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Marantz 2235 Right Speaker Hiss

tlite said:
Winter Park, Florida (Orlando area). There's a local shop here called Skycraft that sometimes has components. Hit or miss though.
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Skycraft is fun to visit but their selection of good components is poor.
 
Here's what the back of the jacks looks like- just want to make sure it looks like it should and hasn't already been fussed about with?

EDIT- the more I look at this the more I'm thinking something ain't right... but maybe that's just me?
 

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tlite said:
Here's what the back of the jacks looks like- just want to make sure it looks like it should and hasn't already been fussed about with?

EDIT- the more I look at this the more I'm thinking something ain't right... but maybe that's just me?
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They look pretty normal to me. If you decide you want to try swapping those transistors, message me with an address. I have a bunch of Onsemi 1845's and 992's. I'll send you enough to get them replaced.
 
So I DeOxited the jacks and still getting hiss so guessing I'm in for some transistor replacement.

That said, the hiss is only really noticeable once I dial the volume up past 50% (12 o'clock or so) and I rarely listen that loud, but it makes me think it's still a sign something isn't performing like it should...
 
Okie doke. Steven came to the rescue and I've got new transistors on the way. Will report back as to results once they're in. Thanks all.
 
tlite said:
Thanks! Replacements are backordered at Mouser, Digi-Key, and everywhere else I found in the last 3 minutes on Google. I hate going the eBay route as too many knockoffs. Might be able to find some at a local shop near me that sometimes has this kind of stuff though.
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Contact @EastPoint or look for the seller peace.love.and.music on FleaBay. Same guy. :thumbsup:
 
So I snagged a Hantek PC based scope. I haven't traced an amp/receiver with a scope before so gotta do my googling.

That said, shamelessly lazy person that I am, I'll go ahead and ask if I'm just troubleshooting the preamp, do I need load resistors? If so will a 50W 8 ohm resistor in each channel do the trick? Thanks- I get a tad nervous when doing something for the first time that can destroy my stuff and/or me. Never stops me from doing it but I'd rather be smart than not smart...
 
No load resistors needed to test preamp. Inject a signal - maybe 1000 Hz - into the Aux inputs. Connect scope inputs to signal in - JE01 ( L channel in) and signal out - JE06 (L channel out). They should look the same, except out will be stronger (adjust vertical and/or volume to make the two signals about the same size). You are looking to see if a clean looking sine wave on the in side looks overly fuzzy on the out side. Also, look with volume at zero to see if out side looks noisy. Hiss will usually show up here unless it is volume dependent. In side should be a flat line - and so should Out. Then check JE02 (R channel in) against JE07 (Right channel out) again looking for a less than clean looking sine wave coming out compared to the in signal. This should also give you an idea if one channel looks worse than the other. You can check your amps the same way (with a dummy load). In is J701 and J702. Out is the speaker terminals. Obviously there is a big difference in voltage, but by adjusting your vertical axis and/or volume, you should be able to get them close in size to compare in and out. Don’t short anything - make connections with unit off!
 
Steven Tate said:
No load resistors needed to test preamp. Inject a signal - maybe 1000 Hz - into the Aux inputs. Connect scope inputs to signal in - JE01 ( L channel in) and signal out - JE06 (L channel out). They should look the same, except out will be stronger (adjust vertical and/or volume to make the two signals about the same size). You are looking to see if a clean looking sine wave on the in side looks overly fuzzy on the out side. Also, look with volume at zero to see if out side looks noisy. Hiss will usually show up here unless it is volume dependent. In side should be a flat line - and so should Out. Then check JE02 (R channel in) against JE07 (Right channel out) again looking for a less than clean looking sine wave coming out compared to the in signal. This should also give you an idea if one channel looks worse than the other. You can check your amps the same way (with a dummy load). In is J701 and J702. Out is the speaker terminals. Obviously there is a big difference in voltage, but by adjusting your vertical axis and/or volume, you should be able to get them close in size to compare in and out. Don’t short anything - make connections with unit off!
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Dagummit, Steve. I already owe you. Now you're just showing off.

(Thanks.)
 
tlite said:
Dagummit, Steve. I already owe you. Now you're just showing off.

(Thanks.)
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Lol. I remember the things that took me a while to grasp. But on the totem pole of expertise, I am the guy on the bottom. I just hope I don’t lead someone down the wrong path, and if I do, I hope someone catches it and corrects me. I don’t mind being corrected. We all learn that way.
 
Things I learned here - most problems are not bad components, rather bad connections (tarior). And always put a tape on your probe to avoid shorting something while moving it around (not a question of if, but of when) (dr*audio).
 
ocdecio said:
Things I learned here - most problems are not bad components, rather bad connections (tarior). And always put a tape on your probe to avoid shorting something while moving it around (not a question of if, but of when) (dr*audio).
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It's been a long time since anyone has asked me to put tape on my probe while moving it around. Ugh. So stupid, but had to be done. I'm new. Don't ban me.
 
As @Steven Tate pointed out you may want to use mini grabbers instead of pointy probes. The only thing is, you need to turn off, set the probes and turn on again. Not an issue for preamps, but amps sometimes take time to stabilize.
 
ocdecio said:
As @Steven Tate pointed out you may want to use mini grabbers instead of pointy probes. The only thing is, you need to turn off, set the probes and turn on again. Not an issue for preamps, but amps sometimes take time to stabilize.
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Cool! Hantek scope came with mini grabbers. I'm sure I'll still find a way to screw something up, though...
 
ocdecio said:
Things I learned here - most problems are not bad components, rather bad connections (tarior). And always put a tape on your probe to avoid shorting something while moving it around (not a question of if, but of when) (dr*audio).
Click to expand...
Good tip here as well- maybe I can get away just reflowing some connections...
 
OK- I am really a noob with oscilloscopes. CH1 is input, CH2 output.

I think I got better at normalizing the waveforms by the amp test.

I have no idea if these graphs show me anything bad or not. It didn't look bad- though it looks like input and output are out of phase at the preamp level- not sure if that's normal or not?

Thanks again, folks...
 

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