Another amp

[li_gangyi]

WOW~! Pretty Nice work on your PCBs there...wondering if you can supply me a set...been watching this tread with great interest...

 

[darkm4n]

Of course !

Yes , of course i can supply you with a set , there ar homemade on 0.4 cooper sheet.

If you want some , i'am from Romania , Bucharest .

About the price .. its under 20 $ ...

If you give me your adress , an how you want me to ship them i will make 2 for u!

Mihai.

 

[darkm4n]

Need help ..

Hi ,

I need some schemes about an good preamp for this amplifier and a good crossover activ network .

If someone can help me i will be very happ y 🙂

Thx , Bye all

 

[darkm4n]

Soft start ?

Is there neccesary a SOFT START circuit for this amp ?

 

[darkm4n]

PCB for DC PROTECTION

Hi again ..

I just finished the DC protection PCB , and i share it here ... maybe someone will be interested in this design or as a inspiration .

Soon i will finish the amplifier new PCB , Power supply with Soft ON PCB and schematic and a case design for this beautiful amp .

 

[darkm4n]

Capacitor

i didn't find 100pF CAPACITORS

 

[darkm4n]

Help

is there any problem if , instad of 200 V i will put 100 pF at 100 V ? i think it is .......

Thanks

 

[JOE DIRT®]

100 volt are fine

 

[darkm4n]

Substitute for TIP121

Hi ,

I can't find the TIP121 at my electronic dealer .. ( from DC protection ) dose anyone know a substitute for this transistor ?

I searched everywhere for it ...

Thank's
Mihai🙁

 

[darkm4n]

Hi again

Some one know what type of relay is that on the DC protection ?? How many V ?

 

[darkm4n]

GOD !!!!

I used the old PCB for this amp , the one on the site , you could tell me what modification's were made in september 2002 on that schematic ?

Thanks.

 

[darkm4n]

Really need help !!!

I complet my amp and my PSU ...
I have a question :

On the Out of the PSU i have 105 V instad of 55 ( at no load ) , is this normal ???
I user a 2 x 38 V Toroidal at 500 VA , 50 AMP 250 Bridge and 4 x 4700 uF 63 V .

 

[JOE DIRT®]

I think your measuring across the rails and not rail to ground

 

[darkm4n]

Yeah...

I think your right . But how i have to connect the amp ?
Using the -55 V and +55 V connectors on the PSU scheme ? Or
+55 with ground and the other 55 with ground ?

As i meseaure on the capacitors output ( i use 4 x 4700 uF )
i have 60 V ( Aprox ) on a pair of 2 and 110 on a pair of 4 .

So .. i think i have to connect the amp's on a pair on 2 eatch one .

Last night i tested the amp on that 110 V and nothing brake .. just no sound in the speaker ..

Thank's

 

[li_gangyi]

Connect your -55V on ur PSU to the one on the Power Amp PCB...+55V from PSU to the +55V on the PCB...and then hook up the ground properly...should do it now...fire it up and see if anything smokes...none right?? measure the speaker outputs for any DC...none also?? Hook up a 10Ohm resistor on the speaker outputs...measure again...see if the resistor gets hot when you pump in a signal...the resistor should be around 20W...be careful with the volume control...leave it turned down...not too loud...after leaving it on for a few minutes and confirming that it is absouletly ok...hook up your speakers and enjoy...after that...if you haven placed it in an enclousure already...do so now...to prevent itchy fingers...be careful around the caps and PSU ok...110VDC is nothing to play around...

 

[carlmart]

Re: Yeah...

I think your right . But how i have to connect the amp ?
Using the -55 V and +55 V connectors on the PSU scheme ? Or
+55 with ground and the other 55 with ground ?

As i meseaure on the capacitors output ( i use 4 x 4700 uF )
i have 60 V ( Aprox ) on a pair of 2 and 110 on a pair of 4 .

So .. i think i have to connect the amp's on a pair on 2 eatch one .

Last night i tested the amp on that 110 V and nothing brake .. just no sound in the speaker ..

You certainly need a ground reference to get the V+ and V- voltages.

But from your comments I would risk you are not aware there's something called "star grounding". This grounding scheme demands you separate your grounds (clean and dirty) on your pcb and only join them at a point called a star.

If you don't do that you will have more noise and hum.

Do a search for star grounding on this site, make a diagram on how you should wire things and try it on your amp. Do not connect your speaker until your output offset is just a few millivolts.


Carlos

 

[darkm4n]

It woked !!!

I risk and it work . I didn't meseaure anything , just connect the ground and the music begin .. !! I didin't measure because i was affraid about something that could blow in my face there 🙂) How know ..

I have to thank to Marcus for this great amp , i complet it abut 10 minutes ago and work very very good !!!

I really recomand this amp .. if you think you can't do it .. try .. just like me ...

I will put some photos soon and some specs ..

Bye . Mihai .

 

[darkm4n]

Bias

Where should i set the bias pot ?? At what value ? In ohm .

Thanks

 

[darkm4n]

URGENT ANSWER ABOUT DISTORSION !

Hi ,

I changed some transistors on the board , all the capacitors , and the distorsion it is still there ...

I notice that the board with the distorsion in getting hotter ( not the output transitors , the MJ15030 and MJ15031 , MJE 340 - bias ) that the board with cristal sound witch is allmost cold ...

The bias is set at maximum resistance on all the board's . I used the same tipe of output transistors , the same resistor's the same all .. it's not diference between the board's ..

The distorsion it's on the 80 - 120 HZ band ...

And of course .. it's not normaly that one board it's getting very hot .. and the other ( no distorsion .. ) no even hot ...
It's getting hot in 2 Minutes since i open the amp .. at half volume .

The bias is set at 850 Ohm on all the boards .

Maybe a resistor it's damaged ? Maybe a diode ? Maybe output transistors ?

Thank's ! Mihai .

 

[Drafance007]

m 250

Did anyone try to push m 250 amp on 2 ohm load ? maybe without short-circuit protection ? I built the amp but dont have that bih transformer!