PINT Problem

[SubRosa]

Voltage is not being split evenly, V- is approx. 9V while V+ is approx. 6V. (With two 9Vs)

EDIT: I measured 15V across C6, that's why it smoked; it doesn't seem the resistor divider is working but I've replaced them and it's still not functioning correctly, what's up?

 

[MisterX]

Quote:

Originally Posted by SubRosa EDIT: I measured 15V across C6, that's why it smoked; it doesn't seem the resistor divider is working but I've replaced them and it's still not functioning correctly, what's up?

Do you have the C7s installed the right way around?
Remember the stripe on the tantalum capacitors marks the positive lead not the negative lead.

 

[SubRosa]

Quote:

Originally Posted by MisterX Do you have the C7s installed the right way around? Remember the stripe on the tantalum capacitors marks the positive lead not the negative lead.

*Kisses-Your-Feet*

I had one of them reversed, I now have a completely working PINT.

*Slaps self for making same mistake twice.*

 

[Filburt]

Quote:

Originally Posted by SubRosa I scrapped my first board and started on my spare, I used new parts all around except for some ceramics and the pot. I turned it on and C6 immediately smoked itself, I'm not sure why that is, but I just took it out. DC Offset is reading 1mv on both channels. Guess what, same symptoms as before except marginally better, I can turn it up with a single 9V battery without crackling until high volume levels and it will sometimes cut-out but I can still hear the music very faintly, rather than not at all. I'm not sure if I'm hearing distortion at normal listening levels. Is it possible that the pot has been the source of my troubles? It's the only thing that got transferred from the old board that should be able to cause this behaviour.

Did you make sure you oriented C7 and C6 correctly?

Edit: I see MisterX asked the same thing before me...hadn't refreshed the page before I posted.

 

[FallenAngel]

Well, I measures 0.8mV across IG-OG, DC offset below 9mV, but chip still oscillates. Current draw now starts from 40mA, then jumps to 80mA and it steadily goes up from that.

I guess I'll start measuring all the nets to see if I find something off, and if nothing pops up obvious, guess it's LM6172

 

[mb3k]

Tangent, maybe I'm looking at the schematic wrong (it's 3:30am) but shouldn't the R4 on the second page of the schematics be in parallel with C3?

 

[MisterX]

the original schematic is fine.

 

[tangent]

Quote:

Originally Posted by mb3k shouldn't the R4 on the second page of the schematics be in parallel with C3?

Why do you believe that? Seriously; I'm curious.

Here's the EAGLE version of the schematic, which is tightly coupled with the board layout. The only way to get a board layout that doesn't match the schematic in EAGLE is to commit a design error, and I run frequent automatic design rule checks while laying out a board.

 

[mb3k]

Quote:

Originally Posted by tangent Why do you believe that? Seriously; I'm curious. Here's the EAGLE version of the schematic, which is tightly coupled with the board layout. The only way to get a board layout that doesn't match the schematic in EAGLE is to commit a design error, and I run frequent automatic design rule checks while laying out a board.

I'm most likely getting mixed up with the mini³fied version where R4 is in parallel with C3.

 

[MisterX]

Quote:

Originally Posted by mb3k I'm most likely getting mixed up with the mini³fied version where R4 is in parallel with C3.

Still not right cause L1 is outside the feedback loop in the mini3fied thing.

 

[mb3k]

Okay, forget what I said completely.

Today I constructed a Mini³fied PINT with a gain of 4 (R3=1.33kohms, R4=4.02kohms) and a ELNA Cerafine cap for C4 (ELNA Cerafine 470µF/25V) running off of a STEPS supply at 24V.
I get these test values:
Current Draw: 0.11A
IG to OG: 2.2mV
OG to OR: 2.0mV
OG to OL: 3.9mV
Both opamps gets very hot, but listening to the amp it's perfectly fine - no distortion when I turn the pot either. The ELNA cap gets very slighty warm too.
Do these values, especially the current draw, sound reasonable?

EDIT: I do not have C6 installed.

 

[cire]

your current draw looks to be twice as much as it should. something has to be wrong.

 

[dhp]

hm, what problem would occur if you failed to cut pin 7 on the ground opamp?

 

[kklee]

I've been lurking here for quite a while and figured it's about time to give back to the community.

I built a PINT (default parts, not Mini³fied yet) that seemed to be working fine, but had a high current draw of 170mA. The really strange thing was that it would turn on with a draw of 50mA, but would slowly creep up to about 80mA and then shoot up to 170mA within a few seconds.

The problem went away as soon as I added C6. I'm guessing that there was an oscillation that took a little time to get started.

...Ken

 

[mb3k]

I finally got a steady 50mA current draw somehow, and I didn't even touch the circuit, but now there's no sound from either channels.
My best guess is the op amps finally fried. Frustrating.
What's everybody's opinion on C6?