Cobra 25 unhacking project

[LeapFrog]

Buy a cheap-o solder sucker from Amazon for under 10$, buy a more expensive one the first time, and you won't have to spend twice.

I used the hell out of a 7$ "Button Plunger" spring loaded type solder sucker for 3 months, I couldn't tell you how many ounces of tin/lead that thing removed before it wore out & gave up, once you get a feel for solder you can remove it fairly easily, at times adding some rosin flux helps the stubborn corroded solder to "wick" again {become molten} and flow. The (potentially) corroded surface area of the old solder will act against you, lightly sand it, or use a solvent/tooth brush to remove grime first.

Use the common 60/40 solder w/ rosin core and make sure the entire pool of solder-metal becomes molten and is not disturbed when cooling. The amount of time/heatt required depends on your iron, never use pressure of the soldering iron to force components around, this is a sure-fire-way to ruin a circuit trace or damage the p.c. board.

If you're serious about doing a lot of soldering then buy a good one, beware the spring loaded ones are tricky because you have "like 3/4 of a second" to "grab the solder" before it hardens again, & you must use both hands at once.

If it's just this one radio you plan to work on, buy a ten $ "spring loaded" or "bulb type" and you'll be fine, it makes cap changes much more possible, & easier; trust me on that one!

I'm not a huge fan of solder braid, but I've heard great things about it!

 

[Tallman]

The amount of time/heatt required depends on your iron, never use pressure of the soldering iron to force components around, this is a sure-fire-way to ruin a circuit trace or damage the p.c. board.
If you're serious about doing a lot of soldering then buy a good one, beware the spring loaded ones are tricky because you have "like 3/4 of a second" to "grab the solder" before it hardens again, & you must use both hands at once.
If it's just this one radio you plan to work on, buy a ten $ "spring loaded" or "bulb type" and you'll be fine, it makes cap changes much more possible, & easier; trust me on that one!
I'm not a huge fan of solder braid, but I've heard great things about it!

Get a hold of some scrap electronics to practice on. Old DVD,CD, or computer boards are good for this.
There are situations where Solder braid is the only way to go.
I have two industrial/commercial de-soldering stations, Spring loaded Solder Vac, solder braid, and the sqeaky toy solder bulbs. Do not sand on a circuit board. If you need extra cleaning power, 200 proof grain alcohol and a stout denture type tooth brush will usually fill the bill. You can also use a soft wire brush like the brass type for really messy boards. Use this method only in well ventilated areas and be sure it is completely dry before turning on. You don't need a flash fire inside your station.

 

[LeapFrog]

Do not sand on a circuit board.... You can also use a soft wire brush like the brass type for really messy boards.

Yes, I don't want to be "the guy who said to sand my p.c.b." lmfao, I should have been more specific (any crud on the surface area of the solder is what can make things tough) DO NOT EVER SAND a circuit board, the wire brush is a great idea, watch that you don't remove any (usually green) solder mask.

I like 99% isopropanol alcohol, that will clean the pcb well enough most times. Always use proper ventilation, as Tallman said you don't want a flash fire.

 

[Tallman]

I like 99% isopropanol alcohol, that will clean the pcb well enough most times. Always use proper ventilation, as Tallman said you don't want a flash fire.

I like the grain alcohol because I might take a nip every once in while.(Kidding)

 

[LeapFrog]

I like the grain alcohol because I might take a nip every once in while.(Kidding)

No doubt, that's why my "Everclear" mason jar stays on the work bench, it's dual purpose lol!

 

[338_MtRushmore]

I have a 40 watt iron, what do you all use for typical through hole radio stuff? I am working on an order and trying to get everything. What size solder is a good general use .03-.04ish? Trying to cross reference and decipher components is amazingly hard for the inexperienced. Thanks guys. I gotta get back to sanding all this green stuff off the board now

 

[Robb]

If my Weller station were to go belly up w/o remedy, pretty sure I would go for one of entry-level Hakko adjustable stations. Pretty reasonably priced with a high build quality standard. Wouldn't think twice about that one.

I'd get two diameters; one for small stuff ('thru -hole'), and a larger diameter for connectors, like a PL-239 connector. But I use a 120w soldering gun for that stuff.

 

[338_MtRushmore]

Those Hakkos do look nice. My brain is to fried trying to decipher components. Mylar is polyester

 

[LeapFrog]

Cobra 25 LTD 1995, China made. This video contains some incorrect jargon, I was trying to sound smart. Also at this point my test bench still had a ground/cmm issue somewhere.


The Cobra 25 LTD is a great little radio, they work fine in stock format with a good/clean tune!
They don't need much, zero mods is fine I promise you will enjoy the radio still.

 

[LeapFrog]

Cobra 25 LTD 1995, China made. This video contains some incorrect jargon, I was trying to sound smart. Also at this point my test bench still had a ground/cmm issue somewhere.


The Cobra 25 LTD is a great little radio, they work fine in stock format with a good/clean tune!
They don't need much, zero mods is fine I promise you will enjoy the radio still.

This was using a ghetto speaker method, not a proper AF signal gen; So I cannot tell you what the input signal level is with any certainty. I cannot recommend this method.
Time/Base, Volts/Division, Trigger settings on the 'scope are all wrong.

@ 6:54 when I mention you cannot reach 100% modulation unless you "reduce the carrier" that is a flat out lie, I didn't know better when I shot this video...
[I'm going to add some annotations, eventually.]

I have a 40 watt iron, what do you all use for typical through hole radio stuff? I am working on an order and trying to get everything. What size solder is a good general use .03-.04ish? Trying to cross reference and decipher components is amazingly hard for the inexperienced. Thanks guys. I gotta get back to sanding all this green stuff off the board now

Lol please don't smh, I know I worded my suggestion too loosely


A 30-40 watt iron will work for through-hole just fine, don't use the iron as a tool to forcefully push components out, you can damage traces that way, also don't use too much time/heat, or pressure.

338_MtRushmore,
I got by with this cheap ass china junk "30 watt" for a long time, just avoid using the tin based solder (unless that's what is already present like on RoHS compliant radios) & get some real 60/40 rosin core solder (never use acid core or plumbers solder), the smaller/thinner the solder the better. (It's easy to add too much if you use the large diameter when just starting out).

-LeapFrog

 

[Robb]

Nothing ghetto about it. Tallman's test center uses exactly the same means. If you understand what it is doing and know what to look for with the scope, you can achieve exacly the same end. Been over this already; no?

 

[338_MtRushmore]

Does the input level not matter, or is there a way to measure it?

 

[Robb]

Does the input level not matter, or is there a way to measure it?

Of course it matters; but that is not the only way to get there.

 

[LeapFrog]

You can make a cradle and pipe a 1000Hz test tone to a speaker in the cradle, some CB test centers came this way, back in the 70's when they used to be sold new.
Example, the cushion w/ speaker grill @ bottom-center is the test tone cradle:

We kind of covered this in another thread, for personal setups nothing wrong with even using a computer speaker for the test tone, this is only true because you can look at the final output and see your modulation (and adjust until clean).

 

[338_MtRushmore]

I knew I saw tallman mention that somewhere, but I have read too many threads to remember which.