Charge-Coupled JBL 4435 Networks

Zonker92 · Feb 27, 2015

I use CAIG DeoxIT D5S-6 (although I'm not an expert on all the DeoxIT options; it's just the one I happened to pick). Lying on my back, I stick my head into the woofer hole looking upward, and from there it's easy to see the pots with a flashlight. The rheostat for the HF is exposed so you can spray the wiper and element directly. The L pad has a cover but it has vent holes that let you spray into it using the tube that comes with the spray can.

I give them both a good hosing down and then use the flat end of a plastic pry bar (for working on car stereos) to rotate each control knob a few dozen times; cleans them up nicely.

If you look here at page 5, figures 7 and 8, you can see what they do (on a 4430). I have read that it is best to set them both flat, then set the mid control to taste, then finally the HF.

gonzomeep · Feb 27, 2015

Superb.

Very impressive! Nice and clean. I had a pair of 4435's years back that I purchased from the Annenberg Theater in Palm Springs, CA. The 2234's had rotten surrounds, but were mint otherwise. They still had the factory plastic over the level adjustment/foilcals. IIRC, they were actually plastic instead of aluminum? Had a cat from Colorado offer me $3500 plus a pair of JBL L220's for them. I paid $1300 cash for them and believe it or not, the guy drove all night in an old Datsun pickup and arrived at my house with the 220's and a wad of $100's :yes:. I only regret that because of the surrounds being toast, that I never got a chance to hear them! They must be wonderful, and even more so, now that they have CC'ed xovers. Well done Sir, Steve G-

Zonker92 · Feb 27, 2015

Thanks, Steve! Sounds like you did extremely well on that deal.

The "foilcals" do look like thick plastic, but I've seen them scratched and under the paint I think they are aluminum. However, they are much thicker than normal foilcals, so "foil" is not a very accurate term with regard to the 4425s, 30s and 35s. (I use it anyway, because it's convenient.)

gonzomeep · Feb 27, 2015

You are welcomed.

Yeah, it was a good deal for both of us, as we both walked away happy. He had always wanted some and knew of me through the LHF. When you think of the absolute quality of these vintage speakers and that we have to pay much more these days in hopes that we even approach the SQ that vintage systems deliver in spades :yes:. Keep the projects going and the posts flowing, I enjoy them, SG-

Zonker92 · Feb 27, 2015

My pleasure; thanks!

4343 · Feb 27, 2015

Tying the grounds together _can_ result in smoke when bi-amping, depending on the amps of course. The better (safe) way is to use 2 batteries so you don't have the grounds tied.

I like to use this battery box:

http://www.newark.com/bulgin/bx0023/battery-holder-9v-panel/dp/92C3807

I've used it on my 4412A's, Indignias and various others like my EconoWave top box and Deluxe Waves...

They have a dual version called BX-0026:

http://www.digikey.com/product-search/en?mpart=BX0026

Zonker92 · Feb 27, 2015

Ah, good stuff; thanks.

In my case, I have the 9V(-) wire running into the LF and HF circuits through 3 megohm resistors; one resistor for each circuit. That should protect separate amps, non?

Rob41 · Feb 27, 2015

I just wanted to say thank you for all your contribution to this site Zonk. You always make for a great learning experience!

Zonker92 · Feb 27, 2015

Wow; thanks, Rob! I really appreciate the kind words. I'm a total electronics ignoramus in a lot of ways, but when I figure something out (or at least think I have) I love posting it here!

Rob41 · Feb 27, 2015

Maybe so but you made it very clear and easy to understand. I think it makes it easy to consume the information for just about anyone. Really easy for someone who wants to duplicate your steps.

Zonker92 · Feb 27, 2015

Thanks; yeah, I try hard to explain things clearly; often it helps me think them through myself.

Scott 99 · Feb 27, 2015

Zonker,

Thanks for the tips for cleaning the L pads. The Deoxit looks perfect for the job.
In regards to setting the L pads, you mentioned, "it is best to set them both flat, then set the mid control to taste, then finally the HF." When you say "flat" does that mean knobs are full counter clockwise, mid travel or full clock wise?

Sorry, I am a novice with these L pads.

Thanks again,
Scott

Zonker92 · Feb 27, 2015

No worries. Flat should be the "0" setting on each knob, wherever that is; somewhere between the high and low positions. From there, each "tick" mark up or down is plus or minus a stated number of dB.

Scott 99 · Feb 27, 2015

Great, Thanks

4343 · Feb 27, 2015

Zonker92 said:
Ah, good stuff; thanks.

In my case, I have the 9V(-) wire running into the LF and HF circuits through 3 megohm resistors; one resistor for each circuit. That should protect separate amps, non?

Ahh, that should work fine. I don't believe the extra 3M ohm will affect anything other than how long the caps take to charge. I've been using two batteries since Zilch said to do it that way, but looking at the price of the battery holders, especially the double one, I do have to say your way is lots cheaper...

rvito · Mar 1, 2015

Zonker, Would those resistors be the Mills 62R ?

gcarlberg · Mar 1, 2015

4343 said:
Ahh, that should work fine. I don't believe the extra 3M ohm will affect anything other than how long the caps take to charge. I've been using two batteries since Zilch said to do it that way, but looking at the price of the battery holders, especially the double one, I do have to say your way is lots cheaper...

. . . or even cheaper yet, would be to replace the battery with a diode.

george

Zonker92 · Mar 1, 2015

Mills 62 12-watters; yup.

I looked into the diode but wasn't quite sure how to implement it.

Scott 99 · Mar 4, 2015

Zonker,
While cleaning my 4435 Lpads, I noticed each speaker has a different Lpad. One has a metal housing facing me (while head is in the woofer hole) with holes for spraying cleaner. The other Lpad has plastic housing facing me with no holes for cleaning. Wondering what your Lpads look like and what the resistance range is.
I measured both and came up with different numbers. Measuring between the red E19 wire and the brown E20 I measured a range of,
.16ohm to 29.3ohm on the metal Lpad with holes.
Then measured .3ohm to 38.1ohm on the plastic Lpad with no holes.
This is after I cleaned all but the plastic Lpad. This is a significant difference. Not sure what the correct range should be. I am unable to post photos at this time, sorry.
Scott

Zonker92 · Mar 4, 2015

Huh. My L-Pads are, IIRC, both the metal types. I don't have their DCR figures in front of me, but I can check when I finish up this move in a few days and dig back into them.

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