Strange crossover component!

[david]

Hi,
I have been upgrading the crossovers of my Elac FS 207s. The crossovers have the usual mix of bipolar electroytics and inductors plus two unknown components.

These look like ceramic disc capacitors. There is a larger one in the bass crossover, and a smaller one in the treble crossover. The marking on one is XTC X090.

I can't see why there should be a small ceramic capacitor in each part of the crossover or what else it might be? Could it be some sort of overload device?

Anyone any ideas?
Thanks
David

[david]

Hi,
I found a dataspec for these. They seem to be some form of solid state fuse. I'm a little the wiser! David

Radial Leaded PTC FRX Series
Electrical Characteristics(23␣)
FUZETEC
Application:
Wide variety of electronic equipment
Product Features:
Low hold current, Solid state Radial-leaded product ideal for up to 60V Operation Current:100mA~3.75A Maximum Voltage: 60V Temperature Range: -40␣ to 85␣ Agency Approvals: UL(E211981),
Part Number
Hold Trip
Max.Time Maximum
Rated
C-UL(E211981), TÜV(R3-50004084)
Typical Resistance Tolerance
Current Current to Trip Current Voltage Power RMIN
R1MAX
IH,A IT,A
at 5xIH
IMAX,A
VMAX,Vdc Pd, W Ω Ω
FRX010-60 0.10 0.20 4.0 40 60 0.38 2.50 7.50 FRX017-60 0.17 0.34 3.0 40 60 0.48 2.00 7.00 FRX020-60 0.20 0.40 2.2 40 60 0.41 1.83 4.40 FRX025-60 0.25 0.50 2.5 40 60 0.45 1.25 3.00 FRX030-60 0.30 0.60 3.0 40 60 0.49 0.88 2.10 FRX040-60 0.40 0.80 3.8 40 60 0.56 0.55 1.29 FRX050-60 0.50 1.00 4.0 40 60 0.77 0.50 1.17 FRX065-60 0.65 1.30 5.3 40 60 0.88 0.31 0.72 FRX075-60 0.75 1.50 6.3 40 60 0.92 0.25 0.60 FRX090-60 0.90 1.80 7.2 40 60 0.99 0.20 0.47 FRX110-60 1.10 2.20 8.2 40 60 1.50 0.15 0.38 FRX135-60 1.35 2.70 9.6 40 60 1.70 0.12 0.30 FRX160-60 1.60 3.20 11.4 40 60 1.90 0.09 0.22 FRX185-60 1.85 3.70 12.6 40 60 2.10 0.08 0.19 FRX250-60 2.50 5.00 15.6 40 60 2.50 0.05 0.13 FRX300-60 3.00 6.00 19.8 40 60 2.80 0.04 0.10
FRX375-60 3.75 7.50 24.0
40 60 3.20 0.03 0.08
IH=Hold current-maximum current at which the device will not trip at 23␣ still air. IT=Trip current-minimum current at which the device will always trip at 23␣ still air. V MAX=Maximum voltage device can withstand without damage at its rated current. I MAX= Maximum fault current device can withstand without damage at rated voltage (V max). Pd=Typical power dissipated from device when in the tripped state in 23␣ still air environment. RMIN=Minimum device resistance at 23␣.
R1MAX=Maximum device resistance at 23␣, 1 hour after tripping . Physical specifications: Lead material: FRX010~FRX090 Tin plated copper,24 AWG.
FRX110~FRX375 Tin plated copper,20 AWG. Soldering characteristics:MIL-STD-202, Method 208E.
Insulating coating:Flame retardant epoxy ,meet UL-94V-O requirement.
1

[Richard]

Hi David,

yes, they sound like protection devices, like these here,
http://www.valutronic.se/hsv1e.html

Interesting site that btw,
http://www.valutronic.se/

[david]

Hi Richard,
It sounds like these as you say 'We also include an electronic, self-resetting overload protection component. It is a kind of ”electronic fuse” that cuts the current to the speaker at overload. When this happens, just turn down the volume completely (or shut off the amplifier), and wait about 30 seconds before turning on again.

Presumably this must make some difference to the sound and they would best be removed? I could even short them out and put them back in circuit for parties?

David

[Richard]

Hi David, I really don't know about a sound difference but I imagine they must be wired in series so all the signal goes through them, have you had a look? These were used by a few manufacturers such as MS I seem to remember. I can't see them being needed for hifi by a sensible user so worth taking them out for a listen I think, but check the parallel or series connection first, I really have no idea how they're wired perhaps you've drawn out the circuit?

[david]

Hi Richard,
I thought I would find out what they were first-which we've now done! My guess too is they will be in series but I will have a look and report back.

If in series, then even if the evice does not affect the sound-which I would doubt-you still have full signal travelling up an down the slender legs of the devices!
Cheers
David

[david]

Hi All,
Yes these electronic fuses were in series and these are definitely hi fi speakers as reviewed by Hi Fi World and my ears! I have now taken them out of circuit and can say there is not a huge difference but all the same a small increase in leading edge dynamics and transparency. So it appears they did their job without too much sonic damage!
Cheers
David