Capacitor drain resistor

[AmberB]

Just a question, Do you use a high resistance resistor to drain the voltage in the power supply caps when you shut off the amp in your amp builds?
If so, so you put it on the highest voltage cap, or the lowest high voltage cap in the power supply?

[Latole]

Amp unplug from wall outlet

If I have to work on the amp soon, I use a 22K 10 watts resistor on the highest voltage caps. It discharge in few minutes.
On any Power Supply cap it work too.

If I will not work on amp soon, I live the Stanby Switch on Play position. No Stanby Switch, I live Power ON .
All caps will discharge on amp circuit ( if amp is almost finish) in few hours or less.

[tubeswell]

Just a question, Do you use a high resistance resistor to drain the voltage in the power supply caps when you shut off the amp in your amp builds?
If so, so you put it on the highest voltage cap, or the lowest high voltage cap in the power supply?

It’s related to power handling capacity. A 56k 5W resistor in parallel with each 100uF in a Marshall SuperLead reservoir cap ‘stack’ will do as good a job as a 220k 1W resistor in parallel with each 70uF in a Fender Twin Reverb reservoir cap ‘stack’ (or a 100k 0.5W across the 100v 220uF cap in the top of an RI DR reservoir cap stack and the 470k1W across the 47uF 500V cap in the bottom of an RI DR reservoir cap stack). 8-)

[Williamblake]

300k will drain most caps empty in a minute or two. You can also use the resistance to get your voltagereference for the heaters so you would take a well filtered power node. You also get 1 - 2 mA to power an LED that indicates high voltage is present.

[AmberB]

In the past, I've put a 1 meg, 1 watt resistor from the first B+ nose to ground in a couple of my amp builds.  With a standby switch in the amp, I have to leave it on to drain the caps when I shut off the amp.  I've also tried the 1 meg 1 watt at the last B+ node.  I don't see much difference in either setup, to be honest.  I was wondering if there is a preferred setup for it. 
If the amp doesn't have the balancing resistors like the first B+ node on a fender with the stacked caps, it can hold on to a voltage charge in the power supply for quite a while.  The Bogan amp that I'm working on is a good example of that.

[Willabe]

Your right, there's no preferred place to put the B+ voltage drain R.

In an amp without stacked caps and voltage sharing R's, you can put a R from B+ cap node to ground on any node you like.   

[PRR]

...first B+ nose ...the last B+ node.  I don't see much difference in either setup....

The difference is like 32k, no? From start to end of the B+ nodes we have 220r, 10k, and 22k, or sumthing like that. Compared to 1Meg. Hardly matters which end of the 32K we stick 1Meg on.

We may have 40u+22u+10u or 72uFd. Rounding to 100uFd and 1Meg we have 100 seconds to decay by 63% (to 37%), or from 400V to 148V. Still a sharp shock. Another 100 seconds is 55V, hardly lethal; almost another 100 seconds to get down to 20V which is generally accepted as safe. Note that this is nearly 5 minutes. Going for much less than 1Meg (for quicker bleed-out) means more than a 1/2 Watt part, so we are talking real money.

[dude]

If the bleeder R is on the first node and you have a tube rectifier and filter before the standby, (which is needed to save the life of the tube) the standby should be on, power off. Or you’ll be bleeding just that rectifier tube’s filter and not the others.

[Willabe]

Going for much less than 1Meg (for quicker bleed-out) means more than a 1/2 Watt part, so we are talking real money.

   

[sluckey]

I built two amps with a 220K bleeder acrose the node A cap. Built two more with a voltage divider on the node A cap to elevate the heaters. This also serves as a bleeder. When I'm working on an amp I'll connect a ground strap gator clip lead to the plate of the first preamp tube. When I'm impatient I'll just connect the ground strap directly to the node A cap.

If you are being paid by the hour your boss is going to tell you to quit wasting time and just crowbar it with a screwdriver.

[dude]

If you are being paid by the hour your boss is going to tell you to quit wasting time and just crowbar it with a screwdriver.

And let him pay for the pitted new screwdrivers. 

[sluckey]

Of course.   I have several 7 level screwdrivers with scars.