Rocket w/ Reverb

[amplifiednation]

Are you referring to the opaque component that appear to be under the board? I believe that is a bleeder resistor.

Yes, that's what i'm referring too. So if it's a bleeder resistor is it wired to the positive side of the filter cap section, then to ground? Bleed out the power when the amp is off? Does that affect the amp's voltage while it's running?

[angelodp]

As you are mixing a couple of building styles on this, I will let more experienced heads answer the question on the need for the additional bleeder resistor. I do not think that the bleeder resistors have any effect on tone.

[amplifiednation]

I guess more concern would be the overall concept of the bleeder resistor. I'm pretty sure it helps drain the filter caps when the amp is off. Does it bleed them dry so it's safe to work inside the amp?

If it's bleeding power when the amps is off, it still must be bleeding when it's on...so thats why I was asking about effect on voltage. Just if it was significant or not--it's not on your amp?

[M Fowler]

The Mode pilot light is available from rjguitar.net and the MOV is available at some Radio Shacks.

[Colossal]

If it's bleeding power when the amps is off, it still must be bleeding when it's on...so thats why I was asking about effect on voltage. Just if it was significant or not--it's not on your amp?

Yes, it's bleeding a very small amount of current while the amp is on and serves to drain down any caps when the power is turned off (provided of course there is no switch between the bleeder resistor and the caps such as a standby).

Supposing you used a 300-0-300 PT and a tube rectifier and a 220k 3W bleeder resistor you would have:

300VAC * 1.2 (tube rectified) = 360VDC
V=IR
360V = I * 220,000R
360V/220k = I
I = 1.64mA

...so this results in a very small current across the 220k bleeder resistor. You can increase the size of the bleeder (e.g. 470k or 1M...whatever) but it will take more time to bleed the caps down to a safe working level. Regardless of the size bleeder you choose, always check the caps before diving in!

[Cliff Schecht]

Yeah I need to add a bleeder to my Rocket build, it holds it's voltage for a long time. I found a bunch of old 10+W Dale power resistors in large values that I can strap directly across the B+ cap instead of doing the bleeders like KF does.

[angelodp]

Even with the bleeder resistor's you will want to check with a DMM to be certain that the caps have drained. And re-check as you work to see if they are building a charge again. On older Fender amps I think its a good idea to leave the cap drain device in place while you work and withdraw it before power up.

[RJ Guitars]

I can't find the MOV/Varistor 150A/50V or power section cathode resistor 25W/50R. Do I need the MOV? It's not on the normster layout. If anyone has these parts or a mode pilot light let me know I will buy them!

I bought all they had as they were discontinued from inventory over at Newark. .. still got a few. With a bit of study I think there are plenty of substitutes. The Big resistors are a standard Dale part and you can get them from most electronics vendors.... I have a few of them also. I also bought all the amber pilot lights I could find. Lots of guys have these around.

Whether the MOV's are needed or not - well if a MOV takes a good hit, it can go south but your amp can go back on stage for another day. I have never had anybody ever ask for a 2nd one yet. Could be that I just don't sell that many parts. They are cheap insurance and not a bad idea, especially if you ever plan to play outdoors using a portable generator.

rj

[Zippy]

And re-check as you work to see if they are building a charge again.

Where would that come from???

[Cliff Schecht]

Electrolytics are notorious for being able to retain some of the energy even after being discharged by shorting through a resistance. The bleeder resistor might not be small enough in value to pull out this excess stored charge either. But we're talking a few Volts here, not a couple of hundred. You'll see exactly what I'm talking about if you ever reform high voltage caps, you have to short them for a good while before the stored charge is truly depleted.

[amplifiednation]

to what point in the power section does the bleeder resistor connect?

when i do work I usually just drain all the power from the plate of V1 and leave my bleeder line in place until the amp is ready to go back together to avoid any recharge...you just gotta remember it's there!!

RJ, thank you. I've been meaning to PM you for some parts!

[Normster]

The 220k resistors in my power supply are balance resistors. (I'm using totem caps.) They do double as bleeders, but that's just a bonus.

[angelodp]

I finally installed the network of caps and resistors to remove any DC on my volume pots with the VVR at minimum setting. This cleaned up any scratchiness. For any that might be heading in that direction.

I used Dovemans recipe for the install, which came from Dana, so thanks guys.

2- 1 meg resistors, 2 - .047/600v caps, remove 1 meg from input.

[IMG:720:582]http://i260.photobucket.com/albums/ii9/ ... RR-VVR.jpg[/img]

[M Fowler]

For the boost do you just have the cap wired to the pedal jack and back to ground? Nice and simple! I have been meaning to do that.

[angelodp]

Yes indeed, Tom had that idea a while back.