500W PA amplifier with Limiter

[jalou1995]

I am using low power transformer , could that be the reason.
I have checked the tracks continuity, Its fine.

whats the voltage you used?

 

[viki_v2]

i did it, i checked each and every pin for shorts and cold solders, there were 2 shorts at mje340 and 15032, i cleared them, still the problem persists.

 

[viki_v2]

whats the voltage you used?

24-0-24 3 amperes, after rectification it is 37-0-37.

 

[Josip_Del]

Maybe fake, some transistors?

 

[viki_v2]

Maybe fake, some transistors?

not at all, all are original toshiba trannies.

 

[aman khalsa]

post some more pics bro....

 

[viki_v2]

post some more pics bro....

Check the pics and guide.

 

[yosie48f]

it is real 500w rms? can anybody tell me?

 

[irvynejay]

Grounding

I can't see input ground to PSU did you follow this?

 

[electra_ina]

Hi..Viki.. I see your B500..that original resistor 47K (red code), but applied 4K7..is wrong..this picture:

 

[viki_v2]

Check the pics and guide.

The sound is very low and distorted.
The resistor 0r22/5w in front of 2sa1943 on psu board got burnt .
My psu 24-0-24 before rectification, after rectification 37-0-37.

 

[viki_v2]

I can't see input ground to PSU did you follow this?

Yes i followed the diagram. connected the psu gnd , input gnd and out gnd at a common point on gnd next to out

 

[viki_v2]

voltage on negative terminal drops to 20v, after connection to b500.
positive voltage is proper at 37v.

 

[aman khalsa]

call me bro...09872589611

 

[mihailo]

Hi Apex. i have a problem with your amplifier.
It all looks ok when connect him, and play song. But when volume reachs half, speaker starts broming(brrrrrrrr) very loudly. I turn off amplifier, reduce volume and and turn again on, and all looks again ok. Where is the problem? Please help me!!!!!!!

 

[AndrewT]

could it be Low Frequency instability of the PSU to amplifier interaction? Used to be known as "motorboating" in valve amplifiers, because that is what it sounded like.

 

[irvynejay]

voltage on negative terminal drops to 20v, after connection to b500.
positive voltage is proper at 37v.

did you test MJE340/350 and 2n5551,5401 unmount it on the pcb then test it with multimeter

 

[viki_v2]

I tested them, seem to be ok.
I changed 5401 near -90v . The problem of voltage drop is solved. Equal voltages on both terminals.
Psu is also stable and fine no burning , no heating of any parts.
Still no sound.
No current on out.

 

[aman khalsa]

U use 33E or E33 for emitter?

 

[AndrewT]

U use 33E or E33 for emitter?

I think you mean 33E = 33r = 33ohm resistor.
If that is the case, then E33=0r33 = zero point three three ohm resistor.

Do not drop the leading zero. It is important to accurate transfer of information.