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I've got a 5.1 home cinema setup with a yamaha RX-v685 and a BK gemini II subwoofer (they are physically fairly far apart). it sounds good when its working, however often when I power on the sub it appears fine (display comes on and goes through the sequence), but doesn't actually play any sound (and neither does the little graphic eq lights light up as sound comes in). I'm using the low-level input (ie the proper sub feed) with the crossover in the sub wound right off.
what is odd is.. when its not working, if I thump the top of the sub a few times, it starts working for the rest of the evening.
now, if it was a dodgy connection (ie a wire not attached properly) my expectation would be that it might work when I thumped it but then stop straight after (as the connection closes, then opens again).. or that the sound would be patchy, but neither of those happen.
what else might it be? I don't really know much about solid state components - can resistors (or similar) start working only after a bump? I'm ok with doing some amature hacking but I'm not super good at soldering (on larger things I'm ok, but detail work suffers) - so I'm wondering if its just doomed to the tip (which is a shame, as its a nice, not in-expensive sub)..
That sounds distinctly like a dry joint to me - that’s what us electronics people call a solder joint that was poorly made and has subsequently mechanically fractured. Not unreasonable with the vibration in a sub enclosure.
But that’s just a guess. Perhaps you can find a local old school hi fi repair type to investigate. As you say, probably worth repairing. If it is a solder joint it will be easily repaired but the skill is in finding the failed joint.
thanks for the suggestion 🙂
so (and this is my lack of knowledge) - why would a dry joint fail for hours before a thump, then work for hours after a thump, then revert to failed again - wouldn't a dry joint be failed, then work whilst the vibration is still wobbling things around, then when it all settles its 'broken' again - I'd expect (as I don't know this stuff) the 'working' state would only last a second or 2?
You have checked that this is not the connecting cable or the connectors thereon?
If there is an alternative input to the sub try that with an appropriate source? If not, try an alternative source and cable into the low-level input with the sub volume set low. That might help determine whether the problem is in the connector, the low-level input section, or deeper in the gubbins.
Does the sub power up correctly? I have one that has 'auto-on' - ie 'wake up when you get a signal'. I got foxed when it wouldn't power up sometimes. Turns out, obviously, it would only power up when it got a signal and some things didn't spur my RX-V381 into 5.1 mode but 5.0 mode. When I sorted that out I then found that the sub cutoff that the auto-setup had picked was very low and so there wasn't always a signal to turn it on or make sound out of - I raised the crossover frequency in the receiver's settings and then used the sub's crossover and volume knob to tune it to fit in with my floor standers.
The effects of beating the sub could be coincidental hence my 'have you...' waffle but failing that I agree with @goldfish24 : could be a dry joint. I just like to try all the other, 'easy', options before opening something up, inspecting, and then getting the multimeter out.
I have tried it with a different source & cable (my mobile, standard aux cable) - but I will re check. It does have stereo in, and it appears (but again I will check) to happen on both inputs (I assume it bridges them to mono fairly early on in the flow anyway)
it appears to power on fine, there's no auto on-off, and there is a 'start display' and then a 'running display' - it goes through both (very basic display).