This is a long post as I found factory errors during my upgrading and it is a "How to" because I mounted crossover components differently than others have done. The work involved is described.
Factory Error in 1.2TL crossover board circuit:
After completing the rebuild of 2nd xover and while checking the circuit with the schematic, I learned the 750pf bypass cap and 22.5 ohm resistor which together both bypass a 12uf capacitor, are not even connected in the circuit because Polk forgot to install a jumper wire on the board. (One jumper exists on the board, 2 jumpers are required.) These parts only effect tweeter #3. - I note this again and more about it in my listening observations below.
This required jumper is shown & explained in the photos. My guess is many 1.2TL's out there have this error. The way the board traces are laid out, there must be 2 jumper wires on the board. If your board has 2 jumper wires, it is correct. If you have 1 jumper, your xover circuit is wired wrong. Unless you have a board made for the 1.2TL which is different than mine. But I have read of no one stating they have a xover board different than mine.
Tweeters in one of my cabinets were connected incorrectly phased. It appears a 1.2 wiring harness was used by mistake. The 1.2 and 1.2TL use different tweeter phasing. On 1.2's all the (-) terminals of the 4 tweeters connect together by a trace on the xover board. On 1.2TL, the (+) terminals tie together.
The (+) and (-) markings are incorrect as painted on my 1.2TL xover boards. Markings are actually reversed. Most likely the same board was used for the 1.2 and TL model which is why marks are wrong. (Correct for a 1.2 board) To tell if your board is marked wrong and/or tweeters are properly connected in proper phase to the TL xover board, look at the trace on board that connects 4 connector pins together. On TL's the 4 pins connected together should be marked (+). All 4 tweeter (+) terminals should connect to these 4 connected pins on TL's no matter what the board markings are.
NOTE: If you upgrade your xover from 1.2 to TL model, you must also rewire the 8 pin connector on your tweeter wiring harness to match the 1.2TL schematic. (Just rearrange the pin locations) The schematic drawing of connector does not match the actual connector. Go by the pin #'s on drawing. On actual connector, Pin #1 is on one end of the connector.
Upgraded parts and mounting: See the photos which show holes drilled, relocation of parts, have notes and explain the circuit error due to a missing jumper on xover board. I do not know if photos will post large enough to read notes on them. I reduced size of posted photos. Send me a PM if you want larger photos.
I used Sonicaps for High freq side, Solens for low freq side.
The 13.5uf capacitor was replaced with a matched pair of Solen 6.8uf caps. (Pair for each crossover measured 13.47uf & 13.56uf) To have both caps mount flat on the board, one of the two large inductors on the board had to be moved. It was moved toward the outside edge of the board until the inside edges of the 2 inductors lined up. This provided 1/8" or more space for the Solen caps. Just the hot glue was removed to relocate this inductor and 2 small inductors. No unsoldering was required as all inductor leads were long enough.
R3, R4 & R5 were relocated to provide room to stand the Sonicap 12uf capacitor vertical. The 2 small inductors near each other also had to be moved a little to make room for this cap.
R3 used the factory holes in board, but the body was mounted over where the long lead hole was.
R5 body was mounted over & thru existing hole for C6 lead. (Same trace) A new hole for R5's long lead was drilled near the top of the 5 on the board printing and just on outside edge of the square for the body. (Between the inductor and R5 drawing on board.)
For R4 a new hole was drilled for the body by the 6 in C6. (C6 is not used in this circuit) The long lead of R4 attached to the hole the body was originally over, and this lead runs on top of board, under the 12uf Sonicap. A rubber washer about 1/8" thick was placed between the capacitor and the board with a cutout for R4's lead. (Washer made from plumbing sheet gasket material I had. Sold at Home Depot, it is red, two 5" sq pieces in a package.)
To mount vertical, the above 12uf capacitor required a new hole be drilled under the center of the cap. The lead that runs thru the board was insulated with tight fitting insulation removed from a piece of wire. A drop of Super Glue was placed on the wire by the cap before the insulation was pushed against the cap body. This to hold the insulation in place & prevent a short with the trace. If an insulated lead thru the board went thru a different trace, I also scraped the trace away around the hole so the lead could not short out. The rubber gasket under the capacitor allowed the leads insulation to protrude 1/8" above the board to prevent a short. The 12uf lead going thru the board connects to hole marked "L" on the board, the long top lead to "A". (Same as original connections.) Moving the 2 small inductors and resistors provided room for a space between the capacitor and resistors, needed as these resistors can get hot.
The 27uf Solen cap was mounted the same way as the 12uf cap above, on top of a rubber washer. 2 new holes had to be drilled to mount it as the larger cap covered one original hole and a hole was needed under the center to mount vertically. Moving the closest large inductor not only toward the edge of the board (for 6.8uf Solens space) but also tight against the other inductor provided enough room so the cap did not overhang the board. NOTE: With the 1/8" thick rubber washer, the cap lead does not have to run thru & under the board nor be insulated, it can run on top of board thru a cutout made in the washer. Running the lead under the board makes a much better mechanical connection and holds the cap ridgidly in place. The lead can be soldered where it comes thru the hole as is on same trace, but I ran insulated lead to original hole.
The order work was done:
Removed old parts from board, .25uf capacitor on inductor last. The 750pf Mica bypass caps were not removed as used again. (I expect to remove bypass caps after Sonicaps burn in awhile.)
Removed as much old solder as possible with a solder sucker.
Scraped old flux from solder connections & cleaned board with 90% alcohol, a toothbrush & rag to make a good solder connection.
Measured and recorded value of all old parts. Amazingly all parts except 2 caps were within about 2% tolerance, some were right on, none were bad.
I use a Fluke 189 meter which compensates for lead resistance/capacitance, though proper lab procedure calls for measurements to be taken at room temp of 72F.
New parts were measured (again) and values recorded just before they were installed. Caps in parallel & resistors in series were measured after being soldered together, before mounting to board.
Relocated inductors & glued them in place. They had to be held in new location, glued and held until glue dried. (No unsoldering was required, just glue removal.) Photos show where located to. NOTE: Make sure the leads are long enough to allow movement before you try moving them!
All holes needed should be drilled after the inductors are moved and before any parts are permanently installed other than the .25uf cap on the small inductor which should be glued in place when installed.
Next I temp mounted the pair of 6.8uf Solens side by side, flat on the board, centered in the space & against the large inductors to determine where to solder their leads together. Soldered one caps leads to the other. (They connect in parallel, only the leads from one cap go thru the board) Then removed them from the board to have room to work on resistors and 12uf cap to be mounted vertically. These cap leads do not have to be insulated.
Round cardboard templates were made the diameter of capacitors to be mounted vertical, with center hole for lead, to check fit between components. Templates were used to mark board where lead hole had to be drilled under the cap. (Do not mark or drill for long lead from top of cap until you know where other parts will be located.) R3, R4, R5 placed on board temporarily to determine where 12uf cap would fit and outline was drawn on board around cap. Resistors removed then holes drilled for cap. All installed temporarily again to make sure all fit, the parts removed again.
Determined where the 27uf Solen cap would mount vertical, marked and drilled the 2 holes required for its leads. Temp mounted cap with insulation on the leads to check fit & proper hole locations, then set it aside. Mine does not overhang the board. It intentionally sits tight against the inductor so it can be hot glued to inductor for mechanical strength. The lead hole location under the cap must be exact because it is tight against inductor.
In the 4th photo it shows a new hole used for R5. Actually this hole & hole below it was used as 2 resistors in series were used. This is shown in the photo of bottom side of board.