Sherwood RX-2030R: amp fell silent after cleaning

A

arroca

New Member
Hello everybody, I'm feeling a bit stupid this morning. I would like to consult the group about the following matter.
I have a Sherwood RX-2030R amp which I bought 20 years ago. A pretty tough and resilient amp, I would say. I opened it yesterday for the first time ever, in order to clean it, because some pots were noisy and two buttons hadn't worked for years (CD-selector and surround speakers).
Everything inside was coated in ash from years of wood fires. I vacuumed up the worst of the mess (with a plastic tube on the vacuum cleaner). Then I cleaned all contacts with Dueci electronic's R-11 contact cleaner: the jacks, the speaker connections, the pots, also all the buttons. I can confirm that the CD button has started working again after cleaning.
However, when I power the amp up, there is total silence. No sound at all either in the speakers or the headphone jack. Not even a hiss. Total silence.
To clarify: the amp powers up, the display works, the various selector buttons work as far as I can see.
I suspect that the problem may be in the panel on which the buttons, LED display and volume potentiometer are mounted. Any suggestions or advice on how to proceed would be very welcome.
Rob
 
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I hope my post doesn't come off as condescending but I do not know the details so I post this in the spirit of leaving no stone un-turned. It might be "wet". Many people use too much deoxit and don't allow drying time. Hopefully that's all it is. Possibly disconnected something while working or shorted something using a steel probe? Sounds like a speaker relay issue but I am no expert. Sometimes we forget to make the right settings on switches and buttons after a cleaning. Tape monitor switch/button set correctly? Volume on? Source switch in the right spot? Speaker selection on A or B or both as the case may be? Did a fuse blow? It could be something that simple and very easy to overlook the obvious. It could also be that some part decided to expire in its natural due process of aging or a cold solder joint decided to rear its ugly head right at the time you were cleaning. Double then triple check the boards, connections and switch/button settings. Here's a link to the right way to deoxit:

http://audiokarma.org/forums/index.php?threads/the-idiots-guide-to-using-deoxit-revisited.207005/
 
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Not condescending at all! Many thanks for taking the time to write back.
I think you're right about the speaker relay, and I also think you may be right about me not allowing enough drying time. Concerning your other suggestions, I'm afraid that there is definitely no output whatsoever.
I was reading around during the day and examining the machine, and have more or less concluded that the the speaker relay is refusing to close.
Whether this is the only problem, or just the discernible manifestation of a bigger problem, I can't say.
The relay worked fine before I cleaned the contacts. If I was to suggest a cause, I think I turned the amp back on too soon and shorted something. Sadly, that would suggest that there are other problems elsewhere, wouldn't it?
Anyway, for now the question is how to test a relay without removing it.
 
how to test a speaker relay

Post a new thread with this for a title then get traffic to both. Also try various entries in the search bar - it'll probably come up as having been covered previously in some other thread. ;)
 
It gets a bit tricky from here as now you need to figure out if the relay isnt closing due to too much DC coming from one or both power amps, or if there is an issue with the protect circuit itself.

If you feel confident trying to fix this issue you will need a DMM, soldering iron, and the service data as a minimum
 
slimecity said:
It gets a bit tricky from here as now you need to figure out if the relay isnt closing due to too much DC coming from one or both power amps, or if there is an issue with the protect circuit itself.

If you feel confident trying to fix this issue you will need a DMM, soldering iron, and the service data as a minimum
Click to expand...

I wouldn't say that I'm confident, but I'm interested in trying to proceed with testing, partly in order to learn and partly to know what to say to a repair person if I don't manage to fix it myself. First, I will have to read a bit about the question, then I'll do as Dave suggests above and start a new thread.

A question for now: what is the most likely causal connection that you can imagine between my cleaning the amp with contact cleaner and a subsequent problem (apparently) with a defective relay?
 
arroca said:
A question for now: what is the most likely causal connection that you can imagine between my cleaning the amp with contact cleaner and a subsequent problem (apparently) with a defective relay?
Click to expand...
Who knows.

The stuff I posted are as a starting position to trouble shoot issues when your relay isnt working. Thats what you need to start looking at IMO
 
arroca said:
I wouldn't say that I'm confident, but I'm interested in trying to proceed with testing, partly in order to learn and partly to know what to say to a repair person if I don't manage to fix it myself. First, I will have to read a bit about the question, then I'll do as Dave suggests above and start a new thread.

A question for now: what is the most likely causal connection that you can imagine between my cleaning the amp with contact cleaner and a subsequent problem (apparently) with a defective relay?
Click to expand...
Post #2_:)
 
I'd venture a guess that the contact cleaner had little to do with the problem that popped up and it's more likely that you bumped something loose in there or maybe bumped a component over so it's now making contact with something else that it shouldn't.
I'd pull the top again (unplugged of course) and carefully look at any wire connectors and make sure they are tightly in place. If there are any circuit board cards that plug into the mainboard make sure they are not knocked askew. If that looks good then look around at all of the components poking out of the board. See if any are laying over or laying over on top of each other. If so gently straighten them out with your fingers and keep looking until you are sure that's not the problem.
If that doesn't work you can then plug it in and gently tap around on the board and relay with a non conductive something or other (chopsticks are great) and see if any particular area causes the relay to click in. You may have a bad solder joint that finally gave up the ghost when you were poking around in there with the nozzle. If that works then touch up the joint and see if it works. If so, inspect for any others that look questionable and repeat the repair.
 
Thanks everybody, thanks OMGCat for the further input. As it happens, I detected sporadic signs of life last night. Turn it on: nothing. Turn it off & on again: the hiss of AM frequencies suddenly audible in the headphones. Then gone again. Aha!
I should add that I was tapping on the case, moving the amp, prodding the relay with a rubber-handled tool, etc.
This evening I reckon I might repeat the process I went through, of removing and then reconnecting the front panel. I will look around very carefully for bent-over components, disconnected stuff, etc. I thought I was careful, but we shall see. I will report here.
If that doesn't work, then it's the service manual and a multimeter, as Slimecity said.
I appreciate the input folks.
 
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