Need guidance repairing a Denon DRA-345R that doesn't turn on

[FBMinis]

It was working before, then I didn't touch it for over 1 year and it doesn't turn on when I press the power switch.

1) the fuses are intact, same as power cord;
2) the voltages on the secondary coils of the transformer are correct;
3) bridge rectifiers are intact;
4) output voltages of the voltage regulators are correct;
5) output transistors aren't shorted

When I press the power switch there is no output from the speakers or headphone and the display doesn't turn on. The unit looks like it hasn't been turned ON but I can measure the voltages mentioned above.

I don't own an oscilloscope.

Any suggestions on what to check next?

[Swake]

Check if the relay is working.

While the amp is not powered you can measure the coil resistance & the contacts.
After power on: check if the coil gets actuated and if an audio signal gets up to the relay's contacts.

[Swake]

check if 5v power arrives till the display board (top right schematic)

[Swake]

Service Manual: https://www.hifiengine.com/manual_library/denon/dra-345r.shtml

I can hardly read the schematic you posted.

[Swake]

I see now there is a standby circuit in that big chip near the display. I think the chip is IC701 or LC701.
Check the Power on/off signal. Green arrow on the connector. On the chip I think it is pin 27 (red arrow).

That signal activates TR415 which then wakes up the +16,4V  and -16,4V lines.

[abdulbadii]

pretty good thermal camera snapshooting PCB as it's on might do life easier, tracing wherever is open
if it's fairly expensive $115-125 just rent or borrow for minutes/hour

[David_AVD]

I've seen DRA-345R and similar models with cracked joints on the main PCB. From memory there's a regulator near the heatsink that is often the culprit.

The other thing on those models is traces that have been eaten away by glue gone bad. Check the main board, especially towards the front edge.

[FBMinis]

All right guys, thank you all for your suggestions. I've been probing the board taking in account the components you mentioned.

TR417 and TR413 show the correct voltages;
IC201 (TC9164N) shows close to -16V and 16V on PIN1 and PIN28; The rest of the pins show 0.1V, even those that show 0V in the schematic but I'm using an inexpensive multimeter...

The relay coil is not open and it does not click when powering ON. You can see in the service manual there's a page that mentions testing points side by side with the relay. They should measure 500mv but are at 0V at all times.

Regarding the main controller, I checked the voltages at the connectors CN8A and CN11A:

CN8A:

1) 0
2) gnd
3) and 4) measure 4V AC between them
5) 5.44V
6) - 26V
7) 5.18V
8 ) 0V (schematic reset should be 5.2V)

CN11A

1) 2.35V (schematic mute T should be 0V)
2) 0.02V
3) 0.02V
4) 0.02V
5) 0.02
6) 0.02
7) 2.75V
8 ) 0V
9) 0V (schematic Hold should be 5.2V)
10) 4.30V
11) 4.30V

As you can see, some values are weird. For example, I followed the Hold trace and tested TR616 and TR615 but they are ok...

I've already fixed a couple of cracked solder joints belonging the the bass potentiometer and redone others that looked weird.

 

[Swake]

Sorry not much time right now to go into detail but one thing: There is surely a buffer capacitor before the 5V regulator. 1000µF or 2000µF something like that. Unsolder and check capacitance and ESR. If you can't measure replace (temporarily) with (Salvaged) cap of approximate capacitance and same voltage or higher.

[FBMinis]

I have one of these component testers; I will check the caps: https://www.aliexpress.com/item/32761468474.html

[David_AVD]

Another common fault with amps is the capacitor for the power good signal. When the cap goes low capacitance, the power good signal keeps the relay (and optionally the micro) off.

In this case it's C647 (2.2uF 50V), located ZD601 and D607 in the power supply area. Look around the middle / rear of the heatsink.

The collector of TR616 should be 5.2V or close to it. You could also check pin 22 of IC701 (front panel micro) for that 5.2V HOLD signal.

Maybe also check pin 21 of IC701 (RESET) to make sure it's also 5.2V or so.

[FBMinis]

I was just testing that area because Hold and Reset are 0V.

TR615

C 4.78V
B 0V
E 0V

TR616

C 0V
B 0.67V
E 0V

Z601 shows 19V on the cathode

I think TR615 isnt getting activated, maybe C670 or C647 are leaking? I will remove from the board and test...

[David_AVD]

If C647 has gone low in value, that will cause issues. It's a really common failure in amplifiers, be they in receivers, subwoofers, etc.

[mbz]

I was just testing that area because Hold and Reset are 0V.

TR615

C 4.78V
B 0V
E 0V

TR616

C 0V
B 0.67V
E 0V

Z601 shows 19V on the cathode

Schematic suggests D607 cathode at +19V so 19V at ZD601 cathode may suggest D607 failed short.
Also with 19V at ZD601 cathode shouldn't there be aroud 11V at ZD601 anode/TR615b but you have 0V
so maybe ZD601 failed open. TR615be 11V would make that part suspect.
Suggest recheck measurements in this area

[FBMinis]

Ok, I got it working by replacing the 43Kohm resistor below D607, which failed open.

Previously I mentioned I measured 19V at the cathode of ZD601 but it was instead on D601, I must have confused both when wrote it down.

Anyway, the device still presents some problem:

1) when using the tuner, the speakers Pop! when I press buttons on the front panel;

2) the left channel presents some noise/distortion (same volume as right chamnel)

3) the source selection switch has become faulty most likely, because when I play a tape and a cd, both are audioble and pressing the different source button makea no difference.

I will clean all the potentiometers and order a replacement selector chip.

Thank you for your help once again.

[David_AVD]

I have seen the analog switch input selector ICs go faulty on various amps. Sometimes one side will die, other times there will be a large DC offset that causes issues further on. One even had a similar fault to yours where one input was always selected.

[FBMinis]

Found a couple of threads pertaining to the DRA-345 and DRA-545 (same schematic), with similar symptoms:

https://forum.allaboutcircuits.com/threads/denon-dra-545r-stereo-receiver-no-speaker-output.172033/


https://maker.pro/forums/threads/denon-dra-545rd.291165/


https://forum.allaboutcircuits.com/threads/denon-545r-stereo-receiver-no-speaker-output.157320/

[FBMinis]

The socket for the TC9164N is an SDIP with 28pin, 1.778mm pitch and row distance of 10.16mm

These don't seem to be very common nowadays but I found some on Aliexpress and LCSC

https://pt.aliexpress.com/item/4000650549013.html
https://pt.aliexpress.com/item/32892631536.html
https://www.lcsc.com/product-detail/IC-Sockets_CONNFLY-Elec-DS1010-32T1NX_C72253.html

https://pt.aliexpress.com/item/1005002044628988.html (chip itself)

[David_AVD]

No need to socket that chip. Just solder it in.

[FBMinis]

Replaced the chip and the receiver is now as good as new. Thank you all for your help 

[Swake]

Yeah !
Gives a good feeling when it works again, isn't it?

[FBMinis]

Indeed! And it's motivating because I have other hi-fi gear that needs repairing