Search found 520 matches

by kcbooboo
Fri Nov 09, 2018 4:41 am
Forum: AM Radio
Topic: RF Ammeter resistance
Replies: 15
Views: 487

Re: RF Ammeter resistance

Perhaps it is Be/Cu alloy. Whatever it is, it's incredibly hard and refuses to be bent other than where it's bent now. It took a lot of effort to scratch it, and the residue was minimal. It could also be some sort of brass alloy. I agree that it should be replaced with plain copper, possibly two or ...
by kcbooboo
Wed Nov 07, 2018 6:28 am
Forum: AM Radio
Topic: RF Ammeter resistance
Replies: 15
Views: 487

Re: RF Ammeter resistance

As for the original meter that changes with temperature, I gave that back with the caveat that the readings may not be consistent unless the meter is left running with the same 10A of current flowing through it for 10 minutes. Three other 20A meters were way out of calibration, which is probably why...
by kcbooboo
Tue Nov 06, 2018 4:55 am
Forum: AM Radio
Topic: RF Ammeter resistance
Replies: 15
Views: 487

Re: RF Ammeter resistance

Shouldn't have happened. This meter is on a J-plug and is only used when fiddling with the ATU or making impedance measurements. It's out of the circuit and inside the xmtr/studio building hanging on the wall when not in use. I doubt the CE would have gone outside during a t-storm to measure base cu...
by kcbooboo
Mon Nov 05, 2018 2:58 pm
Forum: AM Radio
Topic: RF Ammeter resistance
Replies: 15
Views: 487

Re: RF Ammeter resistance

I tested some other (Weston) ammeters this morning. While three of them were about 50% off calibration, none exhibited the drift of the first meter I encountered. I adjusted the 15A meter's zero adjust screw so it tracked within 2% from 6 to 15A. I set things up for 10.0A and connected the meter, wh...
by kcbooboo
Fri Nov 02, 2018 4:32 pm
Forum: AM Radio
Topic: RF Ammeter resistance
Replies: 15
Views: 487

Re: RF Ammeter resistance

I would agree, a Delta CT makes more sense, but this is a meter that's swapped around into the J-plugs in the tuning houses of several towers, and Delta CTs are a lot more permanent, requiring one to disconnect the current-carrying conductor that passes through the CT to relocate it. They're great f...
by kcbooboo
Fri Nov 02, 2018 10:38 am
Forum: AM Radio
Topic: RF Ammeter resistance
Replies: 15
Views: 487

Re: RF Ammeter resistance

I measured about 0.25V drop across the meter terminal studs with 12A flowing, so there's 3 watts to generate some heat. The metal straps are also losing some voltage but I can't be sure if the connection to them is good. They're very hard and the clips aren't making a good solid (scratch the surface...
by kcbooboo
Fri Nov 02, 2018 8:47 am
Forum: AM Radio
Topic: RF Ammeter resistance
Replies: 15
Views: 487

Re: RF Ammeter resistance

All the connections seem to be tight. I had loosened and removed the nuts and washers and pulled the straps off the threaded meter studs but they sprung right back to where they were. This is the strangest metal I've ever encountered. It's almost like the spring inside a wind-up clock. Perhaps it's ...
by kcbooboo
Fri Nov 02, 2018 7:30 am
Forum: AM Radio
Topic: RF Ammeter resistance
Replies: 15
Views: 487

Re: RF Ammeter resistance

Thanks for the 1 ohm resistance of the 1A meter. One thing I noticed is that my dynamic load shows only 4.5V across it at 12A flowing. I know the supply isn't drooping; it's good for 70A. The wires are all pretty thick. That 1/2 volt drop at 12A is 6 watts, which is plenty of energy to make things h...
by kcbooboo
Thu Nov 01, 2018 3:27 pm
Forum: AM Radio
Topic: RF Ammeter resistance
Replies: 15
Views: 487

RF Ammeter resistance

I'm testing a Wenschel 15A internal thermocouple-type RF ammeter. It seems to be accurate enough, within 2%, however with 12A DC flowing through it, the back of the meter, the terminal studs, and the metal straps between the meter and J-plug are getting hot, and I don't think that's normal. This doe...
by kcbooboo
Fri Oct 05, 2018 3:29 am
Forum: Everything else
Topic: New UPS suggestion
Replies: 9
Views: 487

Re: New UPS suggestion

Some true on-line units are very picky about the incoming power quality, which to me makes no sense, as all the incoming power really has to do is charge the battery and provide DC for the always-running inverter. TrippLite in particular wouldn't run on a mechanically-governed generator at an AM sta...
by kcbooboo
Tue Oct 02, 2018 6:25 am
Forum: Ask the Engineers
Topic: Dead Relio Revived
Replies: 13
Views: 653

Re: Dead Relio Revived

Inner foil layers are a definite possibility. In the past I have actually and unfortunately pulled the plated-thru hole "tunnel" when removing some caps. If there are just top and bottom layers you can just solder both ends of the lead, but the solder just won't flow along the lead by itself if you ...
by kcbooboo
Fri Sep 28, 2018 8:39 am
Forum: Ask the Engineers
Topic: Dead Relio Revived
Replies: 13
Views: 653

Re: Dead Relio Revived

Once the iron softened it, it sucked out like solder. It just took a tiny dot of 60/40 solder at the tip of the iron to get the heat into the joint to get it to soften enough so I could wiggle the capacitor lead out about half its length, then I had to heat the other lead and wiggle that one, and ba...
by kcbooboo
Fri Sep 28, 2018 3:40 am
Forum: Ask the Engineers
Topic: Dead Relio Revived
Replies: 13
Views: 653

Re: Dead Relio Revived

Pricey stuff. I have heard of ChipQuik flux, which seems to be quite helpful for soldering SMT parts. I just do so little SMT work, and don't have a hot-air workstation, that I just learned to "make do" with ordinary soldering tools.

Bob M.
by kcbooboo
Wed Sep 26, 2018 1:39 pm
Forum: Ask the Engineers
Topic: Dead Relio Revived
Replies: 13
Views: 653

Re: Dead Relio Revived

I've never heard of de-soldering alloy. I know there is brush-on flux and that might have helped a bit to wet the surface. I don't know how they even made this board, since there are leaded parts on top and SMT parts on BOTH sides. They couldn't wave-solder it with all those parts underneath. I did ...
by kcbooboo
Wed Sep 26, 2018 6:38 am
Forum: Ask the Engineers
Topic: Dead Relio Revived
Replies: 13
Views: 653

Re: Dead Relio Revived

I had my soldering iron up to 425C, way hotter than is normally used with Kester 60/40. The joints just didn't look shiny, and the iron didn't seem to melt anything until I added a dab of solder. The tip was cleaned for each one, too. I would think that the tin would make it shiny, not the lead. Thi...