HIFONICS ZX6400 damage

[rafcio363]

Hi.
I'm new on this forum

My hifonics was damaged., repair is dificult.
My technical English is enought to write about damage,but i try.

When i set volume at radio at 50% was much disortion and green diode on amplifier was pulsing.
I put other amplifier to car and works ok.

But Hifonics was better


I open car amplifier, disconect DC unit from other elements.
Diagnose - low power from capacitors.
I change all in DC unit.

I check power transistors, replace new all capacitors.

Checked DC-DC unit (14V to ~30V) and its fault, it dont have current.(Voltage at working amplifier is 13-19~).
Should was be ~30-35V.

When i put "1A 12V bulb" to DC unit out then get down to 6V.
All capcitors is ok(new).
DC unit is based on KA7500B.

I need scheme for this model or any sugestion.

Greetings.

[rafcio363]

I found broken capacitor smd working in KA7500(TL494) he set frequency of dc unit.
I set it to 36kHz. (Resistor 3k and capcitor 1nF).

Now i connected to power supply ,set volume 50% and amplifier play and off and red diode protect was lighting.And dont play.

If i disconnect Remote and connect again,amplifer "play" at low volume only.

Should i change broken capacitor to other than 1nF?
Frequnecy is too low?

[Perry Babin]

If the frequency on pins 9 and 10 is 36k, it should be OK. If the oscillator frequency is 36k, it's too low. Mathematically, I think those values would produce an oscillator frequency of 366kHz which is too high.

Drive one channel at a time. Does the amp shut down when driving any individual channel to full power?

[rafcio363]

I dont know what is frequency at output becose I don't have osciloscope.

Original was Rt 3kOhm and Ct was broken and i checked in other amplifier like Magnat 4 channel build too on Tl494 and when i calculate Fosc it was about 56khZ.

Then i try to recalculate to hifonics good frequency.

Fosc=1.1/Rt*Ct

= 1.1/0.01uF * 3k

=1.1/0.03= 36kHz - its ok?

Rt- pin 5
Ct - pin 6

And set Ct to 1nF to = 36kHz.

I checked to 1 channel connected to 12" subwoofer and protect was lighting.

[Perry Babin]

A 36kHz oscillator frequency is too low.

0.01uF = 10nF

[rafcio363]

1n = 0,000001 F
3k= 3000 Ohm

= 3000 * 0,000001 = 0,003

1.1/0.003 =366 - Hz?

[rafcio363]

How capacitor should be correct?

[rafcio363]

WORKING !!

I set Rt=10k and C=1nF.( i found in google this value shout be 50kHz).

And working.

But tell me how to calculate this ?

Hz=1.1/Ct*Rt

1.1/0,000001*10000=110 ??? Where is the 50kHz


Sory for post by post.


How is good frequency to this amplifier?

[Perry Babin]

The 50kHz is the output frequency of the IC (pins 9 and 10), not the oscillator frequency. The oscillator frequency is 2x the output frequency.

That's a bit higher frequency than most amps use but it may be OK.

[rafcio363]

Should I change it to 40kHz?
It isn't much work to change it
Thanks for help of course.