Rabco SL-8E Linear Tonearm

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In the old days the 60s and 70s, the Rabco was considered one of the best tonearms ever made. My Rabco is gone. I had my turntable and the Rabco shipped to me when I moved and both were damaged. That's life. Do you still have your Rabco? Please post your pictures and any mods you have done to it.
 
In the old days the 60s and 70s, the Rabco was considered one of the best tonearms ever made. My Rabco is gone. I had my turntable and the Rabco shipped to me when I moved and both were damaged. That's life. Do you still have your Rabco? Please post your pictures and any mods you have done to it.

SL8E modified with low mass viscous damped unipivot arm and photoelectric variable speed servo drive.
 

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@audiostar, you don't have PM enabled... I think I know who you are but thought I'd ask to be sure.

Probably the weak link in an updated Rabco is the track + traverse mechanism. But oddly enough, as truly simplistic as it is, it does work ok. There are much more high precision methods to do the job. Goldmund did essentially this. For a lot of money.

Al's version uses the old "cats wisker" contacts to move the motor and traverse the carriage. This works out ok, probably the error is less than you get with a just slightly offset center LP. So, the tracking error is low, and lower than your better pivoted (non compensating) arm. Imperfect in theory, regardless.

My version used a lamp and a phototransistor circuit for proportional control of the motor. So, properly set the max error was less than the all or nothing contact method, and of course would tend to be rather fixed error for a record whose spiral was "faster" than normal (cut hot)
since the pivot offset of the arm to keep up would slightly more than a standard LP where the arm would have been set up to turn on the phototransistor just enough to continuously move the arm.

Maybe an ideal version would be a linear motor of some sort, or maybe a bi-directional motor with a nil-loss push-pull belt to drive it, so the arm could be set to track back-and-forth with an offset LP.

But there are so many slick arms and slick techniques today (not to mention just air bearings) for arms and tracking error correction that I doubt there is much of a market for an updated arm of this type. The price would be super-high to produce it as a precision product, I would expect.

Anyone want to sign up for the pre-sale roster??
 
bear,
Thanks for your comments. I really liked the Rabco and I am disappointed that it is not feasible to build a new Rabco like tonearm. But there is an alternative to the Rabco. Please check out the thread here at diyAudio DIY linear tonearm started by vynuhl.addict. This is for a linear tonearm that is mechanical without a servo and no air bearing. Your expertise and knowledge would be welcome on the thread. Would like to see your version of a tonearm in regards to this thread.
 
Well, it is quite feasible... but you have to do all the work.

A small machine shop would be quite sufficient.
Small lathe and mill.
Even those combo Chinese late/mini-mills would be sufficient, that and a source for the proper bits of metal... you could even transplant the gimbals and bearings from a standard tonearm assembly...

But as a product, that's a horse of a different color. That gets expensive quickly.
 
I'd like to have some more details about repairing/updatig the sl8e. I've had one for years & it's not doing to well. Both servo motors are good, but it failed to track. It is somewhat disassembled, and the electronic assembly was certainly primitive. I have plenty of the 2n 3705 transistors.



Thanks
 
I'd like to have some more details about repairing/updatig the sl8e. I've had one for years & it's not doing to well. Both servo motors are good, but it failed to track. It is somewhat disassembled, and the electronic assembly was certainly primitive. I have plenty of the 2n 3705 transistors.



Thanks

Start by visiting the Rabco section at Soundfountain:

Rabco SL-8E SL-8: Tangential Tonearm, Servo Control, Parallel Tracking, Functioning, Drawings, Construction, Manual.

It's important to get the original basic system working right before making modifications. Hope this helps.

Ray K
 
Ray: thank you, but I've seen that before. For a while my arm worked well, but a few years back started acting up. I haven't parted with the fee for this manual.

I was trying to find out what improvements might be made, that is departing from the factory electronics, to see if substantial improvements in reliability could be made.
 
Ray: thank you, but I've seen that before. For a while my arm worked well, but a few years back started acting up. I haven't parted with the fee for this manual.

I was trying to find out what improvements might be made, that is departing from the factory electronics, to see if substantial improvements in reliability could be made.

A service manual can be downloaded for free here:

Rabco SL-8E Owners Manual, Service Manual, Schematics, Free Download | Vinyl Engine

The biggest improvement to be made on the factory electronics is to replace the catwhisker contacts with photoelectric control. I made such a mod for my SL8E and it has been 100% reliable since. A side benefit to the mod is that the arm now operates in a continuous variable speed mode to keep pace with the groove pitch - very smooth. You can see part of the mod if you look at my photo gallery. Give me some time and I will put together the circuit diagram and post it here. Someone suggested I start a new thread describing all my mods to the arm. If there's enough interest, I'll summon the energy to do that. Anyone interested?

Ray K
 
I had a Harmon Kardon Rabco ST-7 when it first came out. Sure was pretty compared to my Lenco L-85. No matter how hard I tried, I could never adjust the arm to track well. I was always adjust and adjusting… It forced me to record all of my records to a Revox A77 half track and use that for my primary source. I'm not sure what happened to that ST-7… I still have the hinges but I think I dropped the table out of a window!
 
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