[Collins] KWM-2A help additional

[Al Parker]

Hi Jerry, et al,
	It is a round emblem, and has the FA case filter, so I guess a later 
one, but not late enuf for the 6EA8 osc. tube.
	I'm with you on the trimmer peaks, only 2, like I said, at abt 2/3 
cap., at least for that one.  I think others are OK, but will double ck, 
and go back to the beginning on the alignment.  & I'll ck those later 
manuals.
thanks again for all your interest & work.
73,
Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 9/19/2010 6:13 PM, Dr. Gerald N. Johnson wrote:
> The crystals must be replacements because by '74 it should be a meatball
> emblem or Rockwell. Meatball for sure because that change happened about
> '65. Which mechanical filter does it have? Y case or FA case?
>
> 73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association
>
> On 9/19/2010 4:31 PM, Al Parker wrote:
>> Hi agn, Jerry et al,
>> Well, still no joy. My xtals are dated 8/74, and the skem I'm using is
>> from a Nov. 60 manual. Both the xtal osc., V13A & cath follower, V2A,
>> are 6U8A's, on the skem & on the chassis. I forgot to mention ystdy that
>> I'd also re-tightened all ground screws, some were pretty loose. I tried
>> a different 6U8A for the osc., and a 6EA8, no dif.
>> C65, the 14mc trimmer in the xtal osc. plate peaks at abt 2/3
>> capacitance only. As Jerry analyzed, that ckt won't resonate at the LO
>> ~3mc signal. I do need to look into L5 & the possibility of a missing
>> C26 or problem in that "balancing" ckt because it seems like there's an
>> awfully big 3mc component in the output of the mixer. But that may not
>> be a causing the problem, because---
>> I had earlier been looking at the signal at the grid of the 6CL6 driver
>> tube, V8, being 9v p-p @ 7.1mc, & only 2v @ 14.1. I looked back to the
>> plate of the previous tube, V7 RF amp, before the C44 coupling cap, and
>> find 14v & 10v respectively. There's much more loss at 14 than at 7.
>> That made me suspect the driver tube, possibly bad with more grid to
>> cathode capacitance, just plain leaky, etc. Swapped in a new 6CL6, no
>> noticeable difference. Now maybe I need to look at the tuned ckt there,
>> but like C65 at the osc., C115 peaks OK, and the signal at this point is
>> pure.
>> I may get back into it tonite, but have another job to do in the AM, so
>> it might be later tmw b4 I get at it. One thing I do plan to do is cut
>> the plate & screen voltages to the finals, and measure actual signal at
>> the final grids. It's not enuf now on 14mc to make any grid current.
>> I feel close to the problem. I have another driver 6Cl6, maybe try that.
>> The fact that all bands above 7mc are very low points away from
>> individual band tuned ckts.
>> Still need help, thanks for all the thoughts & suggestions.
>> 73,
>>
>> Al, W8UT
>> www.boatanchors.org
>> www.hammarlund.info
>>
>> "There is nothing -- absolutely nothing -- half so much
>> worth doing as simply messing about in boats"
>> Ratty, to Mole
>>
>