Post by dan on Nov 18, 2013 15:05:36 GMT -5
Hello,
Per Newey's suggestion I am posting my question in this Amp section which I posted originally to a thread in the Guitar Wiring forum as that is where this subject was. Go figure.
The original thread is here: Installing leds into amp foot switch It is about putting LED's into a foot switch for a Peavey Classic 50 and then later the Classic 30. I have the Classic 50.
I read this thread many times to try to understand what was happening when I applied solder to the parts and finally based on sooty's results just went for it. I put it all together yesterday and tested it today. It works! So what's my problem? With ChrisK and others postings I still don't get why it works.
In short, the Peavey classic uses a circuit to create the pre and post amp volume controls. Thus you end up having what might be considered 3 main amp volume controls. The Master and then 1 each for the normal and gain channels with the gain channel having the added pre amp control. This gain circuit has to be turned on by a main switch on the front panel otherwise the foot switch has no effect and the amp only play through the "normal" channel. There are schematic at the original post.
At the original post there was the subject of -27 volts and possibly 32mA at the channel switch of the foot switch. The reverb switch was seeing below 20 mA. The plan by Chris was to use a resistor in parallel with the LED. Everything I was reading said LED's need to be wired in series. I googled 5 pages in and could find nothing regarding resistors in parallel. But, it worked for Sooty so...
I had measured my switches before I did this and had 23.5 V at both switches and 20 mA at the channel switch and 14 mA at the reverb switch. (Analog, my digital broke.)
I wired up the LED's (3v, 20 mA ratings green and yellow) in series with the diode (protection for the LED I understood that part of the discussion) for each switch (gain/normal and reverb). I put the one 150 ohm resistor in parallel across the LED for the gain switch as directed by all the pictures and drawings. It all works as I tested it today.
Here's the thing. I rechecked the voltages out of curiosity. For the channel switch on (closed) there is 22.5 V across the polls. In this position the LED is off and the amp is running in the normal channel. There is no voltage measured across the LED. With the switch off (open) there is no voltage across the switch, the LED is on and there is 2 V across the LED. In this position the amp is running through the high gain channel (pre and post amp volumes). I used the green LED. If I try to measure the mA, the LED goes out.
The reverb channel works the same. With the switch off (open) the LED (yellow) is on and there is reverb. 2.8 volts across the LED. Zero across the switch. When the switch is on (closed) there is 20 V across the switch, nothing across the LED.
I just don't get this as to how there can be power in the LED with the switches open thus no connection to the common ground. When the switch is closed how is it that the LED is not popping with 20+ volts in the circuit?
I'm happy this works as I run a touch of gain and then add more with pedals so it is hard to tell which channel I'm on at times and the LED's solve this. But, I do like to understand what it is I just did with this little electronics project.
Thank you for your input.
Per Newey's suggestion I am posting my question in this Amp section which I posted originally to a thread in the Guitar Wiring forum as that is where this subject was. Go figure.
The original thread is here: Installing leds into amp foot switch It is about putting LED's into a foot switch for a Peavey Classic 50 and then later the Classic 30. I have the Classic 50.
I read this thread many times to try to understand what was happening when I applied solder to the parts and finally based on sooty's results just went for it. I put it all together yesterday and tested it today. It works! So what's my problem? With ChrisK and others postings I still don't get why it works.
In short, the Peavey classic uses a circuit to create the pre and post amp volume controls. Thus you end up having what might be considered 3 main amp volume controls. The Master and then 1 each for the normal and gain channels with the gain channel having the added pre amp control. This gain circuit has to be turned on by a main switch on the front panel otherwise the foot switch has no effect and the amp only play through the "normal" channel. There are schematic at the original post.
At the original post there was the subject of -27 volts and possibly 32mA at the channel switch of the foot switch. The reverb switch was seeing below 20 mA. The plan by Chris was to use a resistor in parallel with the LED. Everything I was reading said LED's need to be wired in series. I googled 5 pages in and could find nothing regarding resistors in parallel. But, it worked for Sooty so...
I had measured my switches before I did this and had 23.5 V at both switches and 20 mA at the channel switch and 14 mA at the reverb switch. (Analog, my digital broke.)
I wired up the LED's (3v, 20 mA ratings green and yellow) in series with the diode (protection for the LED I understood that part of the discussion) for each switch (gain/normal and reverb). I put the one 150 ohm resistor in parallel across the LED for the gain switch as directed by all the pictures and drawings. It all works as I tested it today.
Here's the thing. I rechecked the voltages out of curiosity. For the channel switch on (closed) there is 22.5 V across the polls. In this position the LED is off and the amp is running in the normal channel. There is no voltage measured across the LED. With the switch off (open) there is no voltage across the switch, the LED is on and there is 2 V across the LED. In this position the amp is running through the high gain channel (pre and post amp volumes). I used the green LED. If I try to measure the mA, the LED goes out.
The reverb channel works the same. With the switch off (open) the LED (yellow) is on and there is reverb. 2.8 volts across the LED. Zero across the switch. When the switch is on (closed) there is 20 V across the switch, nothing across the LED.
I just don't get this as to how there can be power in the LED with the switches open thus no connection to the common ground. When the switch is closed how is it that the LED is not popping with 20+ volts in the circuit?
I'm happy this works as I run a touch of gain and then add more with pedals so it is hard to tell which channel I'm on at times and the LED's solve this. But, I do like to understand what it is I just did with this little electronics project.
Thank you for your input.