TCA9555 port 13 defect ?

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hellmuth
 

Posts: 12
Joined: 14 Dec 2022, 13:59

TCA9555 port 13 defect ?

Post by hellmuth »

Today I found a new mistake on my CLASSIC RF Board, wich was brand new.

Port 13 from the TCA 9555 - its for the 10m TP Relais - does not work.
On port 13 ( TCA9555) there is a constant voltage from 1,6 Volts DC.

All the other ports from the TCA955 ( 11, 12, 14, 15 ) are with 0 Volt DC.

When I put the Scope probe to the Ports 11, 12, 14, and 15 (TCA9555)
I could see on the Scope short Pulses from 0 up to 5 Volts , by BAND change with Encoder.

Only on Port 13 was the constant 1,6 DC Voltage and on top of this 1,6 Volts a short puls up to 5 Volts.
BUT the RELAIS , here for the 10m LP Filter does not work . I could not hear any Relais click.
So think this 10m Latchrelais does not work .
Its well soldered.

And .... if the TCA9555 device would be defect , I think it was very difficult to get a new one
and its difficult to solder a new one on the board.
very sad.
hellmuth , df7vx
N6WLM
 

Posts: 20
Joined: 12 Jul 2022, 03:15

Re: TCA9555 port 13 defect ?

Post by N6WLM »

My TCA9555 had issues as well. In my case the relay for 80 and 30 doesn't work. I ended up removing the relays and using a manual DPDT switch. I might change the switch to jumpers. If it is not too late you could try asking for a refund or a replacement board.
N6WLM
 

Posts: 20
Joined: 12 Jul 2022, 03:15

Re: TCA9555 port 13 defect ?

Post by N6WLM »

Quick update. I replaced my TCA9555 and it resolved my issue. I have a friend who said that the relays could back EMP spike each time they turn off. This can potentially damage the IC over time and there is normally a diode anti-parallel with the replay coil to divert the sudden voltage spike.
dl6sez
 

Posts: 399
Joined: 30 Dec 2021, 22:54

Re: TCA9555 port 13 defect ?

Post by dl6sez »

Hello OM,

you both are the only two OMs which had a problem with the Port expander IC.
I have two (tr)uSDX and never had a problem with switching of TCA9555PWR.
If you look at the data sheet one can see the IC has already 2000V ESD protection included inside,
also 1000V ESD charged device discharge protection (Jesd22-C101).
So it is more likely a production error of these two ICs :)

73 de Chris
Chris DL6SEZ, JN48XL near Ulm, Southern Germany
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