U1-74ACT00 fried

[CR7BAQ]

Hello all !

The U1-74ACT00 IC fried while I was testing a new classic board.
All worked great for a few minutes, them, the LCD went dark, there was no power at TX and I saw that the 74ACT00 was getting a lot of hot.
I removed the 74ACT from the board and tested alone with 5v. The IC gets hot a lot. Its fried.
Without 74ACT, the RX works fine.
As Im waiting for a new 74ACT00 to solder, I would like to know what would be the causes for the 74ACT00 getting fried.
I have to mention that I had tested the new classic board without L15 on the board until I saw that there was no power coming out, and saw that L15 was missing.
I soldered L15 and all went just fine, until a few minutes, when the 74ACT fried.
Would L15 missing be enough to cause this ?
My mainboard is one of the first batches from *Rxxxx*, and the classic board a new one from approved dealer.

[dl6sez]

Hello OM,

Rxxxx changed maybe the main board, but it is also not good to use the Drive chain without power source connected trough L15 to the PA FETs
I would also check the PA FETs and RX mute switch Q1 before using it with another 74ACT00.

73 de Chris

[CR7BAQ]

Hello all !

I replaced the fried 74ACT00 with a new one.
On another RF board that I have with 3 BS170, the (tr)uSDX works.
With the new board with FDT86256, I dont have power.
Is there a good way to test the FDT86256 ?
It probably also fried because of the lack of L15 in the inicial test.