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board is covered in solder dots, why?

gcb

Mar 26, 2012
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i know some boards have test pads... but this one just have too many of them. looks like something done for aesthetics. Any idea why?

It's from a very nicely made Motorola CDMA phone from an '92 BMW

I will reuse the AL case and antennae connector for other projects. So i don't really have to learn why those dots exists... only for curiosity sake now.
(sadly there's very little i can reuse from that board with my limited knowledge, if you see anything interesting i can send it your way)

here are the pics:
P1040023.JPG


the back
P1040026.JPG
 

gcb

Mar 26, 2012
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Also, isn't it nice that a cellphone from 1992 already had a RJ45 port for Tethering and today AT&T tries to charge you extra as if it's a new feature they provide or something?
 

gcb

Mar 26, 2012
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Also bonus points if you can identify the huge blue part in the middle, with the heatsink. it's "motorola 74N09 (9201) malaysia" 9201 i guess is the date code as it's a few months earlier than the cars.
 

CocaCola

Apr 7, 2012
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All the 'random' dots are through hole vias connecting multiple layers to create a larger distributed thermal/ground plane...

The Blue chip is an RF power amplifier/transistor

The R45 connector was where the handset plugged in, not for tethering... Remember these were analog phones, tethering back then meant physically interfacing the phone to speaker and microphone assembly and sending the data real slow through the same handset you talked over, using audible analog tones...

Ah, the memories... I never got to see many of the bases as they were made in a different factory, but I saw a bunch of the handsets for them puppies as the factory I worked at was cranking them out all day long, that was until the flip phone took over like a wildfire out of control and the factories were retooled in an instant...
 
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gcb

Mar 26, 2012
32
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Mar 26, 2012
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All the 'random' dots are through hole vias connecting multiple layers to create a larger distributed thermal/ground plane...

The Blue chip is an RF power amplifier/transistor

The R45 connector was where the handset plugged in, not for tethering... Remember these were analog phones, tethering back then meant physically interfacing the phone to speaker and microphone assembly and sending the data real slow through the same handset you talked over, using audible analog tones...

Ah, the memories... I never got to see many of the bases as they were made in a different factory, but I saw a bunch of the handsets for them puppies as the factory I worked at was cranking them out all day long, that was until the flip phone took over like a wildfire out of control and the factories were retooled in an instant...

ha! i thought it had a modem, since it's twice the size of the portable cheap motorola of the time... and it had a cover in the RJ45 plug, the phone was connected in the serial-port-like-connector next to the antennae plug.

awesome, thanks for the info. pretty interesting! also, i bet i will have a hard time desoldering anything from there without cutting around the board right?
 

CocaCola

Apr 7, 2012
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ha! i thought it had a modem, since it's twice the size of the portable cheap motorola of the time...

They where still quite popular even in the later days, and in under developed countries... Don't quote me on the exact values but the 'car' and 'bag' phones like that had something like a 3 Watt radio while the new generation of hand held phones coming out were limited to something like 1/2 Watt because of the proximity to the head... Thus in a day and age before the cellular network was as massive and distributed as it is today, that extra radio power made a huge difference in getting a signal in many locations... And I'm not talking about rural areas, I had a 'bag' phone back then and I lived in the suburbs of Chicago, reception was still quite patchy at the time... But, I was in my early 20s looking cool with a car phone :) I think my package was like 30 minutes a month and $5 each additional minute, so it's not like I made many calls... And it was cool to everyone except the stupid cops that would instantly accuse me of being a criminal, as in their opinion criminals were the only ones that needed car phones at my age back then :rolleyes:

the phone was connected in the serial-port-like-connector next to the antennae plug.

Was the handset integrated into the car? For bag phone use and 'portable' or aftermarket quicky installs the handset plugged right into that R45 jack, for more integrated or OEM systems they might very well have use the data port for the handset hookup...

i bet i will have a hard time desoldering anything from there without cutting around the board right?

I would place it in a toaster oven (one you don't use for food) and bring it up to reflow temp slowly... Basically start at about 300 F for 5 minutes, then 400 F for a few minutes then full blast broil/on... Remove with gloves or pliers and pluck parts for a few minutes, place back in over and repeat, you will be able to pluck stuff off no problem... Doing it with a solder iron might be a challenge, even a heat gun might not work so well for some parts, they might have huge internal thermal planes, it was common for them to do this...
 

gcb

Mar 26, 2012
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Heh, a cooworker have a history of when he used to live in chicago he worked at a fry's (or equivalent) and that he sold lots of cellphones for drug dealers, and also cellphone listening devices for the cops.

thanks for the oven hints, if i really really need anything form that board i will try that... don't even have a non-food oven yet.
 

CocaCola

Apr 7, 2012
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and that he sold lots of cellphones for drug dealers, and also cellphone listening devices for the cops.

Back then all you needed to listen was an over the counter scanner... It was all in the open analog transmissions...

And get a toaster oven, they can be had new for $20 on sale or a buck or two at a garage sale... It's a heck of a cheap tool if you want to depopulate boards or even do quick reflow work...
 
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