LPC mech gets snagged all the way left

[Ron Rich]

Eric,
Difficult to tell from this photo--I would suggest some safety solvent,and a burnishing tool should be your first choice-- If you still see/hear arching, that usually indicates miss-adjusted contacts on this type relay--It MUST be adjusted so you have an air gap on all contacts as the swinger changes position, also, as I said earlier--the blade control material, MUST be tightly attached, to the metal armature. Ron Rich

[babycat]

indeed - i did a burnishing and adjustment on the G contact, and the arcing cleared up!

But the J is arcing more heavily - perhaps i set the gap too narrow? after pulling the relay and getting a closer look, the J contact looks nasty - carbon and pitting marks. seems like the burnishing tool may not be enough on that one.

i actually dropped the tool late last night, and it has completely disappeared in the juke! i'll pick up another on my way home. i searched for a half-hour! only when i buy another one, will the old one re-appear...

i'm going to try to find a point file too, just in case.

[Ron Rich]

Eric,
That relay MUST be adjusted so that when changing form non-energized to energized, or back, there MUST be an air gap on all six contacts at one point, as the center blades travel. Also, you need to find that burnisher, or it surly will find something to "short out". Ron Rich

[robnyc]

Eric, permit me a few points here;

It is neither possible not necessary to completely eliminate the arching on those contacts. The reason is that they break the circuit of a coil (motor here) under power. When this is done the collapsing EMF in the coil kicks back a large voltage against the last set of contacts to open. Depending at what millisecond the break occurs in the AC sine this voltage can be as much as ten times the line peaks. There are ways to quench the resulting arc, but none of them are present here. The designers determined that the contacts have enough surface area and force to not risk getting welded or lose too much contact face too quickly.

The only critical points are that the center contact --never-- be in direct contact with both upper and lower contacts at the same time and, there be an adequate air gap to quench some of the arcing. Adequate overtravel (wiping) of the contacts is necessary as well. That is what I checked for in these machines and never looked them again. Even after 20 years of commercial service there were no problems in this area. These machine were designed to hold up under conditions of heavy use and minimal maintenance. The one thing they can be unforgiving of is lack of proper lubrication...even then after a thorough oiling (several times) the mechanism will usually forgive.

You are at the point of diminishing returns and, in my opinion, on the wrong track regarding the bucking.

As I mentioned a few posts back, if the machine reverses reliably at other points of travel then the problem is at the left end and most likely related to someone tinkering with either the actuator or bumper. I suggest you set it up as i suggested a while back.

Rob

[babycat]

thanks fellers. been away from the box for a bit, but i just did another round of cleaning and adjusting, and now i've got minimal arcing, and sometimes none at all!

Rob - i really appreciate your point on a certain degree of arcing being normal. i got a bit obsessed with this, as i believe it was these same contact points that when i first got the machine (last year) were arcing heavily on reversal and eventually started blowing the main fuse. after a full bath of the mech last fall, that calmed down again. but started to build up a bit lately. now i think my crude adjustments have finally fallen into place.

i'm gonna take a closer look at the actuator and bumper as you had suggested. good news is, since the additional lubing of the clutch hub yoke and related bits, and cleaning/adjusting of O, G and J contacts, the bucking has been happening much less frequently. the last two times it got stuck, it only bucked for a few pulses before self-correcting.

Ron - i heard the little tool drop, to what sounded like the bottom wood (or my wood floor)... but i still haven't found it. that, and one of the tonearm spring and screws from last year.  luckily it was at the bottom of the mech when i dropped it, so i'm pretty sure it's not hanging in the mech somewhere. i'm gonna pull the TCC and TSA and look in there too, just in case.


now i can start playing records again and see where we are at!

[Ron Rich]

Hi Eric,
One thing I think I mentioned on that rev. relay--make sure the material that holds the contact blades is tightly attached to the metal armature at a 45 degree angle--If that material is "flopping", the relay contacts WILL arch ! I run a bead of glue on both sides of the material. for floppin stoppin---- Ron Rich

[babycat]

indeed, Ron - i had not quite understood what the contact blade holder was, when you brought this up earlier. i was thinking it was the phenolic material with the screws through them that make the stack of blades.

but sure enough, on the last round of cleaning and burnishing, i bumped the other phenolic piece that is closer to the contacts, and it moved quite easily. i suddenly realized what you meant. yes, that little vertical piece is not very firm. it doesn't seem to move at all to my eye when changing directions, but, i'm gonna try gluing it. - Thanks!

these days the mech only gets snagged very briefly, a couple of 'bucks', then moves on proplerly... once every four days to a week. much better behavior. mebbe that little phenolic piece is slipping ever so occasionally.

i also had a 'sit and spin' moment all the way on the left - like it was playing a ghost record, one slot left of A1. curious.

[Ron Rich]

Hi Eric,
Iffin you don't understand somphin--why donju axked ?? --Make SURE to glue it on top, and bottom, AT a 45 degree angle !
You GOTTA stop the bound-sin, or you will destroy either the clutch member, or the pinion gear pin!!

[babycat]

i *thought* i understood, until i bumped that piece and noticed that indeed it can move. THEN it made perfect sense that you would mention it!

do you mean 90 degrees? like a perfect 'L' shape, yes?

[Ron Rich]

Yep--90-- I flunked basic algebra--may have been looking at some other kinda bra--??
Ron Rich

[babycat]

Mar 22, 2017 13:39:16 GMT Ron Rich said:

Yep--90-- I flunked basic algebra--may have been looking at some other kinda bra--??
Ron Rich

 i completely understand 

[babycat]

i can finally say that it's running nicely and it has not gotten snagged once over the last three weeks of daily use.

the final foible was quite elusive, but it eventually came to mind.

all of the cleaning and adjusting of the contacts had gotten the problem down to a minimum.  but it would still get snagged on the left every now and then.  i had done Rob's procedure for checking the reverse switch actuator and end bumper and everything looked kosher.

it would happen pretty infrequently, but i was determined to SEE the position of the relay whenever it got snagged.  a while back i had removed all three of the blue front panels, so that i could really watch the mech and relay when the speaker doors were open.  of course, everytime i sat there in front, running it with the doors open, it would run just fine.

otherwise, whenever i would hear it get snagged, i would run over and open the speaker doors to look at the relay. but it would always correct itself by the time i got the door open.  i was beginning to think the juke was really teasing me.  maybe it was haunted or something.  this same situation repeated many times, though infrequently...   the only bit of logic i could deduce was that every time i opened the door, the relay would release and the mech would reverse as it should.   


BUT WHAT DOES THE DOOR HAVE TO DO WITH THE RELAY???    


i felt like i was on to something, but was honestly too embarrassed to bring it up here...  it just didn't make sense.   a couple of times i thought... MAGNETISM?   ...could the magnetic field of the 8-inch speaker actually be interfering with the magnet of the relay or it's contacts?   it seemed unlikely to me, but then when my girlfriend was making a selection while scanning, it snagged.   "Should i turn it off"?  she asked.   "nah, just open the left door".   she did, and the mech went back to work.

"Why does opening the door allow it to work??", she asked.  "that doesn't make any sense".  she's a super fun gal, but quite logical.  

only from this perspective did i realize that there truly was a cause-and-effect going on here.  i thought about the potential magnetism and realized that replacing the steel blue panel might interrupt any magnetic effect.  i only placed the left panel back in, as that one is smack in between the 8-inch speaker and the relay when the mech goes all the way left.  

sure enough, it has not snagged ever since.  i also realized that i had replaced those speakers back in November with a coaxial set that has a fairly large magnet, perhaps stronger than the original Utah's. might have been a factor, maybe.

of course, it mostly came down to the cleaning and burnishing of the relay contacts.  and perhaps a slight adjustment of the G and J contacts.   i might have been done with it a month sooner if i hadn't pulled that panel out!

[Ron Rich]

Whut kin be sayed, other then RTFM ? Someplace, in one of the manuals are words something like ---use only Gen-u-whine Seeburg replacement parts--- Seeburg Engineering was very good at assuring that the parts they used in the speaker systems matched not only the amp, but the cabinet into which they were fitted. Ron Rich

[babycat]

aye, Ron. but my new speakers (and amp and phono preamp) sound so much better!
it really is a fantastic sounding LPC now.

i did think about those engineers when putting the blue panels back in. i'm guessing they were thinking about the speakers' proximity to the mech, among other things when they developed those.