Need some help

Hello:

I'm new here. I would really appreciate some help.
An acquaintance of mine, (who is quite good at DIY Audio) built me a DAC off of the Gigawork Upsampling DAC with CS4398 DAC, up-sampling chip, and R-Core transformer.

It was a work of art.

He made several modifications to the board - including: bypassing the second op-amp, upgrading the op-amps, making a different LPF, changing out some output capacitors from stock, etc. I can get you more detail if it would help. Needless to say he did most of the changes that were presented on this forum except for the transformer outputs. He stayed with the op amp design. We ended up using BB 627 single chips on a converter board - for stereo output. He also put a synchronization light on the front case along with a switch to change from Toslink, Coax, USB. The case was much bigger than needed but steel with standoffs. (Once again - all quality work)

This thing worked flawlessly on both my HTPC and as an upgrade to an older Sony ES CD player via Toslink. It sounded as good as it looked.

I mean this guy does outstanding work and it shows.

One morning I was playing a CD just fine, then I put a different CD in and all of a sudden no audio output. I checked everything - my amp, cables, etc. This didn't make sense. I didn't change anything. Just changed the CD. Now I know it was just coincidence.

So - I didn't panic and read that others had had bad up-sampling daughter boards. If that board fails, no audio output. I thought for sure that was the problem. So I removed the board and put the proper jumpers on all pins except for GND and 5V. Still no audio output.

I then thought that maybe the op-amp went bad. Changed it out with another stereo NS 49710 opamp that he had built for me. Still no change.

The problem is I can't get hold of the guy who built it for me. I can't return the board as it has been highly modified, and I can't figure out what happened to the audio outputs. I don't know what happened to the guy but I have been unable to get hold of him for over 6 weeks now.

I do know that the board still synchs to both a CD and USB signal. (The front synch light lights up when it get's an input) - so I figure the receiver chip is still working? The USB light on the board lights up when plugged into a live PC. I also see that all power lights on the board are lit - so I would assume it's not a bad R-Core transformer - although I haven't measured voltages to the input of the board.

I just don't know where to go next. I am hoping you guys could point me in the right direction. I am pretty handy with electronics - but am not an expert with DAC circuits by any stretch. My son is an EE and is coming home for Xmas and I have a good multimeter for testing.

Could this be a bad DAC chip itself? Should I be checking his output modifications? Did something else go out on this board? I don't see anything obvious - nothing looks burnt and there are no electrical smells of any kind. This just totally baffles me!

Any advice on what to test next would be greatly appreciated.

I hope I got to the right board - if not, I apologize as I am new to these forums.

Thank you in advance for any help you could provide me. I invested a lot in this project and hate to just throw it all away. I'd be willing to send any other information or details you may need in helping me troubleshoot this.

Once again, I would be grateful for any advice.
 
Sorry, wrong board/vendor. Even if someone is going to try their darnest to help, it would be really hard as you have mentioned that it is highly modified, and doing diagnostic over the forum is not going to be easy.

One suggestion I have is to send 60Hz signal to your DAC, and measure if there are any analog output at all. Since 60Hz signal is going to be easy for the multimeter to pick up (just set it to AC voltage), and you can see if there are any analog output and it there are, where in the chain did it broke.

Just out of curiosity, did you put the original CD back in when it first happened?
 
OK - now that I am on the right thread - sorry about that - I will give you an update.

I contacted Ian at Gigawork. (The vendor that sold the board to the DIYer who built this for me. Ian via e-mail suggested that I re-seat the DAC board and take off the upsampling board to see if it is defective. I took off the up-sampling board twice and jumpered it properly to no avail.

Stupid me - while I was pulling off the DAC board I bent two pins. While trying to straighten them out (carefully) I broke two pins off. Does anyone have a suggestion on how I can solder two pins back on? I can't find the broken pins. I have bought solid wire as small as 20 gauge but it is still too big to fit in the socket. I can't seem to find a wire this small to re-solder the broken pins.

I can't seem to communicate with this Ian Chinese guy. First he says he will send me a new DAC if I send him $35.00. I sent him payment via paypal - the next thing I know he is refunding me back. The guy has terrible customer service and does not seem to be interested in anything but selling new boards. You are lucky to get a response from him every two days. And when he does respond he makes no sense.

BUYER BEWARE that if you purchase one of these boards from him and have a problem you bill be on your own. He has NO interest in servicing you and only wants to sell new boards - where the quality is very suspect.

In the meantime - I am in desperate need of help. First - I would like to get the DAC chip back in - but don't know if or how I can get these two pins back on the socket. I'm sure someone here has done this before. I have pretty good soldering skills - but don't know the best way to get the two pins back on and in the socket.

The guy who built and modified the DAC will not respond to me. I feel totally screwed.

I'd be happy to send it to one of you and pay you if you would be willing to help me fix it. I have spent over $300 on this project and have nothing to show for it. It worked perfectly for the first couple of weeks but then just died one morning.

If someone would like to buy this from me for parts - please send me an e-mail at [email protected]. I'd be happy to work something out with you as I'm just trying to recover some of my loss here. The case alone is worth over $100.00.


I'd be in debt to anyone willing to help me.

I'm a stupid noob sucker for ever getting into this situation. :( I should have never ventured here and have learned a good lesson.
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Perhaps if you could post some pictures of the problem socket/pins etc. You talk of a DAC board and then a DAC chip.

All fault finding has to be logical... you can not guess. You say the thing failed while in use... so you need to check all the supplies for a start (and that means ALL) to all the IC's.

And with the greatest respect please remember you are asking for help on something that some one else built, and then modified, and now you have had a look and broken something.
That's not a good combination :)
 
Here are the pictures of the DAC chip where I broke a couple of pins. It is a CS4398 - the DAC s the Gigawork Upsampling DAC. I hope this helps.

Yes I broke the pins - but the DAC was not functional before I did this.
 

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OK - so I went down to Radio Shack and bought some solid core 24 gauge wire. Got out my trusty iron and got the pins back on. Put it in the machine and still the same symptoms. No audio output at all.

I used my multi-meter to check voltages on the input side of the R-Core. The R-Core is putting out proper output voltages. The DAC board lights all come on - (all 5 of them) So I'm assuming voltage is good to the board.

The board synchronizes to both Toslink and USB inputs. I have changed out the Opamps. All to no avail. I see no signs of anything burnt on the board.

I also did continuity checks from where the board outputs to the RCA output adapters. Everything checks out fine.

My thinking is it is either still a bad DAC chip or something on the LPF or output stage is not working.

I have offered to pay Ian for another DAC chip. He refuses to respond to me.

Does anyone know where I can purchase a CS4398 on an adapter board like is on this Giga Board? I'd like to try out another DAC chip to see if that is the problem. It seems unlikely to me that a DAC chip would just go bad - but I suppose it is possible.

If anyone has any other thoughts on how I could check this board I would be most appreciative.
 
I am entirely unable to help troubleshoot inside your box, but I have a question/suggestion: have you tried alternate sources and/or confirmed your source is good? You may have a bad CD player for example. If you have a known-good source, the next thing I would try is chasing the signal with an oscilloscope inside your suspected-failed box. Doing this over the internet is impossible or very nearly so, which is why even folks as helpful as are found here will not even try.
 
why didnt you take the opportunity to post pics of the whole thing when you took the photos of the dac chip assembly above? we can only imagine what it looks like and what the problem might be. even with pics however, this will be very difficult, all lights on, but al chanels of music stopping on a dac with single opamps pretty much rules out the opamps, the dac could be screwed and you are right to get a new one. I dont own this dac, hopefully someone else can help YOU to fix the problem, but you have to post pics, as you say its highly modified
 
I am familiar with this dac board. Unplug your opamps and check for an audio output at the 4398 output pins. The output from the chip is very robust, over 6V P-P. If you are operating without the upsampling, make sure you have the dip switches in the correct positions on the 4398 board. From memory, I believe they should be up,dn,up,up with the upsampler pulled.
Is the output relay picking up when you get signal lock? If not, the problem is related to the 8416 receiver chip. If everything is working but no sound, a scope would be necessary to look at the I2S, or else replace both daughter boards.
 
Thanks for your replies and sorry for the late response.

am uploading a picture of the board with the modifications circled in different colors. I am also attaching the text of the modifications he did in his own words. See below:

Let me try an go through the few mods I did. Attached is a picture of the board with colored boxes around the different areas where I made changes..... the picture should be attached

----------------------------------------------------------------------

Green - LPF: Changed the low pass filter components to fix a high-end roll-off problem with the original values. Supply decoupling capacitors were placed under the board for op-amp stability and supply noise reduction.

Yellow - Removed and bypassed the electrolytic DC blocking caps.

Purple - Removed the "buffer" op-amp and all of its components. The only components after the LPF op-amp now are just 100R output resistors.

Red - Replaced all of the sketchy looking capacitors on the outputs of the regulators with low ESR Panasonic FC.

Blue - Added a PULSE transformer to the COAX digital input.

White - Reconfigured the muting relay to shunt the output signal to ground when no digital signal is present. The original configuration passed the signal through the relay contacts when active (audiophile kryptonite), and then disconnected the output and left the amp inputs floating when "muting" (just plain wrong).

----------------------------------------------------------------------

I did unplug the up sampling board - put jumpers on everything except 5v and Gnd - (I did not realize that you needed to change the dip switches) I tried as you suggested with the upsampling board out and the dip switches changed but still no audio output.

I will try and measure the voltage on the DAC chip with the op amp out as you suggested.

How do I tell if the relay is working? I know the guy who built this changed the relay on the board as you can see from his modifications. Could this be the issue?

He put a synch light on the front of the case - it turns on whenever there is a signal going to it. (Both Toslink and USB) The USB light also goes on when the USB cable is put in.

Once again - I am grateful for your help and am sorry if I caused confusion by posting on the wrong boards, etc. I'm new at this.

The Chinese guy - Ian - (who he bought this board from -Gigawork) refuses to communicate with or help me. I'm hoping I don't need any parts as I won't be able to get them from him.

Perhaps one of you could try and get it from him, if needed, and I could pay you via paypal?

Let me know.
 

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wakibaki

Banned
2008-01-08 11:51 pm
OK, your picture is tiny when clicked to expand.

My thinking is it is either still a bad DAC chip or something on the LPF or output stage is not working.

I have offered to pay Ian for another DAC chip. He refuses to respond to me.

Does anyone know where I can purchase a CS4398 on an adapter board like is on this Giga Board? I'd like to try out another DAC chip to see if that is the problem. It seems unlikely to me that a DAC chip would just go bad - but I suppose it is possible.

The chip itself is available from Digikey for $12.60 in the US and probably from other suppliers if you feel inclined to try replacing it. This is an awkward job that can go wrong, but it is far from impossible.

Ideally you would use a hot air desoldering tool to remove the original chip, or a decorating-type hot air gun (e.g. De Walt) if circumstances permitted, but in this case there is too much risk of the other components or pins detaching from the board.

The chip can be removed by cutting through the pins one-by-one with a small sharp blade (surgical scalpel or hobby knife) with a chiselling motion. Do not try to saw through the pin. Ideally you would do this with the aid of a magnifier, I like to use a jeweller's loupe. Place the tip of the blade on the pin and bear down hard on it with one of the fingers of your other hand. Cut through the pins as close as possible to the IC body, so that the blade is arrested by contacting the little ledge that is usually present on these SMT chips and prevented from striking the board and damaging it. You can feel a distinct 'click' when the blade cuts through the pin. Work slowly and deliberately and do not try to cut more than one pin at a time. The pressure required on the tool is quite considerable.

When you have cut all the pins you should be able to remove the chip body.

Working quickly with a reasonably hot iron, gather up and remove all the cut pins from the board, they should all just stick to the iron due to the surface tension of the remaining solder when it melts. Clean the pads on the board by trapping a piece of solder wick against them with the tip of the iron. Be gentle and work quickly as there is a risk of lifting a pad from the board while it is hot. Allow the board to cool.

To attach the new chip, position it on the pads and secure one of the corner pins with a minimal quantity of solder. You can 'steer' the chip around to get it in exactly the right position while the solder is molten. Once it is in the right position secure the opposite corner, and then the remaining corners. Once the corners are secured, quickly flood all the pins on first one side with solder, then the other side. Use an excess of solder and drag the bead down the row of pins without consideration of the bridges which will form between the pins, just make sure that all the pins have a good joint to their pad.. Once this is done you can remove the excess solder and bridges with a solder sucker or solder wick.

Good luck.

w
 
The problem is I can't get hold of the guy who built it for me. I can't return the board as it has been highly modified, and I can't figure out what happened to the audio outputs. I don't know what happened to the guy but I have been unable to get hold of him for over 6 weeks now.

The mention of the figure of $300 makes me wonder if you're speaking of this guy? If so, perhaps his disappearance is easily explained.