Meat Plow wrote:
On Fri, 21 Nov 2008 14:36:33 -0500, "Gary L. Woodruff"
wrote:

Meat Plow wrote:
On Fri, 21 Nov 2008 10:22:25 -0500, "Gary L. Woodruff"
wrote:

Gary L. Woodruff wrote:
Howdy, I have a optimus 3170 that came to me with blown output
Transistors on one channel. I replaced the outputs with subs as
originals were not available. I also found a couple of open resistors,
and diodes. I now have power and audio in both channels at low volume
but get the protection relay clicking on and off on one channel when
volume is increased. I do not have a print and it would be very
difficult to check anything under power due to the configuration of heat
sinks and board layout. Please Help!


thanks, Gary

The original transistors were 2SC3281 and 2SA1302, they were replaced
with NTE2328 and NTE2329. The other components replaced were Q512, D520,
D522, R612, R614. any help would be greatly appreciated.
Thanks, Gary
My guess is DC shorted out whatever couples the protect circuit to the
output or there is too much DC offset on the repaired channel. Do some
voltage / current comparisons with the other channel provided it is ok
and not harboring some underlying problems too.
Thanks for the help. I measure Dc offset @ the speaker terminals and get
12.6 mv & 14.5 mv. The left channel is fine and does not trip
protection. My biggest problem is the way the hs mounts to the board the
foil side of the board is not accessible to probe. This makes
comparing voltages between the two channels impossible. If i could
locate a print it would make life much easier!

thanks, Gary


Yeah they can be a pain in the ass. A print would be nice for trouble
shooting in this case. I've done manufacturer warranty for the majors
including Radio Shack and know where your coming from in regards to
getting access to the foil side. At one time I had an HS jig that I
made to give the devices some sinking while allowing exposure to the
foil side on certain models.

You are hopefully not using your customer speakers but using known
good speakers and or a dummy load?



Thanks, I am using my bench speakers to test. (I have even swapped
channels just to be sure I didn't loose a speaker!).