New year amp question

[nonprof]

Happy new year around the world!

Please help, i have lanzar 2000opti drive. The problem is distorted output signal, if i injected 100hz sine wave, it produces sawtooth like waveform at speaker terminal at 100hz also. Looking waveforms at +in of driver board i have a perfect audio signal but at -in shows a sawtooth like waveform with the same frequency. I believe speaker out follows -in signal
I dont have sch. Please help and happy new year!

 

[Perry Babin]

Is this one of the clones with the fan between the driver board and the two inductors?

 

[nonprof]

Is this one of the clones with the fan between the driver board and the two inductors?

Yes perry! Thank u!!

 

[Perry Babin]

I don't have a diagram for this amp but I should have something close. Email me.
babin_perry@yahoo.com

The 6th pin from the 'RCA' end of the amp on the driver board should transition from near positive rail voltage to near ground after the mute delay. Is that happening in this amp?

 

[nonprof]

I don't have a diagram for this amp but I should have something close. Email me.
babin_perry@yahoo.com

The 6th pin from the 'RCA' end of the amp on the driver board should transition from near positive rail voltage to near ground after the mute delay. Is that happening in this amp?

Yes perry, It happens. Transition from +75 to gnd
.
Previous history of this amp, the + rail accidentally touch to heat sink through drain output transistor
It play for a minute then blow out the negative rail bulk caps. I replaced defective capacitors.

You got.mail.

 

[KriszXJR]

opti2000d schematic

 

[nonprof]

Thank you! Problem in the driver board got a coounterfeit part mpsa42, rreplaced it with 2n5501.

 

[nonprof]

After I replaced the 2 identical BJT driver of the driver board(MPSA42), the amp gives a good music for few seconds then started to hear weird sound, the power supply current start to fluctuates high and low and these transistor becomes very hot.

I'm thinking I bought a counterfeit transistors I used 2N5501 and KPSA42(replacement maybe) but no luck.

Any input?

 

[Perry Babin]

Did the output transistors fail?

 

[nonprof]

Did the output transistors fail?

No, still working. If I heard a whizz/pump sound and the pre driver transistor gets hot I turned it OFF. Powered it ON, sounds nice again after a few seconds, start to have a pump/whizz sound again. The power supply current cycled high and low.

 

[Perry Babin]

Q124 and Q125 operate at very high temperatures. That's normal.

If you shine a bright light behind the driver board, can you see dark ares in the board around Q124 and Q125?

 

[nonprof]

Sorry Perry, I'm not in my bench.

Q124 and Q125 are the MPSA42? the emitters are connected to GND.

Any possible problem that I can check? nice output but after a few seconds the amp whizz and sounds like beating.

 

[Perry Babin]

The collectors are connected to ground.

 

[nonprof]

Ok, i overlooked. Can you pls give the resistor value of r174?, r192, r175? Thanks perry!

If someone can provide the schematic of this driver board very much appreciated. Willing to trade, i have audison/eletromedia and jl sch.

 

[nonprof]

Thank you guys, perry.

I think i solved the over heating issue. I created small holes between legs.

 

[Perry Babin]

Were the holes drilled to remove conductive fiberglass material?

 

[nonprof]

Were the holes drilled to remove conductive fiberglass material?

yes, I created holes surrounding the transistors and in between legs. To decrease conductivity and increase air flow through transistors.

 

[Perry Babin]

To get better air flowing over the transistors, you install them with long leads so that they're nearer the fan.

 

[nonprof]

To get better air flowing over the transistors, you install them with long leads so that they're nearer the fan.

This is very clever idea. If I have time I'll do this.

Perry I have more question, Is it safe to used 2n5501? I don't have original MPSA42, instead I used the 2n series.

 

[Perry Babin]

I don't know. I've never used the 5501. From the specs, it appears that it would be OK but specs (for as much as I can understand them) don't tell everything.

One more thing... In some amps, they use better inductors that don't run hot. For those amps (clones like these), you can turn the fan around and blow it on the board directly.