apache-labs.com

Hello,

As you know I was struggling with heating up the amplifier to 40-42 quite soon and then receiver sensitivity used to go down.
Later I realised that they are different issues. Sensitivity was going down because of the J3-J3 cable between the Antenna selection board and the control board.

The problem disappeared after taking out the cable and inserting again for some time and came back again but the problem is there because of the cable and also probably because of a relay.

Once sensitivity goes down, It comes back after some time and the radio needs to shut down for an hour or more. If it does not comes back even then, and I press tune momentarily and the radio gets life again for some time. In your opinion this pressing tune business relating to the relay?

Today I was looking for something in various reviews of this radio and found one such review by Mark Abraham NI0Z of sdrzone (https://sdrzone.com/index.php/en/56-ana ... dle-review) and noticed the picture of amplifier board and noticed R22 & R32 are touching the heatsink compound to probably sense the temp of the heat sink and both the legs are insulated while in my board these are in the air above the slot on the PCB. Attached, please find both pictures. Please let me know if it would be beneficial in any way if I insulate the legs and put the heatsink compound in the slot and let the sensor touch it?

Thank you for your support

73
Bhanu
VU2MB

I regret that I'm unwilling to pull my 8000 out of the rack it is in and disassemble it to see how it is built. Perhaps someone else might have easier access to their 8000?

However, it certainly looks like it ought to be built like NI0Z's.

Perhaps you might try contacting the factory for advise on this, first.

Dear Scott,

Thanks for your response. Yesterday late at night I have done that already.
removed both of them and insulated the legs and put thermal compound in the slot
and now both of them touching the surface of the heatsink.

The issue I might encounter now on is this-
If it was taking 20 minutes of FT8 use (50W) to 40 degrees Celcius temp may now take less.

Regarding the sensitivity issue, I opened the circuit and checked J3 - j3 cable and 2 pins carry dc power and the rest 3 pins select antenna port depending on which port is getting power. Either DC lines are blocked after some times and that's why the radio loses connection to the antenna port but sometimes even after shutting the radio for a few hours and then switching it on it looks like blanks on the pan adaptor until I press tune and then it comes back to life. That's the challenge for me.

73

Bhanu
VU2MB

Sounds like a bad relay.

Hi Scott,

Thanks, That's what I feel so now will see which one is the culprit.
My guess is the one that's on the TR Switching board. Will check it during the day. It's quite late now.

73

Bhanu