Altec HF driver repair. How to fix an open voice coil.

**kilohertz** · February 2nd, 2023, 06:20 PM

Hi all,

Fired up a rebuilt set of Radio Craftsman tube amps last night that I just bought only to find one had a short in the phase splitter which caused a tremendous growl-hum gawd awful full output noise, shut down as fast as I could but not before it took out the HF driver in my Big Reds, buggar!

So today out came the 604 and I removed the HF voice coil assembly and found the problem...yup, you guessed it, broken lead wire to the diaphragm right where Altec put the 90* bend in the flat wire from the terminal to the diaphragm. This apparently was a design flaw from the late 60's and into the 70's, and mine being from the mid 70's had this type of lead wire. After an hour of trying to remove the insulation on both ends of the flat wire, not sure what it is but it's impervious to MEK and Xylene, I finally got it by gently heating the leads and then the coating film came off in a neat little strip. I was then able to solder the 2 pieces back together and I put in a little bit of radius to avoid this happening again. It was also obvious once I got it apart, that one side had already failed some years ago and had been repaired in the same manner.

Just thought I would share my experience in case any of you find yourself in a similar situation.

Cheers

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**Art J.** · February 3rd, 2023, 12:07 AM

Test 1 2 3. Just seeing if I can still post after all these years. Looks like you and Ron gave up on your 9846 plans.
Glad you guys are still around. Art...

**RonSSS** · February 3rd, 2023, 11:33 AM

Nice repair KHz. That’s delicate work! I have to use a microscope for that stuff now.

Hey ART. Good to see you check in. I actually dug the 9846’s back out with plans to get back to it. I’m currently trying to recone the woofers myself. Having some issues with the kit. Non-stock parts. And I’m missing one N-501-8A crossover.

**kilohertz** · February 3rd, 2023, 01:30 PM

Hi boys,

Thanks for the compliments, it was a little tricky but not bad. Nice to be back as well, it`s been a while since I have spent any time with hifi, just seems work and the property and other projects and life just gets in the way, but I'm back in full force. I've mounted new shelves for my amps and am in the process of building some tube pre/power amps, 01A, 300B etc. Still working on the design but all DHTs.

As for the 9846's, I am still going to build them, I look at the 411-8As every few months, I have the new surrounds for them, several drivers, 802D, 808-8A, 806A and 802-8G to play with....it's just my shop is currently filled with my '49 Ford F1 build and '68 Firebird rag resto and I'm reluctant to fill it with sawdust. My Dad is giving me his commercial table saw whenever I want it but I fear once that arrives, the vehicle projects will pause and I'll be building speakers for a while.

I have all new caps to upgrade my Mastering Labs xovers and might do that this weekend while I'm smoking bacon.

Keep well.

Cheers

**RonSSS** · February 3rd, 2023, 09:11 PM

Car guys and audio. My Turbo LS Nova is in the garage, which is where I will have to sand and repair the 9846 cabinets. So that will have to wait for nicer weather. Sanding dust and car parts don't go together. And it's a 1 car grudge.
Same for the basement where my audio room is. I build engines down there too.

Like you, I come and go from the audio hobby. Been awhile, I forget how much I enjoy it. And you don't get grease under your fingernails!