Wirewound resistors

[volta]

Just ordered some parts for a tube project but I couldn't find a 5w resistor that wasn't wirewound.Actually Vishay has a non inductive part number NS, but RS was all I could find.
http://www.vishay.com/docs/30204/rsns.pdf
Has anyone ran into problems using an inductive(wirewound) resistor in series from H.V. to plate?

 

[CJ]

here is some good reading.

LINK

i am ok, Mods can go back to sleep now.

 

[PRR]

> I couldn't find a 5w resistor that wasn't wirewound.

Huh? You sure? They can hide anything inside those cement bricks.

The standard LOW-cost 5W brick, such as hoffmanamps.com and dozens of other guitar-amp part shops sell, is a 1W carbon-film inside a cement shell.

Another now-standard part is a "1 Watt" body in Metal-Film with a 3 Watt rating. At 3 Watts it must glow in the dark, and toast bread; but I believe it. Couple/three of these will give you a very low inductance 5W heat dumper.

> Has anyone ran into problems using an inductive(wirewound) resistor in series from H.V. to plate?

No, but a wire-wound in the Cathode with a plate lead running nearby can make some hot-tube fun.

 

[CJ]

Yes, I can vouch for that, our 1/2 watt metal film mil spec looks Exactly the same as a 1/4 watt, the only way to know the difference is by what parts bin they are in.

And yes, they do get hot, but they don't drift, thus, the new metal film can be made more stable at a higer temp, allowing new packaging .

Of particular value for the guitar players is the late Ken Fischer's cool Volume pot mod.

 

[volta]

Thanks for the links and info guys.I've already ordered the Vishay wirewound so I'll give that thing a shot before trying the metal or carbon resistors. :thumb:

 

[soundcollage]

I've been using these (dale) power resistors exclusively in all my scratch builds and repairs and have yet to encounter any issues. They are lighter than the cement block versions (so I imagine the leads are less likely to break due to vibration), and are more aesthetically pleasing to me.

 

[thermionic]

For Zobel networks on amps (where you least want an inductive resistor), I've been using Metal Oxide resistors. I've seen them in 3W - not sure how big they get.


Justin

 

[thermionic]

[quote author="soundcollage"]I've been using these (dale) power resistors exclusively in all my scratch builds and repairs and have yet to encounter any issues. They are lighter than the cement block versions (so I imagine the leads are less likely to break due to vibration), and are more aesthetically pleasing to me.[/quote]

As of last week, when the second :evil: custom job I'd performed was sent back (second return in 12-months - it goes on the road to gigs) due to lead breakage on WW resistors, I have vowed to smother all WW resistors in epoxy to prevent future occurrences.

The downside is that you have to overrate the R massively so it doesn't get hot and melt the epoxy...

Justin

 

[CJ]

Somtimes having thinhs to rigid can be their downfall, just when you think you are improving things.

Try to bend a coat hanger in half, count the turns, then take a piece of 104 starnd wire and try to break it, count the turns, so think mechanical first, then electrical, then thermal, and you will have a reliable product.

Thinkl of all those loose carbon comps that fender had bouncing around, do you think he was an idiot?
Of course he was!
He just ran the cash register.
Doc Kaufman was the idiot.
I mean RF to audio genius.

RF can rattle parts like a microwave, torque on inductors, look how strong some of those rf tank coils are, they have the resonant frequency tuned to the lead length,. when ever you have an electro mechanical device, you havea vector in the physical uinioverse.

There is mechanical force on the coil in a transformer when it is working, so un like carbon comp, you have a mechanical force inside that resistor , such that, when you resonate the inductasnce of the wire wound coil with what ever guitar note you are playing, and at high volume, if you do not believe this, put a mechanical senmsor on a wire wound resistor, and on carbon comp, and measure the delta.