heathkit hw-8 rfc3 burned choke

[wa5ddz]

Hi all:
   First time post--reader for about a year. This seems to be the place for-----
Picked up a heathkit hw-8 at hamfest. In the final amp circuit the zener diode  shorted and the RFC3 choke burned to a crispy black powder. I need to know the wire size and number of turns for this choke. Saved the form so a rewind is possible. Or can this choke be purchased? Any help would be usefull.
 Thanks, WA5DDZ

[WD5JKO]

Bruce,

  I let my HW-8 go years ago to a would be Novice who never returned it. That was 20 years ago. 

That RF choke will need to work 80-15m, so some experimentation might be needed. The schematic says 26 uh for RFC-3.

Maybe the JW Miller series carried by Mouser will do. The 27 uh choke there should work for 80-40m, but the self resonance frequency (SRF) is 7.6 Mhz, so as choke it is good up to the SRF, but beyond it looks more like a capacitor than an inductor. Maybe the 22uh in series with the 5.6 uh would do..

Good Luck,
Jim
WD5JKO

 

http://www.bourns.com/data/global/pdfs/77F_series.pdf

[KA2DZT]

I read Jim's comments about JW Miller having a RFC.  I had the JW Miller catalog right next to the computer, didn't even have to hardly move to reach for it.

I'll check to see what JW has for RFC's.  Well, there are 20 pages of RFC's that JW makes.  Most of the sub-miniature 27uh chokes have a high SRF around 30mhz.

I'm not sure what style choke is in the HW-8.  Most all of the single layer 27uh chokes have SRF above 30 mhz.

I would suggest checking the manual for the HW-8 to see what Heath shows for a replacement.

Ohmite also made a series of single layer chokes.  I'll have to go downstairs to get the Ohmite catalog, BRB, stand-by.  I'm back,  seems that Ohmite only made about 7 models, one is 44uh (SRF 23mhz) and another is 21uh (SRF 41mhz).  The Ohmites made not be what you need.  I have a lot of these Ohmite chokes and they are not that small and may not fit on the PCB of the HW-8, if the HW-8 even has PCB's.

Fred