Digest for sci.electronics.repair@googlegroups.com - 13 updates in 4 topics

"Ralph Mowery" <rmowery28146@earthlink.net>: Mar 25 11:22AM -0400

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:nd3b52$q7b$1@dont-email.me...
> ?
> If actual rust holes , from thinned metal that does not survive rust
> cleaning, then how to deal with that.?
 
The dish needs to be smooth or there will be some loss. If already rusted,
you should get a new dish. That is assuming you are using one of the small
units for Direct tv or Dish. The very high wavelength needs a smoother
surface than the older 10 foot size dishes.
 
The paint should be of the type that does not have conductive particals in
it.
Jeff Liebermann <jeffl@cruzio.com>: Mar 25 08:59AM -0700


>No reception problems , even in heavy rain, but presumably will do some
>time.
 
Most of the 0.6m DBS reception problems I've seen are the result of
bad or unstable dish aiming. However, if you experience fades and
dropouts, the easiest fix is to just buy a bigger dish. Mine is 1.0m
diameter:
<http://802.11junk.com/jeffl/pics/DBS/slides/101b.html>
 
>If the dish completely rusts over , so no longer smooth, but not
>actually pitted with holes or distorted, would there bound to be
>received signal loss associated with rust rather than paint?
 
Yes. Ferrite (iron oxide) is an RF absorber. If you want to turn
your dish into a radar invisible stealth aircraft simulation, just let
it rust a little. To be fair, the layer of rust has to be fairly
thick in order to have an effect, so you might be able to get away
with it.
 
>What sort of paint over the front surface , when the rust is cleaned back ?
 
Paint that contains no carbon, graphite, iron oxide, or any other
additive that might be considered an RF absorber.
 
Or, you could just let your imagination run wild:
<https://www.google.com/search?q=paint+satellite+dish&tbm=isch>
 
>If actual rust holes , from thinned metal that does not survive rust
>cleaning, then how to deal with that.?
 
I'm all for repairing things, even if they're not worthy of the
effort. I would use automotive body putty to fill the hole, and a
piece of aluminum foil to replace the missing part of the reflector.
Getting the foil to simulate a parabolic shape will be difficult, but
not impossible. I suggest a wooden form.
 
Also, note that the color and surface finish of the dish is rather
important. The common gray color is designed to both reflect and
absorb a minimum amount of heat from the sun. If the dish were a
mirror finish, when the sun goes behind the satellite belt twice each
year, the reflected light would burn up the LNB. I've had it happen
on larger dishes. If the dish were painted flat black, it would
absorb enough heat to distort and temporarily loose shape. I don't
know how Dish Networks gets away with black reflectors. The surface
finish is a compromise between smooth for maximum gain, and matt for
minimum light reflection. Whatever you do, don't paint it with glossy
paint or you will cook the LNB.
 
 
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Andy Burns <feb2017-usenet@adslpipe.co.uk>: Mar 25 04:30PM

Ralph Mowery wrote:
 
> "N_Cook" <diverse@tcp.co.uk> wrote:
 
>> If actual rust holes, from thinned metal that does not survive rust
>> cleaning, then how to deal with that.?
 
Is it a solid dish or a mesh one? I don't think I'd be bothered to
repair a dish unless it's something special, buy a new one for £20-30.
 
> assuming you are using one of the small units for Direct tv or Dish.
 
From the email address, I'd say it's more likely for Astra 28.2E
satellites.
amdx <nojunk@knology.net>: Mar 25 08:14AM -0500

>> I need to purchase a magnifier so that I'll be able to do things like replace eproms and other small SMT's. I'm not looking to do LSI's with 150 pins Etc. Just mostly smaller stuff. For instance I currently have a board that needs an 8 pin Eprom replaced. I thought that I could do it with the magnifiers I have but the stuff is Just too small. I tried using a high res TV camera with a varifocal 3.5 to 8 mm lens but it doesn't make the image large enough. I was wondering what people are using to do this. Thanks, Lenny
 
> I also have a headset magnifier with a pair of acrylic lenses. There is so much optical distortion through the plastic though that they're just about worthless.
> I have a customer who does SMT repair work and I recently had him help me. I watched him replace an 8 pin SOT for me. He had a dual lens machine like something you might see on CSI.I don't know what the magnification was but when looking into this thing it appeared as though you were looking at an 8 inch by 8 inch field of view. It was really pretty impressive. The chip took up the entire field and the spaces between the legs were very well defined. With a small enough iron and a pick it was possible to first lift each lead one at a time, remove the chip with a slight twist and then tack the new one down. I was amazed at how easy it was with adequate magnification. I think the magnification was a lot more than 10X though. I also have a headset magnifier with glass lenses that I've used for years. It has about a six inch working distance and is just slightly better than reading glasses, but looking through this guy's machine was like seeing a whole new world. Lenny
 
What we really need is a dual lense optivisor type headwear.
I would like at least a 12" working distance.
Ebay has these but I don't know that two times magnification is enough
and I don't see the focal distance.
> http://www.ebay.com/itm/Eschenbach-Max-Detail-Binocular-Magnifying-Glasses-Made-in-Germany-w-Hard-Case-/182035640447?hash=item2a622b707f:g:vTUAAOSwX~dWp6Qt
 
Mikek
captainvideo462009@gmail.com: Mar 25 07:49AM -0700

> I need to purchase a magnifier so that I'll be able to do things like replace eproms and other small SMT's. I'm not looking to do LSI's with 150 pins Etc. Just mostly smaller stuff. For instance I currently have a board that needs an 8 pin Eprom replaced. I thought that I could do it with the magnifiers I have but the stuff is Just too small. I tried using a high res TV camera with a varifocal 3.5 to 8 mm lens but it doesn't make the image large enough. I was wondering what people are using to do this. Thanks, Lenny
 
These look like very good "reading " glasses. I don't think these would do the job.Lenny
"Ralph Mowery" <rmowery28146@earthlink.net>: Mar 25 11:08AM -0400

"Look165" <look165@numericable.fr> wrote in message
news:nd32tq$1tdb$2@gioia.aioe.org...
 
> Multi-coated Acrylic Lenses offer a choice of 4 magnification powers via
> combination of fixed , flip-up and monocle lenses: 1.5, 3.0, 9.0 and 10.5
> Adjustable light incorporated.
 
Problem with that is the first magnification is ok, but as you get to the
higher powers you have to almost have your nose on the circuit board. I use
one and for some work it is ok, but for fine work something else is needed.
 
After about 3x the lenses put your eye so close to the work it is difficult
to get the soldering equipment in without getting burnt.
captainvideo462009@gmail.com: Mar 25 08:35AM -0700

> I need to purchase a magnifier so that I'll be able to do things like replace eproms and other small SMT's. I'm not looking to do LSI's with 150 pins Etc. Just mostly smaller stuff. For instance I currently have a board that needs an 8 pin Eprom replaced. I thought that I could do it with the magnifiers I have but the stuff is Just too small. I tried using a high res TV camera with a varifocal 3.5 to 8 mm lens but it doesn't make the image large enough. I was wondering what people are using to do this. Thanks, Lenny
 
The dentist wears a headset rig that allows him to work from at least an arms length away. I've seen pictures of doctors wearing similar magnifiers. I don't know what the magnification of these things are though. Anyone know the specifics on those? Lenny
Chuck <chuck@mydeja.net>: Mar 25 08:16AM -0500

On Fri, 25 Mar 2016 05:48:15 -0500, "Mark Zacharias"
>fucking years old!
 
>I'm reminded of Chevy Chase's rant in Christmas Vacation...
 
>Mark Z.
 
Back in the late 70s we repaired a compact stereo that used RCA jacks
for speaker outputs. The customer came back with the stereo claiming
there was no output. We hooked it up and it worked fine. I had him
bring in his speakers. He had wired both the plus and minus leads to
the center connector on both speaker plugs. I kept a straight face
but unfortunately one of my techs went off on him.
 
---
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amdx <nojunk@knology.net>: Mar 25 08:19AM -0500


> i'm surprised that Yamaha is covering this. Usually, customer caused failures are not covered. I recall having discussions with customers about similar types of repair requests. It seems that they think that anything that failes regardless of the cause is covered. Not the case. Physically broken parts are not usually covered. In one case, a Sony diskman (portable CD player) had the cover broken off. The owner actually thought that this would be covered under warranty. I questioned what manufaturing defect "caused" this problem and did not get an answer...
 
> Dan
 
Back in the 70's my Pioneer SX-828's protection circuit did it's job
and saved my several repairs.
Mikek
"pfjw@aol.com" <pfjw@aol.com>: Mar 25 07:05AM -0700

On Friday, March 25, 2016 at 7:49:13 AM UTC-4, N_Cook wrote:
> picks up the nearest wallwart, having mislaid the original one, because
> it looks the same size black lump and the connector pushes in, so it
> must be ok .
 
Once upon a time, there was movement to color-code and size-code these things... It never quite took.
 
Peter Wieck
Melrose Park, PA
"Ralph Mowery" <rmowery28146@earthlink.net>: Mar 25 11:17AM -0400

"Mark Zacharias" <mark_zacharias@sbcglobal.net> wrote in message
news:LH8Jy.77627$NL6.55721@fx22.iad...
> How is it a grown man cannot understand the concept of keeping two wires
> separate?
 
Reminds me of when I was working on the CB radios around 1973. Fellow
brought in one that had a diode inside that is connected across the 12 volt
power line that shorts and blowes the fuse when connected in reverse. I
asked him it he hooked it up backwards and he said probably as he moved it
from his truck to the car. About a week later he was back in with the same
problem. Repaired it, and a week later he was back again, but said it would
be the last time for me to repair it. I said "oh". And he said he bought
another radio so he could leave them and not have to swap back and forth.
jurb6006@gmail.com: Mar 24 01:28PM -0700

>"Don't waste your time trying. CRTs don't short that way. "
 
Actually I have had a few that did, mostly Sonys.
 
But you are right on the rest of it, at the very least the output transistor will fail before it can burn up the flyback.
jurb6006@gmail.com: Mar 24 01:41PM -0700

>"I think you've hit the nail on the head, in terms of wanting to >keep it as original as possible. I realise that may not be possible >eventually, but I so want to try. I have bought a converter ready, >and tested it but could not for the life of me get an image to show."
 
I think most of those convertors are designed for NTSC input, and this might not be NTSC. It could be anything.
 
If you have to retrofit a different fly in there that can be hairy, even scary. The first thing to know is how many pins are used. It may have eight or ten pins, but the less of them used the better. Also look se if there is a focus output, if monochrome it might be automatic focus which gets you off the hook there.
 
Ideally, there would only be three pins on the bottom connected. If so you got to balance three parameters. One is the pulse width and amplitude for the yoke. Then you have to get the right HV level at the same time. It may require compromises.
 
If there are scan derived sources off of it the plot thickens. Best to just figure on replacing those sources somehow.
 
Now, if you get a flyback for it with an open core you can put some windings on it. Either bucking or boosting, or maybe for a supply. I had to put a bucking winding on one a long time ago to match a yoke on a replacement CRT because the yoke native to the chassis would not converge properly. But that was then.
 
Scan derived sources are not as common in stuff like this as they were in TVs. You might get lucky.
 
Retrofitting the wrong fly in there can be tricky. You will need a variac. Also probably a selection of capacitors. And then you might have to install a regulator to get the HV where it needs to be.
 
In this case, since it is probably reactive scanning, the vertical sweep will tell you when you got it right. You are playing with the horizontal so you can't count on that.
 
This can be done, it is just a matter of how much time and trouble it will take.
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