Recently repaired 6400 is having problems with power and disconnects

Santiago Mejia HI8O

In July 2024 I got my 6400 serviced by Flex for a couple of issues wich resulted on a new LPF board and a new PA100 board too. Once received, everything was working fine for a couple of weeks, until recently the radio is behaving weird:

• The radio is disconnecting from SmartSDR due to low voltage when in TX (meters shows it drops down to 11 volts during tx from 13.6 during rx).
• After this happens radio disconnects from SmartSDR and have to reboot the radio
• On 6m radio does not get to 100w (I'm afraid it was the reason we had to change the PA100 in the first place. new one on the horizon???)
• TGXL works fine connected to the same power supply
• Power Supply is an Astron SS-30M
• Tried with a Samlex 1235 with the same behaviour
• Checked both power supplies and they are working fine

Running latest SmartSDR software.

Any idea on what this could be before I open a ticket and inquiry on the previous service.

73, Santiago

Erik Carling EI4KF

Personally speaking, and others may disagree but this is what I find with my 6400, 13.6 V on RX is not enough to maintain normal operation of the radio on TX. I now have 14.3V on RX.

KD0RC

Hi Santiago, I agree with Erik. If you can move your voltage up, it will help.

What size wire are you using and how long is it? A 2.6 V drop is a LOT. This can be caused by too small and/or too long of a power cable. It can also be dirty or loose connectors, including the fuse.

Al_NN4ZZ

Santiago,

Here is some detailed info on voltage setup, cable size, and troubleshooting on my web page.

Link:

http://nn4zz.com/Flex6600.htm#Astron_Power_Supply

Al / NN4ZZ

Santiago Mejia HI8O

Thanks for your comments and suggestions. I'm using the original cable that came with the radio. Nonetheless, I will re check cables and will into upping the power supply voltage.

73, Santiago

David Decoons, wo2x

check at the back of the radio with a voltmeter with probes into the Power Poles. Use FRStack, Node Red, or other utility to measure the internal voltage of the radio. Do this on receive and transmit.

Over time the Power Poles develop slight corrosion and can cause resistance to have a significant voltage drop.

73 Dave wo2x

Santiago Mejia HI8O

Following on this matter. Astron is giving 14.3 on RX and 13.6 on TX at the PS and at the 6400, Next step is to check internal fuse and change power cable (in the process of ordering a new one from Flex). Hopefully this solve the issue and wont require another trip to Texas for the radio.

73, Santiago

Mike-VA3MW

Before you take the radio apart, load FRStack, put the radio into 100% tune and see what voltage is returned while in TX.

On mine, I was getting a 2V drop. When I added some Deoxit (or similar) to the power poles, the voltage drop was 0.1V.

Santiago Mejia HI8O

Thanks Mike. I did that, and voltage while tx drops down to 10v on FRstack and SDR Monitor, while the Astron PS reads 14.3 thw whole time. Nonetheless, I prepared a new power cable with new powerpoles to check it out before opening the radio.

Santiago

Mike-VA3MW

Don't forget the Dexoit or something similar. Your voltage drop is likely due to some corrosion on the PP connectors. It only takes about 0.5 ohms of resistance to make a big difference in the supply voltage into the radio.

We have seen this before and it has always been corrosion on the power poles. Even if you change the cable, that is only 1/2 the connection, so keep that in mind.

Santiago Mejia HI8O

excellent point. Thanks Mike.

John KB4DU

Other items to check are: Using the minimum length of power cable, minimize the ohmic loss at the connection to the power supply, using ring connectors if possible, rather than power poles, confirm the power supply has adequate capacity for the radio (25 amp minimum).

Santiago Mejia HI8O

Good morning. Went to the remote site yesterday and checked up on the 6400 issue. Still same results, with new shortest cable possible. Checked and cleaned power poles, checked different power supplies. I guess only thing left to do is open up the radio (which I'm reluctant to do) to see the fuse. Left my backup rig (Yaesu 991) working for the moment and brought the Flex home because I didn't want to open it on the remote site.

73, Santiago

Santiago Mejia HI8O

Good morning. To update you all on this matter. Finally yesterday I had the opportunity to check on the 6400. Opened it up and everything inside looked right, nothing burnt, loose, inflated or with corrosion. Powerl poles were fine and clean, so did the fuse holder. In other words, everything consistent with being well serviced recently at mother ship.

The only thing I did was to reinforce some solder points on the fuse holder and on the power pole terminals (which already looked good). Just in case, because the radio was already opened (it is out of warranty anyways).

I tested the equipment and made several contacts using FT8, with 50w and with 100w and it stayed above 13 volts during transmission consuming 10 and 20 amps. In other words, normal behavior.

Now I am waiting to take it to the remote station, do a stress test there and leave it operating.

Thanks to all for your advises.

73, Santiago HI8O