sci.electronics.repair@googlegroups.com

Today's topics:

* Rectifier wiring - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/b087d99e9ce594b1?hl=en
* continuous action solder sucker - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/1447a02166d89d01?hl=en
* Epson Perfection Scanner Problem - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/e3e2ff1db77f9673?hl=en

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TOPIC: Rectifier wiring
http://groups.google.com/group/sci.electronics.repair/t/b087d99e9ce594b1?hl=en
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== 1 of 1 ==
Date: Thurs, Jul 1 2010 10:10 pm
From: "DoN. Nichols"

On 2010-07-01, Ignoramus14602 <ignoramus14602@NOSPAM.14602.invalid> wrote:
> I have this rectifier: GPBC 50A
>
> http://tinyurl.com/25fmjfu
>
> It has four terminals, but they are not marked. The datasheet is pretty
> sparse, too. Which of them are AC and which are DC?

The terminal nearest the corner which is cut off is the positive
output. (Also, it is at right angles to the other three) The diagonally
opposite one is the negative. The other two are AC input.

You can verify this with a multimeter in the ohms or the
diode-check positions. Positive probe on the negative terminal will
show conduction to the other two adjacent terminals. Negative probe on
the Positive terminal will show conduction to the other two adjacent
terminals.

The diodes are arranged pretty much like the schematic symbol
for a bridge rectifier, and surround the center mounting hole as shown
here. Always positive and negative are opposite corners, and the AC
inputs are the other two corners. Something will mark the positive
terminal as different -- here the cut corner and the blade being at
right angles to the rest of the blades. Sometimes there is a red dot by
the positive terminal, black near the negative (except on black potting
epoxy), and yellow on the two AC inputs.

I guess that they did not spell this out on the data sheet
because it is so common a construction -- and has been for at least
forty years or so. Or -- it might be spelled out somewhere else in the
Comchip products manual -- and you only have two pages out of that
manual.

Enjoy,
DoN.

--
Email: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

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TOPIC: continuous action solder sucker
http://groups.google.com/group/sci.electronics.repair/t/1447a02166d89d01?hl=en
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== 1 of 1 ==
Date: Thurs, Jul 1 2010 11:21 pm
From: "Michael A. Terrell"

Jim Yanik wrote:
>
> zekfrivo@zekfrivolous.com (GregS) wrote in
> news:i0iabg$r25$3@usenet01.srv.cis.pitt.edu:
>
> > In article
> > <732fbe89-97bd-499f-ad18-99066ece2603@d37g2000yqm.googlegroups.com>,
> > rush14 <rush14@columbus.rr.com> wrote:
> >>On Jun 29, 11:05=A0am, rush14 <rus...@columbus.rr.com> wrote:
> >>> I'm attempting to fabricate a continuous action solder sucker along
> >>> the lines of those used at work
> >>>
> >>> when repairing circuit boards. =A0They were fast, clean, easy to use
> >>> and prevented damage to the circuit boards from excessive prolonged
> >>> heat.
> >>>
> >>> Unfortunately I'm now retired and the factory work has all been
> >>> outsourced overseas. =A0There's nobody left now from work who would
> >>> know about this.
> >>>
> >>> As I recall they consisted of a vacuum source (unknown to me), a
> >>> flexible hose connected to a small cylinder with a tuft of steel
> >>> wool inside to trap solder and a =A0teflon sucking tip at the other
> >>> end of the cylinder.
> >>>
> >>> Apparently there is more to vacuum technology than I imagined
> >>> because all my attempts have so far failed miserably. =A0When I
> >>> adapt a short (~3 foot) flexible hose to my vacuum source the
> >>> suction at the end of the hose is almost non-existent.
> >>>
> >>> My first attempt was using the air intake of a 12V automotive tire
> >>> inflator, an idea I got from extensive Google searching, although
> >>> not intended for that purpose. There seemed to be plenty of suction
> >>> at the air intake itself but almost no suction at the end of the
> >>> flexible hose.
> >>>
> >>> I then decided to go to extremes and adapted the hose to the vacuum
> >>> port of a powerful shop vac. =A0I actually expected the hose to
> >>> collapse from excessive vacuum but instead there was again almost no
> >>> suction at the end of the hose. =A0I then added a secondary intake
> >>> port to alleviate what I thought might be excessive load on the shop
> >>> vac then tried using the shop vac exhaust port to create a vacuum.
> >>> =A0Neither attempt worked.
> >>>
> >>> I would normally give up but I know the theory behind it works from
> >>> my experience at the factory. =A0I'm apparently ignorant in the
> >>> physics of vacuum.
> >>>
> >>> I'm also familiar with other desoldering tools including plunger and
> >>> squeeze bulb solder suckers, solder wick and built in suckers on
> >>> soldering irons. =A0I've found them all lacking in one way or
> >>> another compared to the gizmo I'm trying to imitate from the
> >>> factory.
> >>>
> >>> Any ideas from you guys about the error of my ways will be greatly
> >>> appreciated.
> >>>
> >>> Thanks a bunch,
> >>> Rush
> >>
> >>I appreciate the 5 responses I received and all your advice is well
> >>taken. I admit to being obsessed with this challenge. I'm retired
> >>from industrial electronics and now consider myself only a hobbyist so
> >>the commercial equivalents of what I'm trying to do are just not
> >>feasible.
> >>
> >>I still don't understand why the small pumps used in commercial
> >>desoldering equipment far outperform the shop vac I had tried. The
> >>shop vac experiment was only an overkill step in an attempt to begin
> >>fine tuning the solder sucker idea.
> >>
> >
> > High volume is not necessarily high vacuum. You will have to measure
> > the vacuum. My little 170 cfm radon fan will suck two inches of water.
> >
> > greg
> >
>
> you can buy a venturi vacuum generator from Harbor Freight at very low
> cost,they make one for evacuation auto air conditioning systems.
> It needs a compressed air line. it will work continuously,off a small
> compressor.

They also have 2.5 & 3.5 CFM electric vacuum pumps.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

==============================================================================
TOPIC: Epson Perfection Scanner Problem
http://groups.google.com/group/sci.electronics.repair/t/e3e2ff1db77f9673?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Jul 1 2010 11:36 pm
From: JD

Hi Experts :-)

I have an Epson 1640SU that worked very well until
today. Now, when I press the start button, it
click-clicks and the carriage does not move.

I removed the screws and tried to take the top
off. The front of the top has catches that project
into the base so it does not allow me to lift up
the front. I removed the screws from the back and
it will lift slightly but seems to be caught in
something. I don't want to force it, so if someone
has experience of this model I would appreciate
advice on how to take it apart without wrecking it.

TIA

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