Optonica RP-4705

DonQuixote99

just give me some truth
Scored one of these today, and it basically works....

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It's also classy-looking with it's glass dustcover and brushed-steel high-style headshell. But there are issues.

It's supposed to be an automatic turntable, but right now it's a manual. The function buttons function as follows:

The Play button lights up if you manually move the tonearm into the play area. Moving the tonearm also starts the platter.

The Cue button lights up if you press it.

Pressing any of the function buttons has no other effects.

I'm guessing (and hoping, since it wouldn't be a rough fix) that the machine lost a belt that powers the tonearm movement stuff. Anyone had any experience with troubleshooting these tables?

You'll also note pics of the headshell and the cart that came with it, an Empire LTD 400. Annoyingly, I busted a couple of the headshell wires taking the cart out, but never mind that. The LTD 400 lacks a stylus, and what I want to know is, is that piece of metal I see up the stylus hole a broken end of a stylus, that should be removed? Or is it something else?
 

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Optonica 4705

I just picked up one of these for free. I have the same problems you had, power on and turning, but no control of the cue or play. Mine won't even play manually, as it seems to be stuck trying to cue back to the rest.

My question is, were you able to fix this? Should I try, or just throw this out?

Any advice would be appreciated.
 
Never got around to working on it before I sold my Pioneer PL-550, and put this into service in manual mode. So I've got no experience inside it, I'm afraid.

I'd say you at least ought to be able to disable the troublesome residual automatic function, and use it manually....
 
Optonica was Sharp’s brand of hi-fi equipment, and their better turntables were well up with Technics, JVC, Sony, Denon, Pioneer and other Japanese brands for performance. It certainly looks like it would be worth fixing – there are some service manuals for some of their models (but not yours) here http://www.vinylengine.com/library/sharp-optonica.shtml . It may be worth looking at one, say the RP-5200H or RP-7100H, which may have similar arm transport methods. The RP-7100H was much more complicated, as it had a track locating system (the thin arm next to the main tonearm), but apart from that looks very similar to yours.
 
I opened it up to take a look. There was nothing mechanical to fix - no belt to drive the tonearm, it was all electronic. All wires and connections seemed to be in place. The inside was relatively free of dust, but disgustingly had some dead roaches and beetles on the bottom plate as I took it off. There was some rust, as this had been stored in someone's basement for 20+ years. The rubber feet were also decaying.

Since I wasn't getting any lights or response from the Cue/Repeat/Cut/Play buttons on the right side, I suspect there was some fault in the TDK board that runs those switches. If this turntable was in better shape, I might have tried to switch out that board, if I could find a replacement.

As the tonearm seemed to be stuck in a "Cut" mode, I took off the spring that was holding it back and disengaged a metal contact that was also causing friction. Moving the tonearm over to the record still engages the motor, so it works just fine manually. Thanks for the suggestion to disable the auto functions.
 
I'd be hitting those switches with DeOxit and working them a lot. I'll be there is surface corrosion on the wipers and contacts?
 
I looked at the RP-7100 H service manual. There is a small motor and a little belt sort-of hidden under the tone-arm pivot on that one. If the 4705 is similar, and it looks similar except for the additional track-locating stuff, it will have such too. There has to be some way of imparting motion to the automatic tonearm.

Deoxit on the switches is always worth trying, although it can be hard to get the stuff into button mechanisms....
 
Well, looked inside the RP-4705. There is no belt, or other operating connection between the tone-arm motor and the tone-arm. Something may be missing or disconnected--would need good diagram or a working unit to compare. Design seems different that shown in the RP-7100 manual--that has a belt right off the motor shaft, while the 4705 has a chain of gears that gets close to the arm pivot.

In any case, the motor never runs, and I can't trigger any vestige of automatic function, except when I hit the cue button, the black control cam at the bottom of the pic turns to the left position. Cuing would actually involve the motor turning the big gear in the middle--the bottom of it pushes up on the lift when the motor turns it. I'm not totally sure how motion was transfered to the arm pivot, though it would seem to involve that same gear and the long lever on top of it, but it seems pretty moot, as the motor never runs.

I could try to measure if the motor ever gets power, but I'm fairly discouraged at this point. Either the motor gets power but doesn't run, in which case I need a motor I'm not likely to get, or else it never is powered, which probably means some bollix in the control electronics I'm not likely to diagnose or repair. So it looks like this will stay a manual turntable. Which isn't so bad really.
 

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Heya, ancient thread, I know!

But, I do have some experience with an RP-4705. Thought I would put it here for posterity.

Mine did just what you describe. There's a wimpy little DC motor with a worm gear that drives the auto mechanism. It had old, gunked-up grease on it. Once I had that cleaned up and greased with white lithium, the motor started turning and the mechanism started moving! But then it wouldn't return the arm all the way; it would get stuck about an inch away, before giving up and playing the record again.

The culprit is a kind of crappy mechanism design. It uses a sort of rubber fingertip on the end of a lever to drag across a semi-circular plate attached to the tonearm. It moves by friction. The fingertip thingy is made of some kind of hard plastic rubber, and it dries up and loses the friction it needs to move the tonearm. I super-glued a thin slice of pencil eraser to replace it. I figure the pumice will always drag well on the steel plate, even once the rubber hardens.

It works great now.

As for the turntable itself...? meh.

On the plus side, it looks really cool! Glass top is a nice touch. External controls. It comes up to speed fast, and holds really steady. Easy to adjust.

But the auto mechanism is SLOWWWWWWW! Like waiting in line at the DMV for your record to play.

It's got a real problem with microphonics. No suspension on the tonearm at all. It's just mounted to the plastic chassis, and it picks up everything! I was able to improve this a surprising amount, just by applying dampening sheet to the chassis plastic around the tonearm mount.

Technics, Pioneer and the others never had anything to worry about from Optonica. The engineering just isn't on the same level.
 
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Hey, great info! Mine's in a very secondary role around the mancave these days, but it would be cool to get the auto mechanism going. I'll have to do the grease job and see if the motor revives.
 
I owned one of these many years ago. It was wonderful to look at, but that's about it. It was VERY hard to isolate, the issue with microphonics was very real, and I had a heck of a time getting some cartridges aligned with that arm/headshell.

After getting it to work and finding some ilk of AT cart that would fit up and align properly, I gave it to a friend who lost his stereo in a tornado.
 
I don't know how many units were affected, but both of mine suffered from what I judge to be a manufacturing defect which nullified the suspension effects of the feet. The springs are too tight, so they are extended against the stops at all times. Reversing them brings them into contact with a different part of the molding and gets the table floating.

I traced some arm movement trouble to setting the arm too high, so it was scraping against the lid.

Other mechanism troubles traced back to dirty microswitch contacts. Check them first.

It's been a couple of years; I hope I'm remembering this right. I measured the arm geometry. It seems to be meant for a Stevenson alignment, but on a 7" record! There is not enough overhang range to achieve a standard alignment. That was using a generic headshell; it's possible the supplied shell is longer.
 
It's been a couple of years; I hope I'm remembering this right. I measured the arm geometry. It seems to be meant for a Stevenson alignment, but on a 7" record! There is not enough overhang range to achieve a standard alignment. That was using a generic headshell; it's possible the supplied shell is longer.

It's been a long time, but I think I was able to coax it into *almost* being aligned with the stock headshell using the EnjoyTheMusic free protractor with an AT3600. I couldn't get anything else that I had at the time to line up. And at that, I think I used a dremel tool to lengthen the slots and had to mount the cart at a slight angle. It was a shame as mine was in very nice condition.
 
It's been a long time, but I think I was able to coax it into *almost* being aligned with the stock headshell using the EnjoyTheMusic free protractor with an AT3600. I couldn't get anything else that I had at the time to line up. And at that, I think I used a dremel tool to lengthen the slots and had to mount the cart at a slight angle. It was a shame as mine was in very nice condition.

Try using 50mm "factory short cut" for the cartridge alignment. :music:
 
I didn't look at that manual now, but I did read it back when I was repairing my 4705's. I think the arms are the same geometry. I was questioning what kind of alignment the shortcut gives you.

Thanks,
Dave
 
I have an RP-5100 that is doing (or not doing to be more precise) exactly the same your 4705 Don, and the photo you posted of the internals look exactly the same as mine, did you ever get anything working on yours?

I'm not too worried about getting all the buttons working, although would be nice if I could.
But I would like to get the auto return working if possible?

I'm not an electrically minded person, so I have no idea how most of these things work, but i'm wondering if the LED at top left of the picture has anything to do with it?
The plug coming off it seems to have an alternate position available on the board, any ideas what this might do?

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I own 2 Optonica RP-4705 turntables, both of which exhibited the similar but not exact symptoms. My wife and I purchased them new back in the 80s, both with AT237E cartridges, Having recently, retrieved them from storage and finding they both were not functioning correctly, I focused on problems related to oxidation. So I grabbed my trusty can of Deoxit and proceeded with the most likely culprits. I disassembled ALL of the buttons and cleaned the contacts without success. After locating the original owner's manual and consulting the schematic, I focused on the tonearm actuator/server motor. ALL of the problems were resolved by cleaning, exercising and adjusting the 3 red microswitches in this section of the turntable.

Depending on the conditions of these three microswitches, different symptoms will be exhibited; turntable always on when power button operated, cue function locks up, buttons not functioning, etc.

It's best just to clean all three. They appeared to be sealed, but I was able to deox them by wedging a toothpick into the actuator button (while in the down position) and spraying deoxit into the gaps around the button. Some must have gotten in as continuity was verified with a meter after spraying and "exercising" the button. One switch required two attempts. Also note that clearance between the button and the associated actuating part appears to be sensitive. Some adjustment can be made via the "play" in the mounting screws holes.

I'm not sure how long these microswitches will work, but should the condition return, I'll just replace them.

Great direct drive turntables! Specs rival if not exceed all but the very best in today's market.

Hope this helps.
 
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