Selecting Inductor values

[Mr_bibbles]

Hey y'all,

Got a question for the old heads-

What parameters are important for selecting replacement inductors for what I believe to be a filter circuit? It's part # L1/L2 from a Peavey max 115, specs to follow.

(INDUCTANCE) 22 UH +/- 20% L LOAD 4.9A L DROP 10% WIRE: 0.7MM ENAMELED COPPER TEST FREQ. REF @ 1KHZ 0.25V DCR 28MOHM MAX
DC CURRENT 4.9A MAX TURNS 11.5T REF OPER.TEMP. -20 TO 80 DEGREES C CORE: POT CORE, FULLY SHIELDED, EPOXY SEAL

I already checked with Peavey and they do not have any replacements on hand. So when sourcing, bviously 22UH is the main factor here, but I'm guessing I should shoot for the same MAX DC current too? Are there any other things I need to consider for this application?

Only one has snapped off, should I replace both to ensure that they are matched? or is this unnecessary.

[nickb]

I can't find L1 or L2 on the BOM, layout or schematic for the MAX 115. Where is it?

Peavey_Max_115_Schematic.pdf

[Mr_bibbles]

[QUOTE=nickb;526326]I can't find L1 or L2 on the BOM, layout or schematic for the MAX 115. Where is it?

Here is the schematic for the power amp! Not sure sure what model the above one is, but this one matches the board:

https://music-electronics-forum.com/...4&d=1518814296

After finding this I'm realizing that it's probably not for filtering, but to be honest this circuit is above my head.

[nickb]

[QUOTE=Mr_bibbles;526332]

I can't find L1 or L2 on the BOM, layout or schematic for the MAX 115. Where is it?

Here is the schematic for the power amp! Not sure sure what model the above one is, but this one matches the board:

https://music-electronics-forum.com/...4&d=1518814296

After finding this I'm realizing that it's probably not for filtering, but to be honest this circuit is above my head.

I see that's a newer model. That's why it always a good idea to include a schematic with the original post.

These don't need to be matched but the current and core losses are critical to the design. The DC resistance and screening are of secondary importance.

It's worth a try, by whatever means you can, to disassemble the existing core and then rewind. Failing that, you make well be able to find something off the shelf that is designed for Class D amps. Try looking at Coilcraft. Big distributors just as Digikey and Mouser may well have something suitable.

[Mr_bibbles]

Awesome! Thanks for the information. It's not my amplifier so I'm hesitant to try a rewind as it's something I've never done before. I'll try and source something with appropriate current and core loss. Thanks nick!

[Mr_bibbles]

[QUOTE=nickb;526333]

I see that's a newer model. That's why it always a good idea to include a schematic with the original post.

These don't need to be matched but the current and core losses are critical to the design. The DC resistance and screening are of secondary importance.

It's worth a try, by whatever means you can, to disassemble the existing core and then rewind. Failing that, you make well be able to find something off the shelf that is designed for Class D amps. Try looking at Coilcraft. Big distributors just as Digikey and Mouser may well have something suitable.

Would this be a suitable replacement?

https://www.digikey.com/products/en/...=1&pageSize=25

I couldn't find any values for "core loss" but this one has the same UH and DC current and the DCR is within 3MA.

[doctor]

This inductance is used as a filter and it is recommended by the TDA8954 manufacturer.
You can see this in the TDA8954 datasheets.
The important parameters are inductance and rated current.
The 998AMF134 power inductor is usually used for the TDA8954.
Its parameters:
Inductance: 22 uH
Rated current: 6.2A.

The inductor that you found is not suitable.

[Mr_bibbles]

This inductance is used as a filter and it is recommended by the TDA8954 manufacturer.
You can see this in the TDA8954 datasheets.
The important parameters are inductance and rated current.
The 998AMF134 power inductor is usually used for the TDA8954.
Its parameters:
Inductance: 22 uH
Rated current: 6.2A.

The inductor that you found is not suitable.

Thanks for the knowledge doctor! Just to be thorough, on the parts list sheet in the above schematic from Peavey, L1 is listed as a 5A inductor; The specs from the parts department are as follow, listed at 4.9A:


(INDUCTANCE) 22 UH +/- 20% L LOAD 4.9A L DROP 10% WIRE: 0.7MM ENAMELED COPPER TEST FREQ. REF @ 1KHZ 0.25V DCR 28MOHM MAX
DC CURRENT 4.9A MAX TURNS 11.5T REF OPER.TEMP. -20 TO 80 DEGREES C CORE: POT CORE, FULLY SHIELDED, EPOXY SEAL


Is there a reason they might choose a different rating than the usual inductors paired with TDA8954?? Schem for reference:
https://music-electronics-forum.com/...4&d=1518814296

[nickb]

[QUOTE=Mr_bibbles;526370]

Would this be a suitable replacement?

https://www.digikey.com/products/en/...=1&pageSize=25

I couldn't find any values for "core loss" but this one has the same UH and DC current and the DCR is within 3MA.

I doubt it. The datasheet has very little useful info. If core losses are too high it will simply bake itself to death in no time.

I'm confident this will work even thought it's nominally 20uH but I have no idea if it will work mechanically https://www2.mouser.com/ProductDetai...b2C1AdKg%3D%3D

There has to be someone making these for the TDA8954 since they are a common part. I couldn't see a recommend part number in the TDA8954 datasheet or app notes that I've looked at. The part the Dr suggests might be a Toko part but I couldn't that anywhere.

PS:
Here's a couple more suggestions. These are designed for Class D but they don't give loss data (Watts for given Irms and frequency). You can simply try one and see how hot it gets.

https://www2.mouser.com/ProductDetai...Kotcg7Mw%3D%3D

or it's higher current and larger sibling

https://www2.mouser.com/ProductDetai...Pcg6ziFA%3D%3D