[AMRadio] Elmac A54

[Collin]

I had a similar experience on a Globe King 500 with loading capacitor presenting little if any change to plate current. I tore the whole PI network out looking for a smoking gun and did not find any gun. It turned out to be parasitic oscillation. Of coarse the King didn’t come with chokes on the plate leads but I made some and then the rig straightened out and tuned/loaded normally. May want to try this, doesn’t take much to whip up a choke. 

Good Day, Collin

> On Apr 18, 2019, at 5:56 PM, JAMES HANLON <knjhanlon at msn.com> wrote:
> 
> Charlie,
> 
> I have an A-54 in my collection, not currently on the air, and an AF-67 and AF-68 both on the air, so I do have some experience with Elmacs.  
> 
> As to the A-54 manual, the copy I have, probably downloaded from BAMA years ago, has an original page with microphone and power plug illustrations and Tuning Procedure.  Those Instructions are only partially legible, and there is another page in the package In clear print that appears to be someone's recreation of the Tuning Procedure.  That page calls for initially setting the Loading for 105 ma and then dipping the Plate Tuning for minimum, and repeating this procedure until the minimum dip is 300 ma.  That is, as you observed, an obvious error probably made when the author was struggling to read the the partially legible original.  Looking at the schematic, you'll see that the meter measures plate and screen current together.  The max total plate and screen current for an 807 should be about 105 ma, certainly not 300 ma.  So that takes care of that part of your concern.  
> 
> As to the (lack of) action of the Load cap, that is not normal for an A-54.  I run my A-54 into a 50 ohm load system, and the Tune and Load controls act like those on any conventional pi-match.  It sounds like your Load capacitor might not be properly connected in the circuit.  
> 
> The final tank circuits in all of the Elmacs were probably designed so that they could match to a typical, inductively loaded mobile whip antenna.  But in my experience they all tune up into a 50 ohm system as well. 
> 
> And if you want to keep your 807 alive for a decent amount of time, keep its plate current to 100 ma or less.
> 
> 73,
> 
> Jim, W8KGI
> 
> Sent from my iPhone
> 
>> On Apr 1, 2019, at 11:22 AM, CL in NC <mjcal77 at yahoo.com> wrote:
>> 
>> One thing you get when you ask questions on some  sites about gear, is a lot of pontificating, useless suggestions,  and no info.  Amphone always seems to have more meat on the answers. On the Elmac A54 meter for plate current, it has a 150MA scale, and a tic mark at 100MA.  I seen no mention of the scale being X 2, the actual tune up procedure in the manual,  says load to 300MA or as near as possible, that has to be a misprint.  On one site, a fellow puts 600VDC into it and loads to 200MA.  That seem like a heck of a lot for a single 807.  
>> 
>> Other comments say the plate tank is designed for a whip antenna, and not a 50 ohm load.  Is that a true statement?  The one on the bench right now I'm working on, I put 450 VDC on the plate and am getting about 35 watts out, but the load cap has minimal effect, like none, you can set it anywhere and does not change plate tuning but a tiny bit, and still gives 35 watts into a dummy load.
>> 
>> Charlie, W4MEC in NC
>> 
>