QRV-04 failure

[savinalexandru]

Hi!

I have a problem with my newly built QRV-04. I will try to be as accurate as I can. My skills in electronics are somehow limited.

I powered up the QRV-04, and plug it to my laptop and feed my headphones.
1 channel hear really-really nice... 2nd was hearing pour, with lower volume and some color and reflexes!?!?
I change the wires and the problem went on the other ear, so no headphone problem.

I measured the voltages:
21V after rectification on both rails
13.75V after stabilization on both rails

Only thing I think I have done wrong is to overheat the IC's during the soldering but I don't know if AD8610 or the BUF634 is broken.

I have no shorts, I've cleaned the PCB with alcohol ... all parts seem good soldered.


Wait for your replies!
Kind regards,
Alex.

[peranders]

Hi!

It's hard to destroy an IC by soldering.

Which channel is working?

Check how the opamp is turned? Pin 1 in the right spot?

Have you mixed up caps with resistors in some location?

Can you take a very good close up photo of the faulty channel?

[savinalexandru]

Still have no picture... But i will do it when i have the time.

No shorts, no caps mixed with res, all seems ok.

I took a 1khz signal ( youtube :) ) and fed the amp.
I don t know how i touch the output with the probe but i shorted with the  v+ pin.... And this was on the good channel. It gave some 0.7v reading before short....0 after. No sound at all...just a big humm
The bad one gave almost zero reading....so it s clear that i ve busted both of ad8610.(pin 1 is oriented ok for both Op amp)  How can i check the bufs? I dont want to change the ad and then figure is the buf broken on the other channel.

[peranders]

Do you still have smooth 12V DC voltage? Which frequency has the hum? 50 or 100 Hz?

[savinalexandru]

heaveno!

First, wish you a Happy New Year !
Regarding the problem, I don't have smooth voltage. V+ is 12.74V and V- is 11.8V.
I remove the AD8610 and shunt the pin 3 with pin 6.
Same problem! :(
So definitely there is a problem with BUF.
What is remarkable, is when I power off volume becomes really loud and the 2nd channel that is not working (humming) si hearing for a couple of seconds till fades off as the QRV remain without power.

So now I really don't know what to do.

Alex.

[peranders]

I'll suggest that you replace the BUF's. Before you solder new BUF's and opamps make sure that the regulators work.

[savinalexandru]

Hi P-A!

OK!

Do you have some hint soldering-unsoldering the BUFs? I think there something went wrong!

Kind rgs,
Alex.

[peranders]

Cut all pins of the BUF's. Then heat up the tab and remove the chip.

[savinalexandru]

Hi P-A,
Back again! Don't quit till I make this amp work!
So I've attached a picture with all voltages. After I removed the BUFs I've tested the output directly on the AD8610, and even very low output something was wrong on one channel so I've decided to remove them too.
The voltage schematics are with BUFs and ADs removed.

These days I will resolder the new ICs again!

Kind rgs,
Alex.