Yamaha HTR 5940 audio problem.

[tejasnaidu]

Dear all,

I have problem due to IC BD 3816K1 on my Yamaha HTR 5940.

Problem is if audio source is connected to multi channel input -output from amp is fine, but when audio is connected to any other i/p like DVD, CD,MD, DTV, DVR, Tuner there is no output. Volume control/selector switch has no effect -- no audio output.
When i go into service mode there is breaking audio with noise during analog bypass and DC/Temp menu, rest of the menu options the amp is silent.

Checked the above mentioned transistors, Output voltage is + -7V, So i guess they are OK.
Please advise whether the BD 3816K1 is faulty and needs replacement or any peripheral component has failed.

Regards,
Tejas naidu

 

[davenn]

on one of the inputs that isnt working you need to use an oscilloscope or some other ausio signal tracer and start at the input terminal and work your way into the system and see where the audio stops.
Maybe the input selector switch has failed and is only working in one position.
Check the power supply rails to the preamp ccts of the non-working inputs

Do you have any circuits or other service info ?

cheers
Dave

 

[tejasnaidu]

Thanks Dave for the reply.
Unfortunately i do not have a scope, just a DMM.

Have checked the circuit in following steps.
1) Checked +-12V supply from DSP board to Function board-- Found O.K..
2) Checked +- 7V supply on function board ---- Found O.K..
3) Checked path between RCA i/p and I.C. i/p ---- Found O.K..

Another point to note-- when amp is started cold, it goes into shutoff after 3 seconds due to DC protect (Approx 7V D.C. at spk terminals) . Have to disconnect speakers and forcefully start in service mode for 1 minute for the amp to warm up. Then the amp starts normally.

Amp works normally in 6.1 channel mode. All 6 inputs work normally. In 6.1 channel, the DSP Board is completely bypassed and audio is sent without processing.

All other input ( DVD, CD, Tuner, MD, DTV, DVR) have problems that there is no o/p. These signals are routed through DSP. As per diagram removed Cap C2036 in function board for the left channel signal coming from DSP board (DAL) to isolate the line. Injected audio signal externally into the DAL input to I.C. BD 3816K1 via external cap. Still no audio during normal operation. There is breaking audio in service mode ( Analog bypass and DC/Temp mode).

Find attached Service diagram.