powered monitor troubleshooting

[dubathonic]

hi all, first post. apologies if this has been discussed elsewhere, didn't see this specific issue after an admittedly cursory search, so please point me to the relevant thread if it has.

my issue:
i have a set of powered studio monitors (yamaha hs80m) and one of them keeps cutting out after a brief burst of static. i can solve the problem temporarily with a power recycle, but fyi the static burst usually happens again when i turn it off and on. the monitor works fine again for awhile, usually a few minutes to an hour, then i have to repeat the procedure.

i expect some internal component is dying a slow death. i've confirmed it's the speaker itself, not my computer or soundcard.

any thoughts on what to do?

thanks in advance!

[g1]

schematic/service manual available here:
YAMAHA HS80M HS50M Service Manual free download, schematics, eeprom, repair info for electronics

[Enzo]

It is an amp and speaker that cuts out. You can get sound back by cycling power. Next time it stops making sound, ball up your fist and whack the top of it hard. Does that make the sound come back? And conversely, when it is working, does whacking it make the sound go away? or at least crackle or something? Whacking exposes loose connections inside. They may be actual loose wires, or they may be cracked solder joints.

When it quits, do any power or indicator lights go out, or do they stay on? Does that little logo at the bottom light up?

When it quits, spread your fingers and gently push the speaker cone inwards to move it. Does that make sound come back?

This is a two way speaker, so when it quits, do both drivers go silent, or only the woofer or only the tweeter? A bad woofer would not make a tweeter stop working. Especially since each has its own amplifier circuit.

When it quits, does turning the level control help any? And also flip those little switches up and down a time or two to see that they are not involved.
I assume you have two of them, so swap speakers. Pull the plug from the input on the left one and plug it in the right, and vice versa. We need to verify the signal is not the issue.