Sacrificial Lamb Cobra 19 Ultra III

[whiteastro]

Well I re-acquired this radio today that I gave to my neighbor a while ago and he never did anything with it. Him and his wife are moving to Florida and driving separate vehicles so I made sure they had 2 good working radios for their trip. ( Good neighbors I'll miss them ) Well I put this radio on the bench to test the mic because I thought it might be bad. ( Long Story ) When I turn the radio on the display shows The Busy display and if you key the mic you hear a crackling sound, the transmit display lights up but you hear nothing on a receive radio. The mic works fine in the PA mode. When I try to do a transmit my Dosy TFC-3001-S freq. counter shows it is way off freq. and the dead key needle never moves. I originally bought this radio at a yard sale just for the microphone and the guy threw the whole radio in on the deal so I have no idea what has been done with this radio by someone else. The whole thing cost $10.00 so I think it is my chance to try my hand at a poor-mans alignment and dead-key adjustments, anybody got any Pot #s to suggest so my Golden Screw-Driver can get busy. I'd like to try the dead-key first to see if I can get my meter needle to at least move. Who knows it might have been screw-drivered to death but I guess I'm not losing too much and I just might get lucky. LOL Thanks in advance !

 

[nomadradio]

Hmm. Big problem with the lowest-price three-knob mobile radios is that nobody has any experience working on them. A shop that charges for repair labor will recommend the customer ditch it, rather than spend more than the replacement cost for a repair. He won't have that first-hand experience.

This means you'll have a hard time getting first-hand advice from someone who has experience with that model.

Now, as a personal project, I wouldn't seek to discourage anyone from a learning experience. But if your objective is a radio that these folks can use and depend on, I recommend one of two strategies.

Either start with a cheap radio that's not broken. They do have a deadline to leave town, right?

Or maybe start with a more widely-used model that other folks have real-life experience with. You'll get more helpful advice that way if you need it.

And there is one more obstacle to getting the Ultra III back on the air. No technical data. No schematic diagram, no parts list, no alignment procedure.

Even a pro will find this to be time-consuming.

On the other hand, there's nothing to keep a person from tracing down every circuit and hand-drawing a schematic diagram for this radio.

Just a matter of what your objective is.

73

 

[whiteastro]

Just a matter of what your objective is.

73

Thanks for your reply and I agree with your thoughts. The main objective of this project for me would be to keep from filling the land fill with another worthless piece of electronic junk and maybe learn something in the process. The last yard sale I had a young lad came down and looked at my Magellan hand held GPS device but of coarse he didn't have enough money for it so in the end I remembered when I was in his shoes and just give it to him. He went away Happy and I felt good that a Old Lad could help a Young Lad. At 72 YO it is too late for me to think about starting radio repair business but not too late to learn. I opened the radio last night after internet search and found only a few adjustment points but the board has 19DX-IV & GEPC-994-A9 marked on it. Of coarse some of the info from the internet didn't make sense but I'm sure there were different versions of that radio. I won't spend a lot of time on it but if I can leave this world with a little less pollution I will have done the best I can !

 

[brandon7861]

but the board has 19DX-IV & GEPC-994-A9 marked on it.

the 19DX-IV schematic and service manual are in the CBTricks archive. Schematic and block diagram are on this site under the DX Radio Tech section.

 

[whiteastro]

the 19DX-IV schematic and service manual are in the CBTricks archive. Schematic and block diagram are on this site under the DX Radio Tech section.

Thanks for the input. I was just looking at the radio and looks like it could fit in a crevice on the motorcycle. I'll check out your info. Thanks again ! Happy DXing

 

[Handy Andy]

Having some experience with similar model - same series. The DX series is pretty much SMD - little if any real work mods that the Cobra 29, 25 or even the predecessor the 19 PLUS can do, this really can't.

If you're gutsy enough - the "swing mod" people use on the 29 can be done to this, but due to it's size, the variable of that mod is not the best way nor easiest to do.

What makes this radio a keeper, is the simplicity - but that is only due to the quality they once had, not what they've turned into.

The VCO section is the coil and a square shield case cutout that houses the older "exciter" section most 19's used back in the late 70's onto the 90's - so to know the earlier models - this one is not different, but the technology used in it, makes this a challenge for discrete mods versus just using it as it is.

That may be where most of this problem with TX is, the Final in such units worked fine, but no power because the "shift" they needed from the TX frequency to the RX and back again, that 455kHz shift - usually put the thing out of commission as being out of lock and useable until you tweaked that VCO coil to get it to fire again.

At least in that season of temperature and humidity, else Winter and Summer - it only worked in one, not both seasons when the VCO coil is goofy like that.

You think this is bad, remember the older units that used vertical cards? Those failed miserably when in a environment that flexes that case - making it useless in mobile installs, They addressed this in the DX line by making the board single layer SMD versus trying to populate the boards modularly by using vertical pre-tuned cards that broke their traces when bounced in a vehicle or sandwiched between the seats. At least an angry driver - in their frustration - they can throw them out the window and if not smashed onto the concrete of the pavement - tossed onto the side of the road, left for dead.

That's when the "Keep The Highway Clean" crew could come along and throw their find in a garage sale or on eBay and sell it as "Gently used"

 

[whiteastro]

I read somewhere that this radio uses a

Electret​

type microphone and it has a Cobra CA73 mic with it, so was wondering if this is the proper mic for this radio or is it a dynamic mic and the reason it doesn't fire the needle on my meter when I key the mic? Plus generates static when keyed.

 

[whiteastro]

Having some experience with similar model - same series. The DX series is pretty much SMD - little if any real work mods that the Cobra 29, 25 or even the predecessor the 19 PLUS can do, this really can't.

.
"

After reading your post a second time I don't really want to do any fancy mods to this Ultra III and try to make this little Cobra something it wasn't meant to be. I just want to make it do what it was designed for so I can get rid of it to some beginner and not fill the landfill with it. It's not showing a dead key on my meter and I don't know if it is cooked or someone was tinkering in there. Or maybe it's got the wrong kind of mic. someone thru on it. The info I found so far is Hazy and if it becomes a real pain I could throw it in a wood stove and render it down to smaller pieces. LOL That would be a shame because this morning it was bringing in stations pretty good, but probably not like it did when it was new.

 

[Handy Andy]

To get some stations in is a good start, that is why I mentioned the VCO "exciter" that is where the RF for IF, being either for TX or 455kHz differently - the RX side, the work done in that little shielded case does the magic of heterodyning to tune in all those channels.

The VCO and it's coil was/is/are prone to causing out of lock and no transmit problems because the VCO can't tune there. It needs a little help - simply due to age and thru a quick tweaked turn can bring back TX just because if the shift the exciter needs to accomplish, using the VCO coil - but can't quite get there because the original tuning position was for when it was new, now it's aged and that coil has aged too. So it just might need a little work.

Can you post a pic or two?

 

[whiteastro]

To get some stations in is a good start, that is why I mentioned the VCO "exciter" that is where the RF for IF, being either for TX or 455kHz differently - the RX side, the work done in that little shielded case does the magic of heterodyning to tune in all those channels.

The VCO and it's coil was/is/are prone to causing out of lock and no transmit problems because the VCO can't tune there. It needs a little help - simply due to age and thru a quick tweaked turn can bring back TX just because if the shift the exciter needs to accomplish, using the VCO coil - but can't quite get there because the original tuning position was for when it was new, now it's aged and that coil has aged too. So it just might need a little work.

Can you post a pic or two?

I will do the pic tomorrow as this old buck is ready for the sack but thanks for the concern. It would be exciting to see that little tiny box working proper because it is actually clearer & Louder than my new Lincoln II+. That radio would be easy to stash almost anywhere, just too bad it isn't SSB. LOL PS. right now it is really cranking the SuperBowl an a few others !

 

[whiteastro]

Can you post a pic or two?

OK I'm not a photographer but took 8, sending 4 because not sure of size limits. Can send more later if need be. Thanks!

 

[Handy Andy]

Just brief ...

Review this video, there is some info that can help you.



You have not taken a pic of the bottom yet, which reveals this radio is even more frustrating - it's where most of the semiconductors reside and several SMD resistor and caps are in critical areas.

The LRx numbered cans are for your receive, the thing looks more like a TRC- 419 in the Finals section those coils are LTx - the area in and around that 2078 bolted to the back, there is a 10Ω resistor back there for the Driver (a 2314) that mimics the Realistic layout almost to a tee.

The YT Vid can help more - but the premise is this radio is a Readers Digest ™ Condensed version of the Cobra 19 series. So they skipped several plays and went right to the chase.

To tell you how cheaped-down they went, they even removed the Power Filter Choke and went straight to a YOUDA (TDA Toshiba-knockoff) audio chip

 

[whiteastro]

Just brief ...

Review this video, there is some info that can help you.



You have not taken a pic of the bottom yet, which reveals this radio is even more frustrating - it's where most of the semiconductors reside and several SMD resistor and caps are in critical areas.

The LRx numbered cans are for your receive, the thing looks more like a TRC- 419 in the Finals section those coils are LTx - the area in and around that 2078 bolted to the back, there is a 10Ω resistor back there for the Driver (a 2314) that mimics the Realistic layout almost to a tee.

The YT Vid can help more - but the premise is this radio is a Readers Digest ™ Condensed version of the Cobra 19 series. So they skipped several plays and went right to the chase.

To tell you how cheaped-down they went, they even removed the Power Filter Choke and went straight to a YOUDA (TDA Toshiba-knockoff) audio chip

Thanks for the video and help, I'll take a pic of the bottom out in the sunlight to eliminate the shadows when I get a little time. Have to run to the hospital to visit a relative today. If a miracle happens and I get it working I would probably give it to one of the young guys in the neighborhood to keep the interest in our hobby going because their parents won't teach them anything anyway. LOL