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Old 26th June 2013, 08:40 PM   #1
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Location: Syracuse NY
Default Restoring a Realistic STA-85

Though this old receiver seems clean and otherwise works well, it has one big problem. The ON-OFF switch is a 2-part wafer switch one section selects speakers and the other section is ON-OFF (power).

The power switch arcs internally and causes noise and flickering lights. I'm not sure if I caqnb get inside the sealed wafer for the power contacts, but I did spray (maybe an opening) with DeOxit, without results. Seems there is a "surge supressor" soldered to the top of that switch, but it does not good I exercised the switch without and with power applied (wall plug) and the arcing got worse. I think those old contacts are too pitted to be used. OK, so I will bridge that switch wafer's contacts.

Problem with that idea is I'm not sure I found the proper contacts to bridge. I've measured some AC voltages around the "surge supressor" and those seem to be about 120 v when the unit is turned off. When the unit is turned "on" the voltage is variable while the lights flash, until in a few seconds they stop flashing and then the voltage is zero across the supressor/switch. Seems to me that the varying voltage is the voltmeter's averaging of the switch's contact flashing problem. And when the arcing settled down the voltage settles to zero, or near zero, then this is the point to bridge the switch.

At least I'm going to try it. Good luck to me.

Thanks for your time and suggestions.

My proposed solution is to bridge

Last edited by FredsBands; 28th June 2013 at 01:47 AM. Reason: typos
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Old 26th June 2013, 09:26 PM   #2
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Change the switch. If you don't know where to look for that type of switch, ebay and Gumtree are useful.
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Old 28th June 2013, 01:46 AM   #3
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Join Date: Jun 2013
Location: Syracuse NY
I found info on the switch, but don't know if it's available now. Anyhow the OEM switch is not a long term solution. I looked for a place on the chassis front and back where a separate switch could be placed, nothing. Unless I want to remove the funtionality of an existing chassis protrusion, which i don't.

BTW the power switch bridging worked, but I can't say the same for the surge supression device initially installed across the power switch in the receiver. There are several devices more sophisticated than an RC series network to do that. Whatever RadioShack suppliers put in here was completely inadequate. I could see lots of arcing inside the plastic switch cover when I turned out the room lights, even though there seems no way to disassemble the switch. This unit will now be switched on thru a power strip.
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Old Today, 07:40 AM   #4
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Join Date: Feb 2015
Default STA-85 Power Switch

FredsBands - Any info on where you found a replacement switch? I have the same receiver and the same shorting problem. This is the second post I've seen for the issue. THX Wundbar
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