Marantz SR92

[Yorama]

When both probes connected to one channel it is all lined up

 

[Yorama]

Please find pictures showing the difference. Thank you.

 

[dankik]

You can try to isolate the phase difference between the Preamp or Main amp by removing the PreOut to Main In jumpers for the L & R Front channels then connecting your oscilloscope to the PreOut RCAs. See if you see the same phase difference as on the speaker outputs. If you do, then it is in the Preamp, if not then it is in the Main amp.

 

[Yorama]

Looks like the problem is at the Pre Amp? (preamp output to scope)

 

[Yorama]

Interesting that even when nothing is playing, there is difference between the channels. (connected to Pre/Out)

 

[dankik]

If you were injecting the sine wave into the AUX inputs, I want you to do the same test (still looking at the PreAmp outputs), but this time inject the signal into the TAPE IN RCA jacks.
Does the L/R still look imbalanced?

 

[Yorama]

Previous test was with CD input. this picture done with Tape in RCA input (there in no AUX on this receiver) imbalance R/L persist.

 

[dankik]

A couple of more thing to look at to try and isolate where the imbalance is.

1. Check both the INPUT LEVEL and INPUT BALANCE controls. Make sure that the balance is centered (maybe a detent). See if you can balance the L/R channels using this INPUT BALANCE control.
2. Feed you sig gen into the TAPE IN inputs, then hook your scope to the TAPE OUT RCA outputs. See if the channels look balanced. The only difference should be the BUFFER amp QV52.

 

[Yorama]

1. Main Balance Control can equalize signal levels (not phase) when OFF center (see picture)
2. When signal input at TAPE IN, I get NO signal out at TAPE OUT (tried the same with VCR1), got the same result. No signal Output.
3. When signal input at CD, I get signal out at TAPE OUT (see picture)
3. Noticed= Input Balance Control does not response logically.

 

[dankik]

Thanks. Let's try and work backwards from the Tone Amp.

• The PE04 gets its input from the Master Volume control and its output essentially goes to the PreOut jacks.
• Start off by putting your scope probes on JE02 (Input to the PE04).
• It has 3 conductors L, GND, R. Attach one probe on L, the other on R.
• Do you still see the phase shift and amplitude difference?
• If NO, then the signal is good at this point and the problem is on the PE04 board somewhere.
• Next, move your scope probes to the board output on JE03, same thing L, GND, R.
• Do you see the phase/amplitude difference here?
• Now we need to narrow it down to where on this board.
• If there is a difference at the input connector JE02, then we need to move further back on the signal path.

Input to the PE04 board:


Output from the PE04 board:

 

[Yorama]

Please find attached test results for probes at JE02 and JE03

Thank you.

 

[dankik]

Still have an amplitude and phase difference. Lets move back another board.
Can you get to this board or is in buried in the front panel?
I'm not sure about the pin L/R.
QUESTION: What are you using to generate the sine wave input? Does it have a L & R or single channel that you split into two channels?

__

 

[Yorama]

Results from PG04 (RG04), probes at JG01 R & L, JG02 is connected to JE02 (see previous)

From the phone, assume stereo output

 

[Yorama]

Your question made me think, and I checked the setting on the phone, it was not set equally R/L, it was 100% on the R and 86% on the L.
I have checked again the receiver output, and it measures ok now.
I am sorry, amateur!!! (but it was good lesson) When you don't know, you don't what you don't know.

Thank you very much for your time and patience. I'll put it all together now and hope for the best.

THANK YOU.

 

[dankik]

Sounds like everything is OK now.
We would have gotten to the same conclusion as we worked backwards to the input and saw the same problem.
But I would check your phone output directly driving the scope. It looks like it might have an unintentional phase shift between the channels as you reduce the volume in one.
Happy listening!

 

[Yorama]

I'll check and compare how clean and accurate the signal is.

 

[Yorama]

Probing direct from the phone. (see picture)
Something is wrong with the input
Looks like there is a short between the R/L input, CD, LD, Tape they both play which ever Input is used.
I get very scratchy distorted sound when on Tuner as if the input volume is too high.

 

[Yorama]

Something is wrong with the input
Looks like there is a short between the R/L input, CD, LD, Tape, both speakers play which ever Input is used.
I get very scratchy distorted sound when on Tuner as if the input volume is too high

remember I said the input Balance act weird (the main Balance control, works ok.)

 

[dankik]

OK, so you are saying that the following inputs are OK:

• CD
• LD
• Tape IN

but when you select Tuner the sound is distorted? Does this happen for both AM and FM and only on these? Is Phono input OK?
Also, the balance control works as it should on all inputs except the Tuner?
Is it on both L & R channels?

 

[Yorama]

All inputs sound clear when only one input rca used but the sound play on both speakers
With the tuner I have no way of disconnecting one channel, it sound like R and L input shorting with each other