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Marantz 2235 Right Speaker Hiss

So, given that I'm about to receive some components from @Steven Tate , (I thought about referring to this transaction as having been with "Steven's House of International Transistors" but I don't know anyone here well enough to incorporate that acronym, so playing it safe.)

Anyway- transistors should arrive today and in a couple of days I may take a crack at it. Before I do, any feedback on the charts from Post #40?

No idea how to read these outside of what you've already indicated (look for fuzziness), but it didn't look bad to me? Might be I'm not producing the right graphs, but I think I did...
 
This PC based scope doesn't have the best resolution, but the right side out looks to have more fuzziness than the left side out (I'm assuming the green trace is the out). That could be your hiss. The plus and minus peaks will show the distortion best because that is the toughest part for the amp to reproduce.
 
I am not too familiar with this topology but it seems like it is one of these transistors (which you probably have or wiil have them soon):

upload_2021-6-8_17-3-26.png
 
ocdecio said:
I am not too familiar with this topology but it seems like it is one of these transistors (which you probably have or wiil have them soon):

View attachment 2252550
Click to expand...
Appreciate it- and yep- I got the transistors in yesterday (thanks, Steven). To you, does the oscilloscope reading at zero volume make it look like something isn't as it should be? Or is that level of "fuzziness" normal?

Just want somebody with more experience than I have to opine on this before I take the soldering iron to the preamp... I don't want to remove any parts with "mojo" from the unit unless it needs it. But if it does, I'm goin' in.
 
As Steven pointed out, these digital scopes are not that great for this type of work. However the two signals are definitely different, so there's that... now which one is the right channel? I am guessing the bottom part.
 
Not measuring left vs. right, rather in vs. out. The top is Left In, Bottom Left Out on the first PDF, the other is Right In (top) and Right out (bottom). Measured on the preamp, with volume at zero.

Should I measure left vs. right as well?
 
Well then they look similar to me. Are you getting hiss on both channels?
 
Also- any tips on accessing the main amplifier board in order to swap out the parts? I am hoping there's a smarter way to do it than what it looks to me like I have to do...
 
tlite said:
Also- any tips on accessing the main amplifier board in order to swap out the parts? I am hoping there's a smarter way to do it than what it looks to me like I have to do...
Click to expand...
Nevermind. I am a dufus. It's the preamp board, not the main amp board.
 
tlite said:
I forgot to upload the zero volume tests on the preamp. This time it does look a lot fuzzier on the output... another set of eyes would be good. Cough... hint...
Click to expand...
That's kind of hard for me to evaluate. I'm not sure if that is caused by hiss or not.
 
ocdecio said:
What I am puzzled is why would we have hiss on BOTH channels. Usually one goes before the other...
Click to expand...
That's what I was thinking. But on the traces he posted yesterday with a sine wave, the right side definitely looked more distorted at the peaks on the output.
 
I wonder if we have a ground loop somewhere. Another thing that happened to my 1120 was that the capacitors on the preamp were picking up interference, got that solved with some good Vishay films.
 
I reran the preamp test now that I'm a little better equalizing the waveform graphs. I'm thinking the left actually looks a little worse than the right, but overall not bad at all, right? Later I'm going to pull it off the bench and give it another listen.
 

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