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Replacing Diaphragms & capacitors in Chorus ! - any hints or tips?


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#1 KA1J

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Posted 23 July 2014 - 07:22 PM

Hi,

I just ordered replacement caps and tweeter/mid diaphragms for the chorus i from Bob Crites. I saw the how-to pages for the tweeter/mid replacement on his web page.

Does anyone have any suggestions or hints for me that might make it go more smoothly or anything I should do first or last? Should I remove all the horns & speaker first?

Any suggestion is welcome

Thanks!



#2 moray james

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Posted 24 July 2014 - 01:54 PM

yes. cut the capacitors out right where the lead enters into the cap. You can use a fine marker to write on the board where the cap was whet value it was so later it is easy to see where each new cap goes.This will provide you lots of room to maneuver when you remove the old lead wires from the board. Buy a real hand pump solder sucker if you don't already own one and use that to suck the solder from the joints. With a little practice you will find that you can extract the solder from a joint and lift the lead wire out or at worst use a little heat and with your pliers remove the wire clean. This process leaves you with a nice clean board upon which to insert then solder in place your new capacitors. This process will work best if you have a good quality electronics soldering station or iron like a Hako or Weller. I mention this as inexpensive circuit boards like those used for crossover networks in your Klipsch speakers will not handle the extreme heat generated by large hobby soldering irons or the Weller soldering gun so often found in the home tool box. Also use a good quality rosin core eutectic 60/40 solder. Stay away from solder with anything more than a 1/2 % of silver in them as requires too much hear to work with and will only lead to problems, don't make me say "I told you so" (and stay away from lead free solder it is not your friend) . After you are done soldering use a Q-Tip and some lacquer thinner to wet clean each joint thoroughly. While the joints may look to be shiny and clean they will be rosin residue there and over years it can eat away at your already thin copper traces so clean the board well and you will have a professional job. I hope that this helps. Best regards Moray James.



#3 William F. Gil McDermott

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Posted 24 July 2014 - 08:21 PM

I believe you have to remove the horns and drivers to get them out. But I could be wrong.

Are you the ham in Groton? If so, you probably know the following. But the benefit of everyone . . . .

I always recommend that you take pictures and make diagrams and mark wires with tabs of masking tape with notations of what goes where. In my experience it is helpful to proceed as if my stupid self on Day 2 will need the notes my smart self made on Day 1. Really. YMMV.

Of importance is which wires go to which side of the drivers to maintain proper polarity. The voice coil / diaphragm assemblies should be marked with a (+) or red spot at the factory but make sure you note these on the original and replacement units. And also make observations about the woofer in a similar fashion. Note that in a zip cord like pair, usually one wire is marked with a stripe.

It may also be helpful to have a bottle of clear nail polish on hand. It may be that the screws mounting the drivers are in fiberboard which can flake. Hardening up the holes with clear nail polish and letting it dry will harden up the .threads in the fiberboard If the holes / threads strip out you may have to add a sliver of a toothpick.

De-soldering is a bit of an art. As James said, a bulb type solder sucker does the job. Available at Radio Shack You may find the hole in the nozzle gets clogged with solder and you'll have to force it out with a paper clip. Solder wick (also at RS) works too in that it is used to absorb the molten solder.

I am so, so, so in agreement with James about temperature regulated soldering stations. Over the long years I've spent hundreds of bucks on non-regulated soldering irons which always seem too hot or too cold, or both at once. My recently purchased Weller station is magic. I can't say enough.. There are others too, but I like my Weller. (Just for the record, a Weller soldering gun can be good in some situations but some experience is needed to get a feel for the temperature.)

Let me disagree with James on a point. 60-40 solder is widely used and available. It does have a slushy stage if not heated properly and cools or something moves while it is cooling (making a "cold solder joint"). This and similar mixtures are somewhat eutectic. Eutectic means the lowering of the melting point of the lead-tin alloy is lower than either lead or tin.

The actual eutectic mix is a 63-37 combination. It has a slightly lower melting temperature, and therefore solidifying, temperature, than 60-40. But also, it does not have a slushy phase. The stuff is expensive. If you want a yard of it I can mail it to you if you PM me through the board.

Please take lots of pictures and post them and a description of your work in a thread. You can be our new expert and educator.

Best,

WMcD

AB9BE


Edited by William F. Gil McDermott, 24 July 2014 - 08:26 PM.


#4 KA1J

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Posted 25 July 2014 - 02:28 AM

A Ham I am :) 35 years of it. Have a K3, an Alpha 77SX & mostly work CW DX.

Thank you for both of the replies.I am taking photos of what I do although my tripod has taken feet and I'll do my best. I've got both a vacuum tube to suck with and a hollow tio with a shaft & squeeze bulb where you surround the soldered lead with the metal tip & when it melts you release the bulb you've kept squeezed. It works such things real well.

I'm wondering if I need to remove the crossover, it looks like I can access every cap on the two boards.without unhooking therm from the horns speaker. I was surprised no resistor came with the kits. I'll have to decide if it's the same value or if it's drifted out of specs. If it's carbon, its a big one.

Maybe I should remove the tweeter make a note of what color wire goes to each terminal and tie them with an extra long string coming out the front of the enclosure. Then do the same with the mids & reach in & down & remove them from the 15" speaker & tie them together. It might facilitate getting the right wires easily to the right horn, just pull the string in the opening & there are your needed connections from the crossover which was rebuilt when it was pulled out from the Chorus.

Doing this game tomorrow morning. Will be fun to rehab these speakers, they look lovely and sound pretty nice as is but everything is original so it's time to do the logical upgrade.

Gary

KA1J