Broke my radio, part II

[af7ux]

Hello - Authorized AliExpress built device. While probing around on the board (stupidly while under power) I shorted the +12v supply to the speaker connector. That fried the atmega. I got a new mega and reflashed it. The radio powers up, but is all kinds of messed up.

- If I power it up with the RF board attached I get no RX and it makes a weird squeal that descends in pitch for a few seconds. If I power it up with the RF board disconnected and THEN attach the RF board, I get RX and no squeal, but a low volume high pitched whine (not the normal whine that it makes when I turn the volume up as noted in the known issues).

- Band switching doesn't work. The relays work when I apply 3.3v to them, but they don't switch when I use the menu. I probed the SCL and SDA pins, and I see a signal, but I'm not sure how to tell if the signal is correct.

- TX into a dummy load usually says 0 power out, but sometimes it will say it has power out with 99 or 100% efficiency. The amount of power is pretty random. When it says it has power out I don't see a signal on the scope though, either on the antenna or the RF pin.

I have checked continuity on all of the relays, the coils, the header pins from the mainboard to the RF board. I have retouched every non-SMD solder joint on the RF board. I see .5v drop across the BS170s gate to drain and about 3.6meg resistance drain to gate (have not pulled them from the board to put on the tester yet).

There is just so much wrong, I am lost as to what else to check to diagnose this.

[pe1nnz]

Hi af7ux,

Sorry to hear what happend.

In this case it is absolutely important to make sure that the microprocessor is replaced with a genuine atmega328p or atmega328pb chip, and not one of the clones circulating. Some Arduino Nano boards carry a fake/clone 328 installed that are missing some essential features such as EEPROM. They are not proven to be compatible with the (tr)uSDX firmware and may cause the issues you see now.

First, make sure that you have installed the bootloader and fuse settings as described on the DL2MAN website. Program these via an ISP programmer or ArduinoISP.
Next, you can recognize fake 328s when the bootloader is giving a S/N of 58FFDFFFDFFFFFFFFF. It might also be possible that the rig is always resetting settings when it is powered up. Can you confirm this?

My suggestion would be to check above, and to see if you can replace it with a 328 with a genuine one in case it is a clone.

Other things to check, to see if more damage is done; check if the VCC has 5V and if no excessive current is drawn in RX (should be less than 66mA).

[af7ux]

Hello Guido,

Well, I bought the megas from the same listing as someone else on this forum who had used one to repair their radio, but the serial number does match the bogus ones. Settings are not reset at every power cycle. I haven't been able to find a genuine one in stock, but I suppose I could pilfer one from one of my Arduinos, however I'm not sure if either is genuine (one is a nhduino and the other is gravitech.us, both are rather old).

Vcc is 4.9, and it draws 72ma on receive, both of which match what I had before I cooked it.

Thanks,
Derek

Edit: mouser had a few 328p in stock, so I ordered a couple

[pe1nnz]

Ok.

Did you do bootloader and fuse settings over ISP. Can you confirm that the fuse settings are as described in DL2MAN web site?

Thanks

[af7ux]

Yes, I did do the programming via arduino isp using the instructions on dl2man's site. The fuse settings read back from the device correctly, and the chip is detected correctly.

Thanks!

[pe1nnz]

OK.

Does it help, if you try to do a factory reset of the settings? (hold encoder button while rig is powered on).

It s very strange that the relays are not working. You should check if the VCO is oscillating on the advertised frequency. If not, then some device on the I2C bus might be defect, and interfere with the other devices.

[af7ux]

Factory reset does not help. Pins 9/10 of the Si5351A are oscillating at the displayed frequency, and go change when I change bands or frequencies. Ping 6 is not, but I tihnk that only comes into play on TX?

Is it possible that the tca9555 is dead? That would not be fun, since they are unobtanium right now. I'm not sure that would explain all of the symptoms though.

[dl6sez]

Hello Derek,

sounds like a bad TCA9555....
there are on several Forum pages in groups.io/g/ucx the original Forum for uSDX, discussions and replacement chips mentioned for TCA9555.
It is a simple quite common used 16 Bit I2C controlled port expander.

Have a look here:
https://groups.io/g/ucx/topic/89863203#14958

73 de Chris DL6SEZ

[wa2t]

https://www.digikey.com/en/products/det ... 118/735672

[af7ux]

Thanks Chris, most of the alternatives I found were not drop in replacements, but it looks like the PCA9555 may be?

[af7ux]

okay, I officially throw in the towel on this board. I had it connected to a USB load today (because it has an ammeter), and accidentally hit the PD trigger, so it took 12v via the USB port. This worked for a minute until the 74ACT00 rather spectacularly caught on fire. Nothing else burned so I may fix it one day, but for now I'm just going to order a kit, assemble the main board, build the RF board as a high band board, and attempt to get the original RF board working.

[dl6sez]

Hello OMs,

yes WA2Ts digikey link to PCA9555 is the right chip to replace, they are the same function from different manufacturers.
Oh 12V on USB is ....
Derek i hope you will get the Kit soon and get it working with the high band and the classical.

73 de Chris DL6SEZ

[af7ux]

Thank you everyone for the help!