Denon 545R Stereo Receiver - No Speaker output

Thread Starter

hafren

Joined Mar 1, 2019
28
I have a Denon 545R which powers up and display screen operates but there is no sound from speakers. I have connected headphones and at full volume I get a quiet output from tuner section or from an ipod connected in via "tape in". I've owned this from new and has been problem free till now. I suspect there might have been a power surge, electrical spike from a storm but have looked over the internal circuit boards and cant see anything obvious burnt/discolored. I have the service manual but need to some help on where to look in problem solving. Grateful for any help.
 

Ylli

Joined Nov 13, 2015
978
All the fuses OK, beyond that,

First thing I would suspect is that the unit is in protect mode. About 3 seconds after you power it on, do you hear a relay click? If not...

Start by measuring the voltage at the outputs *before* the protect relay. Measure at TP1 or TP3 for the left channel and TP2 or TP4 for the right channel. Voltages should be less than 100 mV. If that is OK, measure the rail voltages, collector of TR323 and TR321. Rail voltage should be +/- 48 volts.

Report what you find.
 

MrChips

Joined Oct 2, 2009
21,869
What test equipment do you have at hand? DMM? Oscilloscope?
Do you have another working tuner/amplifier or a powered computer speaker?
What is your knowledge and experience with electronics circuits?
 

abrsvc

Joined Jun 16, 2018
41
If the volume control appears to work (you get a hint of the input signal), I would suspect the TC9164 as being defective. This is the input switching IC and is a relatively common failure. With a scope, check the pins for signals. You should see the signals going in and out. I suspect that you will see the signals entering the IC and not going out. The hint of a signal at full output is just cross-talk.

Dan
 

wayneh

Joined Sep 9, 2010
16,399
Since no one has mentioned it, I'll ask the obvious: Do you have the right button pressed to select your speakers, the A/B buttons? I have grandchildren in the house and more than once have panicked that my receiver was dying, only to discover that a little finger has been pushing buttons.

[update] Just re-read your first post and saw your comment about headphones. That suggests something else than the A/B switches. You might try disconnecting all speakers (to eliminate any possible shorts) and see if the headphone signal improves.
 

Thread Starter

hafren

Joined Mar 1, 2019
28
Thanks to everyone for your help & I apologize for how long it’s taken me to respond - family duties take over from my projects. Anyway I can update everyone with information/answers I have obtained:

YLLi - After power on I get a relay click after ~ 3 seconds and measured voltage across TP1/TP3 and TP2/TP4 rise to 9.8mV then drop off to approx. 8mV after 3 minutes. Rail voltages at TR323 and TR321 are -47.8V and 47.7V

MrChips – I have DMM and a DSO 062 oscilloscope however I have no experience using an oscilloscope but would love to learn. I guess I would describe myself as a novice in electronic circuits – I can read them, identify components but have a rudimentary understanding of design & operation but again would love to learn.

Abrsvc – I do have a hint of the input signal but would need more help understanding how to connect an oscilloscope (what settings to use and which pins to probe to confirm the IC TC9164 is faulty). Would a dmm be able to determine if it is faulty? I can see IC TC9164 in the schematic (p14 of the manual uploaded earlier) but am unclear how to connect/probe to pins to determine if it is the failure source. I’d appreciate any help before trying to unsolder and replace. Also are IC TC9164 readily available?, are specific types needed for a Hi-Fi receiver?

Wayneh – Yes I have fiddly fingered grandkids too and suspected that at first but no such luck. My experiments were taken with speakers disconnected and just headphones trying 2 different inputs tuner & iPod with same results.

Thanks to everyone again and I’d love to learn more and get this receiver working again.
 

Ylli

Joined Nov 13, 2015
978
So the unit is not in protect mode. Perhaps it is muted for some reason. Measure the voltage at the base TR201 or TR301 or TR302.
 

Ylli

Joined Nov 13, 2015
978
So it is not muted. Let's see if we can get a 'hum' through it: Using a screw driver or other conductive probe, touch your finger to this conductive probe and then touch one side of the balance control (VR301), and then the other. You should get a reasonably loud hum out of the appropriate speaker.
 

Thread Starter

hafren

Joined Mar 1, 2019
28
So it is not muted. Let's see if we can get a 'hum' through it: Using a screw driver or other conductive probe, touch your finger to this conductive probe and then touch one side of the balance control (VR301), and then the other. You should get a reasonably loud hum out of the appropriate speaker.
Yes loud hum on both sides of balance control VR301
 

Ylli

Joined Nov 13, 2015
978
Then refer to abrsvc's post #5 above. Check all the DC voltages around IC201. Either this part is bad or the data/clock/strobe signals to it are faulty. Put it in various modes and use the hum test to trace the signal path back through it.
 

Thread Starter

hafren

Joined Mar 1, 2019
28
Well things are worse than I originally thought. The unit has suffered a power surge and I’ve found burning on the bottom cover and a burned through trace on the main board.Power surge.jpg Power surge chassis.jpg

It looks like the spike jumped from a chassis screw onto the board at jumper wire JV202. I soldered a wire to reconnect the burned out trace and have been trying different inputs to verify if TC9164N (IC201) is faulty. It does look like signals are being input but no output from TC9164N. However today the unit got very hot with I think TR 417 and TR 413 being the source (~130F at the board). I measured the following voltages

TR 417 base -15.8V, collector -35V and emitter -15.1V

TR 413 base 19.2V, collector 30.7V and emitter 26.7V

I’ve been operating this unit of and on over the last 2 weeks with no appreciable temperature rise until today so am I’m unclear what might have changed. I would appreciate any advice on what to look for next.
 

Attachments

abrsvc

Joined Jun 16, 2018
41
The reported voltage readings are wrong. The emitters should read +/- 16V. TR417 is close enough, TR413 is way off.
At this point, remove the TC9164 and check the voltages again. I still suspect this IC as being bad.

Dan
 

wayneh

Joined Sep 9, 2010
16,399
Do you have advice (tips) on how to best desolder the IC from the board
The easiest I’ve found is the completely destructive method: Cut all the pins with a dremel cutoff wheel and the remove them one by one. It’s much harder if you want to recover the part.
 

Ylli

Joined Nov 13, 2015
978
Do you have advice (tips) on how to best desolder the IC from the board
This looks like a through hole part. Most of these single sided boards do not use plated through holes, so if you are careful you can desolder it with solder wick. Just need to be careful to not overheat the pad such that it lifts from the board. Do it one pin at a time....
 

Thread Starter

hafren

Joined Mar 1, 2019
28
I'm struggling to find a dip socket for the TC9164N IC. What is the correct nomenclature for a 28 dip socket that has rows 10.16mm apart. All the images I find seem narrower.
 
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