KEF Reference Model Three Schematic

[kjbruckner]

Update with measured inductors; need help with discrepancy

First, thanks for the schematic! Very helpful in finding the shorted cap

While I was at it, I measured everything else on both channels, the attached drawing shows the average value for the inductors.

HOWEVER - I get a wide (over 20%) variation on L10: 6.5 uH vs. 5.0 uH. It also shows signs of heat stress, so it looks like something is off. Anyone have another data point? Or any thoughts on which is OK? Or if they're both bad, what's the right value?

I did contact KEF in the US, and they have nothing online that they can access. They did say they'd have to search their paper files, but can't get to their offices until the pandemic eases.

Thanks much!

 

[Lojzek]

6.5 uH sounds like a shorted coil if u=micro. The remedy for it is to unwind this inductor completely and install a new magnet wire of the same length and diameter. We can guess the ball park value of the inductor knowing its total wire length and former measures.

 

[AllenB]

Only one looks stressed? That's a possible a data point on its own. Don't add inductance to the smaller value, either rewind or replace it. My first thoughts are to make it the same as the other one until you know better.

 

[kjbruckner]

6.5 uH sounds like a shorted coil if u=micro. The remedy for it is to unwind this inductor completely and install a new magnet wire of the same length and diameter. We can guess the ball park value of the inductor knowing its total wire length and former measures.

Yes, u = micro. Thanks for the diagnosis and the suggestion on a rebuild. I was hoping to replace it with something new with a higher power rating, hopefully without too much of an impact on performance - looking to avoid a repeat failure.

 

[kjbruckner]

Only one looks stressed? That's a possible a data point on its own. Don't add inductance to the smaller value, either rewind or replace it. My first thoughts are to make it the same as the other one until you know better.

They're both heat stressed, thinking they are both fried

 

[AllenB]

In that case I agree with Lojzek.

higher power rating, hopefully without too much of an impact on performance

In theory, if you found a coil with the same resistance but a larger size... However in practice try a smaller resistance, which may mean larger as well. You could always add resistance in series if it makes a difference.

 

[kjbruckner]

Got the info from KEF

KEF came through - they're both fried. L10 is supposed to be 2.7 mH.
Thanks for all your help!!

 

[wkloppen]

Traded my model ones for model three's. Glad I got the schematic already. Can't wait to hear them. Any suggestion on capacitor replacement brand? Original is all Bennic. For the resistors I'm looking at Mill's

thx in advance

reg

willem