Rabco SL8E Photoelectric Servo Control Retrofit

My recommended substitute for the discontinued Omron EE-SH3 is the TT Electronics / Optek OPB852A2. There are plenty of these in stock from a couple of sources:


Mouser OPB852A2 [139 in stock] $2.55

https://www.mouser.com/ProductDetail/Optek-TT-Electronics/OPB852A2?qs=N5kmjX/bzE4H5NWiwjnrYA==


DigiKey OPB852A2 [287 in stock] $2.54

https://www.digikey.com/en/products/detail/tt-electronics-optek-technology/OPB852A2/1637233


The resistors are generic and the listed values from any manufacturer will work fine, ¼ watt is all you need.

Ray K
 

uarnutz

Member
2021-12-29 3:58 pm
Thanks for your continued support with this mod. I am attempting this as a relative novice so, I have some questions to make sure that I am reading things correctly. I am on mounting the sensors. In the notes to photo#8 the spacers are specified for the run and lift sensors. These are not labeled as such in the diagrams and drawings so, I want to check that I have it right. On the drawings, the run sensor is Q3? This would then correspond to the bottom sensor in photo #7?
 
Here are photos B, C, 7, and 8 with added clarification notes as requested.

Ray K


Photo B:
Photo B w'notes.jpg


Photo C:
Photo C w'notes.jpg


Photo 7:
Photo 07_Opto Module Wiring w'notes.jpg


Photo 8:
Photo 08_Parts Test-Fitted w'notes.jpg
 

uarnutz

Member
2021-12-29 3:58 pm
Perfect. More than I could have wished for. Thank you. So, I have assembled and test fitted the sensor block. I must say, that was painstaking work. I am pleased art the result so far. The flag is well centered in the sensor and the offset is 1.1mm on one side and 1.3mm on the other. (Apparently not totally square to the mount.) Close enough?
IMG_20220114_161223765.jpg
IMG_20220114_200114629.jpg
 

uarnutz

Member
2021-12-29 3:58 pm
Thanks. I think that is how I ended up here in the first place. I still am looking for more specific information on my AR XA/Rabco as regards refurbishment. I understand that this was one of the original factory designed configurations sold as a kit. Yet, I find almost nothing out there on this. It seems most went for the Thorens platform?
 

uarnutz

Member
2021-12-29 3:58 pm
I have now wired/soldered the photsensor block and have a very basic question. Do you insulate the connections? It seems to me they would risk making contact with the carriage chassis which also acts as ground, right? Thanks for your patience with the naive question.
 
Looking at your photo, I'd recommend bending the tabs farther down to give yourself more clearance to the back of the carriage. Compare to my photo #22. In any case, it never hurts to add insulation. Sticking a single layer of electrical tape between the tabs and the backside of the carriage should do the job.

I, too, have found hardly anything about the AR/SL8E combination online, except that I seem to remember ads at the time promoting the Thorens/SL8(E) and AR/SL8(E) as the two recommended ideal pairings. I've only seen an AR/SL8E combination over on vinylengine.

I did find an ad for the AR/SL8 adapter in the May 1970 issue of High Fidelity magazine:

_Hi-Fid May'70 SL8 Adapter for AR.jpg


I don't understand exactly how the adapter worked since the arm/table spring suspension on the AR is different than how the spring suspension is done on the Thorens which I'm familiar with. It would be a great contribution to the knowledge base of vintage audio if you could post some hi-rez photos of your AR XA/Rabco setup?

Ray K