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Old 19th January 2003, 09:22 PM   #21
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Hi John,

Ok, SPST in series with 300b filament wire. Here is a link to a .MPG movie file: It's 1.5Mbytes

http://home.attbi.com/~laustin56/mov1.MPG

You can see when I turn the switch off the B+ climbs and then when I turn the switch back on the B+ stablizes back to normal.

So what do you think?
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Old 19th January 2003, 09:22 PM   #22
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Default THE USUAL SUSPECT.

Hi John,

Suspecting a faulty diode?

That peak on the scope sure isn't healthy.

Cheers and good luck with the "patient",
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Old 19th January 2003, 09:37 PM   #23
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John,

I did the switch before your response.

I assumed I was doing the right thing. I will now solder the switch to one of the transformer wires coming from the transformer to the 300b rectifier bridge and post another movie.
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Old 19th January 2003, 09:38 PM   #24
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Frank,

It's not the peak just past the posotive cycle I'm worried about at the moment, it's the fast + and - spikes.
These, I suspect are recovery spikes from the Schottky diodes in Pauls heater bridge.
I attempted to prove this by asking him to disconnect the bridge input. I expected the spikes to die immediately, but they go slowly. That is what I'd expect if he'd dissed the heater wire.

Any idea's?

Paul, it is the input to the bridge you're cutting?

Cheers,
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Old 19th January 2003, 09:39 PM   #25
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Default Ha, ha

Paul,

I saw your reply just as I posted.
Let's see.

Cheers,
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Old 19th January 2003, 09:51 PM   #26
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Default Any idea's?

Hi,

Don't I always say that polyprops are too good for filtering?

John, what you're seeing on the scope can be snubbed away with the lousiest,cheapest caps really.

All that assuming that's where the problem is,of course.

Cheers and bring on the movie,
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Old 19th January 2003, 09:54 PM   #27
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Frank,

Ther's more than one problem here. One at a time.

I like to understand a problem, before I try and fix it.
And if it is; I'll recommend your polyprops.

Cheers,
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Old 19th January 2003, 10:52 PM   #28
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Hi Again,

Yes, we just missed each other on the internet super highway with our last posts.

Here is a movie (1.3Mb) with the switch wired in series with only one of the transformer leads going into the 300b rectifier circuit.

.http://home.attbi.com/~laustin56/mov1.MPG

I cycled the switch twice. The switch is "on" at the start of the movie.

I hope this is it. I am running out of solder moving that damn switch all over the place. ( Just Kidding )
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Old 19th January 2003, 11:37 PM   #29
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Hi Paul,

It's not perfectly clear, but it looks as if the spikes go when thr switch is off.
If that is the case, then Frank's idea of bypassing each Schottky diode with a polyprop cap seems a good idea.
As for value, I'm not sure in high current circuits.
Frank, no doubt has a figure on the tip of his tongue.

Cheers,
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Old 19th January 2003, 11:53 PM   #30
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Default I AM NOT CONVINCED.

Hi,

Handing me the hot potato?

From the mpeg files I watched in a loop I am not at all convinced that's where the problem stems from.

However it won't hurt to try a bit of noise killing...

Paul,

No need for polyprops,a simple polyester cap + resistor would do.
Make a network consisting of a 1K/1W and 0.100 mF/100V cap in series and wire it across each diode.

I notice other irregulaties on the sine waves though...no idea where those come from other then what I said before, polyprop caps let pass too much crap from the mains.
That's why I advise an ordinary electrolytic cap as the first filter cap anyway.

Cheers,
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