[Elecraft] K1 RF Board Trimmer Caps

[Scott Krebs]

Don,

These are definitely not the blue-bodied trim caps. I'm familiar with those as they are used in the KFL1-4, which I've already assembled. No confusion at all as to how to orient the blue-bodied, angular-nosed trim caps.

The C13/20 trim caps I've now installed on my RF board appear to have a white, cylindrical, possibly ceramic body. There are no flat sides on the main body. Underneath the slotted adjusting screw is what appears to be a fiber washer, half brown and half white, with a small blob of what appears to be solder applied between the side of the adjusting screw and white half of the washer. One electrical connector is attached to the back side of the cylindrical body while the other electrical connector is attached to the square protrusion from the other side of the cylindrical body.

The assumption I made during installation was to match the asymmetrical side (i.e., square protrusion) of the trim cap with the flat side marked on the PCB.

Scott

On Dec 24, 2012, at 10:34 AM, Don Wilhelm <w3fpr at embarqmail.com> wrote:

> Scott,
> 
> I figure you have the blue bodied trimmers and not the older ceramic ones.
> 
> Look at them carefully - one end is rounded (that will be the wider end with rounded corners) while the 'shorter' end has angular corners and a flat between those corners.  That is the 'flat' side and should be aligned to the flat shown in the manual.  Be aware that the newer gold looking solder pads do not accept silkscreening, so you must align them like is shown in the manual.
> 
> The consequence of mounting them backwards is that you will have to use an insulated tool to adjust them.
> 
> Does that clear up your confusion?
> 
> 73,
> Don W3FPR
> 
> 
> On 12/24/2012 9:14 AM, Scott Krebs wrote:
>> My K1 RF board ceramic trimmer capacitors C13 and C20 have an outline shape that differs from either that described in the K1 assembly instructions or on the silkscreen outline on the RF board PCB. This is the same question that Dean asked back on 10/27/12. Don's answer described trimmer capacitors with an angular shape. This description perfectly describes the trimmer capacitors on the KFL1-4 filter board (e.g., figure 1 in KFL1-4 assembly instructions) but does not appear to describe the current crop of RF board trimmer caps. I didn't see any additional clarification associated with that thread.
>> 
>> The K1 assembly manual (p. 28) describes C13/20 trimmer caps that "have one side that is flattened." The trimmer caps supplied with my K1 have a round profile with a square protrusion on one side of the profile, sort of like the profile of an old-style keyhole. I'm assuming that the square protrusion side of the trimmer cap equates to the flattened side of the PCB outline (i.e., square protrusion pointing to the rear of the PCB) and have installed my trimmer caps based on this assumption. Is this assumption correct?
>> 
>> As long as I'm pounding away on the keyboard, here's one other question. The K1 "DC voltage check" procedure on p. 30 calls for a power supply voltage of 12-14 VDC. However, my trusty old late-70s-vintage Vanco regulated DC power supply has an unloaded DC voltage of 14.5 VDC as measured with a Fluke 115. I also note that the K1 specifications on p. 5 lists a required supply voltage of 8.5-15 VDC. I also suspect that once placed under load, my Vanco PS will drop to something less than 14 VDC. Is it OK to use this power supply for the DC voltage check procedure?
>> 
>> Scott
>> N4KTR
>> 
>> 
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