"170watt" wrote in message
...
I have a Harman Kardon SUBTS15 subwoofer with problems. I would like to
try fixing it myself. I have basic troubleshooting experience (including
soldering skills), but I don’t know what I should next (besides tossing
it).
Here’s what it does, and what doesn’t.
When I power it up, the front led lights amber, and after a couple of
seconds turns blue (and stays blue). At that moment you can hear a loud
thump (couple of thumps actually). While on, there is no sound coming from
the speaker. If you feed a signal (at the line level, with test tone from
receiver), you can hear it extremely faint (the volume does not modify
that). When powered down, another thump.
What I checked: the relay works both when turning on and off (both times
coincide with the thumps). The +/- 15 V are both OK. At the visual
inspection, there is some discoloration (darkened color) of resistor R146
and 149 (especially 146 that looks a bit burned) but both test correctly
330 ohms. The PCB around them also looks a bit darkened.
Any idea where to look for? I doubt that the issue comes from the
“darkened” area. The troubleshooting flow chart does not help, as the led
does not turn red or green (only blue, and stays blue).


The full service manual is available for free here

http://elektrotanya.com/harman_kardo.../download.html

If you've never used Elektrotanya before, first left-click on the thumbnail.
That will open it into a bigger window. Then use the "X" on that window to
close it. Now look in the text below the thumbnail, and you should see a
tiny and underlined "processing" in the middle of the text. Wait a few
seconds, and this will change to an underlined "Get Manual" Now left-click
on this, and it will open a link to the manual PDF.

Do not click on any large buttons on the site that say "Download", as these
just take you to helper software sites. You don't need to be a 'member' or
to log in, although this limits you to two downloads per day. The site is
'clean' and in a long time now of using it, I've never had any issues.

The schematic looks quite straightforward, and there is a good block
diagram, so you shouldn't have any problem tracing what is amiss with it.

Arfa