DIY AIR BRAKE WITHOUT THE RHEOSTAT?

[horn man]

In either schematic, nothing is wired to the 6th pin on the Lorlin switch?

[dehughes]

In either schematic, nothing is wired to the 6th pin on the Lorlin switch?

Correct...

[horn man]

Thanks for the reassurance, dehughes, thats what I thought. I too, was a little confused about the numbering sequence on the switch. Looking at the back of it, the numbers started from 12 moving clockwise. So I just kept the wiring in order starting with 12 and so on. My pin 7 is the schem's 6, etc. Every thing works fine. However, when I first tried the completed Brake I noticed the 4th and 5th settings produced no sound. It did this a couple of times, then worked fine (by the way, I tested all this on a cheapie SS practice amp). Could I have just not engaged the settings squarely on the contacts? Its been working as it should since then. I just don't want to give this to my son to use on his 18 wt and Soldano if the switch is bad. Any thoughts on this, anyone?

[dehughes]

How did you all manage to get those variable tabs on the resistors to make contact with the core wire? I screwed them on but was unable to get a reading with my DMM. Do you have to sand down the wires, or screw down the tabs super tight, or??? I followed Mark's advice and screwed them down until they were snug, but not tooooo tight. Still can't get an ohm reading on the tabs....it's like they are making no contact...

And yes, I removed the protective paper strip that shipped with the resistor.

I even put the DMM leads up to the exposed wires themselves, and I STILL didn't get an ohm reading....it's like they are coated...

[horn man]

Actually, I didn't measure the impedance of each tap, per se. I just lightly tighted the screws and measured for continuity at every point I soldered, especially from the input to output positives. Someone else will have to chime in about reading the ohms for each tap point. Did you measure from each tap to the end (fixed tap) of the resistor?

[mhuss]

The variable power resistors have a 'covered' side and a 'windings exposed' side. Make sure the little bump on the slider is on the exposed side.

In my schematic, the resistance readings are terminal to terminal, where the ends count as terminals. The exact value is not critical, as long as you get it close.

--mark

[dehughes]

The variable power resistors have a 'covered' side and a 'windings exposed' side. Make sure the little bump on the slider is on the exposed side.

In my schematic, the resistance readings are terminal to terminal, where the ends count as terminals. The exact value is not critical, as long as you get it close.

--mark

Thanks for the clarification on the schematic....good deal. Much appreciated.

Yup, the bumps on the terminals are on the exposed side of the power resistors....still can't get a reading....screwed down snug. I assume I don't have to sand down the terminals or the exposed section of the resistor....so then perhaps I'm just not tightening them down enough?

I'll tinker more with the terminals when I get home...never done this before so it's all learning for me.

[dehughes]

Well, thanks to all who helped this newbie out! I just finished my Airbrake....here's hoping it works when I plug it in!


...and it does work! Pretty darn well, actually. I woke up this morning and realized that I forgot to connect pins 1-3 to the center tab of the top resistor....so I did that and all is great. Thanks Mark, for the revised schematic. Works great with my 8 ohm amp!

[rawnster]

Very cool, David. Here's mine. Not as pretty a wiring job as yours, but it works nicely.

[IMG768]http://i209.photobucket.com/albums/bb15 ... G_1174.jpg[/img]

[IMG768]http://i209.photobucket.com/albums/bb15 ... G_1160.jpg[/img]

[dehughes]

I still can't get over your ventilation solution, Ron. Tedious, but incredibly cool...and all done with a hand drill. Meticulously fine work.

I find that the first three or four clicks of attenuation are pretty sweet....but 5 and especially 6 are a bit harsh, tonally. Not bad, but just noticeably less transparent. Still though, I'm able to take the edge off nicely with my little 1x12 combo amp.

Also, I'm finding that this attenuator doesn't even get remotely hot, even when playing my Club Royale nearly cranked. Granted, it wasn't for an entire set, but still...neither the box nor my PT or OT even seemed remotely hot after a good session of running the amp up high with the attenuator fully or mostly engaged. Pretty sweet. Should prove to be very useful in church and at home.

Next up, the VVR....

[dehughes]

OKAY! So I used the airbrake in church and in practice...sounds good!

However, I noticed that once it is "on" it kinda closes down the high end somewhat. This isn't a progressive thing, as when it is turned up it doesn't continue to reduce the high end more and more, so that's good. It's like it cuts out some of the highs on the first click, and then proceeds to only cut volume as it is turned up (or down, depending on how you look at it...).

So, what are my options? Has anyone tried to install a treble-bleed cap of some sort in order to keep the articulation at attenuated levels? I was thinking of maybe a 500pf or 1000pf cap across the two terminals (A and C) on the rotary switch. Good idea? Any suggestions?

[hendo]

All I did was say G5 and he goes hog wild with the hole drilling ... looks like I could be drilling for awhile wednesday night when I meet up with Ron.

[dehughes]

So, does anyone have an idea regarding a bypass cap to keep the "air" in the airbrake when engaged? I'm thinking start small...like 120pf.....maybe 500pf. Has anyone given such a thing a try?

[rooster]

Wait a minute - Ron, are you insane!!!!!! OMG!!! ..And yes that does look pretty cool. So, I assume you found a piece of factory perferated steel, clamped it onto you box, and started drilling?

If you drew this out, hole by hole, and drilled it, I am going to send you some travel brochures - you need to get out of the house!!!!!!!!

[hendo]

Here is my effort ... only half the holes of Ron but it works fine. Doesn't get too hot with the 18w or 33w amps that I have.