I am working on a Realistic (Radio Shack) HTX-100. I purchased two of these for $45 last May, and was told "one works, one does not". I joined the HTX-HF_Tech Yahoo group and started looking into things.
The initial problem (but not the ONLY problem) was that there was a lot of static noise from the speaker. This noise was internal to the radio (thanks to a troubleshooting tip I got on Google+ that told me to short the antenna center to shield at the back of the radio).
I started poking around at things, and found that a trimmer resistor was dirty and was causing the static. Combined with the fact that the speaker was desoldered from the board (an oh-so-difficult fix!), I thought maybe I fixed it.
Then I hooked it up to an antenna and checked its ability to receive. Nothing. I could tune stations in on one HTX (and on my Ten-Tec), but not on this one. In fact, I couldn't tune anything.
One of the things available (not only on the group but also from a few additional websites) is a repair manual, which is really very helpful. I started into the alignment procedure and noticed that in step 3, I was nowhere near the target value of 10.695 Mhz, and was not able to adjust to get anywhere close. So I started looking at the troubleshooting section for the PLL board (where the coil in step 3 was located). A few steps in the process, I checked voltages on one of the ICs and found a handful of them off. I started checking further, and questioned a crystal. I replaced the crystal and found no change. So, I started looking at other things. I checked the voltages on other ICs and found a handful of others that are off. I looked at capacitors, and noticed a few that have tears that seem to indicate that they've failed. I replaced one that I happen to have, and it fixed one of the voltages on one of the ICs. Progress! I have a few more to do, but I need to order the parts.