Here's the deal. I've got a Hallicrafters Mark II (2) 6 channel CB
radio. This thing is really old - it still has my grandfather's old
radio ID taped to it (xxx####, x=letter, #=number). Anyhow, I took it
to my friend's house the other day, and wired it up to his existing CB
setup's connections to test it.

Positive to positive, negative to negative (case is grounded as well),
attached the coax. Powered it up, lights came on, and got nothing but
static on Channel 19. During a brief (under 1 second) key-up, the
radio squealed - that's the only way I can describe the sound; or
perhaps a whine might also be a good descriptive sound. Also, the red
transmit light (I assume that's what it is) came on immediately after
keying up, turned off before I could release the mic key, and flashed
once again after I released the mic key. During the time the mic was
keyed (tried it several times, never longer than 1 second), the radio
would squeal. I'm not talking about squeal through the speaker, I
mean the circuit itself squealed/whined.

Any thoughts or ideas? My grandpa was a smart man, and kept all of
the documents on this radio (including the receipt and the business
card of the guy he bought it from, they're in my closet somewhere), so
I've got the schematics and the user's manual for the unit. Problem
is, I know almost nothing about troubleshooting radio equipment.
Hence, I have no clue where to even begin. A starting point and any
additional guideance would be much appreciated.

I openly admit, I'm not certified to work on radios. However, once I
can get this thing to transmit without squeal/whine and receive again,
it's going back on a shelf until I can afford to get a cert'd tech to
inspect and tune it as needed. I don't intend to break any laws by
working on the unit, I just desire to get it operational again. I'm
thinking it could be feedback from a blown final transistor (complete
guess).

I consider what I'm going to do akin to fixing your car before taking
it in for a smog test..... I'm just fixing it, and I'm not going to
operate it until after a tech inspects it (and even then, I might not
operate it, instead opting to keep it as a collector's item and family
memorabilia).

My reasoning for wanting to fix this CB rather than use it as a boat
anchor is that it was my grandpa's radio, and I'd love to restore it
in his honor (might seem lame, but it's a personal thing).