Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: phsyconoodler on June 22, 2010, 10:39:29 am
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I just wanted to say thanks to Sluckey for giving me a schematic to do the relay supply.
However,with two relays the voltage drops down from 8.2v to 3.2 when the relays are activated.The channels switch just fine but it won't light up the LED's in the pedal.I know I must be doing something wrong.I just popped in two amber LED's I has laying around and don't know the current draw or voltage of the LED's.
I was wondering how to make the LED's work?I need two LED's,one for each function.I'm using a Marshall two button switch.I added the LED's. :smiley:
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You might want to add a regulator so your supply voltage doesn't drop like that. >50% seems like a problem. I haven't seen the schemo you're working from but typically you put a 1k resistor in series with the LED, and parallel that to the coil. I assume you're switching ground so you'll need the 5V hot down in the foot too. Hope you have an extra unused wire.
-Richard
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Forgive my solid-state ignorance,but a regulator will keep the voltage up as well as lowering it?
I'm using the D'Lite circuit with two relays.It switches ground.The pedal has three wires.One green,a white and a red.I've had no issues using LED's before using a doubled 5V supply.I had 14v before the relays were activated with that system.I didn't need any resistors for the LED's.
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Well I get a mental block sometimes.I wired the LED's wrong.Duh! I'll try again tonight and see what I get. :BangHead:
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I assume you're doing something along the lines of the circuit Doug used in the Stout w/ relay.
http://www.el34world.com/projects/images/18wattstoutReverbSchematic.gif
Note that he has a current limiting resistor in series with the LED. 180 ohm is good for 5V, 1k for 12V. If the LED's are out in the foot switch, you'll need a 4th wire. If you want to add a regulator, simply remove the 180 ohm resistor between the 2 - 4700uF caps and insert a LM7805 in it's place. The 2nd 4700uF cap needs to become something like a .1uF. You don't want big capacitance on the output of a regulator. Might ought to add a 1k resistor as a constant 5mA load on the output of the regulator to keep it stable.
http://www.national.com/ds/LM/LM341.pdf
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Yeah,that's the same as my relay supply.It has 8.14v at the output and on the relays before they are activated.I know that I wired in the LED's wrong,but I may need to use a limiting resistor for sure.
When the relays are on,the voltage is 3. something.Can't remember exactly.They do suck it down.When I use the 5v tap they don't suck down that much,but they do have 14v at the supply.
I just wire the LED's in series,one end to ground and the other end to each of the wires.
There are just two relays,so I only need three wires.One ground.
I'll try it again with a 470 ohm resistor in line.
Thanks for the help guys!
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I use two relays and an LED on the panel for my build's works great.
I tap from the heater supply using a BR don't use the 180Ω resistor in Doug's schem.
A single 1000uf or 4700uf works fine.
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Ok,I went online and got an LED tutorial.Man,they are really easy to figure out when you have the right information!
I'm going to use them in my amps more now!
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Ok,here's my experience with the filament supply and LED's.
I got the LED's working properly and the channel switching as well.
But.....I had to lose any resistors to the LED's.With the two relays and a 180 ohm resistor,the LED's would light up but the relay would not switch.So I tried a few different resistors and none worked properly,so I removed them altogether.The relays work perfectly and the LED's light up just fine.I'm using red led's that came with an Apex pedal.I had to wire the cathode to the switch and wire each switching wire to the anodes.No resistors at all.Woks perfectly and the LED's are not super bright,like they might blow.I measured 3.4v.
End of this saga.
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Ok,I went online and got an LED tutorial.Man,they are really easy to figure out when you have the right information!
Link?
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I'm curious to know how you have this wired. Lighting the LED should be a totally different issue from energizing the relay. Do you have the LED wired in series with the relay coil? Here's a typical way to wire a relay with protection diode and a LED. LEDs must have some kind of series resistance to prevent burnout from too much current.
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If you look at the D'lite schematic or layout,you'll see how it's wired.I tried using resistors from 100 ohm all the way to 470 ohm and they would not trip the relays.With no resistor they work perfectly and they are not too bright,indicating too much current.
There is no connection to the + side of the relay diodes.I can't re-size my document here at work.
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If you look at the D'lite schematic or layout,you'll see how it's wired.
I picked up this schematic from Brown Note. Is this the one? There are no LEDs on this schematic. Can you provide a link to another schematic?
EDIT... Attachments deleted
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On the Brown note forum look at the 'sticky' at the top,where it says "D'lite Assembly guide" Near the end of the thread there is a link to the layout.It's the 'with relays' layout.
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OK, you mean this one... EDIT... file removed
I'll remove that drawing tomorrow, but just wanted to use it for this discussion.
There is no LED on this layout. There's a note by the FS jack that says "Standard Marshall 2-button footswitch (no LEDs)". So, you must be adding the remote LEDs in series with the relay coils. No wonder a series resistor wouldn't allow enough current to energize the coils. That's a funky way to wire it and you got lucky that it functions. The small pic I posted earlier is a more reliable and predictable way to wire the LEDs to work with the relays. But you'll need to run another wire to the footswitch.
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That's the one.Sorry it doesn't show the LED's but you can see there is no connection to the + side of the relays.The LED's work perfectly.I'm using an Apex footswitch that simply adds the LED's in series.I had to re-wire the pedal.
the pedal wiring picture is on the site as well. 'two button marshall pedal'.
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>That's a funky way to wire it and you got lucky that it functions.
So the coil is acting as the current limiter for the LED? I don't think this is going to hold up. At some point the transient caused by the coil will eat the LED regardless of the protection diode. LED's like to fail open at which point your foots switch will cease to work.
>The small pic I posted earlier is a more reliable and predictable way to wire the LEDs to work with the relays. But you'll need to run another wire to the footswitch.
Agreed but the rub with adding the 4th wire is that you can no longer use a TRS 1/4" jack. A work-around might be to use DPST switches and add a battery down in the foot switch.
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Agreed but the rub with adding the 4th wire is that you can no longer use a TRS 1/4" jack. A work-around might be to use DPST switches and add a battery down in the foot switch.
Yep. Sometimes you just gotta 'pay the man' to get it right. Or you could just hard wire the footswitch to the amp like Ampeg did on the old Gemini series. :grin:
Actually, Tubenit just had a discussion on the battery in the footswitch option...
http://www.el34world.com/Forum/index.php?topic=9395.0
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Well guys,I have several of my Overdrive Rocket amps out there with the footswitches wired up the way the D'Lites are done and there has been no failures to date,either LED's or whatever.
The only difference in this amp is the rest used the 5V tap and a doubler circuit and this one uses the filament taps.
The thing that was giving me problems was I tried some LED's that were unknown specs.The red ones in the pedal I bought are obviously the right voltage and current draw.
It takes a while for me to grasp solid state stuff so I look to you guys for assistance.
There are obviously more than one way to skin a cat.
No cats were harmed during this exercise.
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There are obviously more than one way to skin a cat.
Absolutely. But you chose the 'Silvertone' way! I have you on a higher pedestal than that.
Your way requires choosing LED and relay coil currents that are compatible (or just shotgunning 'til you get lucky). The 'other' way don't care if the relay requires 1 amp and the LED requires .01 amp. It works everytime because the LED is parallel to the relay. It's logical design. Nothing to guess about. In the end though, as you say, no cats were harmed. :grin:
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I updated my relay switching pagehttp://el34world.com/projects/relay_switch.htm