Re: DC relay latching voltage

On 8/26/2024 10:00 AM, John Robertson wrote:

Rather, it should be seen as a counter to the "old saw" that you *just* use
a recirculating diode without considering the consequences.  Just like
considering how to *drive* the coil based on how it will be used.
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[Remember the "pull in" coils and "end of stroke" (EOS) switches on flipper
solenoids?]

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Oh, yes, we constantly deal with them, and pitted contacts on the EOS switches in our shop.

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But, you have the advantage of being able to pull the machine off the floor,
and burnish and regap the contacts.  And, you get some idea of how likely
the need base on how many plays it sees.

 Pinball games are more service trouble than most operators want to deal with. Anything we can do to make them more reliable is part of our business model.
 And I hate repeat service calls.

Of course!  My father-in-law (and HIS father-in-law) ran a route.  So,
unlike an arcade -- where there IS a "back room" -- problems meant a
trip to <someplace>, often during THEIR working hours.  (So, it's
neither convenient for you or them!)

If the device in question is on a mountain in tibet...  (yes!  <frown>)
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Would zener diodes across the contacts help reduce pitting?

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An RC snubber might work better.
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But, *maintaining* a pin table is half the fun!  (unless, of course, you
are in a business to make money from them!)

 Ah, but you see that is the point of doing repairs that are better than (improve upon) the original design.

Yes, John.  My tongue was so firmly in my cheek that I looked like a chipmunk!
Pin tables -- even solid state -- are perpetual maintenance problems.  Whether
its a broken rubber, solenoid, jammed coin mech, blown general illumination,
misadjusted targets, etc.  SOMETHING *always* needs attention.
Or, is giving you clues that something WILL need attention.
I always prefered older tables to the electronic ones.  So, that much *more*
maintenance.  "Hmmm... the hundreds reel only advanced by 400 instead of 500.
Something needs to be regapped (and lets pray it's not a mechanism issue!)"
But, I think that was part of the appeal -- keeping such a machine in top
working condition was a point of pride.
[Until you run out of hours in a day/week/month/year to keep up with it!]

Back in the 80s I figured out why one manufacturer's games were blowing up their driver transistors randomly and published the answer in the trade journals of the day. It was a ground issue, where the commons were done through Molex pins and as the pins aged the ground connections generated resistance, which led to transistors not fully biasing off and burning out. The fix was to beef up the ground connections and all subsequent games we serviced never blew the driver transistors any more and customers were happy!
 Need I mention the factory never acknowledged the error and did NOT implement my recommendations.

(sigh)  Don't get me started on that!  I had a piss-poor opinion of many of the
(hardware) "practitioners" in that era.  I used to say that, as cavemen, they
rode around in cars with square wheels (think the Flintstone's car).  And,
after a while, the corners of the wheels would wear off, leaving them ROUNDed.
At which point, they would promptly REPLACE them with nice, new SQUARE wheels!
<frown>
Of course, it's hard to know how to apportion blame.  There was a lot of
emphasis on reuse -- not just designs but actual *assemblies*.  If you're
only making a few thousand of an item -- and, that item is REALLY REALLY
REALLY similar to the last item you made! -- there is a strong incentive to
reuse "what worked" (even if it didn't work all that well!)
Software folks were always pleading for common-sense changes to designs
("Why do I have to serialize a bit-stream to drive the CVSD?  That
sorely limits the types of sounds -- speech! -- that can be generated
and consumes 100% of the CPU!  Why can't you put a frigging shit register
there, instead???  Even if *I* have to clock it, at least I won't
ALSO have to shift the data in the accumulator!")  But, a lot of
pressure on cost (I wonder how much of a price increase the market
could have tolerated to improve the quality/appeal of the product and
reduce time to market?)
Larry & Eugene would have "wet themselves" for something as trivial as
a 2MHz design...

By the 80s they gained a reputation for unreliability that plagued them until they finally closed shop in the mid-90s. Oddly enough the same company was considered the Rolls-Royce of pinball up to the Solid State machines. Their solid state games looked and played great until the ground issues started randomly occurring (fried coils and driver transistors) and then operators would get rid of that manufacturer's games and buy other brand's machines.

To be fair, you are also competing against the garage shops that want
to sell conversion kits (much cheaper than new games -- at least for video)
at the expense of the "original designs".

There are two cases I deal with - commercial and home clients. Both would rather see less of my shop then they have to and I am happy to oblige them because I hate fixing simple things that could be made more durable. Also we've gained a bit of a reputation of machines lasting longer after being serviced by us and I wish to improve that score.

Of course.  I gave away all of my arcade pieces.  But, always to someone who
*could* maintain them (technicians, etc.).  I knew that, otherwise, the
games would quickly be unplayable and just collect dust in someone's basement.
[I've toyed with getting -- or making -- a Robotron (something along the
lines of a DINING ROOM TABLE, instead of a cocktail, so it would hide in
plain sight.  A full upright would be like storing a refrigerator in the
living room!  :<)  But, suspect I would find too many excuses to play it
instead of doing "productive" work.  And, SWMBO would quickly tire of the
hearing that deep bass "thumping" all day!  (plus the next wave fanfares!)]
SWMBO is the only exception to the "could maintain it" rule -- but, then again,
she's got *me*!  :-/

So, reducing contact arcing is very important to me and my customers!
 We only get more business the better we fix the games!!