second aleph3 not working!

[BDP]

positive rail: 29.99V

negative rail: 23.02V

Seems a little too low on the negative rail. Shouldnt they be close to the same? Is that a typo error.

vAC ripple: 0.049V

The ripple looks good. Is that for the positive and negative rail?

BDP

 

[Brian Donaldson]

If the rail voltages are as typed, you may have a weak rectifier putting noise on neg rail?

 

[cowanrg]

oh sorry, the positive rail was 22.99, not 29.99. they are very close.

 

[cowanrg]

that was just the ripple on the positive rail, its 0.047v on the negative.

it seems like all these measurements are pretty much dead on, except for a few minor ones, but that could be because of my lower rail voltage.

 

[cowanrg]

so, after deciding that my measurements are satisfactory, i can only assume that the amp's arrangement and layout is the cause of the buzz/hum.

i am still not sure why i cant get much power out of it, but maybe that's because im not giving a strong enough signal either. in any event, the insides did need to be redone.

so i have gut the amp down to almost nothing:

http://www.cowanrg.mesanetworks.net/projects/images/aleph3/test/DSCF0016.JPG

i took the transformer, rectifiers and my "switch" (a little relay and thermistor for 12v trigger turn-on), and put them on a plate of aluminum, and then further shielded it with a sheet of steel:

http://www.cowanrg.mesanetworks.net/projects/images/aleph3/test/DSCF0017.JPG

http://www.cowanrg.mesanetworks.net/projects/images/aleph3/test/DSCF0018.JPG

then i tossed the whole thing in the the amp, hoping that the power supply is now completely isolated from the rest of the amp:

http://www.cowanrg.mesanetworks.net/projects/images/aleph3/test/DSCF0020.JPG

http://www.cowanrg.mesanetworks.net/projects/images/aleph3/test/DSCF0019.JPG

(the big holes on the sides on the last picture are for the wires for the FETS that sit further up.)

sigh, i hope this works. if not, im at a loss, and this project will just get scrapped (or just sit on a shelf for an undetermined amount of time).

 

[cowanrg]

at this point, i just think im replying to myself, but oh well...

it appears that the rebuilt worked. im not overly excited just yet, as i need to really test it, because ive been fooled before. ive though its worked many times.

I added "wings" to the plate that the xformer sets on that shields the FETS. I thought that if they were in close proximity i might have issues, so i just did it in case.

i havent hooked it up to my main system yet, but all seems to be functioning right. it has more power for some odd reason (its right at its "stated" power, where it was only like 12 watts before). and there is a slight hiss from the speakers, but only audible with your EAR on the cone. my main speakers are much less sensitive, so that might even get lost.

all in all, i think this is it. the rebuild looks a lot cleaner and simpler. it looks much more commercial now.

if you want to see some more, you can goto my site, ive added all the pictures i have.

 

[Taco]

Very nice amplifier, it looks to me it's now finished .

 

[cowanrg]

well, i have to fully wire up the back panel (i have a knob that controls the brightness of the led), and a switch that gives it normal bias, and full bias.

but other than that, its DONE! of course i need to modify my second chassis too...

 

[eLarson]

Nice work!