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Project '79 LS Restore


kzr750r1

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I have my friends La Scala's in the garage now. :) Initial goal is to clean them up and give a listen. These are matching SN 19T605 and 19T606. The deal is if I like them they are mine. If I don't want to keep them I hand them back and he will pay for the restore materials.

Upon the initial testing found one had a bad tweeter and the other had a bad woofer. Both squawkers tested ok.

19T605: T= open, S= 11.1, W= 3.6

19T606: T= 6.7, S=11.3, w=open

So with these understood I called Bob and placed an order. Two new stamped frame woofers and new CT125's, plus a DIY crossover cap replacement kit.

Should be here this week just in time to put back together for the 4th of July BBQ. A couple of old band mates will be here and I can't wait for their reaction to the HT setup thus far.

Addressed a full cab cleanup light soap and water wipe down and fixed rough edges on 605 unit BB veneerer. This cab was the one next to the door to the house. It showed the most wear and tear as it was rotated to point out the door to the yard while he mowed the lawn. No wonder he never heard the distortion that caused the entire surround on the K-33 to disintegrate. Unfortunately there was also some Rodent evidence and not the small kind. Was scary how much dust can accumulate on the bottom lip of the K400. I did also dump a load of oil into the veneer and ran out. Will go get some more later today and keep rubbing it in. For now just making them presentable and if I keep them will do a full dress later.

I would like some advice about one of the crossovers.

606 had a couple of leads get hot and melt the insulators together. The leads that were hot are #2 (red) input and #7 (black) tweeter.... No telling what one was warm and caused the other to fuse together. Unless there are some tests I should complete and ensure the Transformer or the coil are ok....

I'll get some pictures posted but at the moment dealing with work.

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Here is a close up of the leads that showed signs of major heat. Interesting as this was the one with the good testing tweeter. The two black leads under the tweeter protection diodes. Should I be testing the coils for added resistance or anything before replacing caps? These insulators were fused together and looked like some thick shrink tube till I pulled them apart... The other crossover shows no sign of this happening.

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Guest David H

Those Lascala's look good, the crossover issue seems simple enough, you might just consider rebuilding while they are out.

Ooops guess I should have read the original post more thoroughly, you already order the overhaul kits from Bob.

I cant imagine what would melt the insulation off of the wiring, would take alot of current to do that. I would re-wire the crossover and use an expendable driver to test with. Make sure you are getting your LF, MF, and HF from the correct taps, if you verify a concern after the rebuild, post your finding and maybe we can help.

What crossovers are they? AA?

Dave

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Yep AA. Was going to start tearing into them last night but it was already a long day. Called it quits after putting the top end back together. Love the order of operation required with the CT125's larger magnet. So I had to install the tweeters after the K400. Yeah I installed the tweeters twice, no big deal but my knees aren't what they used to be.

After pondering the condition of these wires it did seem to start at the input leg and carried over through this tweeter circuit.

What wire do you guys suggest using for the rebuild? After looking at them I came to the same conclusion all of the interconnects should be replaced. More work than I wanted but should be simple enough. Just need to clear some bench space and prep for the task at hand.

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Guest David H

To keep it simple and reliable, I'd suggest the same 14 gauge wire that shipped with Bob's CT-125's. Relatively inexpensive from partsexpress or local home depot, etc. If you use solder, make sure it's not an acid core type.

Agreed, 14 or 16awg wiring will do fine. I often use 16AWG hookup wire and 60/40 rosin core solder from Rat Shack.

Dave

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Guest David H

Ok I do have several different guages of Monster Cable. Would that suffice for the intrconnect?

Monster will do nicely.

Dave

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Good deal will have to go get some new spade connectors and I'll be ready. Also understand the name brand means very little, it's what I have.

I was one of a few consultants/PM (no longer consulting) that assisted Monster Cable move to their current facility in Brisbane, Ca. What a cluster of a project, but we made it work for them on a shoe string budget. Ahhhh the memories.

The owner Noel Lee's desk was out of hand. It's all carved Koa, one of my favorite hardwoods.

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Crossovers complete... Still need to replace that screw in the inductors. Waiting for the UPS man with the woofers and I should be good to go. Unfortunatly I don't have a sacrificial mid or woofer to test with. All my other 15" speakers are 8 ohm.

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Guest David H

Unfortunatly I don't have a sacrificial mid or woofer to test with. All my other 15" speakers are 8 ohm.

Even the woofer will let you know if you have Low Frequencies going to the mid and tweeter. I dont think you are going to have an issue. You will be rocking out soon.

Dave

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Not finding Auto Transformer tap information as it relates to the LS/AA combo...

Mids are a bit harsh and I'd like to send some more current to the woofer.

Cheers,

Sean

Not sure what you mean by that, so I attached the autoformer T2A picture. Maybe it will help.

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So it seems the best alternative at this point is to leave well enough alone and read some more.

Was hoping I could just change the tap and check it out but now it looks like i need more capacitors.

Would be nice to set it up so I could have a mini toggle back there to make adjustments in the mid and not affect the impedance.

Have each tap and cap combo needed on each leg of the toggle.

Was hoping for a quick fix but now were getting into the interesting stuff. The network. I don't want to wack my amp with a weird load. At least I have them on a separate amp from the AV receiver. Figure a $300 amp is acceptable to sacrifice with these friggen PA speakers.

Any advice on that level you can impart would be appreciated.

Cheers.

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