Does anybody know where I can get some wirewound resistors (E.K.T. doesn't have them)? I'm looking for 220 and 330 ohm resisotrs with 5% tolerance and 3 W power rating (preferably the RS20B model from Vishay).
why do you need wire wound resistor ? modern carbon resistors are much much better.
The wire wound resistors are only better when it comes to withstanding high temp.
J4D wroteThe wire wound resistors are only better when it comes to withstanding high temp.
Exactly, I want to replace the ones on an intraoral x-ray machine which operates at 70 kV.
how are they shaped ? round ?
you can find equivalents.
like =


just go to katranji. dont specify the type. just the requirements :) the metal covered one on the right is sometimes used as a resistance heater ! so heat is not a problem with it.

besides, all these are wirewound ! Katranji should have them all ! iza ma 3endo 3 watt bikoon 3endo 4 watt .
just increase the wattage.
J4D wrotehow are they shaped ? round ?
you can find equivalents.
yep, they're round and from Vishay:


J4D wrotejust go to katranji. dont specify the type. just the requirements :) the metal covered one on the right is sometimes used as a resistance heater ! so heat is not a problem with it.

besides, all these are wirewound ! Katranji should have them all ! iza ma 3endo 3 watt bikoon 3endo 4 watt .
just increase the wattage.
I know better than to go to Katranji without checking for the number on the website (not unless it's something quite common), because half the staff doesn't know about electronics. When I walk in, they directly call Hussam or Habbal to help me out. I talked to Hussam then, and he told me that the closest wire wound resistors which hold the values 220 and 330 ohms are rated at 5 W. Increasing the wattage doesn't mean much an a normal electronics board, but this is a medical application here. They're used to control the dynamic braking of the tank motor. Yes, the value of the resistance affects the circuit operation (also the fact that they're wire wound means their inductance affects the phase shift at high frequencies), but shouldn't the power rating affect it as well? What if something else goes wrong and more electric current surges into them, they would take it (seeing that they can take the heat) but wouldn't the motor be affected then?
How high are those frequencies?

As far as inductance and phase shift are concerned, if they are a major factor in your system/machine, then you can't settle for non-wirewound resistance since the phase shift will be butchered.

Using a higher wattage resistor only means that the resistor will be able to handle more current. The motor will only be affected if the source pushes more current through the resistor. Do you want a lower wattage resistor so that it acts as a fuse too and blows/bruns when more current flows?
@Xserver: The generator can emit frequencies as high as 300 kHz. This is exactly why I need wire wound resistors: a) they take the heat b) their phase shift and inductance matter when high frequencies are generated (which is practically every time) since the inductive resistance changes relative to the frequency generated.
Xserver wroteThe motor will only be affected if the source pushes more current through the resistor. Do you want a lower wattage resistor so that it acts as a fuse too and blows/bruns when more current flows?
That's exactly what I was thinking of. I don't care if the resistors blow up cause they're cheap, but replacing the motor means we have to pay 800 to 1000$ for it (industrial designed motor that's only available at the manufacturing company and cannot be replaced by a common motor with similar specifications).
In this case, and like the old saying goes: "If it's not broken, don't fix it" All you need to do then is find a resistor with the exact same specs. If not, maybe you can look for combinations and put them in series/parallel to achieve your goal, but that may lead to a different inductance/impedance.

If you are suspecting that the motor might be fed, by accident, more current than needed and since it costs $800~$1000, I would invest in a fuse to protect it. Don't count on the cheap resistor to do that.

I tried searching the the resistor's model number on Vishay's website and nothing comes up. Even a google search comes blank!
@Xserver: the problem is that resistors I'm replacing have lost their tolerance and the circuit's not functioning anymore. There's a circuit breaker already, but you never know what could happen on a 30 year old machine. Katranji doesn't have 3W wirewound resistors, the closest to use is 5W (combining the 4W resistor to acheive 220 or 330 ohm would be hell). The search on Google for "RS2B 220 ohm" should give you links to the datasheet of all wirewound resistors at Vishay.
Have you tried looking at the shops in the Dora area? DC electronics, Incotel, Boujikian and the ones near him (azan or something, forgot the names)
Have you checked at Kanafani in bshara il khoury ?
@Flakk: I live in Beirut but work in Saida Monday through Saturday, I tried calling Boujikian but as usual they either ignore the phone or the line is busy. I'll try to go there Tuesday, but I really don't want to waste time going there then finding out they don't have it.

@J4D: Where's Kanafani located exactly in Bshara El-Khoury?
mesa177 wroteThe search on Google for "RS2B 220 ohm" should give you links to the datasheet of all wirewound resistors at Vishay.
In your first post you wrote "RS20B" and not "RS2B". That's why I did not find anything when I searched.

So what are you planning to do now?
Going up from martyrs square towards bshara il khory you will find kanafani to your left. in the last building before you end up in bshara il khoury. once you are there ask around. the shop is well known and in the same building their is a shop that sells juice.

If you dont find any, replace with with a 4 Watt 3a mas2oliyti.
@Xserver: Both are actually correct, but RS2B gives you the correct search results. My bad...

@J4D: Thanks for the help, I appreciate it. Katranji only has 150 ohm 4W wirewound resistors, so I'll use the 5W 220 and 330 ohm resistors if Kanafani doesn't have 3W 220 and 330 ohm resistors. There's a juice shop known as Sawwas, next to the Ministry of Finance, is that it?
Euh, yeah i guess.
Kanafani to the rescue!! Not only did I find my precious 220 and 330 ohm 3W wirewound resistors, I found a DIN socket which saved me a trip to Katranji. All thanks to J4D (Jad ya Jad, yalli mafish zayak fi el bilad) :)