I have a old Kenwood shaft mount KRC 1006 AM/FM/Cass. The station display lights up and shows the station number and other front displays light up so I know its getting power. Its setup for 2 front and 2 rear speakers but there is no sound at all from any. It worked for years, then I replaced the carpet and it worked for two rides but the third time when I started up I got no sound, not even static/white noise. Coincidence? For an easy replacement & install I just bought an identical receiver from ebay and that does the same thing.
I seriously doubt it could be a loose speaker wire because all 4 stopped at the same time. All 6 speaker wires, 2 power (main & memory) wires, one ground and one power antenna (not used) connect to the back of the receiver through one wiring harness connection.
Any idea what could cause all output to all 4 speakers, whether using radio or cassette, to stop at once?

Turn on the Volume :) JK Could possibly be many things, try connections, inputs and settings.

Was your battery recently disconnected? Possibly could have reset some things with your settings. Any mute function? Source-in setting? I noticed you said "old" Kenwood...might be time for a new Kenwood.

Was your battery recently disconnected? Possibly could have reset some things with your settings. Any mute function? Source-in setting? I noticed you said "old" Kenwood...might be time for a new Kenwood.
Just bought a "new to me Kenwood" (I wanted to keep shaft mount) and it does the same thing.

You need all speaker wires attached and working. If just one screws up, they all stop working.
I had this happen to my son when he was trying to hook up my 1979 pioneer. He wanted to hear what it sounded like when he only hooked up one side. He thought my vintage stereo was no good. I told him to be patient and finish the task at hand and it was ok.

I'm still stumped. I took the replacement stereo which doesn't work when attached to the wiring harness and bench tested it. It works on the bench. It works with only the fronts attached, only the rears attached and I even tried 1 speaker and it works.
I still cant understand what would make ALL 4 speakers go out all at once.

Found my problem and here it is if it ever happens to you.
After hours under my dash and doing all types of bench testing, I pulled up the passenger side sill plate cover where the wires to the rear speakers run. One of the four screws holding the plate down perfectly went between one pair of wires (I just replaced my carpet). It didn't sever any wires but just setup a short between the + & -. Apparently the receiver has an internal protect circuit which shut off all output. Once the screw was backed out all 4 speakers now function properly.:cool:
So now I have an extra receiver, totally tested, to sell.

Glad you found the problem.

Internal idiot proof circuitry! :D
Better to have no sound and be confused than to burn up the head unit amp.

Those are the kind of things which are almost impossible to diagnose on the internet.... You need to see the problem for yourself.

Glad you found it.
(Thanks for posting it for future rference!)