trinityamps.com

Hey folks...question regarding acceptable bleeder resistor values...

I normally use a 220K/2W...

However, I don't have one on hand and I suspect I would have to make a special order to mouser just for that...

Soooooo...

I dove through my spare pile and the closest thing I came up with is a:

100K / 3 watt


according to Paul Ruby and his start up document, 100K is the advised value (at 2watts)....

http://www.paulrubyamps.com/info.html#FirstPowerUp


Will I be OK with this value...or should I just bite the bullet and dream up some stuff to order from mouser...

-frank

You'll be OK with 100K, but 220K will present less load to the power supply.

Any chance Rat Shack has one?

_________________
--s2
www.s2amps.com
www.category5amps.com

Radio Shack doesn't stock anything higher than 1/2 watt.....with the exception of a few 10W power resistor values like 10ohm, 50 ohm, 100 ohm....


I'll try to nail down a 220k then....

Dude, go ahead and use the 100K and swap it out some time in the future. Or just leave it off altogether. These things are optional on an amp, because unless something is really broken, it will bleed its own filter caps down. Now, if you are building a preamp or pedal, the bleeder is a MUST!

_________________
--s2
www.s2amps.com
www.category5amps.com

Good point...it'll still work....and I can just drop it in later....


wait...I thought caps will store high voltage for really long periods of time....

How long would it take for the caps to naturally drop down?

A few seconds. Turn off your amp and keep playing the guitar. When you stop hearing sound, your caps are under 50VDC. A few more seconds and they are below 12VDC.

Power tubes and an output transformer will naturally put a load on the power supply and drain it unless the filter caps somehow become disconnected (in which case the amp would be broken and should be approached with an abundance of caution anyway).

I take all this back. Be safe.

_________________
--s2
www.s2amps.com
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depending on your actual B+ at the first cap, a 100k only adds an additional 3-4mA load (which is nothing as long as you don't have 20 tubes in yer amp LOL), and it'll discharge the cap twice as fast as a 220k. a 100k is perfectly fine as long as it's a 3W like you say you have b&v....the resistor will get a little warm (if your B+ is higher than +350VDC), but if yer willing to wait for the Mouser order......

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

Be careful. If you don't have tubes in there (like when you're checking voltages for the first time) and don't have a bleeder then it will take quite a long time for the caps to discharge. Caps can also exhibit "soakage" and effectively redevelop a partial charge after being discharged. Not sure how much this happens in practice, but a bleeder will stop this being a problem too.

To check the effect of different bleeder resistor values, just do a little math. Say the voltage across the resistor is 400v and the bleeder is 100K, then the current passing through it is 400/100000 amps, or 4mA. The power being dissipated by the bleeder is 400*400/100000 = 1.6 watts, so a 3W resistor would give you a decent safety margin.

Cheers,
Rick.

Do you have 2 100k resistors? Put them in series. It'll take up more space but you're done in one go, without modifying your build afterward (or maybe never).

It's best to have the bleeder in during testing; once the amp is up and running, it's not so important. So you want it now and not later.

Right,

but it's been suggested that a 100K/3 watt is perfectly fine...which I have on hand...so why would I go out to get another one of those, just to get to 200K...when I would just buy a 220K to start?

Cuz 100K will work, but 220K is easier on the power supply.

_________________
--s2
www.s2amps.com
www.category5amps.com

frank, what amp and tranny is this thread referring to?

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

Steve's PT and OT (s2)

That's your problem right there. From what I hear, those trannies really blow!

_________________
--s2
www.s2amps.com
www.category5amps.com

well, as long as they blow a couple o' extra ma and frank is using a GZ34, a 100k 3W bleeder is just dandy

FrankenBitsNVolts...use the 100k

I ordered a bunch of 470k 2W ceramic comp for builds and repairs.
Slow bleed (about 30sec or so depending on 1st cap value), but I'm in no hurry.

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

You would know best!

OK guys,

I found some more possible resistors around here....here as some options:

* 2 - 150K (1watt) in series

* 4 - 1M ( 1/2 watt) in parallel

* 1 100K (1 watt) in series with a the 100K (3 watt)

* just the 100K (3 watt)


Which is the best option!?

-F

Send me your address again and I'll mail you a 220K.

_________________
--s2
www.s2amps.com
www.category5amps.com