PINT Problem

[Filburt]

Quote:

Originally Posted by amb It's ok to use a small piece of resistor lead for the jumpering. I am not certain what might be the problem either, but having more eyes to look at the board is never a bad idea... Btw, what ferrites did you use?

I used the ones Tangent lists in his part list from Digikey. The one he notes as being 50 ohms.

I measured the resistance between the two pins and I was seeing what appeared to be less than an ohm of resistance, so essentially nothing. However, do you think it may be causing problems. I noticed the picture from blueworm appears to bridge the two pins with just solder, in addition to bridging to that one end of the ferrite.

 

[amb]

Quote:

Originally Posted by Filburt I used the ones Tangent lists in his part list from Digikey. The one he notes as being 50 ohms. I measured the resistance between the two pins and I was seeing what appeared to be less than an ohm of resistance, so essentially nothing.

The "50Ω" rating is at ultrasonic frequencies (probably 100MHz, need to verify this on the datasheet). When you measure the resistance with a DMM, it's at DC (0Hz). The ferrite is just a wire with ferrous material wrapped around it to give it some inductance, so at DC it's essentially a stright wire with negligible resistance, but the impedance rises at very high frequencies.

 

[Filburt]

Quote:

Originally Posted by amb The "50Ω" rating is at ultrasonic frequencies (probably 100MHz, need to verify this on the datasheet). When you measure the resistance with a DMM, it's at DC (0Hz). The ferrite is just a wire with ferrous material wrapped around it to give it some inductance, so at DC it's essentially a stright wire with negligible resistance, but the impedance rises at very high frequencies.

Okay, fair enough. So any ideas on what to try in terms of modifying. I checked my solder joints and they seem clean. Can you think of anything in particular to watch out for?

 

[amb]

Quote:

Originally Posted by Filburt Okay, fair enough. So any ideas on what to try in terms of modifying. I checked my solder joints and they seem clean. Can you think of anything in particular to watch out for?

Nothing in particular, just go through everything carefully to make sure you didn't make a mistake somewhere, such as using a wrong value part, or installing a part in the wrong location. In addition to visually checking the solder connections, use your DMM to check for continuity where there should be, and open circuit where there shouldn't be connections. Use the schematic diagram as your guide. The circuit is simple enough you should check every "net", and it shouldn't take long to do that.

Your 85mA current is measured in series with the batteries without any wallwart or audjo source connected, and the volume control is set to minimum, right?

Anyway, it's past 3am and I'm going to sleep now. Hopefully you'll solve the problem soon.

 

[Heady]

Here are the pics of my mis-behaving PINT:

Front view

Back view

I was very careful building this as I have read of the problems involved. Please have a look and see if I had made a mistake somewhere.

Thanks.

 

[tomb]

There's a solder bridge between two of the right pins on the Ground Channel opamp (U3).

 

[Heady]

Quote:

Originally Posted by tomb There's a solder bridge between two of the right pins on the Ground Channel opamp (U3).

Yes, it is according to amb's instructions for mini3-fying the PINT.

 

[__redruM]

To start, where is R4. Is it optional in the minified config?

Otherwise, how about using a 10-100Ohm resistor for L1, instead of a ferrite? This would seem to be the next step if you weren't minified. Amb, will this have the same taming effect in the minified config?

 

[Filburt]

Quote:

Originally Posted by amb Your 85mA current is measured in series with the batteries without any wallwart or audjo source connected, and the volume control is set to minimum, right?

Correct.

 

[Heady]

Quote:

Originally Posted by __redruM To start, where is R4. Is it optional in the minified config? Otherwise, how about using a 10-100Ohm resistor for L1, instead of a ferrite? This would seem to be the next step if you weren't minified. Amb, will this have the same taming effect in the minified config?

R4 is under the C3.

 

[nysulli]

i measured my current draw this morning, 62ma without any phones hooked up, seems just a bit high, and the ground opamp feels hotter then the L/R one, do you think its good enough to just let go, or should i track down the slight oscilations i have, I do have access to a scope, but it could be a few days before i can get to it

that being sad, the setup is the standard ad8735 opamp (or whatever the number is), gain of 3, minified, using the L1's tangent originally suggested at the release of the PINT, to add, my DC offsets are all under 1mv, IG-OG, OG-OL, OG-OR, the amp is being powered by 2 9v's

 

[__redruM]

Quote:

Originally Posted by Heady R4 is under the C3.

Interesting, was it just easier to solder that way?

Also, Using a 10ohm resister at L1 may help your issues...

Edit: Did you read the following on tangent's site: "Do not use both C3 and L1 at the same time. They have opposite effects. If you need L1, adding C3 will at least partially defeat its purpose."

 

[Teerawit]

Quote:

Originally Posted by __redruM Edit: Did you read the following on tangent's site: "Do not use both C3 and L1 at the same time. They have opposite effects. If you need L1, adding C3 will at least partially defeat its purpose."

ya, but C3 and L1 are both necessary in the mini^3fied circuit.

 

[__redruM]

OK, I was confusing Tangent "Low Noise" Pint with the Mini3 converted Pint. Does replacing L1 with a 10 Ohm resister help, if it is outside the feedback look?

 

[FallenAngel]

I can't see it very well in the picture, but you did cut the trace on the PCB from the OpAmp (pin 7 i think), right?