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Jeff Liebermann <jeffl@cruzio.com>: Jun 17 10:10AM -0700 On Wed, 17 Jun 2015 05:37:33 -0700 (PDT), Matthew Connor   >Good morning, all. I'm brand new to hands-on electronic repair so please pardon any silly questions.   >I recently acquired a Geiger counter manufactured in 1962 and I am rebuilding it. The PCB is 4" x 4" and 0.062" thick. The part of the chassis to which it mounts has four steel legs that protrude 1.45" perpendicular to the plane of the chassis. The four corners of the PCB screw onto these steel legs.   >I would like to know some options for making the PCB more shock resistant should the unit ever get dropped. Is there any such thing as, say, shock-resistant washers that could go over the four screws and sit between the PCB and the steel legs to which it's mounted? Or is there a better way?   1962 might be a CD-V700M counter. It matches your description: <https://www.google.com/search?tbm=isch&q=cd-v700m> I have one of those. How am I doing. Is there a reason why you failed to disclose the model number?   Maybe small rubber grommets in the holes in the PCB. Something like these: <http://www.customgasketmfg.com/Images/Rubber-Grommets-Bushings.jpg> If you can't find ones that fit, or you don't want to enlarge the holes, use two rubber flat washers instead. You can get those in the plumbing section at the hardware store. You may need to install metal washer(s) on the grommet to secure the head. You can get fancy by adding a coil spring under the screw head.   The problem with such simplistic schemes is that adding a washer between the bracket and the PCB is going to raise the PCB by the thickness of the washer. That means that front panel switches and lights might not fit. If there is the usual big rotary switch in the middle of the front panel, it too will need to be shock mounted, probably with another grommet around the shaft.   Personally, I think you should make these modifications unless you have a good reason to need additional shock resistance. Such mechanical things really should be done with the initial design, not as a retrofit. In 1962, phenolic (paper) PCB's were fashionable, which might crumble if you try to "modify" them. I suspect you might do more damage than good. However, if you MUST make it more shock resistant, such as for transportation in a vehicle without shock absorbers over a rotten road, some kind of foam lined packing case would probably be helpful.   -- 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

etpm@whidbey.com: Jun 18 09:03AM -0700 On Wed, 17 Jun 2015 05:37:33 -0700 (PDT), Matthew Connor   >Any suggestions geared towards a newbie would be greatly appreciated. Thanks, all!   >Kindly,   >Matthew Connor If the PCB was free from damage caused by shock when you got it then I would suggest that it was probably built robuslty enough already considering that it has survived for 53 years. Certainly if you are exposed to radiation strong enough to cause you to drop the thing you won't be living long enough to care if it broke when dropped. What radiation source are you going to use to test it? Many if not most smoke detectors have a little Americium that irradiates the air in a little chamber. Removing the cover allows this radiation to, well, radiate into the local environment and is a pretty good source to see if your counter works at all. Another common source for radiation are the 2% thoriated tungstenTIG welding electrodes. They will not make your counter click as often as the smoke detector source though. The mantles for Coleman type lanterns also used to have thoria in them though I think another rare earth is now being used. Once you know your counter is working it is fun to see what else in your environment is more radioactive than the general background radiation. Certain rocks may be more radioactive as well as concrete. Some green glassware and some glazes on ceramics are radioactive. Eric

"David Farber" <farberbear.unspam@aol.com>: Jun 18 08:47AM -0700 John-Del wrote: > blackened feed through. Single strands from stranded wire is > certainly thin enough, but it won't have the stiffness to push > through most plated through holes.   I decided to take some fine gauge wires and run them around the side of the board to get to the other side. It wasn't the most elegant fix but it corrected the problem.   Thanks for your reply. -- David Farber Los Osos, CA

Jeff Liebermann <jeffl@cruzio.com>: Jun 17 10:30AM -0700 On Wed, 17 Jun 2015 05:09:24 -0700 (PDT), Matthew Connor   >I am brand new to repairing PCBs. I'd therefore greatly appreciate >relatively simple explanations and your indulgence of my ignorance.   This is Usenet. There are no simple explanations.   >I recently obtained a Geiger counter which was in need of being rebuilt. >Because it was manufactured in 1962, the components are large and >provide me with plenty of working room.   Rebuilt? Mechanically, electronically, or both? Maker and model number? For 1962, my guess(tm) would be a bright yellow Lionel CD-V700m. <https://www.google.com/search?tbm=isch&q=cd-v700m> You might also want to look into modifications: <http://home.comcast.net/~prutchi/index_files/cdv700pro.htm>   >After desoldering all components,   If it's what I think it is, the PCB is made from phenolic (paper). Phenolic boards do NOT tolerate much heat, soldering, bending, etc. In other words, the traces fall off and the board delaminates or crumbles. Your desoldering may have trashed the PCB.   >I took a locksmith's file (very small and fine) and took off >just the immediate outer layer of the leads of the components.   Some counters were coated with some kind of conformal coating in order to protect the high voltage that runs the GM tube. You should not have removed it and will probably need to reapply it to the high voltage components and PCB. Phenolic is hygroscopic (absorbs moisture) and will need to be heated for a while to evaporate moisture before it can be coated. Personally, I think you just ruined it. It might be easier to just make a replacement G10/FR4 PCB. You can also add your additional shock mounting more easily. There may also be a market for your unused boards. Check the Yahoo Geiger Counter groups (there are several) for advice on this: <https://groups.yahoo.com/neo/groups/GeigerCounterEnthusiasts/info>   >My intention was to remove existing solder and any other "gunk".   The best of intentions will probably lead to a trashed counter. I suggest that you stop and thing this over before blundering forward.   >As soon as I began to see the copper color of the lead showing through, >I stopped and moved on to the next. After doing this for all components, >I soldered them back in and everything is working perfectly...for now.   Open the counter and just breath onto the PCB. That puts a thin layer of moisture on everything. If it continues to operate normally, you win. If it craps out and recovers when the moisture evaporates, you'll need to deal with replacing the coating that you removed.   >I ran across some information AFTER doing this that tells me that >might have been a bad idea.   We seem to do things in much the same way. I always read the instructions after I get into trouble. It's more fun that way, but does have the disadvantage of destroying things if I miss something.   >Are component leads coated with something protective that I should >have left on?   Tinning, which prevent the underlying copper from oxidizing and turning into green crud. Also, the conformal coating to prevent condensation from shorting out the hi-v section.   >Should I expect earlier-than-usual failure from any of my components >since I filed off this outer layer? Any insight is much appreciated.   No. They're fine. After all, the counter was probably designed to survive a nuclear attack.   Good luck.   -- 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

ggherold@gmail.com: Jun 18 07:16AM -0700 On Wednesday, June 17, 2015 at 11:58:03 AM UTC-4, Phil Hobbs wrote: > a small bottle with a stainless steel needle.   > When the needle clogs up (as it will), just touch it with the iron and > it magically clears out.   I've had old copper wires (In some old insulation.. zip cord type stuff) and it gets and oxide/ coating/ something/ that flux doesn't attack very well.   I end up having to first scrap it with sand paper or a green scrubbie. (Scotch brite) and then tin it.   I've always wondered what the tenacious oxide is.   George H.

joywellb@gmail.com: Jun 18 07:02AM -0700 hi Pieter - from an old post - are you still looking ?   Joy

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