Genius SP-HF1250X - 2.0 speakers

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

will be done tonight people. Once again, you have big thank you for your patience!

Any success?

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

will be done tonight people. Once again, you have big thank you for your patience!

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

Hi ben7.

OK, i plugged it in again, and watched the speaker cone. It doesn't suck in, nor does it push out. It starts vibrating immideately, first small vibrations, for a second, and then with, i guess, full power.

Measured what you told me. Upper black contact measures 0.48, and lower is at zero. Multimeteris set to 20V

edit: that was with the speakers turned off. When I turned them on, voltage on the upper is about 9.27 (it's variable, but around that value), and on the lower is constant -0.7. Multimeter is again, on the 20V setting.

Those black circles are legs of the two caps (100 uf, 25v).

I am looking for the 4558 datasheet so i'll know where are v+ and v- legs. Then i'll do the reading

YAY, a problem! The lower should be just about the same voltage as the upper, but negative. So the lower one should be about -9v.
FYI: I traced the tracks, which was very easy due to the good pictures, and those are the + and - power rails for the opamp.

Can you please measure the resistance of R44 (its a 470 ohm resistor)?

[budm]

Re: Genius SP-HF1250X - 2.0 speakers

Pin 4 is B-, pin 8 is B+ on the OP-AMP. You put the black probe of the meter to the DC ground (you can use the RCA input jack outer body for ground, the red will be used fro checking the voltage with speaker on.

[Evil Lurker]

Re: Genius SP-HF1250X - 2.0 speakers

I see NP on the electrolytics... are those nonpolarized caps?

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

OK, so here's the datasheet:

http://html.alldatasheet.com/html-pd.../1/LM4558.html

What should I measure? And should i do it with the speakers powered on?

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

Hi ben7.

OK, i plugged it in again, and watched the speaker cone. It doesn't suck in, nor does it push out. It starts vibrating immideately, first small vibrations, for a second, and then with, i guess, full power.

Measured what you told me. Upper black contact measures 0.48, and lower is at zero. Multimeteris set to 20V

edit: that was with the speakers turned off. When I turned them on, voltage on the upper is about 9.27 (it's variable, but around that value), and on the lower is constant -0.7. Multimeter is again, on the 20V setting.

Those black circles are legs of the two caps (100 uf, 25v).

I am looking for the 4558 datasheet so i'll know where are v+ and v- legs. Then i'll do the reading

[999999999]

Re: Genius SP-HF1250X - 2.0 speakers

Measure the voltage at the V+/V- pins and ground for the LM4558 as Ben7 suggested. If it is not so high as to damage the opamp, then replace the two large caps right after the diodes. If it is too high and damaged the opamp, replace that too.

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

I do have visual access, but my speakers are at my home, and I'm at work, so I'll do all that when I'm back home!

Ok!

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

I do have visual access, but my speakers are at my home, and I'm at work, so I'll do all that when I'm back home!

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

@budm:

I'm sorry. Somehow I completely skipped answering you. Yes, noise is there no matter what volume, bass or theble setting are.

@ben7:

I'll take them out today when I get to work and post the results.

As for the second post, yes, I replaced those 4 caps after I changed the LM4558.

Do you have visual access to the speakers? If so, when you first plug them in, does the speaker cone suck in, and buzz? or does it push out? If they do one of those, unplug them immediately because there is DC voltage being fed to the speakers, and they wont do well with that!

Ok, do you have a multimeter?

If so, put your black probe where the black circle is, and measure each spot marked in red with the red probe. One should measure anywhere from 15v to 5v, and the other should measure anywhere from -15v to -5v. Please report back the readings.

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

@budm:

I'm sorry. Somehow I completely skipped answering you. Yes, noise is there no matter what volume, bass or theble setting are.

@ben7:

I'll take them out today when I get to work and post the results.

As for the second post, yes, I replaced those 4 caps after I changed the LM4558.

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

On a side note, did you replace these caps did you?

They are used in the voltage regulator for the LM4558.

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

no changes Only thing I didn;t replace are resistors and two big capacitors. I'm out of ideas

Most likely the resistors will be fine.

I would be surprised if the rectifier bridge diodes are bad, although they might be cheapo-chinese rubber electrode ones.

Of course I'd replace the main filter caps also, if the rectifier is bad then the caps could be damaged also.

Can you take out the diodes and measure them with a diode-checker? (I'm referring to the big black ones)

[budm]

Re: Genius SP-HF1250X - 2.0 speakers

I still do not get the response if the noise is there no matter what the Volume control or tone controls are set to. Are there more than one OP-AMP? Some thing bad that is common to both channels.

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

no changes Only thing I didn;t replace are resistors and two big capacitors. I'm out of ideas

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

well, i replaced both power amps, and all the smaller caps (9 of them, 2 types). Results - tonight

thanks!

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

Perhaps a smaller filter cap is bad, causing the thing to self-oscillate.

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

I changed the op amp yesterday with brand new 4558. When i seitched everything back on noise was way quieter for about a second and then it was back on the loudest.

I guess it's not the op-amp

[budm]

Re: Genius SP-HF1250X - 2.0 speakers

Do you hear the noise with the Volume control is all the way down? You can also try heating or cooling the OP-Amp to see if it does have any affect on the noise.
One thing I do not see are the Cotrol panel board pictures, there should be some Op-amp for the Bass/Treble controls circuits.