Yaesu FT-891 Display Issue

About a month earlier, I purchased a Yaesu FT-891 for my new mobile rig.  The current radio was an FT-100D that was getting old and long in the tooth and while I was really happy with the radio, some things started happening that made me think its time to switch it out with something newer.

Being that I have been very happy with Yaesu mobile radio products, it only made sense to try out the FT-891.  I bought one used, and played with it on my work bench - it worked great and I really liked the interface, look and feel.  So... now its time to do the mobile install.

Since I already had the FT-100D mounted, it didn't seem like it was going to take much to do the install of the FT-891.  This whole installation process will be the subject of another post, but I wanted to share something that happened to me when doing the remote head installation.

The installation went generally well, but when I went to turn on the radio one evening after re-running one of the cables, the detachable face would not light up.

Hmm....  Ok, lets just put that detachable face back on the radio and see what happens...

Nothing.

More troubleshooting - Lets take it out of the truck and get this on a solid power supply - maybe something was odd with the power.  

Still Nothing.

My heart sank.  What the heck happened!?!?

A glimmer of hope?

After getting it on the bench, what I found was that when the power button was pushed, you could hear a couple of relays clicking, then there would be a faint beeping (6 beeps in rapid succession). So, the unit was getting power, but it wasn't happy about something.  See a quick video of what it sounded like: https://photos.app.goo.gl/vVa3cbGCcAt1Wcvt9

On some suggestions I found on the internet, I reseated the cable attaching the body to the detachable face, and tried some master reset routine - still nothing.  I even attached the USB cable to do the firmware update, and was able to see that the radio was responding -- so, at least it wasn't dead.

I even messaged my master troubleshooter buddy K9XR at 11pm to see if he can help in the search!

This is what I found

I will spare you all of the details of troubleshooting (I actually just miraculously stumbled across it), and go right to the details.

Watch what kind of extension cable you use for the remote head.  This needs to be a RJ-12 cable, and it has to be a straight through cable.  I accidentally bought a reverse cable or a "roll over" cable.  If you will notice in the snippet of the schematic of the FT-891 main board, the jack for the remote head carries 13v to the remote head.  If you use a "roll over" or reverse cable, pin 4  connects to pin 3 on the remote head (ground pin) - and will then blow the fuse (F1002).  What a major mistake on my part and has me kicking myself for not just buying the YSK-891... But I really didn't need anything from the kit except for the RJ12 cable.

Here it is on the board:

Let the fun begin

So, replacing this fuse is not for the faint of heart. First - Part availability. Looking it up at Digi Key, its only available by a roll of 5000.  I found a place called Radio Parts that has them by the piece for a whopping $0.36 (So, I ordered 10!!). Website here: https://www.radioparts.com/vertex-q0000109 

With that on order, I decided to pull the old fuse.  Unfortunately its a 0603 SMD component, and its tucked nicely (I'm being sarcastic) behind the big RJ12 jack:

A bit more of a close up here:

I really wouldn't recommend doing this with a soldering iron, and would cautiously use your master skills with your Hot Air SMD rework station.  This thing is small, and very fine tweezers are a must:

Replaced the fuse, and now I am a happy camper!