Tried new things on sysasim 5_3 amp

[space2000]

hi, here is the sysasim design and i made change on only power transistor with 2sc2922 and 2sa1216. i dont know is there need to change resistor too. need help. i had power the amp, it works nice but only the power transistor gets too hot. how can i use this transistor on this board?

thank you

 

[MJL21193]

Hi,
It could be oscillating. Do you have a scope?

 

[space2000]

thanks

thanks , i don't have anu osiloscop to check. is there any way i can use it?

thank you.

 

[MJL21193]

Did you build it exactly like the schematic? Did you include the output Zobel (R4 and C18)?

You might want to remove C14 and see if the (possible) oscillation stops.

 

[space2000]

very nice sound

yes, now it's works. no more getting too hot. very nice sound with 2sc2922. i loved it.

i didn't change anythings at all. i found c18 was wrong number now i just corrected it, thats all. thanks lots.


i found 2sc2922 sound quality is more btr then 2sc5200.

thank you.

 

[AndrewT]

what value of C18 caused the oscillation?

 

[space2000]

vlu wrong

hi, the vlu was 4.7nf but it should b 47nf

now the question is, power supply should b 36v. my transformer is 56 volt dc. it functioning well..no abnml heat at all. do you think 56v should b ok or should go down to 36v? i am not good in electronics.

thank you.

 

[jaycee]

With 56v power supplies you will eventually fry the 2n5401/2n5551 transistors used in the 2nd stage of the amplifier, and the MPSA18 transistors at the input.

 

[routhun]

2n5401/5551 will be fine only mpsa18s get fried, but they can also be replaced with high voltage replacements

routhun

 

[space2000]

replacement

i am not using mpsa18s, now using bc547c. do you think its ok?

thank you.

 

[space2000]

replacement of 547

hi, can i replace bc546 insted of bc547?

i know bc546 is more higher voltage.

thank you.

 

[routhun]

If BC547 works, 546 may be fine, but look at the following thread where AAK modified Symasym to work at +/-50V. Few had suggestions on replacing MPSA18s with matched high beta 2n5551s and some other expensive MPSA devices with higher voltage ratings. Key is high voltage (atleast 120v Vceo), high beta and closely matched devices ofcourse low noise too.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=99739&perpage=25&highlight=&pagenumber=1

Thanks,
routhun