Update - It's a Hallicrafters CB-5 Mark II.

I have schematics already. I guess it's time for me to exercise that
capacitor meter I blew $200+ on. I can easily test diodes,
transistors, diodes, capacitors, and resistors, and I'm pretty good at
soldering as well, so this should hopefully this will just be a
time-consuming project.

I was wondering if perhaps someone might know what section of the CB
could be causing this (final stage, etc - it's not the main power
supply section). That might get me going the right direction... as
is, aside from removing components and checking their values, I'm
stumped.

On Wed, 08 Jun 2005 09:55:46 -0400, -ex- wrote:

Dirty Q. Tip wrote:
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.


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?


Bringing a 40-50 year old set back from the dead usually involves a
serious effort of checking/replacing components. If they are (or once
they are) all good then it stands a good chance of working. Any
electrolytic or paper capacitors probably need replacement, maybe even
some of the plastic molded ones from that era (I'm guessing late 60s?).
Check resistor values for drift, clean controls, etc.

Its not expensive to do but if you've never done anything like that
before this might not be the best set to learn on. On the positive
side, you can't hurt it at this stage.

If you want to give it a go, first try to find a schematic for it - ie
road map for an unknown journey. It should be in SAMs which is
available at many big city libraries.




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).

Dirty Q. Tip wrote:

Update - It's a Hallicrafters CB-5 Mark II.

I have schematics already. I guess it's time for me to exercise that
capacitor meter I blew $200+ on. I can easily test diodes,
transistors, diodes, capacitors, and resistors, and I'm pretty good at
soldering as well, so this should hopefully this will just be a
time-consuming project.

I was wondering if perhaps someone might know what section of the CB
could be causing this (final stage, etc - it's not the main power
supply section). That might get me going the right direction... as
is, aside from removing components and checking their values, I'm
stumped.

The power supply and xmtr or AF output stage...which are equally as old
and deteriorated as any other part of the radio That said, all it
takes is a single leaky/shorted cap somewhere else in the ckt to bollox
the whole works.

There's a different philosophy in bringing an old junker back into
service as compared to troubleshooting a radio that just quit yesterday.

-BM

Behold, Dirty Q. Tip scribed on tube chassis:

Update - It's a Hallicrafters CB-5 Mark II.

I have schematics already. I guess it's time for me to exercise that
capacitor meter I blew $200+ on. I can easily test diodes, transistors,
diodes, capacitors, and resistors, and I'm pretty good at soldering as
well, so this should hopefully this will just be a time-consuming
project.

I was wondering if perhaps someone might know what section of the CB
could be causing this (final stage, etc - it's not the main power supply
section). That might get me going the right direction... as is, aside
from removing components and checking their values, I'm stumped.

Hi,

I had two of those babies and I miss them.

The squeal is likely in the T/R switching - the audio isn't getting
cutoff from the speaker and sent to the plate of the 6AQ5 (IIRC) final
tube correctly.

The only caps you'll need to change are electro's and dust off the
variables.

Watch the driver coil assembly - it buggers up and causes touchy tuning.

Enjoy your treasure! :-)

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*

Are you sure you're thinking of the right rig? This critter uses a
pair of "3B4" tubes, and one "3A4" tubes... I checked all three, and
they're all genuine Hallicrafters tubes. And honestly, I haven't even
looked at the scats for it very closely. Driver coil assembly.......
I'll have to locate that and avoid mucking with it.

Just out of curiousity, is there anything "special" this unit can do
if one were to, say, modify an actual functioning CB-5 Mark II in a
manner which it shouldn't necessarily be? I know nothing about these
older tube units other than they can give you a decent lil zap.

Also, I inspected the mic wiring - talk about horrid. I suppose
several years of storage will dry rot some wire insulation. Only the
mic wires are showing this deterioration, and it has been temporarily
rectified. Still, the radio will not transmit nor receive.

I'll be re-capping the electrolytics soon enough, and much to my
surprise, this unit is dust-free on the inside! Well, almost
completely dust-free. I'll also be testing the power transistors
attached to the back - there's four 2N376A's and one 2N555 (all
Motorola) I can check while I'm at it. You might be hearing more
inquiries from me, or you might soon hear that the unit is alive once
again. Who knows. But either way, thank you everyone for responding,
and if you can think of anything else, feel free to pass along the
info.

--Dirty Q-Tip

On Wed, 08 Jun 2005 16:51:23 -0700, Gregg wrote:
Hi,

I had two of those babies and I miss them.

The squeal is likely in the T/R switching - the audio isn't getting
cutoff from the speaker and sent to the plate of the 6AQ5 (IIRC) final
tube correctly.

The only caps you'll need to change are electro's and dust off the
variables.

Watch the driver coil assembly - it buggers up and causes touchy tuning.

Enjoy your treasure! :-)

Behold, Dirty Q. Tip scribed on tube chassis:

Are you sure you're thinking of the right rig?

D'oh!

Brainfart on my end.

CB-3A were the ones I had.

Sorry for the confoosion :-(

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*