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Mitsubishi LT-30 restoration

Clean LT-30 rails?

I cleaned the rails from the top using a soft cloth. I was holding off on doing that until I verified that I wouldn't be removing an essential lubricant.

My cloth got a spot of grey on it, which might have been oil, or just dirt.

Seemed to make no difference with regards to the ticking sound.

I now notice also that when I cue the arm when playing a record, then hold the headshell and release the cueing, I can move the arm back and forth and it does actually servo in both directions.

Then, cue the arm again, push the arm to one side, and release cueing normally (not holding the headshell). The tracking servo engages during the last 30% of the fall to the record surface. If I understand the service manual correctly, the tracking servo should engage right at the record surface, and not above it.
 
The cueing higth adjustment may affect that. There is a relay on the main board that is triggered by a cam switch on the cueing mechanism, it is the tracking function transfer relay that shifts control of the tracking motor from the shuttle buttons and start-return logic to the tracking servo loop associated with the bi-directional arm light gate. Also there is a bit of free space between the forward/back elements of the tracking light gate to prevent over-control oscillation and chattering.
For the clicking noise check everything associated with the tracking cable and it's drive mech'.
 
Observing from below?

Pio1980 said:
The cueing higth adjustment may affect that. There is a relay on the main board that is triggered by a cam switch on the cueing mechanism, it is the tracking function transfer relay that shifts control of the tracking motor from the shuttle buttons and start-return logic to the tracking servo loop associated with the bi-directional arm light gate. Also there is a bit of free space between the forward/back elements of the tracking light gate to prevent over-control oscillation and chattering.
For the clicking noise check everything associated with the tracking cable and it's drive mech'.
Click to expand...

Does that require removing the bottom and observing from below while it's operating? Can you check the tracking cable and mechanism with the unit upside down?
 
Arm base not firm

I notice that the arm base is not rigidly held in position. While a record is playing, I can make it wobble by putting my thumb down or into the side of it in back. It also seems that there is some play in the string or whatever pulls it along. I can make the base move back and forth with just a little pressure.

So I wonder if there are some worn bushings, or a string that needs to be tightened.

Now if I put my thumb down in the back of the arm base, pushing slightly inward, the tick goes away, and the tracking motor is able to overcome my thumb pressure and stay centered anyway.

The arm base seems to ride on a single chromed shaft (that was what I wiped off with a clean cloth earlier, making no difference in operation). But that mounting isn't very rigid, as I just described. I see in the exploded diagram that #25 "shaft-assy" has a thing that looks like a bushing in the center of it, and it gets screwed into a bent metal holder, #26. Perhaps the screws holding the holder in place are slightly loose.
 
charlesp210 said:
Does that require removing the bottom and observing from below while it's operating? Can you check the tracking cable and mechanism with the unit upside down?
Click to expand...

No, not really. Basically a visual inspection with an understanding of how it operates and judicious lubrication. The clicking makes me think stiction binding somewhere somehow.
 
charlesp210 said:
I notice that the arm base is not rigidly held in position. While a record is playing, I can make it wobble by putting my thumb down or into the side of it in back. It also seems that there is some play in the string or whatever pulls it along. I can make the base move back and forth with just a little pressure.

So I wonder if there are some worn bushings, or a string that needs to be tightened.

Now if I put my thumb down in the back of the arm base, pushing slightly inward, the tick goes away, and the tracking motor is able to overcome my thumb pressure and stay centered anyway.

The arm base seems to ride on a single chromed shaft (that was what I wiped off with a clean cloth earlier, making no difference in operation). But that mounting isn't very rigid, as I just described. I see in the exploded diagram that #25 "shaft-assy" has a thing that looks like a bushing in the center of it, and it gets screwed into a bent metal holder, #26. Perhaps the screws holding the holder in place are slightly loose.
Click to expand...

The arm carriage rides on 2 heavy precision ground rail poles, the poles should be firmly immovably set into the baseplate. The worm shaft assembly #25 in the bushing plate drives the gear with the cable pulley, the cable is not fixed to the pulley to allow for slippage if the mechanism becomes jammed somehow to prevent the gears from being stripped and destroyed. I doubt the plate is loose but you could always check. Make sure that the pulley shafts are lubed with light machine oil and I'll put some more thought into this..
 
The TA rides on plastic "V" wheels on one shaft, and a regular plastic wheel on the other. Both of them will collect compressed dust/dirt over time, and cause stiction. You will have to do some dis-assembly to clean them. If the wrong belts are used (too tight or too loose) that will also cause hysteresis problems. My LT-30 is as silent as darkness when it moves, and except for the fact that it stays tangent, it is very difficult to tell it is moving. That is how it should operate.

When you say ticking, do you mean an audible tick when ever the tone arm moves?
 
Need help with removing tonearm assembly

I'm trying to replace the belts on my LT-30.

According to the first post in the thread you don't have to de-solder the connections like the SM says so I didn't do that. Just basically disconnected everything underneath then flipped it over and removed the two screws and L-shaped holder.

I'm up to step 10 in dis-assembly.

According to the SM it says:
"Now, the tonearm ass'y can be removed in the following manner. Dismount the tonearm from the arm rest and remove the ass'y by lifting up the tonearm base diagonally toward the back."

Not sure what that means. I have turned it over (right side up) and tried removing the tonearm assembly and while it is loose it won't come out. Does anyone have advice on how to remove this? Do I even need to remove it or is there something else done to get to the motor? Hopefully the OP can reply with how he got to this motor.

I have photos of the dis-assembly that I've attached. One just before removing the slit plate and another of the tonearm assembly. I have more and can take more. Is there something more that needs to be removed from the tonearm assembly?

When looking at it from the top the problem seems to be the rails and the plastic rollers. I didn't really have to loosen the allen screws referenced in the SM in order to get the assembly to slide all the way to the right. Should I have loosened those allen screws more?

Thanks!
 

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Got it!!!

I hadn't moved the rail out of the way. Also, there was a screw that I swear the SM didn't say to remove but the OP had.

So I did... Got the tonearm assembly out and about to replace the belts.
 
Balifly said:
What size belt do you need? :scratch2:
Click to expand...

Unfortunately I don't have the size. The SM gives a part number of either M07496629 or M07469628. To be honest I can't tell which it is in the SM. I think it's the first one that ends in 29. The only other thing I know is that it is smaller than the one I linked to earlier.

I was hoping since a couple of people have replaced belts on this table in this thread that they might know a source or the size.

Thanks!
 
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Arm tick and motor wow

perryinva said:
The TA rides on plastic "V" wheels on one shaft, and a regular plastic wheel on the other. Both of them will collect compressed dust/dirt over time, and cause stiction. You will have to do some dis-assembly to clean them. If the wrong belts are used (too tight or too loose) that will also cause hysteresis problems. My LT-30 is as silent as darkness when it moves, and except for the fact that it stays tangent, it is very difficult to tell it is moving. That is how it should operate.

When you say ticking, do you mean an audible tick when ever the tone arm moves?
Click to expand...

Thank you. Yes, it make a tiny tick or bump sound just as the arm base starts to move to correct the tracking angle, very much as if the belt is either too loose or too tight. I now have a second LT-30 which is a little beat up, everything a bit looser, but the arm base doesn't make the tick/bump sound. Is there a way to loosen the belt?

I've personally shelved this issue right now, as it doesn't seem to have serious audible consequences. Something else does. The cleaner LT-30 I have seems to have excessive wow, which robs all music of it's glory and especially piano and synthesizer. Though it's still subtle enough that I was uncertain for a whole week. I haven't tested unit #2. Does this thread discuss making the motor servo adjustment or otherwise servicing the motor? The service manual says you need to build a FET buffer to measure the servo signal correctly, and that's the only motor related service described.

Because I like their presentation of pitch and musical solidity, I'm starting to put idler wheel turntables in every room. Any thought of an idler mod to LT-30 ? Another idea I have is redesigning the LT-30 motor electronics to make it more like SP 10 Mk2a.
 
Decatur Greg said:
Unfortunately I don't have the size. The SM gives a part number of either M07496629 or M07469628. To be honest I can't tell which it is in the SM. I think it's the first one that ends in 29. The only other thing I know is that it is smaller than the one I linked to earlier.

I was hoping since a couple of people have replaced belts on this table in this thread that they might know a source or the size.

Thanks!
Click to expand...

I found a thread on vinylengine where someone said they got their belts from turntableneedles.com. Using their search tool where you enter your make and model it said one 5.1 inch and one 3.5 inch. I ordered a couple of 3.5 inch belts.

If anyone who has replaced these belts can confirm while I'm waiting for the belts to arrive that would be great.

I did do a sloppy measure of the drive path. It was a little hard to do given the location. I came up with a little under 4". Allowing for stretch 3.5 sounds about right.
 
TTNeedles sells a kit for the LT-30 that has both belts in the right size. Charles, have you recapped yours?
 
Aerobat said:
TTNeedles sells a kit for the LT-30 that has both belts in the right size. Charles, have you recapped yours?
Click to expand...

Thanks!! I thought those were the correct sizes. Wish I had seen them first, the larger belt was $3 less than where I bought mine.
 
TT Needles set me up with an LT-30 belt set as well. Worked like a charm... once I spent the 2 hours removing the black tar from everything, including my arms and face.

I can't remember removing any rails or the tonearm to change the belts... just to change the bulbs to LEDs
 
Help with LT-30 lamps

I got the belts replaced on my LT-30 but I discovered a disconnected lamp wire when I was putting the table back together. Probably caused by me trying to get the tonearm assembly out.

It looks to me like I can just solder this wire back as there's enough length left on it. It's easier to see the broken connection in the fuzzy photo and easier to see the length of the wire in the clearer photo. The other photo is of the spare bulbs I got with the unit.

Questions:
Since one leg is already disconnected can I test the bulb by connecting my DVM to the legs of the lamp? One side is still attached but one is completely disconnected.

In the event I need to replace the bulb I've never soldered anything with wires this fine. It looks like I can desolder a bit, lay the wire on the pad and quickly apply a drop of solder. Anyone who has replaced these bulbs... does this sound right? Any tips to pass along? I have a Hakko digital soldering iron. What would be a good temp to do this type of work?

I have two spare bulbs that I got with the unit (in the third photo). Are these the correct replacement for this bulb?

If better photos would help I can take more.

Thanks everyone!
 

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You can hook up a 9v battery to test the bulbs. To resolder, just hold the wire against the existing solder with a small screwdriver, then touch the wire and solder with the soldering iron tip until the solder liquefies. Remove the iron and blow on it to cool, and you're done.
 
Aerobat said:
You can hook up a 9v battery to test the bulbs. To resolder, just hold the wire against the existing solder with a small screwdriver, then touch the wire and solder with the soldering iron tip until the solder liquefies. Remove the iron and blow on it to cool, and you're done.
Click to expand...

Thanks Aerobat!

A couple of questions...

Does polarity matter when I connect the battery?

Since the lamp is 5V should I make sure the 9V battery is only putting out 5V?

I'd like to check all the bulbs while I have it open. Is there any danger to the circuits to test all the other lamps while in circuit?
 
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