My Teenage Son and My Rotel RX-950AX

seventy1

Active Member
Well, a couple of weeks ago, my son had some buddys over and they hung out in the basement playing video games and pool. He had his iPhone plugged into my RX-950AX receiver through a mini plug / RCA cable, bass cranked all the way and played rap at high volume. I'm fine with him using the gear and I assumed that the Rotel would be smart enough to protect itself.

When I next went to use it, the left channel was out and the right sounded like poop. I took the cover off, visually inspected and checked the fuses. The only thing I saw that was obvious was some apparent leaking from the two main and three larger caps. I'm not an electronics expert, but I can use a multimeter, identify, solder and replace components. Is it worth trying to source and replace these caps? Other things I should check? This is a well thought of 50 wpc receiver that I'd like to save if it doesn't cost an arm and a leg. I appreciate any input!
 

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That looks like glue to me. If they leaked it would be a thinner substance. It's common to have filter caps glued to help stabilize them. Might try checking resistors close to see if they've been to hot and are discolored. Do you have a volt meter?
 
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Are you sure the problem is the receiver and not the speakers? I would check dc offset at speaker terminals just do be sure. Hook meter to one side than the other. See if there is voltage there. Best is below 30mv. Check this with volume turned down and tone controls normal and loudness off. Does this unit have a speaker relay? If so can you hear it click?

A resistor that's been to hot could clue you in to the problem area.
 
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I'd check it again with a different pair of speakers, if possible. Good luck with the amp.
 
The speakers seem fine - I've brought in a backup Yamaha A-720 integrated amp and the speakers play as before, I think. I measured DC offset as instructed at 85 mv LH and 125 mv RH.

When I was down there, I noticed a couple of suspicious caps that I missed in the earlier photos. I thought that one looked like it might have holes blown in the top, but comparing to the other photo, it just looks like stamped indentations with a black marker swiped over the top. The other has toasty "glue" at the base.

Adding - I hear a relay click right after pressing the power button. I'm not sure if this receiver also had a delayed relay noise later like my other amps, but there's nothing there now.
 

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you might have to find a service manual. be patient and someone else with more knowledge then me will chime in.
 
Ok, thanks for the help. I did find a free service manual for download at elektrotanya, but I failed the mandatory electronics test :sigh: . Apparently I didn't know enough about scopes... I'll take the boards out to inspect when I find time.
 
Greetings;

at eletrotyana you can have 2 downloads per day without logging in. look for "get manual" down page after the page loads.

That's glue. I am concerned with the large mains caps with what appears to be a bulges on both, though this may be normal for that sized cap. probably nothing.

When you say sounded like poop what do you mean? Fuzzy? One side weaker than the other? Dull?
 
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Side note: Evidently the amp is not 'teenage son' proof. Often thought of how you can modify a volume knob and insert a screw or limiting post in the chassis so it hits a stop point.
 
Greetings;

at eletrotyana you can have 2 downloads per day without logging in. look for "get manual" down page after the page loads.

That's glue. I am concerned with the large mains caps with what appears to be a bulges on both, though this may be normal for that sized cap. probably nothing.

When you say sounded like poop what do you mean? Fuzzy? One side weaker than the other? Dull?
The sound was weak and thin in the working channel, silent on the left channel. I'll reconfirm this. The tops of the main caps didn't appear to be bulged. I'll take another look at electrotyana, thanks.
 
Did you check the fuses with your multimeter? Visual inspection is not enough; the fuse can open in the end caps where you won't see the break.

Looks like there are 4 power supply fuses. Also an output fuse for each channel.
 
Did you check the fuses with your multimeter? Visual inspection is not enough; the fuse can open in the end caps where you won't see the break.

Looks like there are 4 power supply fuses. Also an output fuse for each channel.

Wow, I'm glad you asked the question - I missed the two fuses toward the front of the main board (outputs?). Turns out one of the 5A fuses is blown. I don't have a replacement yet, but I'll bet this is it. Maybe the Rotel is smart enough to defend itself against teenagers! Thanks Ray!
 
I was going to recommend fixing it if wasn't that simple, hopefully that's it. Damned good amp for the usable power and thd.

(side note: I'm 62, my dad always told me to tell him if I broke something, he never got pissed.. 'sometimes stuff wears out.. ' When it came to the RCA victrola.. he taught me how to use it. Don't break anything you can't fix or pay for.

Might want to get your son some audio stuff and tools.. may pay off. Time to learn how to fix stuff. I've made a lot of money because I could read meters and diag stuff mechanical and electronic.
 
Well, that was it. I picked up a couple of 5A fuses at HD and replaced both, now the Rotel sounds as sweet as ever. Unfortunately, one of the JBL ARC1000 towers that he was playing is still missing the woofer notes. But these are my son's, our neighbor gifted them when he helped them move. We'll tear into the JBL together to see if it can be fixed. He's already worked with me to replace the surrounds on his Boston Acoustic A60s, so he's learning and appreciating, little by little. Thanks for the help guys.
 
Well, that was it. I picked up a couple of 5A fuses at HD and replaced both, now the Rotel sounds as sweet as ever. Unfortunately, one of the JBL ARC1000 towers that he was playing is still missing the woofer notes. But these are my son's, our neighbor gifted them when he helped them move. We'll tear into the JBL together to see if it can be fixed. He's already worked with me to replace the surrounds on his Boston Acoustic A60s, so he's learning and appreciating, little by little. Thanks for the help guys.

Ah, one of the speakers was damaged. That explains why one channel "sounded like poop". I could see a blown fuse fixing the silent channel (as long as that's all that was blown) but couldn't figure why one channel worked with poor sound quality.

Glad you got it figured out, and even more that you and your son will work on the speaker together. As Binkman said, those skills will stay with him the rest of his life.

You may also want to point him to some pro audio gear. With what he likes to listen to and the level he and his friends like it's the only thing that will hold up! :D
 
Hmm. I have one dead in the water here. I found one guy that said his was a loose screw on the back left of the main board.
I didnt see a screw but i put one in. The thing is i need one of those right angle low profile tools to get it tight. All my fuses are good.
The funny power switch makes it kind of hard to tell if that may be it. It is a touch type that doesnt really stick on or off. Other than that im guessing relay. No power on, just a red light for standby. Anyone have an easy time replacing the relay on one of these? Thanks.
Niles
 
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