How Do I Make a PCB Shock Resistant?

1962 might be a CD-V700M counter. It matches your description: 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: 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.

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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

You can always encapsulate it in two part epoxy. MG Chemicals (and others) sell these kits.

Mind you you won't be able to easily remove the encapsulation later unless you soak the blob in acetone for a day or two to soften the epoxy...

John :-#)#

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pardon any silly questions.

lding it. The PCB is 4" x 4" and 0.062" thick. The part of the chassis to w hich 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 l egs.

t 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 PC B and the steel legs to which it's mounted? Or is there a better way?

anks, all!

Eric, thanks so much for your input! Based on your response and on Jeff's, it's obvious I should have included more detail. My apologies! This is a Li onel CD V-700 Model 6b manufactured in 1962. I do not know what type of mat erial the PCB is made from for certain but I'd like to find out. If I inclu ded a picture, would that help?

As for its condition when I received it, it was in bad enough shape (PCB-wi se) that I had to rebuild it. Many of the wires had all but one or two stra nds broken loose from their respective solder joints so relatively speaking , a lot of electricity was going through very little conductor. Because of the way those and some other components broken, I am suspecting shock as th e primary cause, thus leading me to ask about this modification. I will cer tainly take your thoughts into account. I'm very grateful. Thanks again! -M atthew

pardon any silly questions.

lding it. The PCB is 4" x 4" and 0.062" thick. The part of the chassis to w hich 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 l egs.

t 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 PC B and the steel legs to which it's mounted? Or is there a better way?

Hi, Jeff! Sorry for the lack of details. This is a Lionel CD V-700 Model 6b manufactured in 1962. I like the grommet idea very much...thanks! -Matthew

If you happen to have any Pentax or Carl Zeiss Jena lens from the 60s that have turned yellow, they are a good radiation source for testing a Geiger counter.

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