[AMRadio] HRO Coil Compatibility

[W5AMI]

Jim,

Thanks for the reply and info.  Well, since you asked (I had hoped not to
have to admit it), when I first replaced the tubes back into my HRO-7, I
mistakenly swapped the 6C4 and OA2 in their sockets.  At the time I applied
first power, after recapping, etc., I had the 'C' coil in place.  Within
just a few seconds I was making good smoke!  If I remember correctly, after
seeing what I had done, filament voltage was flowing through the coil at
high enough current to make the osc. coil a tad bit hot.  Not good...

I had hoped I wouldn't have to mention my little oversight.  But since you
ask, my only excuse is that I didn't have my reading glasses on when I
replaced the tubes.  Bad mistake, and I hope that this might prevent others
from making the same mistake!  At least I didn't plug in another coil set
to see what would happen before I put the tubes in their proper sockets!

73
Brian / w5ami


On Mon, Jul 23, 2012 at 8:04 PM, JAMES HANLON <knjhanlon at msn.com> wrote:

>  Brian,
>
> Coils from any series of the HRO up through the 7 can be interchanged and
> expected to work.  That includes individual coil sections as well as the
> four-coil assembly.  The HRO-50 used a lower jack-bar on the receiver side
> of the interface, so if you are going to plug in coils from an earlier
> vintage radio into the '50, you should put washers in between the coil
> assembly and the aluminum coil shield to lower the coil assembly a little.
> I did that with an HRO-7 AC (15 meter) coil set that I have used in my
> HRO-50 since 1951, and it is still working fine.  I recently acquired an
> HRO-50-R1 at a hamfest for free!  but there were no HRO-50 coils to go with
> it.  The fellow did have a bunch of coils from the pre-war era, however, so
> I took along a full set of them, A, B, C, and D ranges.  After I added the
> above mentioned washers, I aligned them in the new 50-R1 and they work
> fine.  The HRO-60 goes to dual conversion on the C, B, and A coil sets, so
> they are not compatible with earlier HRO's, but the lower frequency coils
> from the '60 are cross compatible.
>
> How did you melt that oscillator coil?
>
> Jim Hanlon, W8KGI
>