Panasonic Home Theatre System

[roganty]

My dad was given a Panasonic SA-BTT755 by a mate who had had it sitting in his garage for a few years.

I help my dad set it up, but there was no sound coming from the speakers, we tested this by playing a DVD, there was a picture but no sound. The same was true with 'normal' TV.

All searches for no sound issues point to incorrect connection to the TV, but, we went into the settings for the home theatre system, and went through the test program and there was no sound coming from any of the speakers.

The connection with the TV worked, because when we changed from 'TV speaker' to 'External speaker' the home theatre system woke up and switched to the correct input.

We tried this with both the optical connection and the digital audio connection to no avail.

It is not the TV, because we reconnected the 1980's HiFi system, and got sound from the TV.

Is the unit dead, or is there something that we missed?

 

[Lucid]

If it has been sat in the garage for some time then damp could have got to it. You're fortunate that the head unit appears to work. What you need to do next is test whether the amp in the head unit is dead or whether it's a speaker problem.

The speaker cables will plug in to the head unit with colour coded plugs rather than bare wires. This is partly a convenience thing in that the back of the head unit doesn't have space for regular spring clip terminals. The speakers do seem to have spring clips though, so for convenience you could try the following test on each of the speakers directly.

Make up a little tester with a 1.5V battery and some wired (see image below)

Don't worry; 1.5V in to a speaker is safe as long as you only briefly make a connection. You don't need to be concerned about positive and negative either. All you're listening for is the sound of the speaker cones reacting to a temporary signal. The sound might startle you at first, but you're not doing any damage to the speaker. you're just making the voice coil move and hearing it. Just to reiterate, this is a brief momentary contact. You're not holding these wires on to the speaker terminals. Got that?

If you get a sort of clean 'crack' sound then that's good. If it sounds scratchy then that could be the voice coil got damp and deformed causing it to rub in the narrow gap inside the magnet. Where there's no sound then the speaker voice coil is seized. Before you ask, no, it can't work properly again if released. The coil former is like a bit of bog roll with some wire wrapped around it. The magnet gap it fits in to is a really small space. If the voice coil former gets just slightly oval then it and the coils it carries get wedged. You won't be able to make it circular again. The speaker drive unit is buggered.

I would test each speaker directly. If all good, I would then test with the speaker cables connected. This will take a little fiddling because you'll be dealing with the plug end of each speaker lead so you'll have to finangle the battery wires to make contact. If all the speakers work with the wires attached then you know it's a head unit problem.

There's a manual for the 755 here: Preparing Cables And Making Connection - Panasonic SC-BTT755 Operating Instructions Manual [Page 13] | ManualsLib

 

[roganty]

@Lucid thanks for the information, when I'm up there in the next day or two I'll try what you suggested.

 

[roganty]

@Lucid I have tested all of the speakers and I got a noise out of all of them. So it seems like it is a problem with the head unit.

I've got the unit with me so I can see if I can get it fixed.