DQ-10 80 uF cap soldering trouble

[mitch755]

I recently got a pair of Dahlquist DQ-10s that hadn't been used in decades and decided to do a bit of refurbishing. I refoamed the subwoofers without trouble. Next, I was told to replace the blue 80 uF electrolytic cap (to the subwoofer) in the crossover. Got two 80 uF 100 V matching caps and replaced the old ones; now one sub sounds scratchy.

Photo album: https://imgur.com/a/CvBmWmd

I removed the old 80 uF capacitors from the crossover by cutting the leads (coming out of the capacitor)--I now realize I should have just desoldered from the joint. Even when the solder is hot, I cannot pull the old lead/wire out of the joint (see right joint in album).

I glued the new capacitor down and trimmed the leads from the capacitor to the appropriate length. I removed as much solder as I could from the previous joint using desoldering wick. I soldered the lead from the capacitor to the point where the old capacitor was connected.

Does the wire from the capacitor need to go through the joint or just make contact with the joint? Did I cut the leads from the capacitor too short? I see where the one joint (left joint) is supposed to connect, but the right joint connects to a wire on the underside of the crossover board.

Is this something I should continue to try to fix or bring into a shop? Can I cause permanent damage to the crossover through continued tampering?

What have I done to my speakers?! I fear I have gotten a bit ahead of myself with soldering.

 

[Blue Shadow]

Well the wire under the cap is there and soldered into the eyelet along with the cap lead.

Proper soldering usually consists of making a nice firm mechanical connection and then flowing the solder. You might not have that option with the short lead so what you can do is remove the solder from the eyelet and mount the wire through the eyelet. Then position the cap lead into the remaining opening in the eyelet and solder in place.

The rubbing in the one woofer, Dahlquist has a separate sub, might be a slightly off center refoam job. With no power, just manually move the woofer carefully by pressing evenly on around the dust cap in the center. If there is rubbing, it is time to do a refoam.

Yes, it does look like you jumped in a bit ahead of your posts asking questions on how to do these projects but there is enough knowledge here to get you straightened out and the DQs playing nice.

What do you have for a desoldering tool? Braid, solder sucker, desoldering iron, just you blowing the solder out of the eyelet once it is melted? Any of them will work.

 

[mitch755]

I refoamed it a few days ago and with the old capacitor it didn't make the current sound. I also couldn't detect any rubbing when I gently pressed around the dust cap.

I have braid and a solder sucker for desoldering.

I'll try another resolder tonight using your tips. I already have done these two joints on three separate attempts, with the same conclusion, but maybe this one will be different.

 

[Blue Shadow]

if you need more lead, you can turn the cap around and put the short end on the lead from the resistor that goes to the same eyelet.

 

[sum of sand]

In the future try this technique

A video is easier to understand so ill just post that

Quigs
Use a paperclip to form the coil

 

[Freddymac2]

Generally you have a poor quality solder that is not mixing with the old solder. I am guessing but you may be using lead free. I also agree that the problem is that you are hearing rubbing of the voice coil after re-foam. Connect the woofer wires directly to your amp without any crossover and play music, and that will tell you that it is not a crossover problem.

 

[F1nut]

You have a cold solder joint on the underside at one end of the white wire.