31-07-2012, 04:50 PM
Well I got the set more or less done today so I gave it a first taste of power. I used the valves that were in it originally (except the 25L6) and I left the 50uF caps in. Nothing went bang which is always a plus for me! Some serious noise comes from the speaker even with no volume so I'd say more work is needed on the power supply. On a more positive note there does seem to be RF when I turn the volume up. However, the dropper resistors get seriously hot after just a few minutes so my current solution will have to be revised.
I think I'll tack in the 100uF caps and see if the noise diminishes.
With a 110V supply the B+ measures 80V versus the 105V on the drawing. The bias voltage on R12 is about -15v versus the -7.8V on the diagram. The AC volts after the dropper is just under 70V which seems pretty close to what I was shooting for so I suspect the heater chain current is close to OK.
So, plenty to keep me pondering. Getting an effective dropper setup in such a confined space would seem to be the main challenge at this point.
I have to say I've come to like this little set after all the effort gone into it so far.
Cheers, John
I think I'll tack in the 100uF caps and see if the noise diminishes.
With a 110V supply the B+ measures 80V versus the 105V on the drawing. The bias voltage on R12 is about -15v versus the -7.8V on the diagram. The AC volts after the dropper is just under 70V which seems pretty close to what I was shooting for so I suspect the heater chain current is close to OK.
So, plenty to keep me pondering. Getting an effective dropper setup in such a confined space would seem to be the main challenge at this point.
I have to say I've come to like this little set after all the effort gone into it so far.
Cheers, John
Time flies like an arrow, fruitflies like a banana!
