2022, 08:46:44 pm
content: 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 goesto 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?

author: Martin72
author_rank: Super Contributor
timestamp: December 27, 2022, 09:18:30 pm
content: 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..

author: Thunderer
author_rank: Regular Contributor
timestamp: December 27, 2022, 09:19:34 pm
content: Quote from: guizmo1967 on December 27, 2022, 08:46:44 pmYou 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.

author: Martin72
author_rank: Super Contributor
timestamp: December 27, 2022, 09:20:54 pm
content: LOL, two minds same thoughts..

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 27, 2022, 09:27:21 pm
content: 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

author: Thunderer
author_rank: Regular Contributor
timestamp: December 27, 2022, 09:31:47 pm
content: Quote from: guizmo1967 on December 27, 2022, 09:27:21 pmYou know why you have less than 1V at the left side of the R158? Because the Q151 is conducting, so you see Vce there.

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 27, 2022, 09:41:10 pm
content: 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?

author: Thunderer
author_rank: Regular Contributor
timestamp: December 27, 2022, 09:56:28 pm
content: 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...

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 27, 2022, 10:24:58 pm
content: Just to let you know, I change my ground reference and all voltage have gone up by 0.6V !Yes it's 0V across IC105So everything is fine, the receiver should power on but it does not ......

author: Martin72
author_rank: Super Contributor
timestamp: December 27, 2022, 10:42:26 pm
content: 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)

author: Thunderer
author_rank: Regular Contributor
timestamp: December 27, 2022, 10:47:53 pm
content: 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?

author: David_AVD
author_rank: Super Contributor
timestamp: December 27, 2022, 10:56:45 pm
content: The ICP-N15 type devices that look like 2-pin TO-92 transistors are one-shot.They are not Polyswitch / PTC / resettable devices and usually have a lower resistance than a PTC of the same rating.I've seen them in plenty of gear dating back to well before polyswitches were common.

author: Martin72
author_rank: Super Contributor
timestamp: December 27, 2022, 11:02:35 pm
content: Together with D157, Q117 is a kind of overvoltage protection, the rest is in the hands of the controller.QuoteHe did a RESET on the receiver and the relay switched to on, if I remember it correctly.I strongly guess it will switch off again when the controller detects a (still persisting)failure.Therefore he should check the protection signal also, imho.

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 28, 2022, 12:10:28 am
content: Quote from: Martin72 on December 27, 2022, 10:42:26 pmThat's all true ! PROTECT pin is +4.8VQuote from: Thunderer on December 27, 2022, 10:47:53 pmThe power rails were on because I forced it to be on with the reset procedure I described !The only voltage I get on these connectors is CPU_5.6V (+5.6V) because the main relay (RLY106) is not on .... but if you want I can force it and tell you the rest of the voltages !When I do a RESET, all voltages stays on forever, the CPU don't shut down nothing??

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 28, 2022, 12:19:54 am
content: One more thought, maybe the main CPU is dead but I check what turns on the standby led and it's a 16 pins IC (BU2090F) that DATA and CLK are driven by the main CPU, so it is not dead

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 28, 2022, 12:57:38 am
content: Ok for all following this problem, I did RESET the receiver to turn on RLY106 and those are the voltages I got:CP5551- +16.482- -8.263- -8.264- -33.85- 06- 07- +0.568- -7.319- 010- 011- 012- 013- +4.66CP5561- +5.542- 03- -8.264- -8.265- -23.56- +6.647- 08- 09- +4.9410- +4.9511- +49VThere is an error on the schematic for CP555 pin 1, on the board it is +24VAll reference to anode of D153 !!!!!!! THERE IS something wrong with GROUND !!!!! If you add +8.26 to all the voltages that are not right, then they will be OK

author: Audiorepair
author_rank: Frequent Contributor
timestamp: December 28, 2022, 09:51:00 am
content: Quote from: guizmo1967 on December 28, 2022, 12:57:38 amYes, likely you have a fried ground trace(s) when you shorted the transistor to heatsink.This ground is the one that goes to the 15 volt regulators' ground, which should be chassis ground, which is not the same ground as your Star ground reference.Also the schematics show pins 1 & 3 of CP555 as connected together, where your readings show otherwise.Perhaps this trace is fried (also).

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 28, 2022, 03:32:47 pm
content: how can I found a fried ground when there is no burn trace anywhere ?? What's your technique ??

author: Thunderer
author_rank: Regular Contributor
timestamp: December 28, 2022, 03:51:21 pm
content: Those voltages are so off.It is the time for resoldering. You may have a or some cold solder joints. Look for soldering joints that seem interrupted (I want to say "fissurés") and reheat them. Be generous with the solder. Check with a ohmeter if you have ground, rails continuity.Start with power connections.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: December 28, 2022, 04:16:57 pm
content: Quote from: guizmo1967 on December 28, 2022, 03:32:47 pmPins 1&3 of CP555 and pins 3 & 4 of CP556 should all be connected to chassis ground.The 15v regulator grounds should also be connected to chassis ground, there is a ground trace from the regulators up to CP555 and CP556 which needs to be intact.Check this with a multimeter in ohms mode with the unit turned off.

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 29, 2022, 01:19:48 am
content: QuoteThey all have good continuity to chassis ground !Quote from: Thunderer on December 28, 2022, 03:51:21 pmThey are not, If I use the right ground reference for each voltage I need to measure, they are spot on, even B+ and B- that were so off before.I use these as ground reference, anode of D153, chassis ground (any screws on the board) and pin 2 of CP104.Let's say I want to measure:B+, B-, I use anode D153 as ground.+24V of CP555, I use chassis ground.DSP_+5V of CP556, I use pin2 of CP104 as ground.I have continuity between anode D153 and pin 2 of CP104 but not with chassis ground ?? Is that a problem? Should all grounds be connected together?

author: Audiorepair
author_rank: Frequent Contributor
timestamp: December 29, 2022, 12:02:35 pm
content: Yes I believe they should be connected together, or via a low ohm resistor.Now, what I think may have happened is that you shorted the main Power amps supply to chassis, but the main power amps power supply has the Star ground for its return.So the current must have run through the chassis and then returned to the star ground somehow.That somehow could well be the connection between the Star ground and CP501 pins 3 & 4. The other ends of these gnd pins I think are connected to chassis via the input sockets etc.So possibly the trace between Star ground and CP501 is the one that fried.Or a trace on a board connected between CP501 and the chassis.

author: Thunderer
author_rank: Regular Contributor
timestamp: December 29, 2022, 07:32:17 pm
content: Quote from: guizmo1967 on December 29, 2022, 01:19:48 amHello, you should not have continuity between the anode of D153 and pin 2 or 5 of CP104. Between them is the C159 (1u/50V). Is there a bridge you created with your spark somewhere between the 2 grounds?And you are right about references for measurements you took.

author: David_AVD
author_rank: Super Contributor
timestamp: December 29, 2022, 11:28:07 pm
content: Are you taking these measurements with all boards installed and screwed in?Many hi-fi amplifiers use the chassis as part of the ground system, so if you try an run them without everything screwed down there will be issues.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: December 29, 2022, 11:47:47 pm
content: Quote from: David_AVD on December 29, 2022, 11:28:07 pmAgreed.In this case it seems the Star ground and chassis ground are only connected together if the external boards are plugged in.If they are actually all plugged in as I had assumed, then my previous suggestion would make sense that the shorting issue has indeed burnt this essential ground link open circuit.

author: guizmo1967
author_rank: Regular Contributor
timestamp: December 30, 2022, 02:01:52 am
content: Quote from: David_AVD on December 29, 2022, 11:28:07 pmYesQuote from: Thunderer on December 29, 2022, 07:32:17 pmSo If I follow your drawing, I should have continuity between Pin 2 and 5 of CP104 but I don't ! There is also C138 with C159. I wish there was some discoloration somewhere on the board or a burn component but there is nothing so that's why it's difficult for me to find the problem ......When you say a bridge, you mean through C138 or C159?

author: Thunderer
author_rank: Regular Contributor
timestamp: December 30, 2022, 03:52:25 pm
content: I meant that as long as you have the C138 (good catch!) and C159, there should not be any direct link between the star ground (at the 0V point of the power rails +/-48V).Between 2 and 5 of CP104 there should be continuity via the "CHASSIS GROUND" as per the schematic.Though, looking at that schematic, the ground symbol (the rake look-a-like one) is labelled CHASSIS GND, CHASSIS and a third one with no text at all. Page 72 of the service manual.Good point from our colleagues above: if the connection to chassis is not made, the assumptions I said are not valid (i.e.2 and 5 of CP104 there should be continuity).Can you please post some high quality and crisp photos of the back of the PCB? This one, you can take multiple photos to have a better view at the traces.

author: guizmo1967
author_rank: Regular Contributor
timestamp: February 03, 2023, 09:15:37 pm
content: Hello again !It's been a month since I've worked on that receiver. From the beginning, even before my mistake (shorted one power transistor collector pin to heatsink), I suspected the main cpu (Sony CXP740096) to be dead ! This receiver, even if there was a fault, should at least turn on the display and flash a led to indicate the fault ?? So this is what I did:I soldered 5 small wires directly to the cpu pins (VREF, VSS, VDD, RESET and AVDD)I just plugged the receiver, did not push the ON/STANDBY button and measure these voltages:VREF = 5.25VVSS = 0VVDD = 4.96VRESET = 4.94V (active low, so correct)AVDD = 4.97VChecked the murata oscillator (on-chip grounding cap) if it was working, one pin at 0V and the other 4.95V, so not working !!Removed the murata, soldered a crystal oscillator with two 27pF, like what I do with my microcontroller project and still one pin at 0V and the other at 4.95V !!So my final though, the main cpu was dead from the beginning .... Not wasting more time on that receiver !!But what do you think before I throw away (recycle) this receiver !!

author: Audiorepair
author_rank: Frequent Contributor
timestamp: February 03, 2023, 10:01:00 pm
content: So are you saying you mislead us throughout this entire post?

author: guizmo1967
author_rank: Regular Contributor
timestamp: February 03, 2023, 10:19:29 pm
content: I will not say misleading since I'm no expert !! I just did not know from the beginning of this post why the display would not at least turn on and indicate a fault, that's why I asked for help from more experience members on this forum !!With everything I tried from your suggestions, I just came to the conclusion that the cpu is dead, I may be wrong .....Did not wanted to hurt anyone feelings !

author: David_AVD
author_rank: Super Contributor
timestamp: February 04, 2023, 01:25:52 am
content: That sucks, but it's way things go sometimes. Hopefully you learned some trouble shooting ideas from it all.