Please help with AKSA 100N testing

labusas · « **on:** 24 Jun 2004, 05:11 pm »

Ok, I hope somebody can lend a helping hand. First off all my skills are very amateur but I've got to the initial bias testing. Got a reading of 9.3V at r25. That's too high, then as it says in troubleshooting step 1, checked output+earth and got a 0.1 reading, should be 0.05. I wasn't sure if it's close enought or not, but I removed r12b as it says in the instructions. That should have brought voltage back to 2v but the opposite happened -both r25 and r26 burned out in a second. P1 was cranked CCW more that 60 times with no indication of the end reached though.
What am I doing wrong? I did triple checked my layout with the overlay sheet. The only thing I'm not sure about is d1. I'm not sure if it should be installed in Nirvana, because I don't have that part of the instructions.
Whithout it installed I'm getting 0 reading at r25.
Thanks in advance

labusas · « **Reply #1 on:** 24 Jun 2004, 07:11 pm »

Yes, two hours later and a lot of reading on this site as well as manual and I've got it working.
I replaced the burned out r25 and r26, installed highter 215k resistor in r12b and fired it up. It came back with stable 3v.
r26 was at the same. Followed the instructions further and got -26mV at output/earth. R5 and R6 with ground showed 29.5. Udjusted final bios to 55 at TP1 and TP2 was 55.9. And the final reading was for output and earth again at 25mV.

It sounds like everything is within the range.
I can't test further today, because I still got no volume control. My pot is in the mail. By the way can anybody explain the pot connection in Aksa 100 in simple terms? I just want to be 100% sure.

labusas · « **Reply #2 on:** 25 Jun 2004, 12:28 pm »

Couldn't wait for the Nibble pot to arrive in the mail. I went out and bought a cheap 10k pot for now. I hooked everything up and the magic began. I can't believe I did it with no previous experience!

Thanks to Hugh for his great product and his even greater support! I wouldn't have made it without you.

PSP · « **Reply #3 on:** 25 Jun 2004, 02:56 pm »

labusas,
Excellent!!! This is what DIY is all about. Good for you! I wish there was a "DIYer of the Year" award... with fame, Fabulous Prizes, and appearances with supermodels... instead you will have to settle for the satisfaction that you built this thing all by yourself, it works, and sounds incredible.

enjoy!
Peter

Carlman · « **Reply #4 on:** 25 Jun 2004, 03:13 pm »

As one who observed the requirements of the project and then quickly realized a need to hire Hugh to do the tricky bits, I salute you, sir!

Congrats on getting your amp together. When I installed the transformers and tested the sound in my garage with a pair of old Energy monitors and a CD walkman as a CD/preamp, I was amazed at the great sound quality.

So enamored was I, I never got around to really finishing it. It looked pretty good but I never went back and really fixed things the way I wanted them. So, be sure to get your good pot in there, regardless of how good your new amp sounds with the cheap pot.

Congrats again!

AKSA · « **Reply #5 on:** 25 Jun 2004, 11:26 pm »

Narius,

My congratulations..... you've done very well.

Removing R12B will pull the bias back to virtually zero, so I'm not quite sure why it blew R25/26. Odd. However, with 220R (that's ohms, not K!) it will be fine, and you remind me to include a 220R in all kits in the future so others with this problem can make the amendment easily.

Having only a 100R trimmer in the bias limits range of adjustment, which on a bipolar device output stage is good. But the downside is occasional adjustment of R12B to accommodate correct setting. There are no less than five devices controlling the output stage bias, and since tolerances on semiconductors are broad, you can't always tell what's needed.

Cheers,

Hugh