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 Post subject: 1935-1939era Zenith console radio speaker REPAIR METHOD
PostPosted: Jan Mon 29, 2018 8:48 pm 

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5024
Location: 253 Blanche St. Plymouth, MI USA
I just wrote this in reply to someone seeking a speaker in the Classifieds so thought it would fit here...


Many of these Zenith speakers can be fixed if the field coil is not "trapped" by the FC frame. If you have 4 screws on the back of the FC frame, you are in luck. I have a process that you can do to fix it. I have not made any videos yet but maybe I will get around to it soon. The Zenith FC's go bad typically on the INSIDE windings. What you do is have to get to the FC, then peel the side form back to get to the inside winding area.
1. unsolder the humbucking coil leads and loosen (bend open) the clamp that holds the FC and audio wires to the frame. Un-bundle them so you will have slack to move the FC in the next steps.
2. Unscrew the rear screws. Carefully back the frame/pole piece off the basket. You need to be careful of the voicecoil. you may need to slide a butter knife in between the FC and the frame to get it loose.
3. Bend the side form back and take an X-acto knife with a clip lead to your probe and touch the inner winding area to confirm continuity to the outside winding wire (continuity might be 80% of the rated total but thats OK). Then you clip off the FC wire thats the one going to the inner windings but leave about half inch of it for a tie point. Scrape the side of the inner windings and solder some #28 ga enameled wire there that you have pre-scraped and tinned. Bring that wire out and put some tape across the FC to "tack" it down so its not loose.
4. strip the FC lead that comes from the speaker plug back 3/4" or so and wrap around the stub of where it was cut off. Now bring the new enameled wire over there and scrape clean a half inch of it or so and wrap around that wire and solder it. You are just using the stub of the old wire you cut off to act as a tie point here, not soldering to it.
5. check the alignment of the voice coil in the frame before re-installing the FC/pole assembly. Most of these speakers have two screws holding the spider to the basket so you can loosen them and re-align the VC if needed. You can easily see if its aligned here, adjust if needed.
6. CAREFULLY replace the FC/pole assembly back onto the basket and set the mounting screws in just barely snug. Carefully turn speaker over and check cone alignment. If its OK, turn the screws down. If not, center the pole by looking at it from the front to see which way it wants to go and move it there.
7. Check cone for travel , no rubbing.
8. Double check your continuity. Should be 80% or more of the original and will work like new. Wrap the 4 leads with electrical tape and re-tweak the cable clamp to hold them in place. Re-solder the humbucking leads.
9. Check the audio xfmr for continuity while you are at it.
10... enjoy.... this should take about an hour total.
Mark Oppat

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