Low Power Out from 6400 - any suggestions?

David Okay Patton

Last weekend while operating from my van for a Parks on the Air activation, my 6400 output power suddenly dropped to a few tenths of a watt. Happened in mid-QSO. Radio was connected to three 98 AHr batteries that were fully charged. No difference whether transmitting into resonant antennas or dummy load. I rebooted; no change. Power button was solid green on receive; solid red on transmit. I was operating SSB when the problem stated, but same issue in either SSB or CW. I was not using the internal ATU. Radio had operated normally for a dozen or more QSOs before it failed. Luckily I had my trusty Elecraft K2 with me, so the outing wasn't a complete bust.

When I got home and brought the radio into my home station, it initially exhibited the same symptoms. After about 45 minutes, during which time I was looking at all the settings in SmartSDR, searching the forum for hints, and occasionally keying the radio into a dummy load, the power output suddenly increased to about 70W maximum. I had not made any changes to any radio settings before the power output changed. So now the radio "sort of" works, although not at rated output. I double-checked my station power supply; it is steady at 13.8V DC in both receive and transmit. I'm running SmartSDR v.2.7.6. Max power is set to 100W in the TX tab of the Radio set up.

Any ideas what would cause this type of behavior? I was planning to use the radio in my van for Winter Field Day, but without understanding what happened, I'm reluctant to use the rig for a contest.

73,

David W4WKU

David Okay Patton

BTW, power meter I'm using for measurements is a LP-100, so I'm confident my transmit power out is at or close to 70W, whereas it 100W at full power before this problem happened.

Mike-VA3MW

I opened a support ticket for this. 73

Karl

Hi David and Mike.

It appears i have a similar problem also in that my 6700 has dropped it's power output to 60w.

Setup is as follows.

Flex 6700 set to 100% Output through 24" of RG400 into the LP-100A and then 24" of RG400 into a Dummy Load.
The LP-100A shows 78.6w for the output at best on 14.150mHz with an SWR of 1.08:1.

I also have noise on 14.049 - 7.025 - 3.512 that gradually get louder the longer the radio has been turned on. There are also signs of faint signals drifting across the waterfall.

I've been in touch with Flex and Tim has asked me to run some tests before returning the radio for inspection. (#49113)

What was to outcome for you Dave did you get it fixed and if so what was it ? I think the community and myself would like to know.
It seems lots of these things are opened as a support ticket but the end results are never disclosed or shared for the community to gain knowledge from.

Thanks
Karl. VE6KDX

WX7Y

Important note, What is the Voltage at the Power Pole power connectors when in Transmit mode.

you can use 3rd party programs like https://k9dur.us/downloads/SDRMonitor/SDRMonitorSetup.exe

or FRStack and other to see what the internal PA Power supply voltage at the finals is.

This is very important point because the Anderson power connectors do have a lot of loss, Also in the radio there is a ATC type fuse that may also have a little bit of oxidation on the contacts that could have voltage loss.

I run my power supply at 14.2 Volts which at transmit P.A. it gives me 13.8V so with 2 sets of Power Pole connectors there is .4 Volts drop from what the Power supply is putting out.

Just because your power supply shows 13.8 V doesn't really mean the Radio has 13.8V under load where it is important for full radio power output

David Okay Patton

I opened my radio and reseated the internal fuse, which made a noticeable difference; power output is now 80W or slighly higher on all bands with a 13.6V DC power supply, and stays at the output power level down to about 11.5V DC input. Before resetting the fuse, power out on most bands was between 59 to 70W. I'm measuring output power using FRStack, and generating the test signal with the tune function set to 100W (50-ohm dummy load, tuner bypassed.)

Using either FRStack or SDRMonitor, you can monitor the input voltage seen by the radio: in receive, my 6400 is at the power supply voltage; it drops abt 0.6V in transmit. (Before resetting the fuse, it dropped between 0.7 to 0.9V.)

Yes, there is still something quirky going on with my radio, but I can live with 80W output - that is what I've always run in the van, and at home I have an ACOM 600S amp if I want more power. The radio ran without problem for Winter Field Day. I plan to close my ticket. I won't be surprised if the initial problem of mW output power resurfaces at some point (probably in the middle of a contest!), but until then I just don't want to be without the radio or the $$$ for shipping and repairs.

Karl

> @WX7Y said:
> Important note, What is the Voltage at the Power Pole power connectors when in Transmit mode.
> you can use 3rd party programs like https://k9dur.us/downloads/SDRMonitor/SDRMonitorSetup.exe
> or FRStack and other to see what the internal PA Power supply voltage at the finals is.
> This is very important point because the Anderson power connectors do have a lot of loss, Also in the radio there is a ATC type fuse that may also have a little bit of oxidation on the contacts that could have voltage loss.
> I run my power supply at 14.2 Volts which at transmit P.A. it gives me 13.8V so with 2 sets of Power Pole connectors there is .4 Volts drop from what the Power supply is putting out.
> Just because your power supply shows 13.8 V doesn't really mean the Radio has 13.8V under load where it is important for full radio power output

Thanks for the Reply Bret.

The picture attached tells the story and the radio has been shipped back for inspection/repair.
My power cable is no longer that 18", power when checked at the rear of the radio was the same as on FRstack, Covers were removed and fuses checked and cleaned but the problem is still the same.

It's a $600 round trip for the radio and it made the same trip exactly a year ago for other issues so it's might be time to let this thing go and move on.

--- As of Jan 22nd 2021.-----------------------------------------------------------
David Tkach
Service Center - Austin TX

The service performed on your product under RMA 41300 has been completed. Please see the disposition below.

## Problems / Issues Found:
The following issues were found during the problem assessment phase of the service request:

1. We were unable to reproduce a voltage failure, in house or at a remote shack.
Corrective Action Taken or Service(s) Performed:
The following corrective actions were performed.

1. Replaced the SD card and shipping a new power cable, re calibrated and ran extended testing successfully.
---------------------------------------------------------------------------------

My 6700 was tested on my Astron RS-35M , MFJ-4035MV , PSR1240 and the problem never changed. I like to be 100% sure it's not my end before shipping it back but sometime they still find nothing during test and inspection.

Be leave me when i say this thing is babied and for the price I'm not sure it's robust enough as it had to have some internal voltage regulators change in the past also.

This will be the third or forth time it's been back for work.

Rgds
Karl.

Mike-VA3MW

Hi @Karl

This is one of those strange things that is frustrating on both ends. Rest assured, when they can't recreate a problem, they work hard to try to recreate it. I've also worked on a service bench and had to figure out something unusual like this.

One of the facts we can trust at this point is that it is not the radio. At least, you can trust that data point at this time since our lab is well calibrated. Trust that the radio DC power is good to the edge of the powerpole.

I am not 100% of your setup and technical ability, but here is what I would do to narrow it down.

• Setup the radio into a quality dummy load (not an antenna) and very good jumper cable. One that you can 100% trust.
• Make sure the ATU is off (in Bypass)
• Set your power supply to 13.8V DC (or up to 15% higher -- 15.8V)
• Get a good voltmeter (not a $10 Harbor Freight one :). )
• Set the tune to 100%
• Calibrated watt meter - Bird, LP-100, LP-500, or similar
• Put the radio into TX on 20M
• Measure the voltage on the back of the power supply - write it down - it shouldn't drop much from when in RX
• Measure the voltage on the back of the radio by sticking the meter probes into the PowerPoles
• They should be close to the same (minimal voltage drop). They should be within 0.2V or so.

Let us know what you find.

David Decoons, wo2x

Measuring at the power poles at the cable side may not show a high resistance connection.

one thing I like about Node Red is ability to see voltage at inside back of radio and also at PA (after internal fuse) so you can easily see if there is a bad connection someplace.

Dave wo2x

Karl

Hi @Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

Hi Mike did you click on the image in my reply ? if not it contains my finding that were sent to Tim Ellison.

Setup is as follows.

1. Flex 6700
2. RG400 24" with Amphenol connectors on both ends
3. LP-100A
4. RG400 24" with Amphenol connectors on both ends
5. MFJ Dummyload 1500w Capable
6. Astron RS-35M set to 14.2v resting and drops to 13.8v under load from the Flex.
7. Fluke 337 Meter (6 Months Old)
8. FRStack3 to monitor the radios condition
9. Icom 7300, Icom 9700, Yaesu FT920 all of which have used the same setup as above recently and the
IC-7300 is doing so as i type this without any issue.
10. ME with 35 years of working with military, marine and automotive electrical and electronic systems

Should you wish to look into it the request is #49113 and the radio is in transit to Flex with DHL.

I have trust it will get resolved for good this time.

Rgds
Karl.
VE6KDX

Karl

> @"David Decoons, wo2x" said:
> Measuring at the power poles at the cable side may not show a high resistance connection.
> one thing I like about Node Red is ability to see voltage at inside back of radio and also at PA (after internal fuse) so you can easily see if there is a bad connection someplace.
>
> Dave wo2x

While Node Red has it's place FRStack3 or SDRMonitor are the easiest way to achieve the same goal in this instance.

David Decoons, wo2x

Does Either of those show both of the internal voltage meters? If so, then yes, they would be easier and quicker to use to check voltage drops. Node Red is not practical for the average user to install just for these measurements.

In the API there are voltage at CPU and voltage at PA, along with a bunch of other meters. Voltage @ CPU would show if the Power Poles have an issue and voltage @ PA would show issues with internal fuse when compared to voltage @ CPU. Both under TX @ 100 watt setting to show under worst current draw situation.

Either way you get there they are useful as long as both internal meters are utilized.

My friend has my original 6500 and he had a voltage drop issue. He used some conductive grease on the Power Poles and blades of the ATX style internal fuse. He used a VERY fine coating, enough to enhance conductivity of the connections. I have to ask him the name and where he got it.

73