Dummy Loads for Pl 700's

[JustMike]

I see these on line for around 60.00 bucks. they say they are rated at 500watts @ 8 ohms.
They are around 2" in diameter and maybe 12 to 18'' long.
No heat sink?
what do you guys think?

As my signature says...........................

 

[JustMike]

Here is a pic...................

 

[laatsch55]

If they start to smoke..put em in icewater..

 

[jbeckva]

I say you'd want to put some heat dispersing iron to good use and mount the loads on it.

 

[jbeckva]

Prolly good advice I should heed myself too.. Can put 'em under load longer that way heheh

 

[gadget73]

Mine is a set of 4 5 ohm resistors, I think each rated to 200w. Doesn't quite come out to the right load, but I make do with it. It gets hot as hell if you run a PL 700 at full crank into it. It needs a fan. I expect this won't be much different. The other thing to consider is that its probably very inductive. May or may not be a big deal, but in a perfect world a dummy load is not inductive. I know mine is, I can see the wires coiled on the ceramic tubes. I also paid $4 for it, so I put up with it.

Laying it in a bucket of mineral oil would make for a nice heat sink. The oil would eventually boil but you'd get a lot of run time from it first. That was an old trick for running too much power on things. Not sure if anyone else is into CB or ham radio gear, but those who are probably know the Heathkit Cantenna. That was a 90 watt resistor inside a metal 1 gallon paint can of oil. Heathkit rated that thing to 1kw for short bursts, and it would do 500 for 20 minutes according to the chart on the front.

 

[JustMike]

Mine is a set of 4 5 ohm resistors, I think each rated to 200w. Doesn't quite come out to the right load, but I make do with it. It gets hot as hell if you run a PL 700 at full crank into it. It needs a fan. I expect this won't be much different. The other thing to consider is that its probably very inductive. May or may not be a big deal, but in a perfect world a dummy load is not inductive. I know mine is, I can see the wires coiled on the ceramic tubes. I also paid $4 for it, so I put up with it.

Laying it in a bucket of mineral oil would make for a nice heat sink. The oil would eventually boil but you'd get a lot of run time from it first. That was an old trick for running too much power on things. Not sure if anyone else is into CB or ham radio gear, but those who are probably know the Heathkit Cantenna. That was a 90 watt resistor inside a metal 1 gallon paint can of oil. Heathkit rated that thing to 1kw for short bursts, and it would do 500 for 20 minutes according to the chart on the front.

Thanks Gadget. The info states that these are Non inductive so I'm going to give one a try.
Mineral oil will not conduct electric current, so it would work great for a heat sink.