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Amp issue questions

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(@billyboy)
Estimable Member
Joined: 16 years ago
Posts: 91
Topic starter  

Greetings,

Have a few questions about my Roland JC-90. Any thoughts appreciated.

- The volume knob is sticking. Not physically but it crackles when using it, and the volume doesn't change smoothly but jumps. This something I can fix myself or should let a pro do?

- The power in my apartment is flaky (all the lights dim briefly at times). Can this cause any issues damage to the amp? Is getting a UPS or something similar the safe thing to do?

- Do amps need to be serviced periodically, for anything? I've had it about 5 years.

- Finally, this is a stupid question but the thing is a beast, it rattles the neighbors windows with the volume at 2. Is there any scenario where amps fail catastrophically and you blow your hearing to smithereens? This something to even worry about?

Thank ya
-Billy

"In my dreams your blowin' me... some kisses" - Lets Duet - Dewford Randolph Cox


   
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(@dogbite)
Illustrious Member
Joined: 19 years ago
Posts: 6348
 

first thing : be careful before you poke around inside an amplifier. there is a very strong charge in the capacitor.
you need to know how to safely discharge it.
the volume knob has a set screw. check to see that it is tight on the post.
next, the pot could be dirty. or broken.
you can do some repairs . you could have the amp serviced if it has not been dealt with for a long while.
the speakers voice coil could dry out. for example. take it to a tech.
check the set screw first and clean the pot. sometimes the simple things matter.

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(@hyperborea)
Prominent Member
Joined: 17 years ago
Posts: 827
 

first thing : be careful before you poke around inside an amplifier. there is a very strong charge in the capacitor.
you need to know how to safely discharge it.

The Roland JC-90 is solid state so there should be no high voltages inside. Nothing higher than line voltage and hopefully they'll unplug the amp before working on it. There is a good chance that there will be capacitors and even electrolytic capacitors inside but nothing at all like the bias supply on a tube amp.

You should be reasonably safe in there but don't touch anything you don't understand for your own safety but also for the safety of the amp.
check the set screw first and clean the pot. sometimes the simple things matter.

If the OP can get at the back of the pot (open the amp up) and if the pots aren't fully sealed (are there openings in the casing) then they can spray some contact cleaner with lubricant in there. After doing that turn the pot back and forth from min to max a good number of times to remove any gunk and work the lubricant in. Something like this would work great - http://store.caig.com/s.nl/sc.2/category.188/.f

Pop music is about stealing pocket money from children. - Ian Anderson


   
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(@ricochet)
Illustrious Member
Joined: 21 years ago
Posts: 7833
 

- Finally, this is a stupid question but the thing is a beast, it rattles the neighbors windows with the volume at 2. Is there any scenario where amps fail catastrophically and you blow your hearing to smithereens? This something to even worry about?
You can scare the bejabbers out of yourself by doing something like plugging or unplugging a guitar cable with the amp turned on and the volume cranked. Probably won't blow your hearing to smithereens instantly, but prolonged loud playing without ear protection will. That's worth worrying about. A musician needs good hearing.

"A cheerful heart is good medicine."


   
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