I have seen the future and it is not pretty. Uniden PC-88XL

[Eldorado828]

Maybe not so much the future, but the here-and-now.

Bad news for tweaknicians. Only seven internal adjustments in this radio.

The Uniden PC88XL is the current Cobra 29-equivalent AM mobile CB from that brand. They're done with copying obsolete designs from decades ago. This thing is nearly 100 percent surface mount, and has a total of seven adjustable components.

The component side of the circuit board is a bit like a desert. A few lumps here and there with a lot of empty flat area between.

The transmitter has five adjustments, total. Six if you include the modulation limiter. The three cans are the filtering after the 7310 mixer chip. The MOSFET final has a trimpot for gate bias, and the output has a slug-tuned coil pretty much the same as most older AM CBs.

The modulation limiter has a trimpot, conveniently labeled "AMC".

The empty component positions appear to be for a weather-band feature, not installed in this radio.

Move along folks, nothing to tweak here.

73

Looks like the empty walmart isles when the pandemic first hit.... empty and the look is unfamiliar... a whole lot of nothing and can't do anything about it


Probably sent over from the Chinese too

 

[nomadradio]

The more of this discussion I see, the more it sounds like a previous era of arguments like this.

About 50 years ago.

"Tubes versus transistors* was a big bone of contention at the time. In some circles it still is.

Economics settled the larger issue since those days.

Through-hole technology won't go away any more than tubes have gone away.

The sources just get more scarce, and prices rise year by year.

You can still run a tube CB base radio if you like. Just can't buy a new-production radio built with that technology.

Stuff built with through-hole parts will just get scarcer year by year.

Might just as well shake your fist an oncoming rain cloud. It won't care. You'll get wet.

73

 

[cralt]

Plain and simple, DONT BUY THE JUNK and it goes away.

But is this actually junk?
How is the TX audio, the RX filtering and sensitivity? How well are the front panel switches and controls built?
SMT made with good components will last a lifetime.

 

[nomadradio]

Surface-mount technology:

Pros: Takes longer to break.

Cons: More trouble to fix when it does.

Not an isolated trend.

73

 

[sunbulls]

SMT soldering is challenging, but manageable. The real issue I have with SMT boards is the lack of any provided schematics or service manuals. Reverse engineering is time consuming and such technology bolsters the landfills.

 

[nomadradio]

Massive lack of documentation and diagrams is a separate problem and isn't confined to SMT radios.

The real cost of reverse-engineering the diagram the manufacturer won't sell you is a lot more than the value of the product. No way to make money back you would have to invest to produce them. You would have to price the first copy you sell at thousands of dollars to recover the investment. Once that first copy reaches the internet, you won't sell another one.

Sams stopped using their "Circuitrace" method of doing this 40 years ago. The last couple of Sams CB volumes simply contain reprinted diagrams and parts lists from the radios' manufacturers. Apparently there wasn't enough money in that, and the CB series ceased publishing soon after.

73

 

[Tokin]

The surface

SMT soldering is challenging, but manageable. The real issue I have with SMT boards is the lack of any provided schematics or service manuals. Reverse engineering is time consuming and such technology bolsters the landfills.

Uniden refuses to release any schematics claiming its proprietary. I have no love for this new crap. Looks like i keep collecting the trusty and repairable old stuff.

 

[cralt]

Massive lack of documentation and diagrams is a separate problem and isn't confined to SMT radios.

At least President still puts out a real service manual with schematics.
A very rare thing now-a-days unfortunately.

 

[Staybolt]

The more of this discussion I see, the more it sounds like a previous era of arguments like this.

About 50 years ago.

"Tubes versus transistors* was a big bone of contention at the time. In some circles it still is.

Economics settled the larger issue since those days.

Through-hole technology won't go away any more than tubes have gone away.

The sources just get more scarce, and prices rise year by year.

You can still run a tube CB base radio if you like. Just can't buy a new-production radio built with that technology.

Stuff built with through-hole parts will just get scarcer year by year.

Might just as well shake your fist an oncoming rain cloud. It won't care. You'll get wet.

73

100% agree

 

[Shadetree Mechanic]

If we can figure out how to put a swing kit on it, then it's not a total loss.

 

[Dmans]

Surface-Mount Technology Repairs:

Pros: I have the equipment to do it.

Cons: I don't have the eyesight to do it.
No schematics available in most instances to do it.
No desire to do it.

73
David

 

[Rwb]

I enjoy living in the past and the future. It depends on what mood I’m in at any particular time.

"Remember back in the day when things were made by hand, and people took pride in their work?" Rick Dale

i like his show

 

[Rwb]

Im talkin to a friend on my kenwood tw 4000a on 442.975 + tone 91.5 pl tone ,hows that for old? Its a radio i took 2 n made 1 out of

 

[Handy Andy]

Pay closer attention to the board...

It's a preserved throwback to the days of Analog...this is the results of converting the typical PC66/68 or 76/78 into the SMD version of the Discrete...

The 7310 - The Youda' Years...


But seriously -- this is what SMD has shrunk down to...


The PLL is still "controlled" by the main CPU which holds the channel outlay, and Microcode (codec) to boot everything. This is a programmable unit that can be "programmed" to the various regions -
So if it can use AM - this chassis will use (broadcast/Receive) it.
​

This is not the 687 or 787 - which used a lot of Integrated design - Squelch, AGC, Mic amp - all on a chip array design. That was Uniden's "Upgrade" which followed in the footsteps of the 980 series - and only were sold for a couple of years at the most. Anyone whom owns one, European or American - some got IRF520's others got something yet to be discovered...(I got stung...)

Look more closely at this new one - it also with be sadly - another copy of the C29 and C25...This is a conversion of a discrete biasing design to SMD work - so they did try to preserve some efforts of the Analog days - just no IF coil coupling - all capacitor coupled design - adding to the "white noise and noisy IF strip" problems inherited from using Xtal resonators - sure they are Xtals, but pass everything and the distortion products within the passband - you don't have the luxury of "offset" to overcome some of the peaking and tuning issues you'd experience in some radios that had IF coil coupled designs where the Transistors' impedance and the coils turning range interacted (L6 - Galaxy) (PC-66 1st IF and TX Strip) - allowed many users to over peak the section causing RX to TX issues - this simply will push that "white noise" in with it - no engineering feat here - just copy and inserted caps where coils should be...Took away the coil coupling to save money...

Our loss...

Sadly they did away with much of the older "Analog" AGC tracking - no caps in the strip to be found. - unless Nomads got more on it, there's little help in offering any RX adjustments...

It's the only radio I have seen where they've taken the older discrete and simply kept the design to SMD and left the rest alone - however the IF and all it's drawbacks - this will be another "White noise" candidate.

 

[Shadetree Mechanic]

I think I might buy a case of Cobra 29s before they go surface mount. Maybe some 25s too.