Denon AVR-2105 red light flashing

[occhio37]

Hello to everybody!
I recently bought a damaged Denon AVR-2105 (2005 model). Red LED blinks after a few seconds of power-on. The first thing I detected was 2 short transistors on the Front L channel (Q101FL and Q102FL). I installed new ones and it was the same. I checked the regulators 7815, 7915 and the two 7805 on the power supply, they are all ok. What do you advise to check next? Why does the AVR still fail to connect? no speakers connected (there is no possibility of a short circuit) ... Is the circuit detecting the presence of DC in the audio line? Thank you very much any help in continuing the repair 

[MiDi]

Power rails checked?
Does a relay click before red blinking?
DC voltage on every speaker connectors checked?
Any loose connectors or pins?

[commongrounder]

Since the unit is still in protection, I would check each channel output for abnormal DC offset (more than a few millivolts). A good place to probe would be at the test points 101,104, etc. It’s possible that just replacing the output transistors wasn’t enough. Sometimes, a flameproof emitter resistor in the driver stage will open up, but not show up visually.  Compare voltage measurements at the same component positions on different channels, looking for inconsistencies. Good luck!

[occhio37]

1st thank you for quick help 
I hear 2 clicks and I think they come from the RLY106 relay in the power supply section. The red LED starts blinking when the relay switches off (I think ...). Voltages at the regulators 7805 (IC103, IC104) and 7815/7819 (IC101, IC102) are present (5V, 15V and -15V). After the second click on the relay they disappear. I will make the checks indicated by you .... Thank you very much.
 

[ElecSeb]

Did you check R148, R149 R142 R141 all 0R22 (flameproof resistor - Metal oxide 0.22 ohm 1W)
Just a hunch, but IC201 -> pin 64 PROTECTION? -> did you follow this in the SM?
There is different protects:

• OVER_PROTECT
• DC_PROTECT
• PROTECT

[occhio37]

R148, R149 R142 R141 all ok
R108FL, R109FL, R110FL and R111FL (0R22), all broken
R106FL + R107FL (4R7) with changed  value
I will buy this material to replace all.

ElecSeb can you explain better
"Just a hunch, but IC201 -> pin 64 PROTECTION? -> did you follow this in the SM?
There is different protects:
OVER_PROTECT
DC_PROTECT
PROTECT"

[ElecSeb]

R108FL, R109FL, R110FL and R111FL (0R22), all broken
R106FL + R107FL (4R7) with changed  value
I will buy this material to replace all.

CONNECTOT CP502 - OVER_PROTECT -> R115FL

OVER _PROTECT connects all channels, so check also all other channels, kinda weird that only 1 channel blew! Did you caslo check the Q101FL and Q102FL and Q104FL.
Same for FR (same numbers only with FR instead of FL)
(And if you are at it, check also for C, SR and SL)

And sometimes it is difficult to locate a protect, 9 out o 10 it is power supply circuit.
In this case it is amplifier area... (Follow the OVER_PROTECT signal comming from CP502 )

[occhio37]

Checking the PRE AMP board e detected Q502FL, Q503FL and Q504FL broken too 

Q101FL e Q102FL are new

[ElecSeb]

Checking the PRE AMP board e detected Q502FL, Q503FL and Q504FL broken too 

Q101FL e Q102FL are new

How are the other channels?
Btw I missed that in your FiPo.

Good you found it so far!

Btw2. If you now know this is also completely broken, I would advice to trace it back to the CNT board (IC208A, including R247FL)

[occhio37]

 
Hi! Anybody know what are te specifications of standby transformer? It has 1,8k in primary winding...

[mzacharias]

1. Output transistors.
2. Emitter resistors, .22 ohm x4
3. 4.7 ohm base current limiting resistors, one or both
4. Check transistors and resistors on driver board, associated with that channel. Especially 47 ohm and 1.2 kOhm.
5. Check parts in protection circuit which tend to get damaged with amp failures on this model, like D132, and Q178 and related parts.

[MiDi]

Hi! Anybody know what are te specifications of standby transformer? It has 1,8k in primary winding...

Did you measure output voltage of standby transformer?
It is not unusual that small transformers have high primary resistance...

[occhio37]

Output transistors and 0R22 resistores ok, i I measure on the TP101, 102, 103, all, about 2, 3mv. Base current limiting resistors verified (I had to change 2 because they were open). On driver board all the 7 channels are the same (measured transistors, resistors, capacitors).In protection circuit I have not yet tested the D132 and Q178 ...
Standby transformer has the primary failed. I temporarily installed another 12VAC transformer (to allow the continuation of the tests).
...but now  have another situation    I turn on the AVR on the ON / OFF button and the led standby is in red, then I press the standby button, the led turns to flashing green and after 5 seconds it turns to flashing red... But only now during this process I never hear any relay to to click (I think it should be the RLY106) 
will not the Q117, Q116, D154 and D157 be responsible for starting the relay? (as referenced in the attached circuit)

Thanks again for the help I have received to try to win this personal challenge of repairing my first Denon AVR   

[mzacharias]

I simply do not believe there are no bad emitter resistors on the blown channel. It's not only common - it's universal on these.

As I suggested before, the protection circuit itself is often damaged in these failures.

[occhio37]

Yes, I detected the 4 fault resistors (0R22) of the FL channel and have already replaced them, also the R106FL and R107FL (replaced)
next step i'll check the protection circuit !!   

[kripton2035]

often if you change the output transistor without changing the blown emitter resistor, then the new transistor will blow up again.
check all the previous changed transistors, and resistors.


also you should check the output of all the 78xx 79xx regulators, often the 7815 or 7915 is dead.

[occhio37]

I changed the 2 transistors (Q101FL and Q102FL) first and only after the resistors but I was lucky because these two remained ok. IC101, IC102, IC103 and IC104 with the correct voltages on pin 3 (OUT)

[ElecSeb]

Based on al above, you noticed your pre-amp was blown AND your amp was blown -> ONLY for FL?

Did you trace the damage further back? -> aka opamp I mentioned before -> reason is to know which part of the system is still OK!

I have to admit this is a pretty damaged receiver! 

[occhio37]

ElecSeb you are correct, in the beginning channel FL with output transistors in short circuit and respective preamp also and red LED flashing after and a few seconds of the first sound and relay. Replace transistors and resistors and check all others. unfortunately with the tests, measurements and the on / off the standby transformer malfunctioned in the primary (I put another provisional) and now when turning on the Denon I continue with the red LED blinking, but I no longer have the first relay to sound
I bought this AVR Denon from a friend, already damaged. It is impeccably well maintained. I would really like to repair it  , it would become my second here at home because I already own an AVR-1902.

[occhio37]

I already have agin the relay RL106Y clicking !! I found an interrupted track linking resistor R186 to connector CP555, RLY_POWER (as shown in the attached photo)
Let´s  again!

[occhio37]

Hello guys! after many hours checking the protection circuits, preamplifier, power and so on  I came to the conclusion that Denon only accepts the original Sanken transistors. Here at a local store I bought the Toshiba brand (2SD2390 + 2SB1560). Measuring them with the  I found different values between SK (joints BE, BC and CE). Every time I put them in the circuit, the red led flashing  . The amplifier is now running  without the power transistors in the FL. All other channels are ok (already verified with osciloscope). I already bought the Sanken transistors on the net, I'm waiting .....
It is very strange that the same transistor model is different between manufacturers and I verified this since I bought 2 pairs of TOSHIBA. Has anyone else already checked this ??

[MiDi]

Hm, only really thing that could be different are build in resistors.
Check the datasheets for the differences.
I did not find a datasheet for toshiba, only for sanken - are they really labeled as you stated?

[ElecSeb]

Are you sure there is no other failure?
Your story sounds a bit weird...

If I read all the broken stuff you found already... Did you check that the signals on the actual positions of the transistors match with what should be expected?
Furthermore, can it be that there is further-on in the board there is an error, defect relay of some sort? Which gets shorted when the transistor is put in place.

Have read before that some remove the transistor (if it is an non-important channel) to use the receiver as-is.

[occhio37]

Hm, only really thing that could be different are build in resistors.
Check the datasheets for the differences.
I did not find a datasheet for toshiba, only for sanken - are they really labeled as you stated?

sooner will i put a photo of toshiba transistors

[occhio37]

Are you sure there is no other failure?
Your story sounds a bit weird...

If I read all the broken stuff you found already... Did you check that the signals on the actual positions of the transistors match with what should be expected?
Furthermore, can it be that there is further-on in the board there is an error, defect relay of some sort? Which gets shorted when the transistor is put in place.

Have read before that some remove the transistor (if it is an non-important channel) to use the receiver as-is.

Even thought to remove a pair of transistors SB channel (L or R) that I will not use and put into operation in FL but I decided to wait for the ones I bought.
All Sanken that I measured had a 4M ohmic resistance in the BE and BC junctions (and of course, the traditional 0.65V as a diode). The Toshiba, 2.8M in the BE and around 7K in the BC. I spent money on 2 pairs of Toshiba and none worked. I'll admit, it's very strange    the same transistor has to be equally indifferent to the manufacturer.