"Contacts"- care/cleaning/replacement

[Craig]

ORIGINALLY POSTED ON PHONOLAND BY RON RICH

Hi All,

I have been axked this quite often, so, I'm posting this as a "sticky topic"--
It's strictly my opinion, derived from over 50 years (Gosh, I'm OLD !) of "working with" them--other are invited to agree, or not --
Many factors should be considered in design, some of which are:

Materials used for both the point itself and the blade on which it sits--also, which type, round, or "crossbar" to use where. Pressure/size, needed to carry the current load, and gap to be used.

EDIT: Just got asked something that never occurred to me-- "Where do you start ?" .  OK You "start" with tight mounting screws, and the moving (pushed/pulled ) blade at a straight angle coming out of the insulator. If a bracer blade is used, bias that blade to the bracer and maintain the "straightness" of that blade, using the bracer, while setting the specified gap on the the other blade (once again, if a bracer is used, bias against the bracer). 

That being done correctly, contact points need no "adjusting", if operating as they should !

The MOST often found failure, is contamination. The source of this must be found and eliminated. In order to do so, I use either of the following methods. If, for example, I am washing a Seeburg mechanism, I use a water based "de-greaser" and rinse in hot water. If I am just cleaning one contact, I use a "plastic safe- safety solvent". Once "clean" I examine the point looking for "pits/burns". If found, I use a "point file" AND then, a "burnishing tool", to "dress" the contact. I then check the "adjustments" of it carefully, and set it as necessary to achieve the specs as noted in the Service Manual.  If "no specs" are available, I strive for a 15 ths of an inch, "wipe" after the two contacts touch, as this "self-wiping action" tends to keep them "clean".

HINT: On adjusting contacts--put a piece of white paper behind them when "adjusting", and you can see the contact point, much EZ-ier !

A note on "CONTACT CLEANERS". If the type with any type of "residual" , or "lubrication", these should NOT be used on contacts that "make/brake", as they "attract dirt" ! These are great for "sliding type" contacts, and "slip-ring contacts", but silver/gold contact points, should be clean and dry, IMHO. Also--be careful as the sprays can attract enough dirt to become "conductive"-- attsa can be a bigamess !!

When to burnish ? Seldom, if clean and correctly set as above. (if not broke--do NOT "fix-it" !!!). Remember--filing/burnishing, is, removing silver.

{EDIT} ONLY time a point file is required is if the contacts are "pitted, or burned"-- a burnishing MUST follow filing !
The above applies to "normal", round, silver, contacts.
{EDIT} Asked about sliding switches such as used in a "mechanical keyboard"-- I remove the keyboard from the phono, remove any "coil-solenoid", and/or meter, wash in HOT soapy ( dish washer detergent) and rinse in hot water-then re-wash in hot ammonia water--hot water rinse--blow, or air dry TOTALLY prior to use.
Gold, or "Gold flashed" contacts, are somewhat different. These also must be free of contaminants/pits--BUT MAY be black in color, and should never be filed or burnished ("100%", gold--OK to burnish).
Any contact that is less then 50 % of it "original size" must be replaced, and most often, re-adjusted.
If "adjustment" is necessary, the contact blade, must be "reformed" across the whole blade length to the point connection. Do not "kink" it at any point. Bias it to it's bracer blade, if used, or, in the proper direction. If there is a bracer, use it to achieve the proper gap, if not, just bias it to do so. Pay particular attention to cases of "break before make", and "make before break", contact sets.
{Edit} "Ice cube relays" ( plug in type)--wiping action is done on the center contacts--they all must "hit", and move. or slide, on the stationary blades. These, IMHO must have NO "residue" left on them, as it will collect dust ! The stationary blades are the "adjustable ones".-- (yep, bend them) to achieve "air gaps" when shifting positions. FYI various brands covers, are slightly different--observe which end goes where when opening the covers--some brands only go back on one way !
HTH, Ron Rich

{EDIT}  Been axked about the screws holding contact blades--In most cases, screws should be checked--they must be "snug" and if used, tension plates must have tension on them--if no plates are used tighten the screws as snugly, and evenly, as possible PRIOR to any "adjusting" ! Do NOT "over-tighten" or you will be in danger the screw heads, will eventually snap off.  Ron Rich

EDIT: Been asked "how to check contacts"-- use an Analog meter the same way as on the switches below. Current handling abilities,can NOT be checked with a digital meter !

"Changing" contact points-- If pressed on, file off the "pressed end", and either "press on" the new  silver points, or solder the new ones to  the blade-- if "welded on", file all of the old one off, install a new point by soldering it to  the blade-- use flux, tin blade, and contact-- file off pinning, if there, position contact and heat from underside of the blade till solder flows -- CLEAN it ( I like '99 % rubbing Al-key-haul, or a safety solvent), before using !

[babycat]

Hi Rich - Question:  so, to reform the blade, you very gradually 'bend' it, across its whole length? 'biasing' meaning physically influencing it until it conforms?

maybe use a small flat screwdriver?    

[Ron Rich]

Yes sir, but I can not envision how one would use a flat screwdriver to do this ? I use a small pair of "duck-bill" pliers that were modified a million years ago. One side of the duckbill has been ever so slightly "hollowed out". You could apply bias with a flat. smooth pair of pliers, and your wrist ( I often do this, when I'm too lazy to get the special pliers outta the bottom of my tool box ) Ron Rich

[babycat]

thanks, Ron. how do you adjust for the 'wipe' that you mentioned? is it a matter of repositioning the blade in the stack, or just further biasing with the pliers? and what measurement is 15 ths?

i can see that i have contact on my "O"blade (Seeburg LPC), but i can't notice any wiping action beyond mere contact.

[Ron Rich]

Its 15 thousands, of an inch. Yep you re-form, the yielding member, the one that moves--in the case of the "O" contacts, the blade that moves down.
Ron Rich

[babycat]

gotcha. i have not burnished contacts before. my local supplier has this: is the 0.185" width small enough?

 

[Ron Rich]

Eric,
That'll work--I actually prefer the 9338, which is slightly wider--Ron Rich

[juke46]

Is Deoxit still the best contact cleaner available? Thanks Much! David

[Ron Rich]

Hi David,

IMHO, that depends on which type "contact" you want to clean ! I use a "plastic safe-safety solvent", or a water based de-greaser, to CLEAN all contacts. Open blade types, need nothing more.  On "disc"/ "revolving wiper", or on a "slip ring", type contact, I use the solvent first, then Deoxit-5, which is the best I have found-yet --

EDIT: I suggest you NOT use any residue leaving cleaner on electrical/mechanical "keyboards"--they tend to "channelize" (aka "flash-over") ! My proceedure for these is to remove them from phono-- remove all solenoids/meters/coils, from the keyboard--wash in hot soapy water (liquid dishWASHER det. preferred) Rinse well, dry-- re-wash with (sudsy -- if you can get it) Ammonia, rinse in hot water-- DRY totally--re-lube, install removed parts, and re- install in phono, correctly ( MUST be  some "play" between plastic button and keyboard stem).  Ron Rich

[Ron Rich]

Hi All,

When checking for continuity, You CAN NOT assume that a self ranging meter, of any kind, will work!  Even one with a "beeper" can not be trusted to assure current can flow there --You must use one that has a settable, range switch, and that switch must be at the lowest setting possible. I think a "digital" meter may work, depending on brand/type, but since I can not see your meter, nor have I checked all meters I can not say for sure ! . A GOOD analog meter will always work--- Note : If in doubt, turn power off, and check with a test lamp made from one, AA battery, in series with a # 112 flashlight bulb. Watch the lamp as you close the contacts-once contact is made, it should be full brilliance--no "flicker", of any kind !--The brilliance of the lamp will tell you if the contact is good, or not*.  "L@@king" at contacts can only tell you if there is a gap between the points ( Hint: stick a piece of plain, white paper "behind" them, and you can "see thru them" better, to check the spacing  !)  Also-- if the contact point was "squozen" to the blade, is the "squeeze" still tight ?? Ron Rich

* This is also true for any enclosed switch-- using the test lamp with at least the common un done from the switch, it MUST make well, the instant it "snaps"-- any "flicker" or hesitation-- that switch IS BAD ! 

[gordo]

Hi Ron,

I have been working on my Seeburg C (see other thread).
Now it is working well I have noticed that 2 sets of points give an audible crack and flash when they swipe.

Does this mean they are not connecting smoothly? I imagine this will cause pitting?

Regards

Gordon...

[Ron Rich]

Gordon,
Depends--which contacts--when ?
Ron Rich

[gordo]

Hi Ron,

Sorry, Seeburg C.

The points spark in the O and SC points in the Cam Switch as the tone arm moves towards the record to play.

Cheers
Gordon

[Ron Rich]

Hi Gordon,
On the SC contacts, do they spark every time when playing BOTH, or just one side of the records ? On the O contacts, are they opening just prior to needle set-down, or sooner while there is still a lot of pressure from the transfer cycle. Some intermittent sparking in both places is somewhat normal, or may indicate contaminated silver contact points, if it happens all the time. Ron Rich

[gordo]

Hi Ron,

It is the O contacts that spark just prior to the record playing.
It sparks quite loudly and gives off a slight smoke puff.

Cheers

Gordon..