Amp speaker connection problem

[ellal]

Got an old technics amp - the same one as here

It's developed a new problem as regards the speaker connections.

I lost the left channel so did the usual of changing speakers around and swapping cables etc.
The sound comes back on if I don't clamp the wires, but drops out after a while so I have to wiggle the cables again.
The strange thing is it does the same thing irrespective of whether I use Speaker A or Speaker B connections.

I know some may say bin it, but having adjusted the tone controls it still sounds (to me) really good with my setup.

So any suggestions as to where I start with trying to solve the speaker connection problem?

 

[Wayners]

Make sure everything is unplugged. No mains power.
Buy a cheap multi meter.
Continuity test each wire to speaker connector and shake wire a bit.
If wire is good you hear a continuous sound.

Use to find the break in connection if you have one.

Next pop open case on amp and test the connectors. Should get a continuous sound again. All simple stuff. Loads on YouTube showing you how.

Look up continuity test

 

[ellal]

Cheers.

Got a continuity meter and tested the cables before swapping over.
Not keen on going inside the case, but will have to.

 

[jj4091]

Put some de-oxit in the terminals and try again.

 

[flameport]

So any suggestions as to where I start with trying to solve the speaker connection problem?

The terminals themselves
Where those terminals connect to the circuit board inside
The switch(es) that select between speakers A and B.
The protection relay which switches the speakers on after a short delay.

 

[Lucid]

The terminals themselves
Where those terminals connect to the circuit board inside
The switch(es) that select between speakers A and B.
The protection relay which switches the speakers on after a short delay.

This ^

Speakers A and Speakers B connect to the same amp channel internally. There's only one amplifier module, so A and B are parallel connections to it. It's likely you have a dry joint - a solder connection that has gone intermittent because there's a crack in the solder. The fact that you can restore signal by wiggling the wires would suggest that the problem is at the speaker connections inside the amp. Simply reflowing the solder may well fix this.

 

[Tigercubrider]

Dry joints usually look a little dull compared to others.
Cleaning the connectors doesn’t hurt.
Chopping an inch of the speaker cables and resending up the contacts won’t be a bad idea

 

[ellal]

This ^

Speakers A and Speakers B connect to the same amp channel internally. There's only one amplifier module, so A and B are parallel connections to it. It's likely you have a dry joint - a solder connection that has gone intermittent because there's a crack in the solder. The fact that you can restore signal by wiggling the wires would suggest that the problem is at the speaker connections inside the amp. Simply reflowing the solder may well fix this.

That could explain why I got the same problem on A and B.
I naively assumed they were separate circuits, but reading up on it I should have sussed there was only one amp module given the listed drop in impedance when using both channels.

So a bright light, steady hand, and a new fine tip for my soldering iron it seems is now required!