BATC Forum

I'm testing the filter mod board that I built with the LO and Pi as per the instructions here: https://wiki.batc.tv/Filter_Modulator_b ... _the_board

Pictures are being picked up on the MiniTiouner and I've done a quick check on 2m, 70cm and 23cm outputs - all OK.

The filter mod power regulator is cool, as are all the ICs apart from U41. This is running quite hot - I can put my little finger on it for a couple of seconds before it gets painful.

Is this the usual temperature or could I have a fault with my assembly? I did try to run solder through the vias below the exposed pad as per Colin G4KLB's video, but maybe I didn't do enough.

Thanks and 73

Ray M0DHP

Hi Ray

First of all congratulations on getting it going!

Concerning U41:

- Please check the current consumption of the complete board. Typically they should draw 225mA +/- 10 mA. If it is outside this range it could indicate a problem.

- The AD8345 should draw between 50 and 78 mA at 5V. So max dissipation should be 390 mW. Without heatsinking this may run a bit hot. All the professionally made boards that I have just tested run slightly cooler than yours (but not much).

- Max operating temp for the IC is 85 deg C. If you can put your finger on it, I would guess that it is less than that.

There must be an experienced RF engineer on the forum who could talk about the reliability of an IC that is just too hot to touch permanently. My wild guess is that it is nothing to worry about while you have adequate ventilation, but it may be that your heatsinking is not as good as it might be.

Dave

G8GKQ wrote:First of all congratulations on getting it going!

Thank you! I'm really chuffed that I've got this far with no major problems.

G8GKQ wrote:Please check the current consumption of the complete board. Typically they should draw 225mA +/- 10 mA. If it is outside this range it could indicate a problem.

It's drawing 235mA, so within spec. And U41 isn't getting any hotter even when I've left it running for some time. I'm sure it's well below 85C - an old infrared thermometer is indicating maximum 30C on and around the chip.

73
Ray

Hi Ray

If it's in the region of 30 degrees then you certainly have no problems.

Dave