Building the PINT

[heady 0]

Re: diode, I got the normal axial type, 1A 50V.

 

Edit - confirm the amp is oscillating. With no music playing, it does get warm after a while, about 48 degress celcius.

 

The only difference from Tangent's instructions is that I did not mount the pot on the board. Will try this later today.

 

Edit2 - mounted the pot on the PCB with the same result. Sigh! Anyway, here's the front and back view of the PCB. See if anyone can spot anything I have done wrong.

 

Thanks

 

 

Front view

Back view

Edited April 20, 2006 by heady

[heady 0]

Just added pics of my "bad" PINT in my previous post. Please comment if you see anything wrong. Thanks.

Edited April 20, 2006 by heady

[squalle 0]

looks OK to me

 

just that the C3 caps, I think you might've gotten wrong type?

did u get the NP0 or C0G type?

if you get normal ceramics, it will somehow affect SQ

can read somewhere within tangent's articles

and I've verified that from many other sources

 

o, maybe try take the big diode off, replace it with wire

see if the consumption goes down

I guess it will

oh, btw, you dont really need the diode there

you wouldnt plug the battery in wrong polarity would you?

diodes are a must if you wanna do on-board charging

[heady 0]

Squalle, I did order the NPO type from Farnell but will check it again to make sure it is the right type.

 

BTW - did you cut the trace for pin 6 of the ground op-amp and jumpered the pin 6 & 7? Can't see in your pic cos the wire block it.

 

I placed the diode there for testing. I have blown several opamps in the past due to connecting power wrongly. You know lah, working late at night, become groggy but insist on finishing the amp.

 

Thanks for the help.

Edited April 21, 2006 by heady

[squalle 0]

I didnt do anything to the ground driving op-amp

 

hmm for the cap, then that means OK

from your pic, the colour looks different from what I have LOL

do they look like a bit bluish?

mine do (vs the other ceramics cap which are yellowish)

 

btw, that's a ZERO at NP0, not O

[heady 0]

squalle,

I should have asked you exactly what you did. I made the cut etc. and jumpered pin 6 & 7. And I think you are right about C3, I may have used the wrong caps although I did order the right ones. Man, your eyes are sharp.

 

Ok, microscopy studies tonight. The parts are so small and I am used to handling small stuff in my work but this is worse.

 

Just for my info, can you confirm what you did:

1. All values as per Tangent except for R3 and R4.

2. R4 and C3 soldered together in C3 position

 

And that's all the mods you did?

 

Thanks.

Edited April 21, 2006 by heady

[squalle 0]

yea

I only changed those

I hate cutting traces and such lol

and so far I've proven that it's not necessary

 

and you can lose the diode

just jumper over it

 

for the cap, it's just my guess

you can just chk on the label of the packaging

farnell, even tho very lousy with delivery, they dont give wrong items so far

maybe if really wrong, then they are INDEED LOUSY. LOL

 

btw, those are not exactly small LOL

you shd know there are even smaller SMT parts

[heady 0]

btw, those are not exactly small LOL

you shd know there are even smaller SMT parts

Nooo........ I am going blind! I actually lost one capacitor because it got caught on the package corner and snap into the air. It is now officially part of the dust collection in my diy corner. Can't find it anywhere.

 

Thanks for your tips. I don't think Farnell gave me the wrong items. Probably when I laid out the parts, I probably made a mistake.

 

Will look into salvaging it tonight.

 

[heady 0]

Squalle, I've just checked every component carefully and there is no mistake with the caps. C3 is 10pF 50V C0G/NP0 capacitor. Hmmm..... what do I do now?

Edited April 22, 2006 by heady

[squalle 0]

try take the diode off?

 

I'm still curious if the diode really eats up that much of current

 

[heady 0]

Latest attempts:

1. remove diode and jumpered the diode connections - starting current draw now starts from 80+mA and climbs to 170+ in about 10 secs.

 

2. tried to undo the cut in PCB for pin 6 and reconnect it to original lead - same result, so redo the cut and jumpered pin 6 to 7.

 

3. Remove all the leads for input and output and test - same result for current draw but now oscillations are audible.

 

Just about given up with this PCB. No idea what I did wrong with this one. My only guess left is that there is some flux left under the opamps which i could not remove. I am going to remove all the components if possible, except the power caps and pot to try again. Removing the pot is almost impossible the last time I tried it with a CMOY2 while, I already loosen the trace for the power caps with previous debugging attempts.

 

Wanna built my last PCB for me, squalle?

 

Edited April 22, 2006 by heady

[squalle 0]

hmm

 

u sure it was the flux causing ur current consumption?

how abt u try cleaning it off by using alcohol and wash it away? I did that for all 3 boards I assembled

 

[heady 0]

I washed my board with alcohol and even flux cleaner. Kiasu. I am not sure the problem is the flux just grasping at straws.

 

I am going to remove every component and try again. Hope the board is still usable.

[squalle 0]

mmm

 

try ur best

 

dont put the iron on the board for too long

the board's rather good I'd say

not as easy to take the traces off

[heady 0]

mmm

 

try ur best

 

dont put the iron on the board for too long

the board's rather good I'd say

not as easy to take the traces off

Urp.... removing the SMD resistors and caps were easy. However, removing the opamps and pot is impossible. Some traces are now loose. The PCB is officially declared dead. Ouch! expensive lesson in SMD soldering.

 

Will try to build the next PINT pcb myself but I will do it this way:

1. put in the resistors first and check connections

2. put in the capacitors and check

3. put in the power section and check power supply

4. put in the opamps last.

 

What do you think squalle, will this work?