Confused about Filter Cap Bleeder Resitor and Grounding

[Greg]

Hey guys, I am using Ron's Rocket layout and cannot see exactly which way I should wire these filter caps and bleeder resistors to ground. I have attached the schematic the way I think Ron's layout say to do it.

It is difficult to see exactly where the wires go but I think I figured it out...why not combine C16, C17 and C18?

[Structo]

From looking at Ron's layout, he does have the grounds of the 20uf caps connected together then to ground.
He is using a ground tab on the rect socket.

B+3, B+4 and B+5 come off the + ends of the 20uf caps.

[Greg]

Are most of you guys grounding filter caps at the forward side of the chassis...up where the choke is?

Please post a picture or two if you have a good way to do this?

Also why do some Rockets have the grounding bar soldered to the pots continue to a grounding lug near the chock and some do not?

[Greg]

Ok so I rechecked the schematic and it is a different version than the one i am using...UGH. The latest and greatest does not include the bleeders. Is it fair to say that if you understand the danger and how to avoid stored current and use the appropriate method to drain the caps that the bleeders are not necessary?

Gary, thought it would be a good idea for me...total newbie...to use the bleeders. I have to say that as long as it does not adversely affect the DONNA ROCKETS tone I think it is excellent advice.

So I plan to use the bleeders...anyone have a good picture? PLEASE!!!

[rawnster]

Hey Greg, I posted some pictures of my recent rocket build that shows my filter cap grounding. I connected the 20uf caps together and ran the ground wire next the rectifier. Did the same with the 40uf caps. Should be able to see it the pictures.

http://ampgarage.com/forum/viewtopic.php?t=7978

[gahult]

Greg,
Here is my "Rocket" build with bleeders. Ground lug to B+ pin on Rect.
http://ampgarage.com/forum/viewtopic.ph ... ght=#68834

Express build.
http://ampgarage.com/forum/viewtopic.ph ... sc&start=0

Gary

[Structo]

The bleeder resistors seen on a lot of amps are actually balancing resistors that equalize the voltage to the filter caps.
The side benefit is that they bleed the voltage off when powered down.

[Paultergeist]

The bleeder resistors seen on a lot of amps are actually balancing resistors that equalize the voltage to the filter caps.
The side benefit is that they bleed the voltage off when powered down.

I dug up this very old thread -- using the search function -- because I am looking for information regarding this point. I had assumed -- until I read Structo's post -- that the bleeder resistors on the power supply were only to discharge the filter caps. I have never heard of the "balancing resistor" functions before.

Can someone explain the logic of the balancing resistors to me?

[Tillydog]

Can someone explain the logic of the balancing resistors to me?

You need them if you have filter capacitors in series - usually to increase the voltage rating. They ensure the voltage is equally split over both capacitors. If you didn't have the balancing resistors, most of the voltage would be across the capacitor with the lowest leakage current.

Look at R82, R83, R88 & R89 in the power supply of this (click it & zoom in!):

[img2545]http://www.blueguitar.org/new/schem/fen ... eville.gif[/img]

[Paultergeist]

Tillydog,

That is a perfect explanation; and I think that I understand the issue now after looking at the schematic which you were so kind to link to your reply. Thank you very much for the explanation and assistance.

Paul

[Tillydog]

No problem.

[vibratoking]

Just to avoid a possible confusion. You can approximate the circuit by viewing the caps as open circuits. This result is that the resistors form a voltage divider. If the resistors are equal then the drop across each is equal. You could have resistors of different values which would then provide a different drop across each.