Most common faulty part in old electronic gear

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Regarding this kind of switch:

When it comes to working on old electronic gear from the 1950s thru 70s
or 80s I keep reading the most common fault are the old paper/wax
capacitors and electrolytics.

While there is truth to this in some cases, I have found a part that
fails about 90% of the time on these old devices. They are these old
slide switches (shown above). I just picked up an old Sencor Substitutor
box from the 50s or 60s. The caps and resistors are not looking to be
bad, but all three of the slide switches are junk. Even after sliding
them back and forth 100 or more times, they are erratic at best, or dont
work at all. (I am awaiting a can of Deoxit from an online order, since
I can not buy it locally). I have my doubts that even this stuff will
fix these switches.

Do they make more reliable replacements for this type of switch that
will fit the same holes? Heck, even in the 70's when they were only a
few years old, these switches were troublesome.  

I never understood the reason for gold plated speaker terminals, but
these switches should be gold plated, or something done to them, since
they were always faulty.

Re: Most common faulty part in old electronic gear
On Thu, 09 Mar 2017 01:58:01 -0600, wrote:

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Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things)

void _-void-_ in the obvious place


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Re: Most common faulty part in old electronic gear wrote:

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Oh, yes!  Those old stamped metal slide switches with the phenolic wafer  
with the contacts in it were quite awful, and had a short life before they  
started getting flaky contacts.  It might be partly the open nature of the  
switch, lets lots of air get to the contacts.  I just repaced some pretty  
decent PCB mounted push-push switches that were a definite cut above the  
cheap ones, but still had a sliding contact spring.  But, air and maybe loss  
of lube had caused the contacts to deteriorate.  Exercising the switches  
just made them worse.  This was on 36-year old scientific equipment.


Re: Most common faulty part in old electronic gear
A lot of this has to do with location and storage. I have a lot of Dynaco a
udio stuff - and David Hafler was notorious for using low-bid/surplus/salva
ge and "seconds" stuff - that are generally pretty much fine as they have n
ever seen damp, a garage, or unconditioned space in their 38 - 57 year hist
ories. I have a number of vintage radios (TransOceanics) that are up to 30  
years older that are also pretty good - as Zenith went at least one step up
 in initial quality. These switches get flushed before first use in any cas

But rotary and pot switches are a different story. Those I have had to lear
n to restore and/or rebuild. A PITA, but there are usually only a few bits  
inside to go bad.  

As to caps - unless they are potted or PIO caps, I do not even bother - the
y get replaced out-of-hand. It is not a matter of "if" but "when".  


Peter Wieck
Melrose Park, PA

Re: Most common faulty part in old electronic gear

There are kits out there for restorers:

Peter Wieck
Melrose Park, PA  

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