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Old 27th January 2013, 03:40 PM   #1
tg3 is offline tg3  United States
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Default Help with Rotel stereo amp

My Rotel RA-820BX4 integrated amp has developed a noisy & intermittent Function (input) switch. Jiggling the switch usually fixes the problem briefly. I have treated the switch with tuner cleaner from the Rat Shack, but that only helped for several weeks. The switch is soldered to the main circuit board, so it's replacement would be difficult, even if I could find the part.

Any suggestion greatly appreciated.
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Old 27th January 2013, 04:19 PM   #2
jaycee is offline jaycee  United Kingdom
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The only cure will be replacement if cleaning has failed.
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Old 27th January 2013, 04:34 PM   #3
DUG is offline DUG  Canada
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Or extreme measure:

Take apart switch and repair.

(Just a thought.)

(Not recommended for power switches)

jaycee has the best answer though: replace
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Old 27th January 2013, 04:44 PM   #4
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These appear to be rotary actuated slider switches, like countless Japanese design amplifiers out there. The main issues with these, as I encountered them were:

First, mechanical wear in the helical drive mechanism (uncertain linear position alignment of the contacts, which are in parallel alignment with the knob axis)

The second is the sliding contact condition, which starts out as silver plated alloy but the plating eventually wears away and the metal becomes oxidised etc. The wear also means the contact pressure is lower and this makes it worse.

I think it is likely to be time well spent, inspecting the contact alignment (yes, under that steel cover) to eliminate the possibility that the problem isn't so much contact condition as the position. Without knowing the construction, I can't advise how to go about this in detail but if you are halfway adept at playing with mechanical assemblies, you should be successful, assuming what you find is fixable.

There aren't really a lot of options here unless you find a donor wreck amplifier in bettter condition or you have some luck contacting Rotel service agents. This great site, also the source of free schematics, may get you started looking
http://www.bwgroupsupport.com/manuals/rotel-service
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Old 28th January 2013, 12:19 AM   #5
nattawa is offline nattawa  Canada
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If your ever take the PCB out, you want to go through the solder joints and touch up solder any ones that have developed a crack.
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Old 28th January 2013, 12:27 AM   #6
sreten is offline sreten  United Kingdom
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Hi,

Yes, resoldering all the switch connections to the board is worth a try,

rgds, sreten.
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Old 28th January 2013, 04:23 AM   #7
tg3 is offline tg3  United States
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Thanks to all who have replied.

Ian, your comments on the switch construction were most helpful.

image.jpg

Here is the area in question. The volume control is furthest to the left. Defective switch is next, neatly tucked beneath two cable assemblies. The switch housing is bolted to the front sub panel. Short legs fit into slots on the printed circuit board (hopefully not soldered!). The end of the switch shaft is visible in the little well in the casing top. The shaft is secured by a lock washer. When the switch is turned, the shaft and washer rotate, which moves the slider partially visible at the bottom of the well.

To any who have been here before. If I unbolt enough things, will I be able to remove the switch housing? If so, I might be able to effect a repair.

Resoldering the switch pins on the circuit board is a great suggestion. If I get that far I will give it a try.
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Last edited by tg3; 28th January 2013 at 04:27 AM.
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Old 28th January 2013, 05:13 AM   #8
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Looking at the way the switch housings are mounted to the chassis and the knob shafts are anchored in that recessed tab in the switch housing, you are going to have to remove the board anyway, as Nattawa indicates.

Removing the housing would not be simple. It's apparently soldered in too, like the contacts. That is only part of it, as you still may need to release the shaft to permit the case to come away from switch. Don't disassemble if there is chance of determining whether there is excess play in the shaft movement first. That will tell you if there is any future in this effort.
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