Back on the forum, now with a troubleshoot question, i am building a stereo aleph j amp, as a psu i use the diyaudio universal v3 psu with a 500va transformer. Just a minute ago i fired up the psu and got 25v on the outputs(leds on the psu are shining). Next i connected both aleph boards to the psu (i set r27 to 64k when soldering the boards) and the leds are shining but i cannot adjust the dc offset, as in nothing happens when i turn the trimmer. Any advice?
Some intel on the building process:
- checked every resistor before putting it on the board.
- double checked the bc560 and bc550 if soldered correctly.
- i use a 1 turn pot on r7
Btw, i get aprox 25 volts on the outputs.
Some intel on the building process:
- checked every resistor before putting it on the board.
- double checked the bc560 and bc550 if soldered correctly.
- i use a 1 turn pot on r7
Btw, i get aprox 25 volts on the outputs.
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Silmics are hard to beat! Bypass them with Vishay MKP1837's and throw the WIMA's in the trash! 😛 To me, WIMA are very veiled.
I've also had great success with a Mundorf Gold Evo in the C1 position and of course another opportunity to ditch another WIMA is always welcome.
Can you tell I am biased? 😀
That's a wiring error or blown transistor. The trimmer can move the DC offset approx. 1-2 volts, not 25.
Please post well-lit, in focus photos of your build.
@6l6, thanks for looking into it. have uploaded the photos to my OneDrive account, would you be so kind to have a looksee:
http://1drv.ms/1e3D9zf
quick guide for the cable colours:
yellow = ground cabling
white = V- cabling
green and black = V+ cabling
btw, both channels give aprox 25v dc offset.
http://1drv.ms/1e3D9zf
quick guide for the cable colours:
yellow = ground cabling
white = V- cabling
green and black = V+ cabling
btw, both channels give aprox 25v dc offset.
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did you confirm that you're having both (+/-) rails on channel pcbs ?
what is origin of input JFets ?
what is origin of input JFets ?
I purchased the JFets from spencer.
I think I did, I put my meter on the -v and ground and on the +v and ground, both gave 25v.
I think I did, I put my meter on the -v and ground and on the +v and ground, both gave 25v.
In your photo's it seems you have some metal squares to distribute the mounting pressure on your mosfets. Are you sure these aren't touching and shorting the feet of your mosfets? This could also result in rails voltage on the output in think.
@Mfly, thanks for thinking along with the troubleshooting but i made sure these aren't thouching the fets.
Then you are in the realm of technical circuit troubleshooting where Zen Mod is of far greater help than I could ever be. Good luck! I hope you locate the issue soon.
dehaai
first we need that boys responsible for pcb design confirm from pics that you have properly executed several positions , where exist various choices for parts (jumpers , pot or resistor etc.)
in meantime , you can triple check values and positioning of parts
first we need that boys responsible for pcb design confirm from pics that you have properly executed several positions , where exist various choices for parts (jumpers , pot or resistor etc.)
in meantime , you can triple check values and positioning of parts
I noticed that on pic 5, 6 and 8, Q3 looks like it positioned in reverse. The ZTX450 is C,B,E with the round part of the body facing you. If the silkscreen is correct it should be reversed. But I don't know if there exist ZTX450's with other pinouts...
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that was one of my first thoughts also (that the transistors where reversed), i use a bc550 on this spot and the bc550 has the round part on the opposite side in comparison with the ztx450.
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guys, I found one problem, i placed a bc550 where a bc560 should be...
gonna repair this tonight, see if this solves the problem.
gonna repair this tonight, see if this solves the problem.
6l6, yesterday evening i managed to rearange the bc550 and bc560 on one channel, after that i could change the dc offset with the trimmer. I have one question though. when i change dc offset with the trimmer it can go from -2v to +1.5 volt, is this normal? i thought when you push down the trimmer that it goes to 0 but not any further.
thanks Zen Mod, i will rearange the other board tonight and test again, when this is fixed i will connect the mezmerize b1 board and my new amp can burn 🙂. im so qurious how it will sound 😀
Fantastic that you found the problem!
Make sure everything is tidy, set 0.0v offset (or as close as you can) and have a listen!
Enjoy the music. 🙂
Make sure everything is tidy, set 0.0v offset (or as close as you can) and have a listen!
Enjoy the music. 🙂