Harman Kardon 330B questions

Archived from groups: sci.electronics.repair,rec.audio.tech (More info?)

On 11 Jul 2004 22:48:44 -0700, nothing40@yahoo.com (Nothing40) wrote:

>Hey Gang,
>
> I've got a HK 330B here,with blown outputs (all 4 were 2SC1107's)
>which I've reaplaced with ECG/NTE152 for now.(the 2SC1107 crosses to
>ECG/NTE186,but the 186 seems a little underspec'd to me?). Any
>suggestions to a good '1107 sub to use would also be appreciated.
>I'm wondering if anyone knows/has the bias proceure for this amp?
>Theres two pots in each channel (3K and 100K,I think)..I'm thinking
>one is bias adj.,and one is DC offset adj.? Any ideas? Would anyone
>happen to have a schematic for this reciever?

Blown outputs on that unit were VERY common. The 152 is a decent replacement to
use.

I've got the schematic for the 330A and I am quite sure the 330B was also a
single ended supply output design. The 330C was the first direct coupled amp in
the 330 receiver series.

The 300K pot should be the drive balance pot, which sets the drive equally to
both halves of the outputs, I always set that by watching the output signal for
a sine wave, with an 8 ohm load, and setting it for equal clipping on the top
and bottom of the output when clipping started. The other pot will be the bias,
and it can be set by watching the output into a load with a very small signal
while I fed it a sine wave and turned up the bias until the crossover notch
went away. I uses an AC ampmeter on the supply and could see the current
increase.

Hope that helps.