|From Universal Radio|
Then, in the 90s, I got a pair of FT-990s and the '440 went on the shelf. It stayed there for a few years until one day I decided to hook it up and blow out the cobwebs...but the old faithful '440 just showed dots on the display. Dang. So, I put it back on the shelf, where it stayed a few more years. I probably would have sold it, except I knew no one would give me what the upgrades were worth...and it was a radio I had a history with and didn't really want to sell.
I eventually surfed up info on the "dots" problem and decided I'd try to get the rig going again...a couple years later (last week!) I finally got around to checking it out. I hooked the '440 to a 12 volt supply and hit the power switch - I was amazed when the rig powered up on a frequency and not with dots displayed. But every few seconds, the display would flicker to dots, but would come back on frequency - not as bad as I'd remembered, but still not usable. I had discovered over the years that the dot display was an indication that one of the PLLs in the rig had lost its lock. The primary culprit was some rubber potting compound that Kenwood used that goes bad over the years and becomes conductive. There are several other potential causes, but a cleanup of VCO-5 is the best place to start.
The other tell-tale sign of a problem with VCO-5 is rough audio - which I discovered I had. The QRG was a bit jumpy as well. So, I dug into the rig and popped the top off the VCO-5 shield. Sure enough, there was some "Evil Brown Goo" - I measured about 300-500 mV between the EBG and ground so I knew it had gone bad. There was one spot that seemed worse than the others, so I took some tweezers and pulled a bit of it out and powered the rig back up - and with that little bit of effort, I noticed an improvement - much less dot display. I still had bad RX audio, so I decided to pull the PLL board and dig out all the EBG I could.
At first, I thought I could leave the shield in place, but decided I needed better access so I removed it. I was also going to try to tweeze out all the goo without removing any parts, but there were some parts I couldn't do that for, so I ended up removing a couple caps, a transistor and the varactor, which was a bit stressful, as it's now unobtanium. I also broke a disk ceramic cap and decided to replace a resistor that had gotten a bit beaten up in the de-gooing process.
So after several hours I decided VCO-5 was as clean as I could get it and put the rig back together to see if I needed to dig any deeper. Amazingly, the rig now sounds great and no indication of PLL unlock on any band. So, it looks like it was a relatively easy repair as far as the dots go. I haven't actually put the rig on the air yet, but I'm enjoying listening to it!
There are a lot of online pages devoted to the repair of the dots problem: this one by OZ1BXM was my main reference....that and a lot of info included on the TS-440 Yahoo Group. Thanks to everyone that has documented working on this problem...it allowed even a hack like me to get my old rig going after about 15 years in mothballs!
I'm looking forward to using this one again!