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City: Dover, OH
I picked up a pair of 70's Sylvania speakers today for $20 at the local flea market. Although they aren't in prefect condition, the will still pair well with my dumpster find Realistic. Both speakers are supposed to be 8 ohms, which is perfect for about any 70s or even 60's stereo. They also have two ways to hook up, either RCA connector or two screw terminals on a removable panel on the back. I ohm checked both speakers on the terminals first and one came to 8.1 and the other 7.8/7.9, close enough! I did the same on the RCA connectors and this is where it got funky. The speaker that rated 7.8/7.9 stayed the same, while the other came up at 22-23 ohms each time I checked. Took some fine grained sand paper and cleaned the connectors, but still get the same. I pulled the little cover and can see two Mallory capacitors, a resistor, and a choke all connected right to the connectors and cover. Everything runs through the same components, so what gives?
Note: The issue only happens through the RCA connector.
No matter where you go, there you are.
(This post was last modified: 06-30-2018, 04:19 PM by
Jayce.)
Posts: 2,026
Threads: 367
Joined: Jun 2010
City: Dover, OH
I figured out the problem. It has to do with how the RCA connectors on the speaker are designed and the insulation or foam that is inside the speaker cabinets. Basically, the center pin or positive pin on the RCA connector has a soldered connection to the wire. The outer barrel or negative side depends totally on crimped connections. It is flared down onto a medium sized terminal connector which then has the wired crimped onto it. I found the connection between that connector and wire was fine, it was the connection between the outer barrel of the RCA connector and the terminal connector that was at fault. The foam had caused an odd corrosion to form and it was building up resistance. I cleaned as best I could and got it down to 9 ohms, then finally decided to run a small bead of solder around the cleaned spot I could reach. That got me down to the 8.1 ohms measured across the screw terminals.
I ended up re-flowing the solder on the positive connection then took apart the second speaker and did the same as it was also showing some issues. Now both are just about right!
No matter where you go, there you are.