Beginning the RCA LC-1A adventure.

I’ve got an LC1-a and MI-11411 that I purchased from a guy on AK. The tweeters on both were repaired, though I don’t know what was done or by whom. I believe the voice coils of the original tweeters were repaired somehow but both tweeters now have dust caps rather than than the visible screw seen on the originals, so I’m not entirely sure that a new tweeter wasn’t installed somehow. The seller claimed to have heard them with original LC1’s and could not hear any difference between the repaired and original drivers. I have reached out to the seller to see if he has any additional info on the repair or a contact for who did the work. I’m hoping it may be a remedy for some of those with non-functioning tweeters. I’ll try to upload some photos of my drivers this weekend and will update with any additional info about the repair.
 
Sorry to hear this, I think the tweeter voice coil is the only weak point in this design though I'm also pretty sure that any tweeter voice coils found to be bad were probably hit with WAY more power than they could handle. Like the story I heard about a guy who found one with a bad tweeter that a kid had installed in the back of his car for his car stereo that he then tried cranking up with a couple hundred watt car stereo amplifier! :-( Fried beyond repair! I have a couple friends who have been able to fix a few bad LC-1 tweeters that I've had over the years but they just can't all be fixed, unfortunately. The best case scenario seems to be if the point of failure is on the lead to the coil and if you find that the break is in the coil somewhere, you're probably not going to be able to repair it, unfortunately.
 
Sorry to hear this, I think the tweeter voice coil is the only weak point in this design though I'm also pretty sure that any tweeter voice coils found to be bad were probably hit with WAY more power than they could handle. Like the story I heard about a guy who found one with a bad tweeter that a kid had installed in the back of his car for his car stereo that he then tried cranking up with a couple hundred watt car stereo amplifier! :-( Fried beyond repair! I have a couple friends who have been able to fix a few bad LC-1 tweeters that I've had over the years but they just can't all be fixed, unfortunately. The best case scenario seems to be if the point of failure is on the lead to the coil and if you find that the break is in the coil somewhere, you're probably not going to be able to repair it, unfortunately.
Could I check that without opening up the back of this speaker
 
The tweeter assembly has to be completely removed from the speaker so, you'll need to remove the front screw as well as the two that go through the back of the magnet assemble and into the phenolic/bakelite ring that holds the coil and cone.
 
The tweeter assembly has to be completely removed from the speaker so, you'll need to remove the front screw as well as the two that go through the back of the magnet assemble and into the phenolic/bakelite ring that holds the coil and cone.
Okay thanks for the info but I'm going to try and have somebody professionally look at them. Someone mentioned the guy in Texas his website is dr. Field coil have you ever heard of him
 
No, I'm not familiar with him. If you find someone who can save yours I'd sure like to know though, as I still have one non-functioning LC-1 tweeter, I'll be anxious to hear about it. Good luck!
 
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No, I'm not familiar with him. If you find someone who can save yours I'd sure like to know though, as I still have one non-functioning LC-1 tweeter, I'll be anxious to hear about it. Good luck!
Okay I'll keep everybody informed I just left one place in Lake Worth Florida it doesn't want to touch it 35 years experience
 
Okay thanks for the info but I'm going to try and have somebody professionally look at them. Someone mentioned the guy in Texas his website is dr. Field coil have you ever heard of him
I'd call him - @gable has been out to see him, I don't know how much he's doing right now.

I've heard of someone that might be able to re-wind the voice coil in these tweeters, but I don't know if they're ready to offer these services just yet. I'm going to sit on mine until the right repair opportunities present themselves - they sound glorious when working, really worth getting right.
 
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I'd call him - @gable has been out to see him, I don't know how much he's doing right now.

I've heard of someone that might be able to re-wind the voice coil in these tweeters, but I don't know if they're ready to offer these services just yet. I'm going to sit on mine until the right repair opportunities present themselves - they sound glorious when working, really worth getting right.
Yes they do sound fantastic.Im with you on sitting and waiting til I find someone who knows how to get these back up and running. The guy I saw today in lake worth florida said they are worth more not working than working but altered.But I have no desire to sell them. Sentimental value plus I love the way they sound.
 
Well Dr. Fieldcoil responded to me this morning,(Don) and thought I was selling them.I replied I want to have them repaired and they had sentimental value.
That was around 645am. So far Don hasn't returned my question about rewinding or repairing them. I'll keep updates when he responds.Man I'm praying he can fix them.I know it won't be cheap but I really want them back in working order!! There has to be someone who can help with these I just have to find them.
 
Winding that thin, copper wire around that extremely thin paper hollow cylinder, I'm guessing, is going to be an issue that, though I'm sure can be done, is going to make it too labor intensive for most speaker repair techs to give any serious consideration. Perhaps if there were a boat load of LC-1s out there we'd already have someone making new voice coils for these speakers?

I hope "Dr. Fieldcoil" is able and willing to attempt this but will be surprised if that's the case. 🤞🤞
 
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Winding that thin, copper wire around that extremely thin paper hollow cylinder, I'm guessing, is going to be an issue that, though I'm sure can be done, is going to make it too labor intensive for most speaker repair techs to give any serious consideration. Perhaps if there were a boat load of LC-1s out there we'd already have someone making new voice coils for these speakers?

I hope "Dr. Fieldcoil" is able and willing to attempt this but will be surprised if that's the case. 🤞🤞
Well I'm waiting on his reply but he emailed me 630am and wanted to buy them as far as asking if I new how to pack them so no damage occurs in transit.ill wait to see his response about repairing them.Fingers crossed.If I only knew about these when I worked in rca for 8 years I woulda loaded up on spare parts!!! I do have some parts,the camel bumps about 20 of the. and speaker wire terminals.
 
So I took a moment and downloaded the PDF that RCA NUT shared. Firstly that is one big piece of furniture.
Continuing from there, I'd heard that RCA had used this speakers in some domestic products, but never actual seen anything. Wow.

Reading through the pages, I'm having a hard time with their alignment shim values 0.0001 inches (2.54 micron). Really? A human hair is something like 0.004 inches.

There is a nice exploded diagram on page 6 of the LC1 that is supplied with this console. I'm surprised to see a thin gasket behind the front surround. Gives me pause for thought on a future modification I was entertaining.

Have to say I was a little disappointed in the alignment procedure for the tweeter. Guess I was hoping for some kind of revelation. I've always used Pink or White noise and moved the tweeter until I get the widest/fullest response. I'll have to try a single tone and see if its any easier that way.

My impression of the LC1-A's is that they have always sounded best with a tube amp, and their worst with a solid state amp. Most people I know if they didn't like them it was for lack of bass or for being to forward in the voice. My contention has been that these speakers were built with a specific mechanical damping unlike modern air-suspension designs. Most modern amplifiers would add more damping, sucking the life out of the cone, so to speak.

Well, interesting thing hiding in the schematic for the power amp, an L-pad attenuator. So... the speaker is to loud with a 40 watt amplifier driving it, let's just add an attenuator. I would think this has to limit the effect of amplifier damping, resulting in more bass. I'm going to try this and see if I'm just reading to much into the design.

The output stage of the power amp has some real WTF stuff going on here as well.
 

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  • RCA Secretary LC1 driver-10.jpg
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So I took a moment and downloaded the PDF that RCA NUT shared. Firstly that is one big piece of furniture.
Continuing from there, I'd heard that RCA had used this speakers in some domestic products, but never actual seen anything. Wow.

Reading through the pages, I'm having a hard time with their alignment shim values 0.0001 inches (2.54 micron). Really? A human hair is something like 0.004 inches.

There is a nice exploded diagram on page 6 of the LC1 that is supplied with this console. I'm surprised to see a thin gasket behind the front surround. Gives me pause for thought on a future modification I was entertaining.

Have to say I was a little disappointed in the alignment procedure for the tweeter. Guess I was hoping for some kind of revelation. I've always used Pink or White noise and moved the tweeter until I get the widest/fullest response. I'll have to try a single tone and see if its any easier that way.

My impression of the LC1-A's is that they have always sounded best with a tube amp, and their worst with a solid state amp. Most people I know if they didn't like them it was for lack of bass or for being to forward in the voice. My contention has been that these speakers were built with a specific mechanical damping unlike modern air-suspension designs. Most modern amplifiers would add more damping, sucking the life out of the cone, so to speak.

Well, interesting thing hiding in the schematic for the power amp, an L-pad attenuator. So... the speaker is to loud with a 40 watt amplifier driving it, let's just add an attenuator. I would think this has to limit the effect of amplifier damping, resulting in more bass. I'm going to try this and see if I'm just reading to much into the design.

The output stage of the power amp has some real WTF stuff going on here as well.
 

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  • 16102175851141671838728678645218.jpg
    16102175851141671838728678645218.jpg
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I also downloaded that one, very interesting gives a lot of information.I'm going to show it to Carl at speaker repair Tuesday and go from there.
 
This comment on that service data attachment ties into the observation of the Lpad at the output of the tube amp. Interesting stuff!

1610230165209.png
 
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Well I dropped off one of my lc1a speakers to Carl at Speaker Exchange in West Palm Beach Monday morning. Just waiting for a call from him.Thanks for the blueprint.After I went down to his shop with the schematics he said no problem to disassemble it. Before I gave him the schematics he would not open it up. Very honest guy. PS, he's definitely not looking for work,he's very busy.
 
Just browsing the speaker sites and a guy has an RCA LC1A frame,working voice coil and rear dust cap on for sale.Thay are on Hifishark
 
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