Strange Issue with HTM-200 SEs

[Sphene]

So, this could be (probably is) my receiver, but I was wondering if anyone has any insight.

I've got a pair of HTM-200 SEs powered by a Panasonic SA-HE75 receiver. The receiver was a hand-me-down from my parents when they upgraded, and previously powered a very large pair of speakers (three-ways with 12" woofers) and then eventually a full 5.0 setup for around a decade with no issues.

Anyway, the malfunction is thus: the HTM-200 SEs output no sound whatsoever every time the receiver is powered up, until I exceed a certain volume level on the receiver. After that point, the speakers play fine at all volume levels until the unit is restarted. I don't have other passive speakers to test with, but this occurs no matter which channel the speakers are connected to and no matter the settings (high-pass filter cutoff or "speaker size").

Any idea what's going on? I'm planning to upgrade to a modern AVR when I have the funds anyway, but I'm just curious.

[Beave]

Which input(s) on the receiver have you tried? Different analog inputs? Have you tried any of the digital inputs? Have you tried the FM radio?

If they all do it, it's probably a transistor in the power amp section going bad, or something in the volume control itself (not sure if this model uses potentiometers or an IC for volume control).

No, wait, if it's happening with both speakers, it's probably not a bad transistor, as that would only affect one speaker output.

So maybe the volume control is a potentiometer and that's the culprit - maybe a dirty connection inside it.

[Sphene]

It happens with all inputs, including the test mode and the tuner which are both built-in sources of audio.

[Beave]

OK, thanks. Then I'm doubling down on my guess that it's the volume control (but that's still just a guess)! :-)

[Beave]

I found the service manual online. It does appear to use a potentiometer for volume control, so that might be it. But it's hard/impossible to know for sure without opening it up and tracing signals with an oscilloscope.

If you're handy with electronics, you could open it up, and take apart the volume control pot and clean it.

Edit: No, my mistake, I posted too quickly. It has a digitally-controlled analog volume control IC.

After that, there are muting circuits external to the volume control IC, then the power amps.

Could be the muting circuits or the control line for them coming from the microcontroller.

So guessing is getting me nowhere. You'd need an oscilliscope to follow an audio signal to figure out where the problem arises.

[Sphene]

Cool. I am handy with electronics, but not to the "own my own oscilloscope" level. I'll live with it until I settle on and budget for a new AVR

[Beave]

What happens if you hit the 'mute' button once or twice on the remote when you first power on the receiver and it's stuck in the mode where it's not outputting sound?

See if that brings the audio back before you turn up the volume to bring it back.

Mostly just curious at this point...! :-)

[Beave]

Another question: When you have it working, and then turn it off and then back on, does the volume level setting indicated on the front panel stay the same level as it was when you turned it off? Or does it revert back to a really low level indicated on the front?

[Sphene]

The receiver remembers the volume level. If it's high enough when it's turned on, it doesn't have the issue at all. Mute/unmute doesn't resolve it, just turning the volume up (past "-39") while there is output.

[Beave]

That's really weird. Since it seems to happen consistently and with a consistent cutoff of -39, my guess is that the volume control IC itself has gone bad internally.