audio-talk

Yeah I'm getting that, but the 'scope doesn't lie, most of the noise is coming down the supply wires, which in turn come from SMPS modules.

Also I mustn't forget the sig gen is quite noisy too, hence I mostly want to run it at 1 Volt output or higher.

Also I think the 'scope is picking up RF from the general environment, e.g. there's a lamp on the table with a low-energy bulb in it. Might have to enable the low-pass flter function.

Onwards!

Playing with the new power supply, on the heater circuit:
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Right so - made the filter 'board'. TBH this is better than my original idea (still haven't found those chokes )
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EDIT: ^ One filter (15 mH) for HT, t'other (4.5 mH) for the heater supply. Caps are 100 nF.

Oh and I was right, one of the valves is duff. So at the mo it's using the good Tungsram, and the spare, which is a Siemens. Both 2nd hand used. So both channels work well now, albeit a slight difference in gain. Not a matched pair.

OK so the above supply input filters seem to have got a handle on the noise:
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Also I was sure there's some of bandwidth filter on the 'scope - and there is - second menu item, "BW Limit", drops 100 MHz to 20 MHz...
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Cleans things up quite a bit.

According to the oscilloscope, the rise time (square wave @ 1kHz) is 3.6 µs. As low as that.

Don't know what the sig gen's is, forgot to check
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Aaa-and, according to the 'scope, the OPT ringing freq. is 73.53 kHz.
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I like this 'scope!
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Shot of the working PSU's...
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The heater supply is a netbook PSU...
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Making ack-chewl noises!!
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Well done that man!

This is after a power cut from 4:45 pm until about 7:40.

And I'd just screwed on the bottom plate and was going to plug it all together for some moosik.

More pix:
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Have you noticed the front panel push button switch is replaced with a green neon. The switch packed up - stayed permanently on regardless whether in or out. Took it part, put it back together, now works again.

Cressy Snr wrote: ↑Wed Oct 10, 2018 8:42 pm Well done that man!

Ta muchly ever so very much.

New schematic:
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The second case has arrived so I did a Herculean bit of building today (meaning, did the whole job in one afternoon and evening) and so now have a matching PSU unit.
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Innards of the SMPS:
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