RCA Victor R-93

[Victrolacollector]

These little machines sure seem like they are nice.

[barnettrp21122]

Yes, this could easily be fed into any amplifier "line-in" input, such as for tape, cd, etc. You don't need a pre-amp with these horseshoe pickups; they have plenty of signal output already. Don't plug into a phono input, as these are usually meant for modern magnetic pickups with low output, requiring a pre-amp.
Enjoy the music!
Bob

[ChuckA]

I have not rebuilt one of those pickups myself in more than twenty years. When I did (On an RCA Victor 301 Duo) I cast my own damping block out of silicone rubber, used very thin medical silicone rubber tubing for the pivots, and substituted a pair of appropriately sized neodymium magnets and a shaped steel bar for the original cobalt magnet, which of course was weak.

I have a couple of R-93 and R-94 attachments sitting in the shop awaiting repair, but they will wait until after I get to the RCA Victor 300 which has been sitting in the queue since before my fire.

Bob,

I stopped using silicon rubber for the dampers awhile ago, cast my own also. I found it was too soft and a lot of them were being returned with locked armatures. Seems when I re-magnitized the magnets. the force was to great and if the pole piece got a little too far over from center it would lock against the pole frame.

My new material is silicone based also, but much better to control the armature movement without compromising the compliance of the needle movement. The hardest adjustment to make is getting a symmetrical output, that is equal positive and negative excursions of the output waveform, from the pickup.

I built a test turntable from an old variable speed Lenco unit:




and made up test arms for all the various types of pickups I have rebuilt:

------------------------ Edison C1/C2 ------------------------------------ RCA Plug-in --------------------------------- Victor Single play -----------


The arms can be installed on the turntable easily and the pickup can be terminated in its characteristic load resistance needed to adjust for best
output voltage.

This is a photo of one of the analyzers I use to test output of the pickups,
this one is showing a 1/12 octave response of the output of a typical electric needle cut.
Displays content from about 100Hz to just below 5KHz, everything above that is surface noise.




Chuck

[PeterF]

Upon seeing Chuck's posting and pix of his test setup just now, I completely geeked out - and although I was grinning, my pulse rate shot through the roof.

Gonna go lie down for a little while now.

[barnettrp21122]

Upon seeing Chuck's posting and pix of his test setup just now, I completely geeked out - and although I was grinning, my pulse rate shot through the roof.

Gonna go lie down for a little while now.

Yes, it's too cool for words! Thanks for posting the pictures and information!
Bob

[Uncle Vanya]

Well, that test set up explains a great deal. I see that it takes much of the subjectiveness out of this work. That would be a very good thing for me, now that my hearing is changing ever so slightly.


What are the curves that you find the extended frequency range pickups, say the RCA Victor units used in the R-99 and in the D-22 or the Audak Micromatic?