On Wednesday, 17 June 2015 13:30:40 UTC-4, Jeff Liebermann wrote:
On Wed, 17 Jun 2015 05:09:24 -0700 (PDT), Matthew Connor
Matthew wrote:
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
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Good morning, Jeff! Thank you so much for your insight. My counter is a Lionel CD V-700 Model 6b, manufacture date 1962.
On one hand, I'm a little confused. You mentioned several times different variations of me having likely "trashed" my counter by doing what I did. At the very end however, when I asked if I had done any harm, you said, "No. They're fine. After all, the counter was probably designed to survive a nuclear attack." So I'm not quite sure that I'm understanding if what I did was bad or not.
On the other hand, you have given me lots of details to consider and suggestions in areas I haven't even started to think about. You've obviously got a great deal of experience and I'll be taking all of your suggestions into account as I move forward with my project. I'll be trying the breath moisture thing right away. Thanks for taking the time to educate an east coast newbie!
-Matthew