[Collins] KWM-380 SB-7

[Dr. Gerald N. Johnson]

On Fri, 2008-12-05 at 20:07 +1030, Lee wrote:
> Hello All
>  
> In the service bulletin 7  L1 to L8 are replaced with 560uH chokes. Is
> this value critical?
> I am finding it difficult to find any chokes small enough to fit.
>  
> 73 Lee

How small is small enough? My Mouser catalog shows a Vishay/Dale 560 uh
with the molded body about 0.1" (2.5 mm) diameter and 0.25" (6.5 mm)
long with wire leads for $1.29 US. The price may be different today.
Their catalog number 70-IM2-560
http://www.mouser.com/Search/ProductDetail.aspx?
qs=0GL8V0krZROgno9UAIvoKg%3d%3d

They do export. The on line catalog shows a price of $1.55 US today.

I'm not familiar with the KWM-380 circuits to know the reasoning in the
choice of this part.

I have now downloaded and read the SB. Seems to me, any value from 470
to 680 uH will work, mainly they are increasing the inductance in a
gaggle of low pass filters at the board edge. And these Vishay/Dale (and
I know many Dale parts had Collins part numbers) parts look like they
should fit on the board compared to the DIP ICs nearby. It shouldn't be
so neat, but slightly fatter coils could fit if every other one was
tight to the board and then the intermediate ones were stacked on top.
Its sure that the coils should be shielded so they don't couple one to
another at that close spacing.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer