[tomb]

Quote:

Originally Posted by qusp /img/forum/go_quote.gif again sorry for the noob question. when reading the schematic am I to assume that + will always be on the left when oriented the same way as the lettering indicates ie. with the output caps and everything that IS polar. so when oriented on the same way as the text for C7 or whatever the positive lead will be on the left as a rule??

NO. All I said was, Quote:

"BTW, in the layout pic below - "+" is at left for the LED."

That didn't say anything about any other part on the board. There have been some posts about the missing "+" sign in the silkscreen for the LED, so I clarified that omission, nothing more.

Quote:

ok i'm going to sleep its 4am and i've got a big bantam day tomorrow will check back in the morning befoer I have my jug'o'coffee and get going on it. also is there any booze that I can substitute for pure alcohol for cleaning the PCB after i'm finished?? ie vodka one for me one for the bantam

Remember that C16 goes on the R8 pads while you're drinking that vodka.

 

[Hayduke]

Quote:

Originally Posted by qusp /img/forum/go_quote.gif also is there any booze that I can substitute for pure alcohol for cleaning the PCB after i'm finished?? ie vodka one for me one for the bantam

Why would you want to share?

My booze is for ME! Let the PCB get it's own damn booze. If it's getting drunk, it better not start sluring the lyrics in my music

just in case you aren't entirely kidding...
You use a different kind of alcohol to clean the flux off

 

[qusp]

yeah isopropyl right??

Quote:

My booze is for ME! Let the PCB get it's own damn booze. If it's getting drunk, it better not start sluring the lyrics in my music

LOL and stop playing those dodgy old love balads

 

[JamesL]

isopropyl's the easiest to get.
liquor would work to get the flux off, but it'll also leave other kind of crap on your board.

 

[qusp]

Quote:

Originally Posted by JamesL /img/forum/go_quote.gif isopropyl's the easiest to get. liquor would work to get the flux off, but it'll also leave other kind of crap on your board.

yeah; I figured as much, I was actually joking, but also interested to see if it could be used in a pinch. bourbon and coke would be bad!! sticky and would smell like a bad night out after a day or two

 

[bperboy]

Tomb, current's still going to be flowing thru the caps if I play music but don't hook up another amp further down the chain, correct? Like, I can plug in the DAC, set my iTunes to play, but not hook it into anything, and burn-in will occur? I just didn't bring any of my amps home on break, and I wanted a head-start for when I get back.

 

[JamesL]

current won't flow without a circuit.
Theres no circuit if nothing's plugged into a dac.

 

[cetoole]

Quote:

Originally Posted by qusp /img/forum/go_quote.gif yeah; I figured as much, I was actually joking, but also interested to see if it could be used in a pinch. bourbon and coke would be bad!! sticky and would smell like a bad night out after a day or two

In a pinch, yeah, booze can work. I have used rum to clean a friend's CPU and heatsink before, as we didnt have anything else available. Less ideal when cleaning a PCB, because there is other stuff in the mix that wont evaporate and can cause shorts, or simply increased capacitance in bad areas. Everclear would be just fine though. Acetone works GREAT (but not for drinking).

http://img.photobucket.com/albums/v3...e/heatsink.jpg

Bperboy, I wouldnt worry about trying to force burn in. Just wait until you get back, then listen to some good tunes. Besides, this is a perfect excuse to build another amp!

 

[bperboy]

Quote:

Originally Posted by cetoole /img/forum/go_quote.gif Bperboy, I wouldnt worry about trying to force burn in. Just wait until you get back, then listen to some good tunes. Besides, this is a perfect excuse to build another amp!

Hah, i've already got two Minimaxes in a cardboard box... haven't tried tunes thru them yet, but I'm bringing home some prewired RCAs to hook up... should be quite excellent! Plus I'll have another Bantam to build! (need a source to give my dad for xmas to go along with the starving student I built him!)

 

[qusp]

ahhhh!!!! step 1 and i'm screwed I think. I had the dac pretty much done with point to point. and then I remembered the post on the beezar bantam thread that recommended using the tinned solder wick with some flux in it too to run the tip down the pins and clean it up and make sure everything is soldered at the same time. well I heated the iron up nice and hot prepared the braid and started my way down. of course while you are doing this you cant see whats happening underneath. and when I had finished my way down I noticed that all the ****in traces were crooked

so the het and force needed to get a good bit of squeeking action happening obviously unglued the trace from the pcb.. so looks like i'm oredring another PCB and a dac to make sure. just in case I cant get the dac off without damaging it. I spent a while trying to fix it and its hard to tell whether the bits that snapped off while the pins were still soldered down were just the bits protruding past the joint or whether the whole trace somehow pulled out from underneath also I cant be sure without removing the dac whether some of the traces have become so misaligned that they are now shorting against the one next to it. I had no idea the trace was held in place so tenuously or I would never have even attempted that method especially as you cant really see whats going on. and the 3 pins just above the 2 bottom left unused ones. the 3 that dont seem to be connected to any trace on the board: what are they?? the ones opposite audio ground they are the main problem because they actually broke off (not the pins the trace) when I tried to push them back. alhough i'm pretty sure those pins are still connected . its night time here and I dont think I can get enough light to get you a decent pic. i'll do in the morning. with a macro lense and flash I could get it but because I would heve to get so close the lense would cast a shadow over the dac.

anyway that really pisses me off. had it all fairly well lined up with only a couple of suspect areas where I thought I may have had to realign the pins by pushing them that way and down at the same time with the iron. but nothing drastic. and i'm unwilling to just push ahead and risk doing it all only to find out the one of the traces is gone and then have to desolder everything again. oh well i'll post in the morning and see what you think. but i'm afraid I wont be able to show the extent of the movement of the trace on camera

 

[vattern]

An easy way of desoldering the dac is as follows :

Turn the board upside down, and heat the back of the board with a heatgun . Once the solder starts melting, give it a sharp tap, the dac tends to fall of , assisted by gravity.

 

[qusp]

well I got it off. here was a pic before and now I look at it it really would've been fine with just a dry tip on a couple of the pins certainly didn't need the wick so much oh well the joy after afterthought

this is the pcb now notice the three that I mentioned earlier that I couldn't see any trace for the pads to actually go to whats the go with them?? please dont tell me they aren't needed because they were the only problem before I did that wonderful heatgun trick thankyou for that BTW (now that I can see what was going on under there there wasn't any shorts after all doh). but one pin didn't come off properly and the trace came with it. other than that there wasn't any shors like a thought.


so anyway below is a couple of ideas that I have:

provided those three pads I have circled in white on the left aren't connected to anything, like it seems. if they are vital then i'm screwed BUT...

can I solder the pin related to the missing trace to the bit of trace on the right next to C5 (the left output pin it seems) I have exposed with my scalpel on the right?? or could I use some cardas tonearm wire to connect directly to the left output cap after bending the pin up ever so gently and soldering direct to it?? the one underneath that is actually still there and intact its just bent, so I could solder to that or to the pad on C5?? correct??.

or should I just order another PCB and wait the extra week. and pay the extra shipping. the dac came off perfectly so it'll be fine

 

[tomb]

There are several pins on the DAC that aren't used. You should study the schematic - it has all of your answers. Pins 10, 11, and 12 are not connected to anything. Pins 9, 13, 14, 15, and 16 are only tied to ground.

I hate to say this, but the board doesn't look too good in that pic. Yes, the traces are thin and fragile, but this is no different than any other DAC board, per se. It would be a shame to go through all the trouble again and not have it work because a pin on the DAC is bad or a trace on the board is torn up.

Just an FYI, but I don't really recommend cleaning up the traces in a wholesale manner with a wick unless needed - for the very reasons you discovered. At the same time, I try to stay away from these conversations too much because everyone has their own preference for soldering. If it works, who am I or anyone else to say it's not proper?

That said, the ideal way to "finish" off the pin joints is to wipe in a downward and sideways motion with a hot, dry iron, only. As a matter of fact, that's how I solder a DAC chip, period - the only difference being that I add tiny bits of solder to the iron tip while I'm doing this. When all the pins are shiny, then I quit.

The sideways finishing technique is described on the Bantam website and also illustrated in an excellent manner in Tangent's tutorial on soldering SMD components:
Surface Mount Soldering Techniques

EDIT PS: Just an FYI, but if the iron is dry, it will pick up as much stray solder/bridges as a wick, anyway - just keep wiping the DAC pins and drying the iron tip. A brass wool soldering iron cleaner as opposed to a cold, wet sponge will really benefit this technique.

 

[qusp]

yeah I read the schematic and it seemed to say that 12 was zero (which was cool) 11 was suspend (which could be cool) and 10 was playback (which isnt cool at all or at least doesn't sound cool) but then I see that 10 doesn't seem to match with the schematic because in the schematic 10 would connect to something and the fifth from the bottom in reality doesn't seem to connect to anything on either side of the board. am I reading it wrong??? and a brass sponge is the only thing like that I didn't pick up. only got the wet sponge.I saw tangents tutorial and was going to do all that I know I should have because as you can see in the first pic I wasnt far off track. then I read that post and went with a technique I hadnt tried before stupidly and look where it got me.

edit: you better not tell me that PLAYBACKVOUTR is the full name for VOUTR on pin 19 but it starts next to 10 so it looks like 10 is PLYBCK and 19 is VOUTR and youve included it (PLYBCK) in the schematic because there was room for it with that pin because the left pin is unused and you have only called it VOUTL on 23 because there isn't room. If so then i'm a little confused as to why you would put something so inconsistent in a schematic.That was the main reason I pulled the dac off to see what was going on underneath it, to see whether 10 was connected when it didn';t need to be connected.. sure if you were experienced in reading this stuff maybe you would just go with your gut and what you know. but in my case this is the first SMD or really anything like this so I didn't know to disregard it.

I know this is a work in progress and you guys are doing a wonderful job for us noobs. But might I suggest that you use a smaller type so it is clear that it is all one name rather than looking like 2 that are joined together. and please keep naming consistent or have some other mark to suggest that this pin is unused. i'm going to see if I can do it anyway. because it seems that I still have all the required pads available except for Lout on 19 and I can jerry rig that I think. (you didn't answer that) will that cause any sort of phase in-discrepancy if one is a slightly long??r wire or a different type of wire. perhaps I'll do it with Rout 23 as well

 

[Hayduke]

Quote:

Originally Posted by qusp /img/forum/go_quote.gif yeah I read the schematic and it seemed to say that 12 was zero (which was cool) 11 was suspend (which could be cool) and 10 was playback (which isnt cool at all or at least doesn't sound cool) but then I see that 10 doesn't seem to match with the schematic because in the schematic 10 would connect to something and the fifth from the bottom in reality doesn't seem to connect to anything on either side of the board. am I reading it wrong??? and a brass sponge is the only thing like that I didn't pick up. only got the wet sponge.I saw tangents tutorial and was going to do all that I know I should have because as you can see in the first pic I wasnt far off track. then I read that post and went with a technique I hadnt tried before stupidly and look where it got me. edit: you better not tell me that PLAYBACKVOUTR is the full name for VOUTR on pin 19 but it starts next to 10 so it looks like 10 is PLYBCK and 19 is VOUTR and youve included it (PLYBCK) in the schematic because there was room for it with that pin because the left pin is unused and you have only called it VOUTL on 23 because there isn't room. If so then i'm a little confused as to why you would put something so inconsistent in a schematic.That was the main reason I pulled the dac off to see what was going on underneath it, to see whether 10 was connected when it didn';t need to be connected.. sure if you were experienced in reading this stuff maybe you would just go with your gut and what you know. but in my case this is the first SMD or really anything like this so I didn't know to disregard it. I know this is a work in progress and you guys are doing a wonderful job for us noobs. But might I suggest that you use a smaller type so it is clear that it is all one name rather than looking like 2 that are joined together. and please keep naming consistent or have some other mark to suggest that this pin is unused. i'm going to see if I can do it anyway. because it seems that I still have all the required pads available except for Lout on 19 and I can jerry rig that I think. (you didn't answer that) will that cause any sort of phase in-discrepancy if one is a slightly long??r wire or a different type of wire. perhaps I'll do it with Rout 23 as well

The schematic looks clear to me. The pins are labeled above the pin. The text inside the DAC is lined up with each pin.

I had problems soldering the 4 test pins at the "bottom" of the DAC. When I went to see what they did, I used the schematic AND the layout pictures. If you look at the layouts provided on the site, it seems pretty obvious to me which pins are not used.

It's a bummer you're having all this trouble, but there is a silver lining. The difference between an expert and a beginner is the expert has already made the 1000s of mistakes the beginner has yet to experience

I'm sure your SMD soldering skills have improved as a result of this project, and, in the long run, it didn't cost you a lot of money.