Home |
Search |
Today's Posts |
#1
|
|||
|
|||
What's this ground symbol? Resistor?
Help with this symbol and component, please.
Peavey Classic 20 guitar amp... Schematic: http://www.blueguitar.org/new/schem/peavey/c20schem.gif PC Board Layout: http://www.blueguitar.org/new/schem/peavey/c20laygr.jpg R32, lower right corner of the schematic, tucked under VR1, lower right corner of PC board. Component is a fixed resistor with a value of "47FP". What is that? Also, the two ends of the resistor go to ground. One ground symbol is the traditional inverted triangle, the other is the same triangle contained within a circle. What is that? TIA - Craig |
#2
|
|||
|
|||
"Lumpy" Help with this symbol and component, please. Peavey Classic 20 guitar amp... Schematic: http://www.blueguitar.org/new/schem/peavey/c20schem.gif PC Board Layout: http://www.blueguitar.org/new/schem/peavey/c20laygr.jpg R32, lower right corner of the schematic, tucked under VR1, lower right corner of PC board. Component is a fixed resistor with a value of "47FP". What is that? ** 47 ohms " Flame Proof " type. The resistor will not combust if overloaded , but simply go open . Also, the two ends of the resistor go to ground. One ground symbol is the traditional inverted triangle, the other is the same triangle contained within a circle. What is that? ** The circled one means PCB ground, the other is the usual chassis metalwork. ........... Phil |
#3
|
|||
|
|||
Means circuit ground is 47 ohms over chassis (earth) ground.
Sometimes done to prevent loops. LV Lumpy wrote: Help with this symbol and component, please. Peavey Classic 20 guitar amp... Schematic: http://www.blueguitar.org/new/schem/peavey/c20schem.gif PC Board Layout: http://www.blueguitar.org/new/schem/peavey/c20laygr.jpg R32, lower right corner of the schematic, tucked under VR1, lower right corner of PC board. Component is a fixed resistor with a value of "47FP". What is that? Also, the two ends of the resistor go to ground. One ground symbol is the traditional inverted triangle, the other is the same triangle contained within a circle. What is that? TIA - Craig |
#4
|
|||
|
|||
Lord Valve wrote: Means circuit ground is 47 ohms over chassis (earth) ground. Sometimes done to prevent loops. LV Lumpy wrote: Help with this symbol and component, please. Peavey Classic 20 guitar amp... Schematic: http://www.blueguitar.org/new/schem/peavey/c20schem.gif PC Board Layout: http://www.blueguitar.org/new/schem/peavey/c20laygr.jpg R32, lower right corner of the schematic, tucked under VR1, lower right corner of PC board. Component is a fixed resistor with a value of "47FP". What is that? Also, the two ends of the resistor go to ground. One ground symbol is the traditional inverted triangle, the other is the same triangle contained within a circle. What is that? TIA - Craig Of course LV's right; the circled earth ground symbols are 47 ohms from 'true' chassis/earth ground; two 'slightly isolated' (by 47 ohms) return paths (the other with no circle, straight to chassis) to reduce ground looping (power supply noise in the signal path.) ....and 'FP' stands for 'flame proof' (to use the type of resistor that quietly opens up when it's had enough, instead of spewing smoke and charring the PC board like in the good old days ;-) Also check out the 'secret capacitor' (not shown on the schematic) between pins 1 and 2 of V1 (visible on the board layout as two meshing 'combs'); guessing ~20 pf, to stabilize the first stage preamp from oscillation. -Robert QTS http://www.Braught.com real email addy : (remove NoSpam to reply : Duh!) "Aye sir, the more they overtech the plumbing, the easier it is to stop up the drain." -- Scotty, Star Trek III |
#5
|
|||
|
|||
Lumpy asked:
Component is a fixed resistor with a value of "47FP". What is that? Also, the two ends of the resistor go to ground. One ground symbol is the traditional inverted triangle, the other is the same triangle contained within a circle. What is that? Thanks very much Robert, Phil, LV. craig |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
eScrew OWNS YOU!!! | Pro Audio | |||
Funny story about tubes | Vacuum Tubes |