LPC-480 "hum"

We have a LPC-480 that has a hum when it plays music. The amplifier has been recapped, and in another jukebox it doesn't hum, which leaves the amp out. I also know that it isn't the speakers or the wire that leads to the speaker because they don't hum when hooked up to a stereo. That makes me think it is the mechanism itself or something in it that is causing the hum, but I'm not sure how I could check what it is, if somebody could help me it would be greatly appreciated!

Is the jukebox set on "free play" ? Is the "hum" coming from the speakers, or the cabinet ? Is it louder as the mechanism travels to the right (V-8) end ?
Ron Rich

It is currently set for free play, and it sounds the same on A1 as it does on V8. What exactly do you mean by cabinet? As far as I can tell it comes from all 6 speakers

"Eilindrene" Find out if it's is electrical or mechanical.

Play a record, manually lift the tonearm off the record.

If hum persists it is electrical.

If hum only occurs when the stylus is on a record, it is most likely due to vibration from the motor due to sagging/hardened motor mounts.

Machines that use autospeed unit operate the motors at approx 84 HZ on 45rpm and this becomes more audible than normal 60HZ.

This, BTW is why Seeburg went to using speed units for 45's. It was normal for 33's to be cut at lower levels and thus the machine would bring up the gain to compensate. On speed unit equipped machines this would make the noise more noticeable so native 33 was used for several years.

Rob/NYC

When I take the arm off the hum stops. That does seem true, when its playing a LP the humming is softer and slower.

"Eilindrene" Remove the mech cover and with power off, examine the motor for looseness. try turning it back and forth, ideally it should be held in-place.
Also, look at the bottom of the motor and see if it is touching the "finger" that extends from the mech casting to under the motor. Originally Seeburgs had a rubber plug that supported the motor there. Over the years they eliminated this and when the mounts sag the motor will touch that metal extension causing an increase in vibration and rumble. You can cut a piece of rubber and stuff it under there to isolate the motor if the existing one is missing or too hardened.

Rob.

Thank you a lot Rob, that seemed to stop the humming while it played, but now I have another issue. After about 30 minutes of playing I chose a B side of a record and it started to slow down and eventually it stopped, so I hit the reject button and it rejected it. It moved on to another record on the A side and played it without an issue, but I had one more record in queue before it was done, and it was a B side so I attempted to reject it if it started slowing down, which it did. When I rejected it I heard a loud click like I always did, but it didn't remove the record and it is currently at the far right and not moving. I turned it off and left it that way because I don't want to do anything to make it worse. Any ideas what might have caused that?

Dalton

Rob,
The motor support plug--as it was related to me--the reason that it was eliminated in the LPC model was the motor company raised the cost of the motor, insisting that they had re-formulated the rubber supports, and that they would "never sag". As was further related to me--the Seeburg engineers were furious at this, claiming that it still would sag, and cause problems if the support plug was eliminated. The "bean counters" won that battle, however not the war, as the support plug was replaced sometime later, as the motor supports, did, indeed, still sag. (this change was not noted in the parts books for years).
The point being--the support plug is available today (see "announcements--where to find"-above), but if you chose to "stuff rubber under there", be sure it is the correct thickness, and does not hinder air flow to the motor.
Ron Rich

Dalton, assuming that in placing something under the motor you didn't radically shift the motor out of axis with the coupling, it does sound like the speed unit is failing.

Turn power on, make sure machine is in play mode, then carefully lift the turntable clamp away from the record (watch your fingers) this should switch the motor off the speed unit and back to line. Again, watch your fingers and hands, things will happen fast if this works.

There are contacts on the reversing relay on the mech that can become pitted and reduce or kill power to the motor. try carefully tapping and nudging them with a piece of stiff, non-conductive material (a pen or small dowel etc) you may see some sparking and the motor may change speed, if this is the case the contacts will have to be properly filed so as to remove the pits and brushed with contact cleaner or alcohol. If the pitting is not too serious you may be able to just run a piece of cut up business card through the contacts and again use cleaner.

Obviously power must be -off- and when you do this you'll need to press down on the fiber plate that guides the contact blades so as to force the contacts onto the card material as it is drawn through them.

Be careful not to bend the blades, but also check to be sure that there is adequate 'wiping" action which is slight overtravel when they close.

The above is standard practice for all the relay you'll encounter. It isn't difficult but does require some care.

Rob

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Ron, I guess that explains why I've seen a hodge-podge (who used that term anymore) of mechs with plugs and w/out.

On the few that have needed plugs, I cut an approx 1in square from a sheet of 1/4 thick rubber that was otherwise used for footing and surface protection.

Ah capitalism. Save a 1/2 cent -kill the product.

Rob

I moved the clamp off of the record which didn't do anything to it, the record moved slightly off center, so I pulled it out so I could set the clamp back down. After that my neighbor happened to see me messing with it, so he came up and asked if he could help. Since he's an electrician I figured he could do a better job than me. I went to get rubbing alcohol and a diagram of it, he had a business card and he cleaned them. After that we plugged it in and turned it on to see if it worked. It was playing correctly, so I thanked him. About 4 hours later it slowed down on the B side of another record then went back to speed, so I went to reject it. After that it moved to the right end and looked at the main fuse, the glass was cracked so I put a new one in and left it off so I don't do anymore damage or have to buy a new fuse. Any ideas? I would assume its the mechanism, but I'm not too sure where to start right now.

Well, was the fuse blown or just physically cracked due to mechanical stress.

BTW: Where is this broken fuse located?

Rob

It was blown, and its the main 6 1/4 amp fuse at the bottom left of the cabinet, so nothing was powered on the jukebox

The Autospeed knows not, which side of a record is being played, therefor, I assume the Autosped is not your problem. I assume that there is some damage that has been done to the reversing relay blades, from what you have written. A common problem with this relay, is the fiber section becoming loose at the connection between it and the metal armature. When this happens, "people" tend to attempt to "adjust" the relay blades.
I repair this in the following manor: First, with power off-- move the carriage to the "inspection window" in the center of the record rack. 2.nd, lock the reversing relay down, by lifting the detent lever, and pushing down on the armature. 3.Align the fiber at 45 degrees to the metal. 4. Using ONE drop of "super glue", glue them together. 5. Using a bead of "Testors Model Aeroplane Cement", lay a bead in the connection between the fiber and metal--both top and bottom sides. Detent lever will need to be pushed down once glue has dried, and prior to power being applied.
I further assume that you "looked at" the main 6.25 amp fuse, because you suspected it had blown ? If, the carriage is all the way to the right ( or for that matter , left), an the fuse was indeed, blown, this would indicate that the adjustment of the reversing switch blades has been "mucked-up". See the service manual for the correct adjustment procedure--it's very critical on the LPC models, but once right, it never will change.
BTW, the upper socket on the AC distribution box (which houses the main fuse) may or may not be fused/switched. All PHONOGRAPH units should be plugged into the lower three outlets only, as they are fused/switched for sure. The upper one is provided as a "service" outlet only.
Ron Rich

The Autospeed knows not, which side of a record is being played, therefor, I assume the Autosped is not your problem. I assume that there is some damage that has been done to the reversing relay blades, from what you have written. A common problem with this relay, is the fiber section becoming loose at the connection between it and the metal armature. When this happens, "people" tend to attempt to "adjust" the relay blades.
I repair this in the following manor: First, with power off-- move the carriage to the "inspection window" in the center of the record rack. 2.nd, lock the reversing relay down, by lifting the detent lever, and pushing down on the armature. 3.Align the fiber at 45 degrees to the metal. 4. Using ONE drop of "super glue", glue them together. 5. Using a bead of "Testors Model Aeroplane Cement", lay a bead in the connection between the fiber and metal--both top and bottom sides. Detent lever will need to be pushed down once glue has dried, and prior to power being applied.
I further assume that you "looked at" the main 6.25 amp fuse, because you suspected it had blown ? If, the carriage is all the way to the right ( or for that matter , left), and the fuse was indeed, blown, this would indicate that the adjustment of the reversing switch blades has been "mucked-up". See the service manual for the correct adjustment procedure--it's very critical on the LPC models, but once right, it never will change.
BTW, the upper socket on the AC distribution box (which houses the main fuse) may or may not be fused/switched. All PHONOGRAPH units should be plugged into the lower three outlets only, as they are fused/switched for sure. The upper one is provided as a "service" outlet only.
Ron Rich

Thanks Ron, I see a trip to Hobby Lobby in my future. I'll probably do it this weekend, because I have a busy week and it would probably be better to do it all at once than to stop and go. And just wondering, how should I move it? I would prefer not to just pull it to the middle. The service outlet doesn't have anything plugged into it, everything is plugged into the lower 3. Just out of curiousity, what would be plugged in that outlet?

Dalton