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briskly · 4th Nov 2011, 6:57 pm

I made a lash-up on a breadboard using a BC327 and BC337 for Q1 and Q2 and a 220R variable in line with the 39R and a new BC109C for Q1, as kindly suggested. It didn't work - 5.5V at common emitter point, zero current with no effect on changing the 220R variable. I was about to give up but then tried swapping the BC109 for a BC237. Bingo! 3.1V at the common emitter. 2.8V at the diode, 2.5mA quiescent.It seems to amplify too. I'll now try to wire it up on the original board. It seems using a BC109 was holding things up - this was the 3rd I'd used - anyone have any ideas why? I'm positive the connections were right.

Meanwhile, I'm using an LM386N-4 taped to the back. It seems pretty good at low levels, but distorts a bit a high volume (I would guess around 200mW). It seems to give less distortion than an N-1 I tried though. Are these chips well known for distortion at higher levels?

Thanks agian for all the help,

Andrew

4th Nov 2011, 6:57 pm	#75
briskly Retired Dormant Member Join Date: Oct 2010 Location: Chelmsford, Essex, UK. Posts: 98	Re: Toshiba IC70 I made a lash-up on a breadboard using a BC327 and BC337 for Q1 and Q2 and a 220R variable in line with the 39R and a new BC109C for Q1, as kindly suggested. It didn't work - 5.5V at common emitter point, zero current with no effect on changing the 220R variable. I was about to give up but then tried swapping the BC109 for a BC237. Bingo! 3.1V at the common emitter. 2.8V at the diode, 2.5mA quiescent.It seems to amplify too. I'll now try to wire it up on the original board. It seems using a BC109 was holding things up - this was the 3rd I'd used - anyone have any ideas why? I'm positive the connections were right. Meanwhile, I'm using an LM386N-4 taped to the back. It seems pretty good at low levels, but distorts a bit a high volume (I would guess around 200mW). It seems to give less distortion than an N-1 I tried though. Are these chips well known for distortion at higher levels? Thanks agian for all the help, Andrew