[Pendergast]

Hello!

I just finished a minified PINT, and although I did not have the exact values or sizes recommended, it worked pretty well!

The differences are as follow:

R3 and R4 = 2.37kohms 1/4 W
C1 replaced with 1kohms 1/4 W

R4 have been soldered to C3 but with those sizes, it is a bit ugly.

But it works quite well!

This is very exciting!

 

[civilmonkey]

Nice work, congrats!

I juist finished my PINT. I used the mini'fy guide and followed it to a 'T', with a gain of 6. The amp played great before casing it, chips stayed cool, etc. Then I cased it in a mint tin, and the U1 chip gets very warm now (i'm assuming oscillation.) No sound whatsoever, DC offset 6 and 13 mV, but current draw 61 mA.

I uncased it, and it's still oscillating. The jacks were isolated, the DC jack wasn't. Maybe that had something to do with it.

One thing is that it take 5'ish second for the chip to get very warm (just too hot to keep a finger on, but not burning hot). With other chip problems I've experienced, the chip gets hot much quicker.

Anybody have any ideas?

 

[amb]

civilmonkey, the DC jack's body is actually the negative supply rail. If you didn't isolate it and the tin comes into contact with any part of the circuit that it shouldn't (such as the virtual ground) then you had a short circuit condition. Since the virtual ground splitter and output ground channel are all driven by AD8397s (which has no output protection) do not take kindly to short circuits and may already be blown.

 

[civilmonkey]

hmm, good point. I knew that, and thought it was a little sketchy using a non isolated DC jack, but I saw others were doing that. Perhaps I was unlucky.

I didn't think that was my problem, b/c with the PINT board in the tin, the only thing touching the mint tin is the PCB and the POT (and I didn't have power applied while inserting the board). Still, it's very possible. The fun thing I've learned with DIY is that sometimes you never know...

 

[Jam_Master_J]

I didn't realize tying v- to the case was such as a bad thing. Tangent seems to do it sometimes, but I guess you gotta be careful.

 

[amb]

Quote:

Originally Posted by civilmonkey hmm, good point. I knew that, and thought it was a little sketchy using a non isolated DC jack, but I saw others were doing that. Perhaps I was unlucky. I didn't think that was my problem, b/c with the PINT board in the tin, the only thing touching the mint tin is the PCB and the POT (and I didn't have power applied while inserting the board). Still, it's very possible. The fun thing I've learned with DIY is that sometimes you never know...

One thing to keep in mind, the power switch is after the reservoir capacitor C4. This has the benefit that as you turn off the amp, the power goes away immediately rather than drain down with the capacitor, which removes a possible source of turn-off noise. However, this arrangement means that C4 is charged at all times (when the battery is connected). Even when the battery is removed it will still stay charged for a long time. If, while installing your board into the tin, for some reason the charged capacitor finds a temporary short circuit and discharges into a errant part of the circuit, the opamps are at risk of being damaged.

I don't know if this is what might have happened with your amp, but I recommend discharging the cap completely before putting the board in the tin. To do that, disconnect the battery, then turn on the amp and let the opamps drain the cap for a few seconds. You'll see the LED glow for a brief moment as the charge is being drained. Then, turn off the power, install the board into the tin and check for short circuits before reconnecting the battery.

 

[civilmonkey]

Quote:

Originally Posted by amb One thing to keep in mind, the power switch is after the reservoir capacitor C4. This has the benefit that as you turn off the amp, the power goes away immediately rather than drain down with the capacitor, which removes a possible source of turn-off noise. However, this arrangement means that C4 is charged at all times (when the battery is connected). Even when the battery is removed it will still stay charged for a long time. If, while installing your board into the tin, for some reason the charged capacitor finds a temporary short circuit and discharges into a errant part of the circuit, the opamps are at risk of being damaged.

That, makes sense. I think you have probably figured out my problem. I have two new AD8397's coming in from Tangent, which I will install on the board. I was going to try and figure out how to isolate my DC jack, but as I understand from your post, if I'm careful, I shouldn't need to.

Thanks for the input and help! I'll post the results when it's all working!

 

[CedMan]

Thanks mb3k, the instruction works and I have a working Mini³fy PINT running at Gain 3 and sounds great, that is after toasting a ground AD8397.

Here's how I toasted mine, but I'm not sure exactly what caused it, maybe someone can help me, I have a working Mini³fy PINT, tested and all that, then I decided to case it. I have put it in the smallest Hammond case and I was stupid using all non isolated jacks (in/out/pw), I plug in my wallward and turned it on so obviosly my Mini³fy PINT have a toasted groud channel right away.

What I would like to find out is how I fired it, did I fired it by pluging it in or by turning it on? I guess the real question is, can I turn on the Mini³fy PINT while the wallwart is plug in? or is that straightly for changing only when I uses the W+ and W- connection?

Another problem I was having was that my led doesnot work, it only flashes once when I turn on, but never stayed on, maybe I need a different size RLED? I'm only using a single 9V NIMH. the led does stay on when my groud chip is toasted ...

I'll be using plastic case now ... much safer.

Thanks!

-Ced

 

[NeilR]

Does anyone have an image of a Pint in Mint tin with DC charger jack, top view straight down? Or a link to an image? I am trying to figure out where to put a jack.

I am also thinking about a Serpac H65, but that seems to be a waste of space. I'm like Goldie Locks, trying to find a case that is just right for this board and 2x9V.

 

[Teerawit]

Quote:

Originally Posted by NeilR Does anyone have an image of a Pint in Mint tin with DC charger jack, top view straight down? Or a link to an image? I am trying to figure out where to put a jack.

Aside from the pic on tangent's page

, here is darkisz's:

http://img214.imageshack.us/my.php?image=pint021mn.jpg

 

[NeilR]

Thanks, Teerawit. For some reason I didn't notice it snuggled between the i/o jacks. That is a really tight case!

 

[Teerawit]

Quote:

Originally Posted by NeilR Thanks, Teerawit. For some reason I didn't notice it snuggled between the i/o jacks. That is a really tight case!

Yeah, that's about the only way to do it. Good luck

 

[Heady]

I have just finished a mini3-fied PINT and it sounds great. Only thing is that its current draw seems to be high, at about 175mA. However the opamps are not hot. The L/R opamp is about 35degrees celcius while the ground opamp is about 38degrees celcius. Not even noticeably warm to my finger.

I used all the parts as in the mini3-fied list, but omited U2, R1 and D1. And since I don't have a SMD diode handy (one always forget at least one part when buying stuff), I modified an axial 1A 50V diode and used it for D2.

Anyone have an idea if I got a problem?

Thanks.

 

[NeilR]

I'd like to find a case exactly the width and length of my 5G ipod. I think that is the ideal case size (for an iPod). That would be about 2 3/8" x 4". That would open up about 3/8" of breathing room.

The tins are a good size for the Nano, though.

 

[Teerawit]

Quote:

Originally Posted by Heady I have just finished a mini3-fied PINT and it sounds great. Only thing is that its current draw seems to be high, at about 175mA. However the opamps are not hot. The L/R opamp is about 35degrees celcius while the ground opamp is about 38degrees celcius. Not even noticeably warm to my finger. I used all the parts as in the mini3-fied list, but omited U2, R1 and D1. And since I don't have a SMD diode handy (one always forget at least one part when buying stuff), I modified an axial 1A 50V diode and used it for D2. Anyone have an idea if I got a problem? Thanks.

What are your DC offset readings?