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Power Brake Schematic Online

9/3/1998 11:22 PM
GVB	Power Brake Schematic Online I finished the schematic for the Power Brake finally. I only gave it a quick once over, but hopefully everything is OK. Now that it's drawn up properly and not a jumbled mess like the original schematic (from Marshall), it's pretty easy to understand. The link is below, and here is a brief explanation of the circuit as I understand it. The Power Brake is basically a reactive load, and is almost identical to the electrical equivalent of a speaker found in RDH4. The one variation is that R2 is not in parallel with C1 and L2, and connects to the bridge that drives the fan. I think this may actually be an error on the schematic I have, so perhaps someone with a Power Brake could check for us. I think R2 should connect to both sides of C1. The "multi tap choke" I described in other posts works exactly like an autotransformer. As a quick review an AT (autotransformer), is basically two inductors stacked on top of each other and are coupled magnetically. If the wiper is placed directly in the center, it splits the inductor into two. If you place 240VAC between the top and the bottom and then tap a signal from the centertap to either end you will get half the voltage out. Buy moving the center tap, you will vary the voltage between the center tap and each end. Instead of a "wiper" on the transformer, it has multiple taps that can be used as the center tap, and these are switched through S1b and S1a. S1a controls the signal flowing to the reactive load, and S1b the signal to the speaker. The signal and the reactive load are placed across the autotransformer, and the output to the speaker is taken from the centertap to one end of the transformer. Whew! That's basically how it works, but of course there are few extra things thrown in. A "setting" for 8 and 16 ohms, and the ability bypass the box (0db), and to use it as a load box. I plotted the impedance of the reactive load, and its not really close to any Celestion I've seen, so there is room for improvement. Here the link to the schematic: http://www.oln.com/bus/b13/powerbr.gif Get it while you can, as I won't have it up long. Anybody else who wants to post it, feel free, just don't take credit for it. If you want some more information on reactive loads, here's a link: http://www.geocities.com/SunsetStrip/Studio/2987/speaker.html GVB

9/3/1998 11:22 PM

GVB

Power Brake Schematic Online

I finished the schematic for the Power Brake finally. I only gave it a quick once over, but hopefully everything is OK. Now that it's drawn up properly and not a jumbled mess like the original schematic (from Marshall), it's pretty easy to understand. The link is below, and here is a brief explanation of the circuit as I understand it.

The Power Brake is basically a reactive load, and is almost identical to the electrical equivalent of a speaker found in RDH4. The one variation is that R2 is not in parallel with C1 and L2, and connects to the bridge that drives the fan. I think this may actually be an error on the schematic I have, so perhaps someone with a Power Brake could check for us. I think R2 should connect to both sides of C1.

The "multi tap choke" I described in other posts works exactly like an autotransformer. As a quick review an AT (autotransformer), is basically two inductors stacked on top of each other and are coupled magnetically. If the wiper is placed directly in the center, it splits the inductor into two. If you place 240VAC between the top and the bottom and then tap a signal from the centertap to either end you will get half the voltage out. Buy moving the center tap, you will vary the voltage between the center tap and each end.

Instead of a "wiper" on the transformer, it has multiple taps that can be used as the center tap, and these are switched through S1b and S1a. S1a controls the signal flowing to the reactive load, and S1b the signal to the speaker. The signal and the reactive load are placed across the autotransformer, and the output to the speaker is taken from the centertap to one end of the transformer.

Whew! That's basically how it works, but of course there are few extra things thrown in. A "setting" for 8 and 16 ohms, and the ability bypass the box (0db), and to use it as a load box.

I plotted the impedance of the reactive load, and its not really close to any Celestion I've seen, so there is room for improvement.

Here the link to the schematic:
http://www.oln.com/bus/b13/powerbr.gif

Get it while you can, as I won't have it up long. Anybody else who wants to post it, feel free, just don't take credit for it.

If you want some more information on reactive loads, here's a link:

http://www.geocities.com/SunsetStrip/Studio/2987/speaker.html

GVB

Replies:

marc thanks for the schematic!!... -- 9/4/1998 7:54 AM