Hello,
To mess with amps, a good dummy load is a must. I went to my storage,
and pulled out a Cantenna of unknown provenance that I had purchased about
30 years ago at a flea market. Not knowing what was in it, I assume it's
poisonous PCB transformer oil. I had kept the dummy load in a plastic bucket
with a hole for the coax, sealed with coax seal. Now I figured I'd
dispose of the old oil, clean it out, and put in fresh mineral oil. What
a mess!
OK, the old oil is gone; it'll be headed to the local hazardous waste
dropoff. The guts are all washed out in hot water and detergent. The
heathkit can is toast - rusty and leaking. The silver
straps around each end of the resistor are broken. So I can reconstitute
this thing with new silver straps ( luckily I have some silver sheet
laying around ). And the can - can be replaced with an ordinary one from
the paint factory. Only trouble with that is - 1 gallon paint cans are
now *plastic*, not metal. I guess it'll still work, just the heat
transfer won't be quite as good.
I also scored a 250W load cheap on Ebay. Seller said it came out of a
cell phone installation. I popped it open - the resistor is the size
of a postage stamp! I was messing with one of my SB2-LA's, used that
load - figured a momentary toot from the amp wouldn't hurt it. I was
wrong. Apparently these little resistors are not only heat limited,
but *voltage* limited. I hit transmit, there was a small *pop* and a
puff of smoke. Hole burned right through it.
There are similar load resistors on sale on Ebay - 800W for IIRC $40.
But that's just the resistor, you have to bond it to a heatsink. I
have
the heatsink from the defunct 250W load - I could machine off a big enough
flat spot for the 800W resistor.... failing that, I have a really big heat
sink in my junk.
- Jerry Kaidor, KF6VB
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|