Onkyo TX-L55 / TX-LR55 Dead and asking for repairs

[Hemz]

Hello Everyone,

Firstly, i would like to thank everybody, as the members are always able to help me come out of troubles with their ideas and experiences.

And, that becomes the reason that i always come to this place.

Now, i have undertaken this slim AVR for repairs as the owner is not happy, for the unit being dead.

He wanted to give it away, and so i took it from him, at least to learn the digital home theater repairs.

Details from the first look, when opened.


When connected to power supply nothing, upon tracing found a 5.1 zener shorted, replaced it and now at least it powers up. After few seconds of relay clicks it shuts itself down.

I understand that the protection circuit is playing its part, so started disassembling, one by one, all the connectors.

when the amplifier board connector was removed, at least the unit stays on.

This narrows down my problem to the amplifier board, but its no conventional analog driver and amplifier ckt, its more than that directly driven through some signal processing IC.

Please suggest your inputs if you have come across, this problem / unit.

Regards,
Hemant.

 

[JonSnell Electronic]

It is probably a problem with one of the surround amplifiers.
They are class D and if you are not familiar with repair procedures, you have a problem.
Check the output FETs first.
Best of luck.

 

[Hemz]

i will try "inputting" one amplifier, one by one, may be it will further narrow the problem.

else checking incircuit mosfet, is a pain.

if needed, will go for checking the mosfet out of circuit.

will keep posted.

 

[Hemz]

Each single input feed to the amp section kept the receiver "ON" but as soon as the two pins of APRT and PAPOWER are connected it no longer remains ON, so it confirms that the protection ckt is preventing the amp to turn on.

Now further troubleshooting will be done for the MOSFET IRF530.

 

[Hemz]

Further, one of the irf530 shows 1.3 volts at source all the time, while others dont.

is this a hint that the mosfet or its support circuit has a problem?

please advice.

 

[Hemz]

1 question.

if the amplifier is switches itself off ( for its protection ) is there 5volts available at the sensing inputs of the mosfet driver.

OR

Do i need to remove all the 12 IRF530, and check them outside the ckt.

please guide.

Thanks,

 

[Hemz]

Update;

After some exercise, i was able to get to the fault section of the amplifier that had the TC2001 Hmute pin raised to 5volts.

Other two are normal, now i have changed the output mosfets ( 4 pcs ) but still HMUTE is held high.

also, this chip has the input overload held at 0 volts which should not be the case.

There is no input supplied still, it shows overloaded.

Please advice, any one.

Regards,

 

[Hemz]

Hi,

Has anybody any idea what can be done further..

Please advice