RTA 15TL Project

westmassguy
westmassguy Posts: 6,850
edited February 2014 in DIY, Mods & Tweaks
This was an interesting project in several ways. 1st, unlike previous 11 & 15TL crossovers I've done, this one had the late production, smaller square circuit board, and modified binding post cup. Gone were the large round circuit boards, and snap-in nylon stand-offs. This model's stand-offs are molded into the cup. The small circuit board was attached with self-tapping screws.
The 2nd challenge for this rebuild, was the Decato Mod would be implemented :http://www.polkaudio.com/forums/showthread.php?48075-Modifications-to-the-RTA-15TL&daysprune=-1
This was not a simple re-cap. Essentially, all the Capacitor, Inductor and Resistor values would change. Sonicaps were chosen for the Hi & Lo-Pass for quality, and because Sonicraft was able to give me the custom values I needed. Mills MRA-12 Resistors, and Madisound Inductors round out the new components used.
The circuit boards were removed, and all connections from the binding post cup were de-soldered. The existing Lo-Pass inductor wrapped around the binding post cup's spool, was cut an the leads folded inside. The molded plastic standoffs were drilled and tapped for M4 threads, and M4 threaded studs were in screwed in. Supplemental riser boards were created using 3/16" Masonite, and a 4 1/4" hole saw. The new riser boards were lightly sanded, cleaned, dressed and new holes drilled for the stand-offs. The New Lo-Pass inductor was made from a stock Madisound 1.8mh 16 gauge Inductor. An LCR Meter was used, and the Inductor was unwound to the precise 1.75mh value needed. The New Inductor was secured to the riser board using 3M VHB Tape, and Nylon Wire Ties. The existing leads from the binding posts were brought up through the center hole of the new riser board, and the board was placed on the new mounting studs. New nylon stand-offs were installed to clear the height of the new Inductor.
All components were removed from the circuit board, and their locations carefully marked. The New 0.22mh 19 gauge Hi-Pass Inductors were the exact value needed, so no modifications were required. The spool was cut and trimmed to create a flat spot for ease of mounting. New holes were drilled, and nylon wire ties installed to secure the Inductor. To make room, the 2.7 ohm Mills Resistor was installed on the bottom of the circuit board. All three Capacitors were secured with 3M VHB tape, and again, new holes were drilled to allow use of nylon wire ties. The Polyswitches were replaced with 0.5 ohm Mills Resistors, and mounted vertically. The lead from the new Lo-Pass Inductor, and the existing leads from the binding posts were soldered to the bottom of the circuit board. Nylon screws were used to attach the circuit board to the new stand-offs. As a final step, the polarity of the Tweeter must be reversed. I chose to change the female spades on the wire ends, rather than swap the leads at the circuit board. The RDO-198-1s have different size male spade connectors, so this was foolproof. It's impossible to connect them any other way.

When oh when are they going to straighten out thumbnails.......
Home Theater/2 Channel:
Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer

dhsspeakerservice.com/
Post edited by westmassguy on
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