Why does Fender draw diodes with + at the cathode?

[Randall]

Replaced the selenium rectifier with a robust diode in a Harvard 5F10. When I put in the diode according to the schematic, I was confused by the + at the cathode, and - at the anode on the schematic. So I looked at the layout, and it shows the selenium rectifier as + coming off 6.8K feeder resistor, and - to the 56K.

So I installed the diode with + going to 6.8K, just like the selenium rectifier. Didn't work. I put the rectifier back in according to the layout, didn't work. I swapped it around, and it works. So, the layout is incorrect, this I am sure. But why does Fender draw a rectifier in many of it's schematics with it pointing in the correct direction, but labeled the opposite of it's ends?

[bluesky636]

Fender is showing conventional current flow (positive to negative) vice electron current flow (negative to positive) in their schematics.

http://www.allaboutcircuits.com/vol_1/chpt_1/7.html

Edit: I had it backwards even after looking at the picture in the link.

[Firestorm]

Conventional current flow is usually positive to negative. Blame Franklin.

I never noticed or thought about the plusses and minuses on Fender schematics, but yes, they could cause confusion. The pointy side (cathode) points to the highest voltage, so maybe Fender simplified things for people doing QC.

[EtherealWidow]

It used to confuse me too, because current is supposed to flow when the anode is positive relative to the cathode but in an amp, the anode is grounded and the cathode is at a couple hundred volts (B+). I started thinking of the diode as a DC voltage source, like a battery. Electrons flow from the negative terminal to the positive. In a tube amp, current comes off the anode, going "up" through ground and through the tubes and load resistors where it's seen as B+, and then back to the cathode.

[Structo]

I know I am stating the obvious but this was confusing to me at first with tube amps.

If you are talking about the bias diode in the Fenders, the polarity is reversed to achieve negative voltage for the bias.
And, the electrolytic cap's positive goes towards ground.

[C Moore]

I know I am stating the obvious but this was confusing to me at first with tube amps.

If you are talking about the bias diode in the Fenders, the polarity is reversed to achieve negative voltage for the bias.
And, the electrolytic cap's positive goes towards ground.

I believe he is talking about...for example...the schem for a Twin Reverb. The SS rectifier...with a string of 3 diodes x2...
The Cathode of the diodes have a+ while the Anode of the diodes have a-

[Firestorm]

Pretty sure Fender was just labeling relative voltage rather than indicating cathode and anode. The symbol itself does that.

[Structo]

I know I am stating the obvious but this was confusing to me at first with tube amps.

If you are talking about the bias diode in the Fenders, the polarity is reversed to achieve negative voltage for the bias.
And, the electrolytic cap's positive goes towards ground.

I believe he is talking about...for example...the schem for a Twin Reverb. The SS rectifier...with a string of 3 diodes x2...
The Cathode of the diodes have a+ while the Anode of the diodes have a-

OK, gottcha.

I will go hide now.

[Tillydog]

I believe that the convention used to be to draw diodes with a + on the cathode - not limited to Fender. It sort of makes sense, as this is where the positive DC voltage "comes from".

Interesting to compare it with a bridge rectifier symbol, which also has the '+' on the cathodes:

[img:480:416]http://forum.allaboutcircuits.com/image ... 583523.jpg[/img]

[Reeltarded]

There is a better pic around here with a cat.

[C Moore]

I know I am stating the obvious but this was confusing to me at first with tube amps.

If you are talking about the bias diode in the Fenders, the polarity is reversed to achieve negative voltage for the bias.
And, the electrolytic cap's positive goes towards ground.

I believe he is talking about...for example...the schem for a Twin Reverb. The SS rectifier...with a string of 3 diodes x2...
The Cathode of the diodes have a+ while the Anode of the diodes have a-

OK, gottcha.

I will go hide now.

Communicating verbally is one thing.
Communicating via print/computer is another...separate...and more difficult art in itself.
I was not really sure what we were talking about at first either.
What were we talking about.?

[Randall]

I believe that the convention used to be to draw diodes with a + on the cathode - not limited to Fender. It sort of makes sense, as this is where the positive DC voltage "comes from".

Interesting to compare it with a bridge rectifier symbol, which also has the '+' on the cathodes:

[img:480:416]http://forum.allaboutcircuits.com/image ... 583523.jpg[/img]

That is a very good point, and very interesting. makes sense now.