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OT: PCB coating removal

 
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raymondj(at)frontiernet.n
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PostPosted: Mon Jun 20, 2016 4:51 pm    Post subject: OT: PCB coating removal Reply with quote

Greetings,

I'm working on a PCB that has a clear dip coating. Originally made in
the 70s-80s. The coating will melt with a soldering iron, but I'm
wondering if there is a better way to remove the coating.

The component I'm working is a quartz crystal that is part of the tone
generator on lineman's test handset. If any one is aware of a tutorial
for identifying the value of the crystal, I'd sure appreciate a head's up.

TIA
--
Raymond Julian
Kettle River, MN

The things we admire in men, kindness and generosity, openness, honesty,
understanding and feeling are the concomitants of failure in our system.
And those traits we detest, sharpness, greed, acquisitiveness, meanness,
egotism and self-interest are the traits of success. And while men
admire the quality of the first they love the produce of the second.
-John Steinbeck, novelist, Nobel laureate (1902-1968)


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rampil



Joined: 04 May 2007
Posts: 870

PostPosted: Fri Jun 24, 2016 4:08 am    Post subject: Re: OT: PCB coating removal Reply with quote

I don't recall a crystal in my old 1013A, but be that as it may, it seems odd
that someone would use an xtal to generate audio tones unless they needed
extraordinary frequency precision (an a lot of divider steps).

You might try a bit of MEK on a corner of the board. it should not hurt the components, but might remove the PCB and component printing. The old
potting compounds were pretty resistant to attack.


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Ira N224XS
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raymondj(at)frontiernet.n
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PostPosted: Fri Jun 24, 2016 7:29 am    Post subject: OT: PCB coating removal Reply with quote

Thanks Ira,

I'll give mek a try. The board is from an old telephone lineman's test
hand set so it's generating 12 tones for dialing.

Raymond Julian
Kettle River, MN

The things we admire in men, kindness and generosity, openness, honesty,
understanding and feeling are the concomitants of failure in our system.
And those traits we detest, sharpness, greed, acquisitiveness, meanness,
egotism and self-interest are the traits of success. And while men
admire the quality of the first they love the produce of the second.
-John Steinbeck, novelist, Nobel laureate (1902-1968)

On 06/24/2016 07:08 AM, rampil wrote:
Quote:


I don't recall a crystal in my old 1013A, but be that as it may, it seems odd
that someone would use an xtal to generate audio tones unless they needed
extraordinary frequency precision (an a lot of divider steps).

You might try a bit of MEK on a corner of the board. it should not hurt the components, but might remove the PCB and component printing. The old
potting compounds were pretty resistant to attack.

--------
Ira N224XS


Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=457398#457398



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nuckolls.bob(at)aeroelect
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PostPosted: Fri Jun 24, 2016 4:30 pm    Post subject: OT: PCB coating removal Reply with quote

At 10:27 AM 6/24/2016, you wrote:
Quote:
--> AeroElectric-List message posted by: rayj <raymondj(at)frontiernet.net>

Thanks Ira,

I'll give mek a try. The board is from an old telephone lineman's test hand set so it's generating 12 tones for dialing.

Brings back memories . . . the DTMF tone encoders
of bygone times were indeed crystal controlled.
Here is an exemplar component.

http://tinyurl.com/hzxdjgw

Very popular devices in the ham radio repeater
communities 40 or so years ago.


Bob . . .


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rampil



Joined: 04 May 2007
Posts: 870

PostPosted: Sat Jun 25, 2016 3:15 am    Post subject: Re: OT: PCB coating removal Reply with quote

Ah yes, the sweet simple days of in-band signaling and Cap'n Crunch Wink

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