Are you willing to sell the parts you have? I recently sent my arm to someone in order to have the cartridge wires replaced. The individual could not rewire the arm and sent it back "disassembled" with a few parts missing. I was able to put the arm back together, but need a few missing parts. Also any pictures from the service manual would be helpful. Do you have a service manual? |
Thanks for the memories guys. When I was a kid back in the 70s, I remember seeing the Rabco at a high end audio store. It was awesome. Felt bad because I couldn't afford it then. Good luck with the repair. Just curious, how does the Rabco stack up against modern TT gear?? Whatever happended to the company?? |
Nandric, There are two missing parts that I can determine. One is a small screw located on top of the tone arm wand behind the fixing knob. I believe a ground wire attaches here, under the small screw. Also, I think there is some sort of bent metal part that goes in this location, but I don't have any photographs as reference to check this. Finally, there is another small ground wire located in back of the carriage assembly which is currently broken and I'm not sure where it is supposed to be attached. I could send you a picture, but don't think that is possible through Audiogone. |
Hiho, Vinyengine states the following when trying to download the Rabco service manual: "Important Due to a change in the forum software some users may have to reset their passwords in order to log in. Please follow the 'I forgot my password' link below to reset your password." I've logged in as instructed, but nothing works. |
I owned a Rabco for some time. I set it up with a carbon fiber arm wand, and developed a servo for the motor that actually worked. It prevented the arm from lifting off prematurely, skipping and also got rid of the servo activation noise. The servo was rather simple. I built it up on a little circuit board and hid it inside the motor/battery box. As long as the contact resistance was below 1 megohm it worked fine. That made the arm a *lot* easier to live with! |
Nandric, I believe the "watchmaker" of whom you speak was Herb Papier, the eventual inventor of the Triplanar tonearm. I think Herb used to tell me of his adventures with the Rabco. The Rabco was invented and built here in the Washington, DC/Maryland area as well, by an engineer named Rabinow. (Hence the name of the tonearm.) Herb was a watchmaker by trade (or more likely a watch-repairer), before he got into the crazy business of hand-made tonearms. |
Dear Lew, You are obviously in 'logical' trouble except if Herb Papier had an alias : David Shreve. I now recollect that the Rabco story started before 70is. Back then my scholarship was $250 per month while the Rabco price was the 'astronomical' $1000. I wanted then to know everything about this 'wonder' and think that I dreamed about owning one more than about any girl that I can remember. To get the 'right picture' think about your dreams about the sport cars in your student time. The 'upgrade sickness' started direct after the introduction and I wanted to know everything about any of those while still dreaming about owning one. But my imaginary Rabco upgrade should be done by this American watchmaker who used ruby bearings for the purpose. I have read somewhere about this upgrade and was impressed with the jewels which to my knowledge were only used in expensive Swiss watches. This was my association when Essential and Mosin mentioned David. Regards, |
Dear Essential..., I am really glad for Kisawyer. He also got the pictures of my Rabco spares so he can complete his Rabco. I hope however that David invented some other kind of armwand than those balsa wood kinds. Some Aussie proved (?) that this obsession with the arm weight was badly founded by using his FR-66s for all of his MM carts. I have no idea what Copernicus has to do with the cart compliance but at present physics become a kind of branch of astronomy so who knows? Anyway I myself would use the FR-66 only to defend myself (Hi Raul). But my own question about those ruby bearings is still in need for some answer so Lew may be, as usual, right.Herb deed it again? Frogman, In those times when we were young the girls were, so to speak, for free while any tonearm whatever was not so your VTA analogy looks to me problematic. Regards, |
Dear Nicola, If I am wrong, then so be it. It was just a guess based on (i) the fact that both tonearms were invented by and originated from persons who resided in this geographical area (Maryland, near Washington, DC) by guys who must have known each other (I believe Rabinow was deceased by the time I met Papier), and (ii) the indisputable fact that Herb Papier was a watchmaker who was very conscious of bearing quality, too, by the way. Anyway, if the correct answer is "David Shreve", I am glad the OP will be in good hands. In the 70s, I remember regarding the Rabco as an object of desire but not real craving, I think like you because it was so out of sight expensive. At a much earlier age, the lasting image for my lifetime is that of an Alfa Romeo Giulietta Spyder Veloce pulling away from our car at a stop light, on a cool summer evening in Connecticut, and blasting off into the countryside. I was too young to drive at the time, but my destiny as a car-lover was sealed right then. I later owned a Duetto and several other Alfas and just about every Porsche 356 variant up to and including a 550 Spyder, but never have I found the right Giulietta Veloce. Oh, and I dreamed of women too, but no tonearms. |
Dear Frogman, Sorry I missed your point. Well the optimist among us may think to be able to find the 'sweet spot' in both 'fields' of their activity. A skeptic however will probable state that one kind can fake or pretend while the other together with whatever stylus misses the speech capability to tell. So , obviously, it is a matter of belief. |
I have a complete Rabco SL-8E, not used in 25 years, in the original box, with all literature including mounting template. I had used it with a Thorens TD 125. When I swithed to Oracle, I never tried to mount it. If you are interested, contact me with a reasonable offer and I will pop in a c-cell and make sure the servo works. |
Everything still works, the lateral servo with chain drive, the lift/lower motor, rca to cartridge clip continuity etc. As I remember, it should not be used with a low output, low compliance moving coil, due to the low tonearm mass and servo servo motor noise, but worked fine with a high compliance, high output moving magnet. There is a sensitive adjustment for the fixed post which touches a first wire to turn on/off the motor for the lateral drive, and when when a rapid large displacement (runout gooves) occurs, it touches a second wire which activated the lift motor. |
If I remember correctly in 'the early 80s ' this combo was already available in the second hand market. That is why I could afford the 'treasure'. For about 3 months I was more interested in playing with the Rabco than playing the music. But, as is the case with this hobby, after some time I wanted something better and got the Goldmund . The 'early euphoria' transfomed then in a nightmare such that ever since I never bought something else then the pivoted tonearms. |
Depending on how well the servo is set up, it really can be a linear tracker, much more so than any of the air bearing arms I've seen. This is because its lateral and vertical tracking mass is the same. On an air bearing, the cartridge cantilever flexes somewhat, which can result in the tracking error being higher than a radial tracking arm. So the Rabco was actually capable of the lowest tracking errors of any arm made. The original servo essentially did not work though- it has to be rebuilt if you want the thing to work. |
Is having equal vertical and lateral mass a part of the definition of a linear tracking tonearm? I would not think so. I guess you meant that it is one of the best SLs you've used, because of the low lateral mass, as opposed to any air-bearing SL tonearm which will have a high lateral mass. I have seen the issue of lateral mass argued both ways, high is good; high is bad. I have no dog in that fight. I think high vs low has to do with whether you use a high or low compliance cartridge, but could be wrong. |
But as I have pointed out other posts you can minimise cantliver flex in tangential air bearing arms by employing electromagnetic damping. I used a Shure V15Vmr on an ET2 for about 6 years and the cantilever is still as straight as a die. A small ( nickel size for you guys ) ring magnet under the beam accomplishes this. Servos are like Digital, they are only a little bit out all of the time. Sitting in the listening chair, with a Goldmund Studio, watching the servo lights go on and off constantly with a $10k cartridge on the end is not my idea of relaxing to music. |
Atmasphere, yes I get that and I dont think there was any difference in deflection on eccentric records between a conventional arm and the ET ( with the dampening applied). The amount of deflection will vary depending on the horizontal compliance of each cartridge. The Dynavector arms use the same electromagnetic horizontal damping to counter the high horizontal mass in their biaxial design. Possibly a case here for low compliance cartridges if we assume many records are off centre. |
all technical things aside these arms when setup + working like they did when new... play music period! most others can only dream of...top to bottom they are excellent IMO...I have several including a highly modified balsa wood armwand one that has censor switch instead of the mechanical one... Lawrence Musical Arts |
Dover, You wrote, "The Dynavector arms use the same electromagnetic horizontal damping to counter the high horizontal mass in their biaxial design." Actually, the DV tonearms are some of the pivoted arms I had in mind when responding to Ralph that do deliberately employ high effective mass in the lateral plane, as you say, but do you view the magnetic device as a way to "counter" high lateral effective mass or as a way to dampen resonance in the horizontal plane? There is a distinction to be made. I always thought that it was to dampen resonance. I've got a DV505 and am a big fan of it. |
New to this group, but since there is a current thread going on the SL8E, I'll ask if there is any indication of transistor issues in these? Once, I replaced the caps inside the battery box and things were good for a while. Now, even though both motors operate when "tested" the tracking motor doesn't move. I just replaced those caps again, and don't see anything too obvious. Any thought or recommendations? Thanks... |
Hi Lewm, I'm guessing on the Dynavector, but I would assume that although the Dynavector has a high mass in the vertical plain, because it is a balanced beam, ie the counterweight at the back balances the arm to zero, then they have added electromagnetic damping to minimise excessive overshoot of movement on eccentric records. One thing I know, their argument for high horizontal mass/biaxial design is that the inertia of the heavy beam provides better bass as you have alluded, so I guess the damping may be an extension of this thinking. Certainly on the ET I have to turn the volume down when the e/m damping is applied, which is quite astonishing to think that excessive lateral movement can affect the audible or dynamic output to that degree. |
Nandric, I believe that Morch may be referring to the importance of the moment of inertia around the longitudinal axis of the tonearm. This was first explored by Michell Cotter many decades ago, and was the basis for the development of the Magnepan tonearm of the late Seventies. Mark Kelly discussed it on another forum back in 2005. Here |
Dear Mosin, thanks for you reference to Kelly but his lecture is to complex for me to understand. I mentioned Morch 8 in the hope that some others will investigate what the designer is at and explain to us in the 'layman vocabulary' the issue. We all want to know 'what there is' but are, alas, not all capable to understand without help. This to me is the 'sense' of our forum; to learn from others. Regards, |
