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Rhymes with "Mormons"...

The arm gantry is mounted too close to the platter. It may not be workable further out due to weight distribution, a candidate for a DD table. I find the 3-point Cotter suspension TTs a major PITA to live with anyway due to the tendency to bouncy-bouncy-bouncy.
Still a mega-score find even if mismatched, the arm mod is very unusual.
 
gonzothegreat said:
OK it doesn't *quite* rhyme but I had to have a clever title!

After a few morning errands, I was in the vicinity of my favorite thrift store. It was just a few minutes after they opened and I wasn't in a hurry to get to the electronics area. As I inspected the shelves for fresh meat, I saw something on the bottom shelf and my brain punched the nitro. It was in my hands before I even realized exactly what it was. When my head caught up with my hands and feet, my eyes bugged out and I muttered something to the effect of "Is this what I think it is?!?!" I wouldn't be surprised if I left fingernail marks from my deathgrip on it.
Click to expand...
Yep. Pretty much sums up what my response would have been as well. :D

Nice one!
 
Awesome, jawdropping score. Congrats! Looking forward to following your process on whatever path you choose to pursue for it.
 
I didn't have time to work on it tonight - drat! This weekend for sure even if its just a quick spin with a DJ preamp to check if it can track OK. It will almost certainly need a fresh battery. Possibly some deoxit on the magic switches or motor contacts too.

The owner of the Rabco page didn't have any info on my modded arm. Too bad as it screams high-end 70s gear. He suggested DIYing an ultra-low mass arm like the balsa wood one but the craftsmanship of my arm is just too cool even if it might be inferior.

Since this would be precisely the kind of thing one would find in old issues of "The Audio Amateur", I should shoot them an email and see if anyone remembers this beast. I know they had an article on a DIY linear tracking tonearm that borrowed heavily from the Rabco so maybe the author might have a lead.

As for the 4/5 score, it had some veneer damage and the manual was missing. The dust cover wouldn't have fit over the Rabco as pointed out earlier. Did I mention I can be a picky SOB ? :D

RobRoy - Is your avatar a closeup of a GAU-8 on an A-10? Been a while since I saw one up close.
 
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gonzothegreat said:
RobRoy - Is your avatar a closeup of a GAU-8 on an A-10? Been a while since I saw one up close.
Click to expand...

That was my thought...having never seen one up close. Have seen video of one in action. Gives meaning to the phrase "Peace though superior firepower":yes:.

Gonzo looking forward to your posts about your find. Preston
 
:D Should have asked the employee if there was any other stuff with it - it could have been part of a real treasure trove
 
I took the arm off and the large knob didn't allow adjustment of the arm length nor did either of the two small screws on the underside of the arm. The chain seems to be loose and will probably require a full teardown of the arm. Yikes!

I dug a little deeper and found a Youtube video of a TD125/Rabco SL-8E combo. At the very end of the short video, you can see the Rabco base is mounted exactly the same on his table and mine so that can't be the issue. It looks like the arm is simply too long (duh) and is incompatible with the TD125 w/o surgery. Either I have to remount the Rabco base to the right or chop down the arm since there doesn't seem to be a way to adjust the length. Side note - it looks like the counterbalance and tracking mechanism is stock on mine. The arm tube and cart mount appear to be the only modded parts.

http://www.youtube.com/watch?v=1Td8nXr-5ZA

I haven't found ANYTHING on this arm mod. There is a guy on ebay selling a "Definitive" manual on the SL-8E and he didn't know anything about this specific arm. There is a Shreve low mass arm mod and another similar one from Dean Slindee but neither is like mine.

The BAS Slindee arm mod PDF with a mention of the Audio Amateur article at the end.
http://www.bostonaudiosociety.org/pdf/bass/BASS-05-05-7702.pdf
 
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I was rooting around ebay and found somebody selling a stock SL-8e mounted on a cheap Sony PS-T2 turntable. The auction mistakenly described it as a PS-12 but I knew better. How did I know this? Years ago I bought a Sony PS-X5 fixer-upper w/o a cover or hinges. Later I found a broken PS-T2 with a good cover and hinges. The table was tossed into storage as a possible RCM donor until last week. Since my table has a longer arm, it will have to be mounted on the very edge of the arm area. Here are the pics of the stock PS-T2/SL-8E combo. Note the toggle switch by the speed controls that is probably a relocated start switch.

sonyrabco1.jpg

sonyrabco2.jpg
 
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I had some free time this weekend and I decided to start working on the Sony TT. Originally I was going to use my Dremel but I discovered a bare hacksaw blade worked much better. I'm planning on cutting a piece of acrylic to cover the hole and possibly fill the holes with JB weld to restore some structural integrity.

sonyrabco1.jpg


sonyrabco2.jpg


sonyrabco3.jpg
 
After trying in vain to get the Rabco mounted on the plastic Sony I threw up my hands in defeat. The Sony was a cheap table to begin with and trying to mount a heavy arm on it was a horrible idea. If I ever breathe that plastic dust again it will be too soon. Next week its going to be parted out for the motor and feet.

Time for Plan B! Years ago I found what at one time had been a very nice Sansui SR-717 direct drive turntable at my favorite thrift. The original arm had been removed due to damage and replaced with something the monkey-tech pulled off a middle-of-the-line 70s vintage Pioneer. It was a hack job at best so the table went into storage. Too nice to part out but turning it into an RCM would be a crime. The 20 pole 15 slot DC motor cried out for a classy arm and along came the aforementioned Plan B.

Here is the new intended recipient for the arm. The particle board base will make mounting the new arm far easier than the cheap plastic on the Sony.

sansuitt1.jpg


Initially I was worried that the speed and start controls would have to be mounted externally. Once I removed the control panel, it was obvious I shouldn't have been concerned. The start switch is a single microswitch as is the speed selector. The two pots will be a little tricky but if all else fails I could mount them by the motor control PCB (which will need 6 new electrolytics).

Here is a mockup with a piece of pine to raise the arm. I think it is a far better match to the silver and black of the Rabco. Once I figure out how to get the VTA dialed in, it will be time for vinyl testing.

sansuitt2.jpg
 
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My local used stereo shop has the thorens/rabco combo like yours as well. I guess the 125 was offered with this arm by Thorens? Linear tracker are so interesting. This will be cool to follow.
 
I'm still prototyping - the pine was in the scrap pile. Acrylic is one possibility but I'd like to go with a metal armboard like on the TD125 so I can easily mount a pair of low profile rocker switches for speed and power. Found a metal black matte case from a scrap Technics cassette deck that would do the trick once I cut it down.

The build is stalled ATM. I never tried to power it up because the cord was chopped. Unfortunately it doesn't spin up correctly. It does the initial kick but then it looks like it is only getting power to one or two motor coils - kick, coast, repeat. The driver board has a ton of bipolar caps that look marginal but I'll start with the basics (power supply test/recap, motor coil and driver semis, etc).
 
Major update time!

The platter spin issue was due to operating with the platter removed. Didn't know that would throw off the servos *that* much. <shrug>

I grabbed a piece of fiberboard and chopped some holes for the switches, fabbed a new wiring harness out of a car alarm system harness, installed the switches (from a hairdryer bought at Goodwill for $2), strung together a bunch of resistors to get roughly in the ballpark of the proper pot settings and finally had to track down an open in the right channel wiring.

She's spinning vinyl but she's nowhere near done. VTA probably isn't within a country mile of proper due to the platter height of the Sansui SR-717 but I'll sort that out eventually. The good news is the Rabco arm seems to be functioning correctly. Its dropping the arm and kicking in the arm tracking motor enough to avoid skipping.

I'll start a Frankentable thread in DIY with video and pics. http://www.audiokarma.org/forums/showthread.php?t=402153
 
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