Sticky Speaker Relay Sony Receiver - How to fix?

msg

Hey guys,
working on an old Sony receiver I'm going to gift along with a set of old bookshelf speakers.

It's got some sticky speaker relays, I think. When I play music through it, sometimes only one channel comes in. If I tap or wiggle the relays, the other channel comes in.

If I wiggle the relays with music playing, the sounds will cut in and out, and sometimes affects the sound quality.

I was going to pull the board to have a look at the solder points beneath. I'm wondering whether they're intact. Is this the right path to resolution on this sort of thing? It also looks like I might be able to pop the cover off the relay? Like there's a small release tab at the bottom, near the board?

msg

The "loose" turned out to be just play in the cover/caps for the relays.

I took the opportunity to practice some soldering kung-fu, and desoldered them, took them off the board, popped the caps for inspection, cleaned them, shot them with some canned air to dry, put them back together and soldered back onto the board.

Still seems to cut in and out if I give them a good wiggle, but they seem to be working better.

They looked pretty clean inside, and not gunked up. What happens to these things?

I should have taken a photo, but in this design, there seems to be a vertical inductor at the back, with a switch tab sort of lapped over the top of the coil. When the switch is engaged, it pulls down the tab, which seems to pull in the contact legs to engage whichever speaker terminals are supposed to be active? Is that how these things work?

msg

I also cleaned the volume knob potentiometer, but it's one of those digital controls, not a real knob with stops. Is this still considered a potentiometer?

pkquat

If you can watch the relays with the caps off, you can see whether the contacts are closing. If they are physically closing then it is probably the contacts / pads. Sometimes the relay contacts / pads can get iffy with oxide or dirt. Sometimes the pads can wear out and the relay needs to be replaced. If you cleaned them with deoxit or similar, and it did not help, then if there is space, a little bit of fine sandpaper can help, but if the contacts are already worn, this can kill them. I don't know about these specific relay's only relays in general.

Its not a a real pot in a true variable resistor sense. Some volume knobs are a group of resistors with contacts that act like a pot. These have a stop and are more prone behaving like an old scratchy pot. Others are a group of contacts that tell another circuit to raise or lower the volume. These spin in circles. Sometimes these can have a dead spot, or don't read in certain positions, but are rarely scratchy. Both of these types can be usually be cleaned similar to a regular pot if the contacts are visible. The last type that I am aware of can spin in circles, however there are only two switches, or single double switch that picks up indents in the volume knob to tell which direction it is moving. This tells another circuit to raise or lower the volume. In this case the switch needs to be cleaned, if you can even see it or get to it to clean it.

msg

I missed this response, thank you for this information.

I think the cleaning fixed it, but I've had it parked again for a while and need to give it another test before I send it off.