Suspected fried internal antenna tuner

marwalk

I'm embarrassed to say that I may have fried the antenna tuner in my 6400 radio. I'd disconnected the antenna for the thunderstorms last night and forgot to reconnect it before trying to send a digital message; SWR went through the roof with a burnt electronics smell. Tested the antenna cables and inspected the antennas, no issues observed, and connected everything back up as normal. Also rebooted the 6400 and the computer. The antenna tuner reports success but the SWR on full power transmit is the same as no antenna, with full scale SWR reading on the SmartSDR radio control panel. 

I suspect I'll have to send the radio back for repair, unless the internal antenna tuner is a user installable component that might be shipped to me. Before I pack it up for shipment, does anyone knowledgeable about this have any other suggestions or advice?

Thanks,

Mark, AC3EW

marwalk

@WP4OXG Thanks, ATU replacement with those instructions appears to be very user serviceable. Now to see about the steps to order a new ATU.

Thanks,

Mark, AC3EW

KD0RC

Hi Mark, before ordering a new one, I would submit a help desk ticket. Flex support may have some insights that could help.

wp4oxg

Hi. Yes the ATU on the 6400/6400M is user installable. The instructions are here:

https://www.flexradio.com/documentation/flex-6400m-atu-installation-guide-pdf/

(https://www.flexradio.com/documentation/flex-6400m-atu-installation-guide-pdf/)

Regards,

WP4OXG

marwalk

@KD0RC Thanks, Len. Now that I have more background on it I'll submit a help desk ticket. I do have my profiles backed up in case they have me do a factory reset on the radio.

Thanks,

Mark, AC3EW

David N4IW

I think most of us have done something similar; at least I have. I am curious about what happened with this situation. Was your ATU fried? Did you have to replace it?

marwalk

@David N4IW Hi, David. The Help Desk had me check the SWR reading at 10 watts into a dummy load with the ATU switched out of the line. The meter pegged, and per instructions I went no further. They gave me an RMA for repair and I sent it back to Austin. Here's what they found:

1. confirmed customer's reported problem with the radio is indicating high SWR into a dummy load ( we could not find any visibly burned/damaged component).
2. radio had faulty LPF module: fails CAL BRIDGE Test
3. radio had a faulty ATU: fails most of factory board-level tests.

They took the following repair actions:

1. replaced LPF + ATU modules
2. ran full factory recalibration
3. ran functional tests
4. burn-in overnight
5. final tests
6. factory reset

I've had the radio back and operating for a couple of weeks now, and all is working fine. I observed that when I restored my profile it also pulled in my frequency memory records without having to explicitly select the separate frequency CSV file; everything was there as before. I did have to separately reset the static IP address on the radio (and reboot it to make that active), but that also was painless.

Thanks,

Mark, AC3EW

David N4IW

@marwalk AC3EW. Hi Mark. One further question. About how long did you transmit before you realized there was a problem?

Thanks and 73,

David - N4IW

marwalk

@David N4IW Hi, David. Although I didn't have a stopwatch on it, the time seemed to be about 30 seconds. That was while transmitting a digital message that had the transmitter key down all that time (a normal operation that is usually not problematic).

A friend had commented at the time that there shouldn't have been a problem, as a Flex radio will reduce its power as needed when confronted with excessive reflected power. But it seems the transmitter wasn't the component in play in this situation, it was the ATU. Possibly the only way to have the same protection for the ATU (and also the LPF) is for the ATU (and LPF) to communicate to the transmitter what's happening to them. I could imagine that would require a significant increase in complexity in the firmware and maybe component architecture, but it's an interesting thought experiment.

I've since made a point to notice the SWR reading on the radio control panel while transmitting, just to be sure.

Thanks,

Mark, AC3EW

David N4IW

@marwalk Hello again. Ohhh. 30 seconds! What I have done a few times is to transmit WSJT-X FT8 directly to ground when I have left my Alpha Delta antenna switch centered which puts all ports connected to ground. But I have only done this for a couple of seconds each time because I noticed the SWR was off the scale. I have a ingrained habit to look at that for some reason. Every time I do this my electric blanket (2 floors up in our bedroom) errors out and has to be unplugged and plugged back in! 😬

Like your friend, I thought the radio would protect itself from something like this. Glad it’s working again and that they took care of you. I am guessing that was a pretty expensive repair. 73

David - N4IW