I'm not sure if you are wanting to upgrade the performance of your DQ-20s beyond original, or if you just want to get them back to like-new condition. Sounds like you want to restore them back to like-new.
If so, have you talked with Dahlquist? They offer rebuild/restore services and after conversations I've had about their crossovers, I would suggest you ask them if they would sell you the parts. I have a similar problem with the fuse for my Dahlquist LP-1 Hi/Low Pass.
I see they offer a few Kits for the DQ-20 and the DQ-20i. They're not into being inexpensive, though. For the LP-1, they want $20 for a fuse & they spec'd out a fuse (1/32 A) that I can't find anywhere else. Nevertheless, I would give them a look-see if you haven't already.
http://www.regnar.com/home.html
If so, have you talked with Dahlquist? They offer rebuild/restore services and after conversations I've had about their crossovers, I would suggest you ask them if they would sell you the parts. I have a similar problem with the fuse for my Dahlquist LP-1 Hi/Low Pass.
I see they offer a few Kits for the DQ-20 and the DQ-20i. They're not into being inexpensive, though. For the LP-1, they want $20 for a fuse & they spec'd out a fuse (1/32 A) that I can't find anywhere else. Nevertheless, I would give them a look-see if you haven't already.
http://www.regnar.com/home.html