Yamaha RX-730
- Thread starter Smoky D
- Start date
A little low , should be 5.4.
What is the voltages on either side of D4 ?
Need to know anode side, should be 5.5 .
Athanasios
Check out of circuit . Id also check C57 the 4700uf 5.5 volt cap. that voltages operating area is the same as the voltage going in. To close to SOA , might be leaking to GND pulling the voltage down .
Athanasios
LC6554H datasheet shows 4.5 - 5.5V operating voltage, so probably ok
Think you need to record IC7 Pin 9,10,11 and IC6 Pin 4,5,6 voltages for different inputs PHONO, DAT, CD, LD... maybe that way we can see that the voltages coming into/from IC6 are not/ok
IC7 performs left channel switching, IC8 right channel. Since both channels out more likely upstream (IC6...) issue
IC7 performs left channel switching, IC8 right channel. Since both channels out more likely upstream (IC6...) issue
audiotemp
Super Member
You can test both ic 10 and ic 11 with CD direct engaged. They are both always active and receiving input. Output of one or the other is switched onto preamp out but you can probe before that switch.
But why do it? You have bigger problems...
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Trying to sum up the current issue
IC7,8 perform input selection, pins 9,10,11 by setting either high or low, are used to do this
With CD selected pins 9,10,11 were LLL (= phono) so no audio
The input selection originates from IC4(mcu) then sent to driver IC6, problem could be with either.
Need to look at voltages coming in/going out of IC6 Pins 4,5,6,11,12,13
IC7 and 8 recently replaced, remote chance that one is faulty and dragging down pin 11???
IC7,8 perform input selection, pins 9,10,11 by setting either high or low, are used to do this
With CD selected pins 9,10,11 were LLL (= phono) so no audio
The input selection originates from IC4(mcu) then sent to driver IC6, problem could be with either.
Need to look at voltages coming in/going out of IC6 Pins 4,5,6,11,12,13
IC7 and 8 recently replaced, remote chance that one is faulty and dragging down pin 11???
Some more observations. I tried to connect sound source to the RCA connectors at the back. Only two made it to the speaker.
- CD. Sound only if cd-direct is engaged. Volume works.
- LD. Sound only with Tone bypass on. Volume, balance, loudness knobs work. Can't say if bass/treble work as only one lousy speaker is hooked up. No sound if Tone bypass is off. Funny thing, there is sound on any position of the input selector. The contents of the display changes but the sound still goes on.
- CD. Sound only if cd-direct is engaged. Volume works.
- LD. Sound only with Tone bypass on. Volume, balance, loudness knobs work. Can't say if bass/treble work as only one lousy speaker is hooked up. No sound if Tone bypass is off. Funny thing, there is sound on any position of the input selector. The contents of the display changes but the sound still goes on.
Tone bypass is only for passive elements so maybe bad solder joint, dirty switch, but both channels affected.
On LD output regardless of input selection, yeah reads like IC7,8 but can't say until we see the orders coming out of the mcu, IC6...
You seem reluctant to do this
On LD output regardless of input selection, yeah reads like IC7,8 but can't say until we see the orders coming out of the mcu, IC6...
Do above for each input would be great or just for LD.
You seem reluctant to do this
So pin 4 1.85V should be setting p13 high.
No, not reluctant. IC6 is pretty small and the solder points are smaller too, not easy to get to them. Just being careful to avoid potential short in the ckt. I'll do that.
Voltages coming in/going out of IC6 Pins 4,5,6,11,12,13 with wires on rca LD CD VCR + corresponding source selector set.
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