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Tim Schwartz <tim@bristolnj.com>: Mar 18 07:42AM -0400 Hello all,   I stumbled across this web site:   http://www.americanradiohistory.com/   Which has many old radio industry and consumer publications. Some from the UK as well.   Enjoy! Tim

Paul Drahn <pdrahn@webformixair.com>: Mar 18 08:59AM -0700 On 3/18/2016 4:42 AM, Tim Schwartz wrote: > from the UK as well.   > Enjoy! > Tim Interesting, but missing most amateur radio magazines.   Paul, KD7HB

Cursitor Doom <curd@notformail.com>: Mar 17 05:24PM I can't find any pictures that resemble these things on the web. Following a closer look with a stereoscope, there are outbreaks of these growths in at *least* a dozen places on this board. Here's two more sharper pictures with the problem areas outlined:   https://www.flickr.com/photos/128859641@N02/25236055623/in/dateposted- public/   https://www.flickr.com/photos/128859641@N02/25836586336/in/dateposted- public/   All the pictures I've seen on the net show whiskers as silver in colour but these are dark, metallic plum. They typically spring from vias in a kind of branching, fern-like formation and certainly reach out to touch other traces on the board.   Anyone seen anything like this before? Ideas on how to proceed?

DaveC <not@home.cow>: Mar 17 10:56AM -0700 > but these are dark, metallic plum. They typically spring from vias in a > kind of branching, fern-like formation and certainly reach out to touch > other traces on the board.   Cracks? > Anyone seen anything like this before? Ideas on how to proceed?   Choose one of these, try acetone on a Q-tip cotton ear bud to dissolve the coating (try to not disturb the "thing" that lies below the coating--if, in fact it is below the coating). Get a "burnishing brush" with fiberglass bristles (used to clean oxidation from copper, etc.) and start gently rubbing the site. I think you'll quickly discover if it's a surface growth, or a crack or other phenomenon.   Good luck.

Cursitor Doom <curd@notformail.com>: Mar 17 06:00PM On Thu, 17 Mar 2016 10:56:37 -0700, DaveC wrote:   > start gently rubbing the site. I think you'll quickly discover if it's a > surface growth, or a crack or other phenomenon.   > Good luck.   Thanks. They're definitely not cracks, they're fibres of some sort.

Look165 <look165@numericable.fr>: Mar 17 07:57PM +0100 This type of caps is known for drying inside with time.     Cursitor Doom a écrit :

Cursitor Doom <curd@notformail.com>: Mar 17 07:00PM On Thu, 17 Mar 2016 19:57:11 +0100, Look165 wrote:   > This type of caps is known for drying inside with time.   Yes, I know. But these are not faulty. I tested them with one of these meters:   http://www.peakelec.co.uk/acatalog/jz_esr70.html   Current most likely possibility is shorting between PCB traces due to growths of some kind:   https://www.flickr.com/photos/128859641@N02/25836586336/in/dateposted- public/

Jon Elson <jmelson@wustl.edu>: Mar 17 04:26PM -0500 Cursitor Doom wrote:       > Thank you, Jon. An interesting suggestion! But I was under the impression > that:   > 1. TW growth happened solely inside chips and so was normally invisible.   Absolutely not! I had some Xilinx chips where the leadframe was tinned before the IC was mounted and encapsulated, then the leads were bent. This put strain into the tin plating, and whiskers grew from that. Xilinx' solution was to REALLY FRY the chips when reflowing the board, which I did not think highly of! They seem to have changed their plating to reduce the whisker growth. These were easily seen with a microscope, and were clearly sprouting out of the leads RIGHT at the bends.   Lots of reports indicate tin whiskers on circuit boards, connectors, IC leads, etc. Moisture exposure seems to be an important part of the conditions where they grow.   > 2. tin whiskers were invariably silver in colour. Yes, they should start out that way. But, oxidized Tin can take on a VARIETY of colors. Most of these I'm more accustomed to see where the Tin has been heated (as when soldering) but I have definitely seen Tin turn all shades of purple. Also, the conformal coating may have chemicals that caused the tin whiskers to change color. > all enamel copper seems to be clear, but back in the day the enamel was a > sort of deep plum shade - which is what I see here. I'll do some searches > for pictures of TW and see if some match what I see on this board.... Tin can definitely turn this "plum" shade.   Jon

Jon Elson <jmelson@wustl.edu>: Mar 17 04:33PM -0500 Cursitor Doom wrote:   > kind of branching, fern-like formation and certainly reach out to touch > other traces on the board.   > Anyone seen anything like this before? Ideas on how to proceed?   These do NOT look like the whiskers I have encountered before. But, they could be some sort of conductive stuff that has grown between nets on the board. One possibility is they are fibers from a brush that either cleaned the board or applied the conformal coat. But, they could still be trouble, maybe they start out non-conductive but become conductive when moisture is absorbed. Since you say the sprout from vias, maybe the board had some contaminant left in the vias that slowly creeps out under heat and electrical field. Anyway, not much to lose by trying to remove the conformal coat at these spots and see if the EMU comes back to life. If it does, then you need to get some new conformal coat and re-seal those spots.   Jon

jurb6006@gmail.com: Mar 17 03:25PM -0700 >" wonnder how you can determine an ESR visually !   >And technically, it's not so easy to measure this parameter. "   With a square wave that has a fast enough slew rate for the vertical parts of the scope trace to disappear. The square wave comes from a known impedance and is high enough frequency so Xc is minimal. Measure the amplitude of the parts you can't see and then it is simple ohm's law.   I use 400 mV 1,000 Hz with a 360 ohm impedance which does not make the numbers easy but it makes for quick troubleshooting.

Cursitor Doom <curd@notformail.com>: Mar 17 10:40PM On Thu, 17 Mar 2016 16:26:54 -0500, Jon Elson wrote:   > Tin can definitely turn this "plum" shade.   > Jon   In that case I wonder how I would go about measuring the resistance of these things? Maybe I could lift one off with a piece of sticky tape if they're not too fragile. Can't think of a better way!

legg <legg@nospam.magma.ca>: Mar 17 07:25PM -0500 On Thu, 17 Mar 2016 19:00:52 -0000 (UTC), Cursitor Doom   >https://www.flickr.com/photos/128859641@N02/25836586336/in/dateposted- >public/   You're going to have to get more localized images of individual sites, using a minimum x10 magnification, and enhanced/varying side-lighting. A 'star' group, or part group should occupy a full image. Manual marking should not interfere and should use line widths <<smaller than the image details themselves.   If possible, you should label or datestamp each individually for reference.   The captive metalic detritus on the body of one resistor did not resolve any better in the later image. If possible, angled images can be informative, when monocular, and diffused lighting will reduce glare.   If you do post more detailed images to the same flikr thread, they can be downloaded and examined by IPC Technet group members, with comments at   http://listserv.ipc.org/scripts/wa.exe?A1=ind1603&L=TechNet   RL

Cursitor Doom <curd@notformail.com>: Mar 17 11:34PM On Thu, 17 Mar 2016 19:25:50 -0500, legg wrote:   > at   > http://listserv.ipc.org/scripts/wa.exe?A1=ind1603&L=TechNet   > RL   Thanks for that. Yes, I would have liked to have posted images direct from the stereoscope which is just in its own class for this kind of thing and shows *so* much more detail, but I don't have a suitable adaptor. I'll check out your link tomorrow as it's getting very late here now...

Jon Elson <elson@pico-systems.com>: Mar 17 09:36PM -0500 Cursitor Doom wrote:     > In that case I wonder how I would go about measuring the resistance of > these things? Maybe I could lift one off with a piece of sticky tape if > they're not too fragile. Can't think of a better way! I'm still thinking these were left behind by some kind of brush. But, they could still be trouble after years of exposure to <something>.   Are these on top of the conformal coat or underneath/within it? If they are in the coat, then it will be hard to extract them.   Jon

legg <legg@nospam.magma.ca>: Mar 18 12:07AM -0500 On Thu, 17 Mar 2016 17:24:00 -0000 (UTC), Cursitor Doom >kind of branching, fern-like formation and certainly reach out to touch >other traces on the board.   >Anyone seen anything like this before? Ideas on how to proceed?   Early technet response suggests chemical contamination in vias, but would require SEM EDX to confirm. This contamination could difuse in the conformal coating cure stress lines (ie the pucker).   I don't see vias involved in every instance - some sites seem to develop at pure surface mount pad sites.   There's an image of copper dendrites on Steve Zeva's gallery   http://stevezeva.homestead.com/   http://stevezeva.homestead.com/Dendrite_1.jpg   These tend to be inter-node rather than centrally expanding.   A close examination of tin whiskers should reveal a characteristic three dimensional spike/thread detail. Not likely here.   RL

Cursitor Doom <curd@notformail.com>: Mar 18 08:36AM On Thu, 17 Mar 2016 21:36:17 -0500, Jon Elson wrote:   They seem to emerge from under it and spread along the surface, but I can't confirm that yet as I've resisted disturbing them so far in case they disintegrate and defy further analysis. It's a good question, though, and I expect to be able to report back on this later today. I'll sacrifice one of the patches and find out.

Cursitor Doom <curd@notformail.com>: Mar 18 08:51AM On Fri, 18 Mar 2016 00:07:03 -0500, legg wrote:   > Early technet response suggests chemical contamination in vias, but > would require SEM EDX to confirm. This contamination could difuse in the > conformal coating cure stress lines (ie the pucker).   Can you post a url for this site? I searched but got about a million microsoft support links instead.   "SEM EDX"? Is that something to do with electron microscopy? I have an admittedly huge collection of test gear here, but not a single electron microscope.   > I don't see vias involved in every instance - some sites seem to develop > at pure surface mount pad sites.   True, but they're in the minority. Maybe that's relevant; maybe not. The we don't have a large enough sample here to say.       > http://stevezeva.homestead.com/   > http://stevezeva.homestead.com/Dendrite_1.jpg   > These tend to be inter-node rather than centrally expanding.   Yes, still no precise matches.     > A close examination of tin whiskers should reveal a characteristic three > dimensional spike/thread detail. Not likely here.   Yes, TW seem to come out at right angles to the plain; these are surface creepers.

Cursitor Doom <curd@notformail.com>: Mar 18 02:10PM > They seem to emerge from under it and spread along the surface, but I > can't confirm that yet as I've resisted disturbing them so far in case > they disintegrate and defy further analysis.   Right, basically what I said above is correct. There seems to have been some sort of breakdown of the clear coating which has enabled these things to get a foothold. They then break out and traverse along the board *on top* of the coating. So it's doubtful they could cause any short circuits unless by sheer chance the tip of one of them hits another spot of coating that's broken down above a trace - or a chip pin. When touched with a scalpel blade they break apart readily into shards and can be blown away by an air duster can. The coating has lost its integrity and could probably be scrubbed away with a toothbrush. I personally prefer to use clear varnish for my own boards. It hasn't the depth that this coating has, but at least when it's set, it's set for good. I wonder what the reverse side looks like? Perhaps there's no coating at all, in which case who knows what state it's in.

legg <legg@nospam.magma.ca>: Mar 18 10:37AM -0500 On Fri, 18 Mar 2016 08:51:16 -0000 (UTC), Cursitor Doom >> dimensional spike/thread detail. Not likely here.   >Yes, TW seem to come out at right angles to the plain; these are surface >creepers.     Technet link was previously posted.   http://listserv.ipc.org/scripts/wa.exe?A1=ind1603&L=TechNet   Question is, what is your repair plan?   You don't seem to have any indication of the unit's present state other than sticking it back in the car and seeing if the car starts. No fb on xtal replacement yet.......   The blemishes you're chasing may have nothing to do with actual fault.   The spatter pattern is also suggestive of the impact from an external source, such as a flicked paint brush.   The single metalic entrapment pictured should also flick off with a knife blade. But without some before and after passive probing, you'll never know if this did anything.   RL

Cursitor Doom <curd@notformail.com>: Mar 18 03:20PM On Fri, 18 Mar 2016 10:37:46 -0500, legg wrote:   > Technet link was previously posted.   > http://listserv.ipc.org/scripts/wa.exe?A1=ind1603&L=TechNet   Thanks, I hadn't spotted that link.   > Question is, what is your repair plan?   If there is some formal defintion of this term, I don't know it. But my plans with this unit are to spend as little time as possible on it and if it can't be fixed reasonably quickly, to get rid of it. Items like this are way off-beat for me and I have a pile of other stuff more in my line awaiting my attention in due course.   > You don't seem to have any indication of the unit's present state other > than sticking it back in the car and seeing if the car starts. No fb on > xtal replacement yet.......   I'll get there. I just have to fit this EMU in between other jobs with higher priorities, plus avoiding the usual divorce threats.   > The blemishes you're chasing may have nothing to do with actual fault.   I agree entirely.     > The spatter pattern is also suggestive of the impact from an external > source, such as a flicked paint brush.   Nope. If you could see it through the stereoscope, you'd agree straightaway. I shall have to post to the photo groups for adaptor ideas to make it possible to post much better quality macro shots online than the ones I'm pissing everyone off with at present.   > The single metalic entrapment pictured should also flick off with a > knife blade. But without some before and after passive probing, you'll > never know if this did anything.   Easier said than done (see my update posted 2.10pm local here).

N_Cook <diverse@tcp.co.uk>: Mar 18 12:42PM Confirmed by the owner. I find it amazing that Gibson do not supply user manuals with any new guitar. So how is an owner supposed to know that you have to unplug the guitar lead, to switch off the battery, let alone anything else?

N_Cook <diverse@tcp.co.uk>: Mar 17 05:20PM On 05/03/2016 08:35, N_Cook wrote: > For walkman size bands, I set up a sort of grinding machine with > "Dremmel" and "diamond" disc to "grind" back imperfections of such cut > bands.   For anyone in the UK, go to Aldi , before easter. 3GB , so for less than the price of one flat belt from Farnell, plus VAT etc. Better than those funnels for cutting up into bands.   "exploded view" chocolate easter egg moulds. As close to ideal as possible for supplying flat drive belts as concentric flat rings complete range from 10mm diameter to 87mm diameter. When split would give 50 bands 1.5mm thick, from 1 to 5mm wide, as they are then 5mm wide. Plus 12 thin cylinders that may well stretch to cover failed cassette tape pinch rollers. To go to .5mm thick , I'll try stretching over various cylinders as mandrels plus washers. Cut all the putative bands off the sheet, by cutting through the main plane of the sheet mould so they will evenly lay-up against each other on the mandrel with washer spacers and apply some pressure to keep the rubber from squirming when cutting and set a razor blade in the toolpost and razor through , turning the lathe chuck by hand. Then if non-parallel faces , then "grind" down with "diamond" disc in dremmel ablating back to widest sections. With all such bands then at least one fair face for going against balluster drive pinions.   ++++++++++ Crap commercialism, google cached only it would seem http://webcache.googleusercontent.com/search?q=cache:tJVmebmtr6sJ:https://www.aldi.co.uk/p/68604/0%2Beaster+chocolate+moulds+site:aldi.co.uk&hl=en-GB&gbv=1&um=1&tab=iw&&ct=clnk not for viewing directly from Aldi site,by any potential customers "3D Chocolate Egg Mould Product Ref: 068604020813200 £ 2.99 Make and decorate your own homemade Easter eggs for friends and family. They'll love making delicious chocolate treats with this egg mould - plus it's a great way to get the creative juices flowing.   Design: 3D Egg Dimensions: 30.5 x 30.5 x 1.5cm Material: LFGB Silicone Mould Product Type: Chocolate Moulds   " supposed URL of https://www.aldi.co.uk/p/68604/0# so no pic available to my browser anyway. If anyone else finds a valid URL, please post here

N_Cook <diverse@tcp.co.uk>: Mar 17 05:30PM On 17/03/2016 17:20, N_Cook wrote: > https://www.aldi.co.uk/p/68604/0# > so no pic available to my browser anyway. > If anyone else finds a valid URL, please post here   China has the right idea, pics available from the primary source http://www.alibaba.com/product-detail/3D-Easter-Egg-Chocolate-Silicone-mold_1992750941.html something to do tomorrow, generate a lifetime supply of flat belts hopefully.

"pfjw@aol.com" <pfjw@aol.com>: Mar 17 12:25PM -0700 On Thursday, March 17, 2016 at 1:30:56 PM UTC-4, N_Cook wrote:   > http://www.alibaba.com/product-detail/3D-Easter-Egg-Chocolate-Silicone-mold_1992750941.html > something to do tomorrow, generate a lifetime supply of flat belts > hopefully.   This is SO much *WORK* when, with only minimal searching from any number of active and current sources selling belts of recent manufacture one can find about any belt in about any dimension one needs. Really! Typical cost: Less than US$0.50 per belt.   Peter Wieck Melrose Park, PA

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