Dimmer Circuit for Old Trannies

[silverfox]

Can't recall how I ended up conjuring this circuit but I'm considering building it and have some questions. The PT for the "High Gain Build" is designed for a lower primary voltage. Rather than use the buck method of putting one of the 6.3 volt secondaries in series with the primary to reduce the voltage- as I believe both heater windings will be required; My questions are: Will this circuit put out too much RF for audio applications even though It has a filter section; And, it seems to me the power rating of the Diac-Triac and inductor only need be equal to the amount of power dropped to lower the voltage, with the usual margin for surges, say 25%.

Regards,

silverfox.

[PRR]

That works lousy for true AC motors (smoke). I would expect a transformer to object strenuously.

And at a glance, "nothing will happen" until the wave is half cut-off, because our rectifiers open only for a small period near the peak. Yes, from there down it "may work", though the steep spikes and kick-backs may be brutal or even make it not-work.

The triac MUST carry full current and block full voltage. I can't see anything less than 200V at several Amps. Much more may be needed to cover spikes and surges. I don't think cheaping-out is wise.

Start with a cheap transformer and be sure to load with a rectifier cap and load resistor.

[silverfox]

Now that the power's back on and the Internet is back up I can say: I only have a basic understanding of the posted circuit, more now. The author claimed to have dealt with the transients but likely not to a level for audio applications- Motor circuit. Would changing the trigger level and dealing with RF spikes fix it or is this just a bad solution? The more I think of it, this is a bad solution due to the nature of SCR switching transients into an inductive load.

Does it work better to assume the use of the transformer as is, no Buck or other means of voltage lowering scheme and address the filament voltage through the use of DC heaters and a regulator, (the 5 amp linear regulator circuit of old). What I'm after is a cheap way to recycle old PT Iron. One of the largest costs in amp building and I hate to just toss it... And now it's starting to sound like some sort of experimental amp if I ever sold it...

Thanks again for the FB,

silverfox.

[silverfox]

So I was in the Thrift Store today and spotted one of those AC Voltage Converters on the shelf and got to thinking- I wonder how that works? Can it be hacked to drop less voltage? Iis it an alternative to the circuit posted at the beginning of this thread? Got a price and immediately had a feeling of regret at having purchased another little widget device but, cheered at the thought of at least getting $2.00 worth of enjoyment out of cracking it open at home. What did I find inside? An inductor, a Triac, Diac and a couple of supporting components. One difference between the circuit posted is the inductor being rather significantly larger then the 39 uH specified in the design above. It is also a 3 wire inductor.

The next thing I did was some basic research and ended up reading several of the 195 on-line reviews at Amazon.com. They went something like this: Didn't work; Mine burnt up; It killed my razor charger; Love it. I used it in London to power a blow dryer and it worked great. Ect... The only positive reviews besides the hair dryer read suspiciously like company reviews but I didn't look to see if any were verified purchases. To make a long story short, upon opening it up I found carbon tracks from most likely the mini pot that vaporized. Oh and it's rated at: 800 and 1600 watts conversion power. Not suited to audio, computer or solid state electronics. Okay, 1600 Watts! As in more then 10 amps? There is likely the potential for a Hotel Room fire contained in this little box.

Sometime soon, I intend to remove the inductor and see if it's possible to use it as a voltage drop component. I only need to drop about 10 volts to get the 6.3 VAC for the heaters in my project. All in all I'm rapidly concluding there really isn't much sense in re-using the older 110 power transformers for anything other than research purposes- With a Variac...

Well, I did manage to get my moneys worth...

Silverfox.

[sluckey]

A switching device like an SCR or TRIAC will make your amp sound like a buzz saw. Set an amp up near a lamp dimmer and play with the dimmer brightness and you'll see what I mean.