On Mar 17, 8:44�pm, wrote:

The advice to study an "All American Five" receiver, OTOH,
is very bad, for a number of reasons:

1) You want to build, not take apart. In theory you could take an AA5
all apart and put it back together again, but
that's not the same as building something new.

As a LEARNING experience it costs (almost always) nothing.

There must be tens of thousands still sitting around, doing
nothing.

2) There is a good chance that if you can find an AA5, it
will need to be fixed to make it work. While you can learn
a lot that way, it's still not the same as building something new.

I disagree. The only one I've seen "not working" was
already damaged beyond repair. :-)

I will repeat...it is a LEARNING experience. Since it is
working, one can work backwards from that to see what
makes it (or a stage within) NOT work.

3) The end result of any such effort is going to be a basic receiver
for AM broadcast. Not a transmitter or transceiver, and not a piece of
amateur radio or SW equipment. If amateur radio/SW is your interest,
it seems to me that your projects should be for amateur radio and SW,
not AM BC.

True enough, but such receivers still work by the same
principles that apply to HF or VHF or LF or VLF.

An advantage to using AM BC is the known "signal
sources" in the area. One doesn't absolutely need a
signal generator to check or compare its performance.

4) AA5 receivers are of transformerless, "AC-DC" design. Usually one
side of the AC line is directly connected to the chassis.

I have yet to see one that is so "directly connected to one
side of the AC line." They may exist, but all the ones
I've handled (maybe two dozen all told, different makes
and models) have always used a capacitor to chassis
from one side of the AC mains. As I recall, they all had
UL stickers on them.


... But in order
to work on one, you want it out of the cabinet and powered up.

Yes, but that applies to ALL such things, yes? :-)


Working on one requires a lot of extra precautions to avoid getting a
shock. *Better to focus on transformer-operated equipment whose
chassis can be directly grounded to minimize the shock hazard.

Tens of thousands of tinkerers have gone before you and
still survived without being "shocked." :-)

Electricians seem to survive just fine and some of them
work directly with "hot" circuits...at higher voltages than
a nominal 115 VAC. TV repair folks face 24 KV from
picture tube ultors (the final accelerating anode)...even
when the power is off and disconnected.

If all else is troublesome, a cheap 1:1 isolation transformer
can eliminate all those "hazards." Cost in the neighborhood
of $15-$20 for 50 VA. However, even if used, the "B+" is
still at 140 to 100 VDC and is always there when working.
Precautions are fine but let us use a little realism on
"advice" - tube based devices nearly ALL have lethal-
potential voltages present. The average solid-state
device tops out at +/-15 VDC or thereabouts, NOT a
lethal potential.

73, Len AF6AY

This is the HOMEBREW newsgroup and is about BUILDING at home.
I was trying to focus on the LEARNING aspect of getting
acquainted with the various stages of radios. I picked the
ordinary old table model radio as a representative of such
a LEARNING device for several reasons: There are thousands
....[snip]....

And if you can find a copy of "Elements of Radio Servicing" by Marcus
and Levy, you'll learn even more! I have the 1967 version, and it
covers EVERY aspect of an AA5 down to the last details!

It also includes a little bit about transistor, auto, and FM radios.

--
--Myron A. Calhoun; W0PBV; 2001 Dunbar Road; Manhattan, KS 66502-3907
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
NRA Life Member & Certified Instructor for Rifle, Pistol, & Home Firearm Safety
Also Certified Instructor for the Kansas Concealed-Carry Handgun (CCH) license

Interesting..

Well, I'll let you know how I go about this.

Greg