Started my 1.2TL XO upgrade

tugboat

Got all the parts today and tested each cap and resistor. All was well, so I pulled each XO out and removed them from their mountings. I was going over each board trying to locate each component and figuring out exactly how each new, larger cap will mount. That's when I noticed that my boards are not as depicted in the schematics. The .750 bypass cap and 22.5ohm resistor are connected to no man's land. They dead end into a section of the PCB that has no other connections or components. The 12uf cap bypasses this area and goes directly to the tweeter output.

Until I can get this cleared up, I am not going to continue. I need to know if the 22.5 is needed since it goes nowhere. If it is needed, where should it be located? After the 12uf cap and then connected to the tweeter output like all the others?

I did remove the bypass caps. Can't really say I hear a clear difference, but the highs are a bit more "crisp" and the sound stage is wider (all based on a couple songs I know very well on these speakers.

Also, whoever made the XO in the left speaker should be beaten. The board's back is scratched, exposing the copper in several places, there's flux and other gunk on most of the solder points and webs of hot glue over most of the board. If that wasn't bad enough, the board is dirty, like it sat on a shelf for months before being installed. The inside of the cabinet and wiring is perfect and clean, but not the XO.

Anyway, if anyone can give me some assistance on the 22.5ohm resistor, I'd appreciate it.

Thanks

tugboat

Tried to edit and add a pic, but I can't. I'll add it here. I outlined the areas in blue to show how the bypass and 22.5ohm resistor go nowhere. The bottom blue outline is the jumper bring the signal to the section of the board with the bypass cap and 12uf. The large blue outline is the 12uf cap going from the jumpered area to the tweeter output. The outline just about the jumper outline is the bypass cap. See how it goes from the jumpered area to a section that is only shared with the 22.5ohm resistor that comes from the same section as the jumper. So it would seem that removing the jumper and/or resistor would have no affect on the tweeter output since the 12uf cap is the only connection.

Ricardo

So it did come out exactly as mine. I guess a few of those 1.2 TL's had this crossover, and it does seem that bypass cap and the resistor are not doing anything for the 12 uF cap.

I guess all you can do is wait for someone that actually remembers doing this to a set that had the jumper between R2 and P3, which is what is missing. You can also post this in the troubleshooting forum to see if Ken has any thoughts.

I can tell you though that mine sounded very good with this "flaw". I did not remove the Silver Micas in my pair, as you can see in that picture you posted in the other thread.

Oh, and if you removed them, you either did it keeping the old caps, or with the new caps that are not broken in. Either way, you are not hearing what it will sound like.

ben62670

Keep in mind that these boards were used with other speakers. I forget what speaker it was, but the one I did only had two tweets. I think it was SRS2's. Please don't try to fix any "missing/misplaced components" Joe did his XO's and IIRC he thought there was problem too. Just repopulate the board as is. It was a real pain trying to fix what a speaker repair shop had "fixed".
Ben

Ricardo

Ben, if you look at the schematics and at the xover, there is definitely something wrong. But as I said, mine were like this and sounded great.
It only takes a jumper to make the change, so it might be worth a try.

tugboat

I've been over the pictures many times now and can't see any configuration change that would have any impact. I believe the 22.5 is meant for the bypass cap. Even if you run a jumper, the 22.5 and 12uf will be getting their signal from different areas of the PCB and then connected in parallel to the tweeter output. This would mean the tweeter would be getting a connection with 22.5ohm resistance and a signal with a 12uf cap on it. I don't think this is what they had in mind.

So far I only removed the bypass cap and listened for a difference. Now I'm about to fire up the iron and pull everything. Then fire up the glue gun as well and put one back together. I'll then listen to them side by side (one modified and one stock). If it seems I've done everything correctly, I'll do the other one.

Oh yeah, I got some 20ga tin wire in case I need to lengthen a cap lead. There's no down side to doing this, is there? I'll solder all the connections.

Thanks

ben62670

Thats the way it is on the wiring diagram. This is normal. Sometimes on a crossover you will see an inductor, resistor, and a cap parallel;)

Edit. This is the "XO" in my single driver puter speakers;)

ben62670

And don't eat the glue:)

tugboat

The resistors are standing upright and I'm sure they'd melt the glue (or at least soften it).

I've already eaten a stick (cold). It's not so bad, but needs salt.

ben62670

Tuggy you have been here right?
http://www.polkaudio.com/forums/showthread.php?t=55888

george daniel

Shoot Jesse (F-1)or DK a pm,, they are pretty hip with SDA crossovers

tugboat

Here are a few pics of my progress. If you look at the last two, you can see the R2 where the 22.5 resistor looks like it should go (R2 was empty from the start). Instead, it is connected lower at B and G and the bypass cap is in C and D. So with the bypass cap gone, the 22.5 resistor is connected to nothing. I'll leave it out with the ability to add it later if it turns out that it really is supposed to do something.

ben62670

Don't cut the legs till you have all the pieces in. That 22.5r should parallel the 12uf cap.

tugboat

ben62670 wrote: »

Don't cut the legs till you have all the pieces in. That 22.5r should parallel the 12uf cap.

I've got all but one cap in. So far no problems. I got my hands on some of the wire ties like already being used. They are very flexible and hold nicely.

I only cut after I solder and know it's staying the way it is.

There's not way the 22.5 can be in parallel the way it's installed. If I jumper the missing bypass cap, then the resistor will be connected to the same point on the 12uf, but that would make it in series, not parallel. It was never in parallel as the only path to the tweeter is the 12uf and it would negate the .750uf if it ran through the it.

I'm about to eat more glue!

ben62670

Don't eat too much glue. Stick in colen:eek:
You can piggy back C5 with the 22.5r and it should work just fine;) Tie it right to the cap. F1 has done a few. He is here nearly every night.
Ben

ben62670

Thanks Sal. Tuggy if you haven't checked out his work you should:)
Ben

tugboat

Lasareath wrote: »

My 22.5 was connected to the legs of the L5 Choke.

When i upgraded my crossovers I did not remove the L5 because the legs are so thin that I was concerned that I would not be able to re-solder it back down again.

Why did you remove yours?

Also, Nothing is connected to my "R2" connection. The "C5" Cap gets soldered down to one of the R2's solder points.

You can see my Mundorf .22 straddling the L5 Choke here, I soldered the legs of the Mundorf to the legs of the Choke.

http://www.polkaudio.com/forums/attachment.php?attachmentid=26408&d=1185160991

The L5's leads where wrapped and soldered to the legs of the .25uf and the legs of the .25 were soldered into the board. I removed the glue holding L5, and it came off with the .25uf. I then heated the wrapped copper coils around the legs and slid them off the .25uf. I reversed it to put the new .25uf in.

I see your board has a jumper at R5. Mine doesn't. Hmmm..... Have any pics of exactly where the 22.5ohm and .750 cap connect?

I'm about to post some pics of my finished XO.

tugboat

Here are some pics of one completed XO. Well, almost. I'm about to add some hot glue here and there to add support and reduce vibration.

Let me know what you think. It's my first really major job.

Oh, and I did replace the 22.5, just in case. Also, stupid me forgot to order the 15ohm resistors, so I had to put the OEM one back!

tugboat

Lasareath wrote: »

Joe (Hearingimpared) had me put in a jumper (as per Jesse) from P3 to the middle of R2 as shown on this pic:

http://www.polkaudio.com/forums/attachment.php?attachmentid=26987&d=1187729656

I put the lead of the 12uf back into that hole. I can still put a jumper as it would be the same whether the 12uf lead is in the P3 hole with the R5 jumper in place as it would if the 12uf lead were in the same area as the 22.5 and then they were both jumpered from R5 to P3. Hope that makes sense.

tugboat

Lasareath wrote: »

Any reason why you left the R3 resistor in?, the old 15Ohm one?

Stupid me forgot to order the 15ohms. :eek::o

ben62670

All of those resistors need to be there. I you omit them you will throw off the total input impedance, and the original 12db XO point that controls all of the tweeters will be off. Most all vintage Polk's use the 12uf in series, the .4mh inductor, and 2.7r resistor for the first 12 slope. If you jumper a resistor in the signal path you will drop the overall impedance. IE T1 15r + T2 11.5r + T4 7.5r = 11.3r. Thats the easy part to figure out. Now T3 has a 12uf, 750pf, and 22.5r in parallel. That combination plus the T1 T2 T4 will equal out to one RDO198 tweeters impedance. You throw that off you will raise, or lower the 12db XO's crossover point. Not good. Sal I think what Joe, nd F1 were doing is when Joe thought his XO was wrong they were trying to fix it. Joe's speakers were acting up, but he later figured out that it was the caps burning in.
Ben

tugboat

ben62670 wrote: »

All of those resistors need to be there. I you omit them you will throw off the total input impedance, and the original 12db XO point that controls all of the tweeters will be off. Most all vintage Polk's use the 12uf in series, the .4mh inductor, and 2.7r resistor for the first 12 slope. If you jumper a resistor in the signal path you will drop the overall impedance. IE T1 15r + T2 11.5r + T4 7.5r = 11.3r. Thats the easy part to figure out. Now T3 has a 12uf, 750pf, and 22.5r in parallel. That combination plus the T1 T2 T4 will equal out to one RDO198 tweeters impedance. You throw that off you will raise, or lower the 12db XO's crossover point. Not good. Sal I think what Joe, nd F1 were doing is when Joe thought his XO was wrong they were trying to fix it. Joe's speakers were acting up, but he later figured out that it was the caps burning in.
Ben

Well then since the 22.5 was connected to the bypass cap lead only, I'll put a jumper in where I took out the bypass cap. That will keep the circuit flowing.

tugboat

Well I installed the redone XO and it seems to be working well. Nothing odd, no shorts, etc.... I have just take apart the second XO and will start installed the components after a late lunch (been so busy).

This one I will use a jumper in place of the bypass cap connected to the 22.5 resistor. I'll then take out the first XO I did and do the same.

Thanks you guys for being around. Makes a difference knowing your collective knowledge is only a few keystrokes away.

ben62670

tugboat wrote: »

Well then since the 22.5 was connected to the bypass cap lead only, I'll put a jumper in where I took out the bypass cap. That will keep the circuit flowing.

If you jumper where the 750pf went you will also bypass the 12uf. Take your time. According to the Polk diagram it should be parallel to the 12uf. Hopefully F1 will chime in on this. A little testing with the meter you should be able to figure it out.
Ben

tugboat

Well XO 2 is complete! It went much faster knowing what I learned from doing the first one. This one has a jumper in place of the bypass cap. Let's see if it works. If it does, I'll go back and jumper the first XO as well.

No pictures this time. It looks just like the first one.

tugboat

ben62670 wrote: »

If you jumper where the 750pf went you will also bypass the 12uf. Take your time. According to the Polk diagram it should be parallel to the 12uf. Hopefully F1 will chime in on this. A little testing with the meter you should be able to figure it out.
Ben

Nope, at least I can't see how. If I jumper the bypass, the 22.5 will bring the signal to the jumper, the jumper will bring the signal to the lead of the 12uf and the other end of the 12uf will connect to the tweeter. So it will be in series, right? Look at the pic in the link below (reply #21). Maybe I'm looking at things wrong, but using the jumper can't bypass the 12uf.

http://www.polkaudio.com/forums/showthread.php?t=71846

tugboat

ben62670 wrote: »

If you jumper where the 750pf went you will also bypass the 12uf. Take your time. According to the Polk diagram it should be parallel to the 12uf. Hopefully F1 will chime in on this. A little testing with the meter you should be able to figure it out.
Ben

Okay, how about this. I'm attaching a pic with a couple markings (kind of beige). If I remove the bypass (marked), the 22.5 resistor will be connected to the section outlined. At the top of the outlined section is an unused connection. Just above that unused connection is another unused connection where the 12uf connects to the tweeter output. Now if I put a jumper between those those connection, won't that make the resistor parallel to the 12uf? If so, I'll remove the jumper I place for the bypass and move it up.

Thanks!

Ricardo

That's exactly what I've been trying to say; taht's the jumper that will make the xover exactly the same as the schematics. Seen from the other side, it is a jumper between R2 and P3.

tugboat

Ricardo wrote: »

That's exactly what I've been trying to say; taht's the jumper that will make the xover exactly the same as the schematics. Seen from the other side, it is a jumper between R2 and P3.

Oh, we've been looking at different holes. I see the one in R2, but the other one is just on the outer edge of the R2 box outline. The one closest to P3 is the one I have my 12uf in. So I'm going to jumper R2 to the one just above it. That will make it parallel. Guess I should have paid more attention to what you wrote and compared it against what I was looking at. Would have made things for me so much easier. I'll pay more attention next time, I promise.

Guess I thought I was done. Time to pull it all apart again.

tugboat

Okay, this time I really am done! I took the jumper off the bypass cap connections and jumpered up higher from the R2 hole to the hole next to it. This will take the 22.5 resistor and put it in parallel with the 12uf. They now both terminate at the tweeter 3 output.

So how long does it usually take to break in caps? Does the volume level make a difference in the amount of time? I was thinking of leaving it playing background music for as many hours a day as possible.

Thanks!

tugboat

Lasareath wrote: »

What about final pics?


I played mine for 400 hours straight at around 20 to 30% of their top volume. I played a mixture of different music.

Final pics? The second one looked just like the first one I posted pics of. The only difference is the jumper which isn't visible under the large 12uf cap. That and they're tucked safely into their respective cabinets.

Well I average about 10 hours of music a day at around or just above 1 watt. I hope that's enough since much above that level and it's no longer background music. I have a large compilation of 70s music, so the music varies. Man, I feel like I'm breaking in a new cam. Keep the RPMs up and vary them until it's done.