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The ultimate DIY? A Stax SRM-T2!


spritzer

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Wow this looks fantastic!!

Pity i wont be able to hear it when its finished

Getting very close now, only sockets, pots, and knob to finish. I am so happy about completing it, I'm reluctant to turn it on and deal with the potential to sour my mood if it is not perfect.

p7130299.jpg

p7130300.jpg

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Thanks all. Lil Knight said it is the first rev2 board up. I think a lot of the other people have to deal with case work, which I am so glad I did not.

I'll stick a scope on it to make sure there are no oscillations.

What design issues does the rev2 board set address / change?

Are the crossed resistors now uncrossed?

Is the DACT hole spacing footprint revised?

Is the R identifier(s) nomeclature fixed?

Are the Craig Sawyers capacitor additions implemented?

Others?

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More stupid questions,

What does one look for when hooking up a scope to the outputs of a stat amp / psu?

I would imagine no unwanted oscillations and a clean waveform?

What bandwidth scope is needed? Settings? Are special probe/input adapters needed for the high voltage?

Is a signal generator used in conjunction? What type of signal is injected at the inputs - 1kHz square wave?

It would be a big help to have an idea when it comes time to test this.

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What design issues does the rev2 board set address / change?

Are the crossed resistors now uncrossed?

Is the DACT hole spacing footprint revised?

Is the R identifier(s) nomeclature fixed?

Are the Craig Sawyers capacitor additions implemented?

Others?

Resistors are uncrossed

Dact hole spacing is now .1

Resistor labels fixed

Craig sawyers cap additions, and resistors moved.

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More stupid questions,

What does one look for when hooking up a scope to the outputs of a stat amp / psu?

I would imagine no unwanted oscillations and a clean waveform?

What bandwidth scope is needed? Settings? Are special probe/input adapters needed for the high voltage?

Is a signal generator used in conjunction? What type of signal is injected at the inputs - 1kHz square wave?

It would be a big help to have an idea when it comes time to test this.

I think this is all pretty subjective. For example, you could ask Andy what he did, as he was the most recent person that would have comparable experience and equipment to what you might have.

I really want a differential high voltage probe, namely a Tektronix P5200. That being siad, it's not like I've never floated the earth connection of my scope, I'm just not going to sit down and explain how to do something unsafe here...

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Back when oscilliscopes were actually really oscilliscopes, i saw

people lift the ground, put them in series with a high voltage isolation

transformer, chunks of plexiglass under the scope et all.

At zenith this was standard practice when working on the high voltage

sections. Complete with plastic knob extenders.

These days, oscilliscopes are nothing but highly computerized digital

things, and would likely completely blow up with any number of simple

mistakes.

Isolation circuits can be built that safely do this kind of thing.

But i really don't want to show people how to do this.

I don't want to be responsible for any dead bodies.

I have already been present when it has happened. TWICE.

Seriously.

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Woah.

Yeah, the plexi stuff, isn't that some sorta of safety standard? I remember reading about that somewhere, definitely before my time...

If I had to choose, I'd rather use an isolation transformer than ground lift the scope, but again best not to propagate safety risks.

But what I really want is a P5200 or someone to nick a circuit so I can DIY one :)

The other option is of course matched HV probes. Tek used to (still does?) sell probes this way. Then you do the invert and sum trick across the two channels. Not as cool as the above though, and cannot really be used on PSUs where you want a floating measurement.

Seriously though, ask Andy. He satisfied himself and whomever was working with him, so thats worth something I'd suspect.

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