(tr)uSDX Forum

Relay does not work
Build truSDX_ RF-Classic_ 86256。 The relay does not work. All magnetic rings are not installed, the 86256 is not welded, and the motherboard firmware is normal. I think it is a 9555 fault. Please help me to judge.
Thank you!

Hello OM,

it is a FDT86256, sounds strange if you talk about 86256, sounds more like an EEPROM
Sorry but with your descriptions nobody can help you exactly....
I would resolder all pins of TCA9555PWR (or the equivalent multiplexer soldered on your PCB).
Check the connection sockets of the two PCBs, sometimes the contacts have been to loose when the PCBs are put together. Measure voltages 12V and 5V as a start when plugged in on backside of RF PCB.
Clicking of relays should be heard at startup and every band change.

Hope you will find the error

73 de Chris

Hello OM DL6SEZ:
Thank you very much for your suggestions. First, I checked all the solder joints, and measured the connecting pins between the two circuit boards with a multimeter. The circuits were connected. I replaced the TCA9555PWR, and the fault remained. I measured the voltage on pin 1 of TCA9555PWR at 4.81V, the voltage on pin 22 at 3.25V, and the output voltage of ATMEGA328 SCL at 3.25V. I wonder if this voltage is normal. Please help me analyze the problem.Thank you.
73

Hello OM,

i wondered why you are asking is the SCL voltage of about 3,3V normal
You should also study the schematic.... you will easily see it is okay.
If your skills are not good enough to get this basic information out of the schematic,
i would honestly suggest to go with the (tr)uSDX to another Ham or other electronics man/woman with higher skills on these topics.
From my point of view there must be something wrong on Main board.
Why did you change R6 to zero Ohms, when it is normally 68k and it is not necessary with a normal genuine Atmega328.... Please do the (tr)uSDX completely as shown in the schematics and test it afterwards.
Also C39 and C35 look like someone drilled a hole here to place through hole components.
If this is true, this could also be an issue, the (tr)uSDX PCBs are 4 layer.... this can't be done.

73 de Chris

Maybe the current is too high, as you´re using 4,5V Relays, instead of 5V relays....

Hello everyone, I didn't come to the forum because I couldn't buy medicine because of illness. The reason why the relay does not work has been found. The TCA9555PWR I used did not work after five tests. Now the 9555 works normally.
73

Current machine

I have preliminarily found the reason. This post has no value. Please delete it by the administrator.

storyofyouandme wrote: ↑05 Feb 2023, 06:19 I have preliminarily found the reason. This post has no value. Please delete it by the administrator.

Can you post the fix? I have a similar issue and maybe your solution will help.

Hello, I'm sorry, TRUSDX's firmware is not open source. I can't modify it. If you have the problem that the relay doesn't work, please check from the hardware first. Or adopt a more simple and rough method, that is, weld a new one. If you do not buy the kit, but buy all the parts yourself, you will not lose much money, but you will save a lot of time.
73！