Broken Front End Transformers

[KE0SBX]

Hi everyone...

Well I seem to have committed the gravest radio sin there is...I busted and crumbled not one but two front end transformer cores. I was doing a simple tune up and I suppose my screwdriver didn't fit in the head just right. Now I'm scrambling to look for replacements and...no luck.

Does anyone know of a way to replace these? Is there a DIY way to? They are out of a Midland 13-853 CB for the receiver's front end section, I think the receiver's antenna transformer and the receiver's RF transformer. Both are rated at 27MHz, not sure if that matters. I'm not sure and cannot check inductance or any other information about these transformers as they were made almost 50 years ago. L101 and L102 in the schematic are the broken ones I'd need replaced.

Thank you!

 

[WSAC829]

I can’t help with that, but there is an untested 13-853 on eBay for $18.00. I’d pick it up and use it parts, or fix it if it’s DOA and use it as a replacement.

 

[prcguy]

If the threaded tube and wiring are still good you can usually pick the crumbled bits out and screw in a donor ferrite slug from another transformer. Many factory slugs are glued in with beeswax and you heat up the slug a little with a soldering iron before turning it. And use a proper fitting plastic tuning tool.

 

[KE0SBX]

If the threaded tube and wiring are still good you can usually pick the crumbled bits out and screw in a donor ferrite slug from another transformer. Many factory slugs are glued in with beeswax and you heat up the slug a little with a soldering iron before turning it. And use a proper fitting plastic tuning tool.

This is what I was wondering because everything else appears to be intact. I'll try picking it out carefully and see what happens. If all else fails, there's a CB repair shop not too far from me.

 

[KE0SBX]

One other thing...

How about salvaging the core from this?

https://www.aliexpress.us/item/3256807282822787.html?productId=3256807282822787&selectedSkuId=12000040882370698&channel=detailPageDealCombineFloor&combineBizType=platformFreeShipping&intent_extra_sku_from=from_add_to_shopcart&type=mergeorder&pdp_npi=4%40dis%21USD%212.57%210.92%21%21%2118.56%216.63%21%402103247417419951824555075e1bcd%2112000040882370698%21fus%21US%212976299275%21X&trackParams=%7B%22businessScenario%22%3A%22choiceV2%22%2C%22activityType%22%3A%22CHOICE_FREE_SHIPPING%22%7D&spm=a2g0o.detail.fusionpage.0&gatewayAdapt=glo2usa

92 cents isn't a whole lot and you get some more free parts too!

 

[prcguy]

One other thing...

How about salvaging the core from this?

https://www.aliexpress.us/item/3256807282822787.html?productId=3256807282822787&selectedSkuId=12000040882370698&channel=detailPageDealCombineFloor&combineBizType=platformFreeShipping&intent_extra_sku_from=from_add_to_shopcart&type=mergeorder&pdp_npi=4%40dis%21USD%212.57%210.92%21%21%2118.56%216.63%21%402103247417419951824555075e1bcd%2112000040882370698%21fus%21US%212976299275%21X&trackParams=%7B%22businessScenario%22%3A%22choiceV2%22%2C%22activityType%22%3A%22CHOICE_FREE_SHIPPING%22%7D&spm=a2g0o.detail.fusionpage.0&gatewayAdapt=glo2usa

92 cents isn't a whole lot and you get some more free parts too!

Check eBay for Toko coils and you might look for any part #s from your transformer. The ferrite permeability has to be correct for 27MHz and the windings in your transformer.

 

[KE0SBX]

Got some part numbers...

9R (or A) 828

7A 326

They are also made by Sumida

 

[merlin]

Buy a few scrap CB radios and rob the cores. Heat the beeswax and use a tuning tool made for these.
Often you can extract a broken core, sometimes means removing the can and getting the slug out from the bottom.

 

[RFI-EMI-GUY]

I have a radio where this happened in an IF core. It broke in two (vertically) before I could move it. I bought a spare transformer but never replaced it. I always wondered if that cracked core would impact the performance.

 

[merlin]

I have a radio where this happened in an IF core. It broke in two (vertically) before I could move it. I bought a spare transformer but never replaced it. I always wondered if that cracked core would impact the performance.

Broken cores are usually from people with golden screwdriver, Tweak and peak.
If the core broke still in alignment, the impact is nil.