Hallicrafters SX-28 Restoration Log =================================== NOTE: This is temporarily a text file until I get the desire to convert it to pretty HTML. Pictures will be forthcoming. 10-19-2002 ---------- - Purchased SX-28 from Amateur Radio Consignment Center. Saw it sitting on the shelf and _knew_ I had to have it. Been looking for one for a long time and now the time & price were right. The case is really nice outside. The inside has a little rust. Some metal tubes have some rust. Not too bad. Hasn't been powered on for around 25 years. The previous (and original) owner had it stored in his basement and hadn't been downstairs due to a physical disability. - Brought home the Beast. Set it up on the table. - Checked tubes except for the two 6B8's. Tester didn't have 6AB7 in the list, but allegedly the 6AC7 is a substitute for it. So, tested the 6AB7 with 6AC7 settings and they tested good. Also noticed that the 6SK7 in the RF section had a 6AB7 in it. Put a 6SK7 back in that socket. - Connected to a variac and slowly turned the power up. Nothing. Dead. Tried it again. Nothing. Checked switches. Dead. - Replaced the fuse with the spare and turned up the variac... the lights came on dimly, then brightened. Had headphones plugged in (back speaker connections are for 500 & 5000 ohm speakers). Heard some static. No audio. Even a nearby MW station was not coming thru. Checked all bands, nothing. Have a 8' wire ant hooked up. - Tried the 6AB7 in the 6SK7 in the RF section. No audio. Put the 6SK7 back in. - Put the TS-690 on 29.000 AM and set the SX-28 to 29MHz. Keyed up and heard nothing. Tuned 28-30 and heard nothing. Power was set to minimum. Then discovered that the HF antenna had been moved earlier to the Swan 500C which has been chattering away all evening. Idiot. Put the 500C on 3980 LSB and set up the SX-28 to 3800. Put the 500C in TUNE mode (briefly!!) and heard nothing. Then decided that it may be more productive if I put the SX-28 around 3980. Tuned 3900-4000 and heard absolutely nothing. - S-meter is pegged to the far right (same as when off). Swapped the 2 6B8's, but to no effect. Can tap on it and it moves a little. - Opened the bottom access panel. - Retrieved a small rusty loose screw. - Discovered that the ant tuning knob was loose... tightened that. - Looked over everything carefully. Saw nothing that has obviously failed. - Saw a rather suspicious capacitor... it was on the left side (if the radio was sitting normally). Near the transformer, there was a large cap that was wrapped in electrical tape and unsecured. There were two smaller metal caps nearby in clips holding them, and one clip that had no cap in it. Moreover, a wire that ran from the big cap to one of the smaller metal caps has a wire with white plastic insulation. It is clear this is not original. Looks like a failed cap was replaced. - Sealed it back up and tried again (on the faint chance that the ant trim knob being loose solved the problem). Still no received signal. - MUST get manual & schematic. April 2003 ---------- - Now have manual & schematic. Also did some research on repairing & restoring this thing. It's non-trivial. 08-28-2006 ----------- - I haven't forgotten about this poor thing. Been replacing many dozens of caps in other radios. Replacing caps is not as exciting as most would believe. - Currently working on my S-20R (bad transformer (T13) and BFO is broke, plus some strange heat on resistors). Replaced all the caps in it. - Also have to get the BC-348-P working. Undid the 12AU7 mod (pre-amp) and some other weirdness. It's not working either. That's one's a big stumper. - Going to try to look at the Beast in the near future to re-assess the state of the radio. After almost 4 years, I've learned a bit more about radio. And TV still sucks. 12-20-2009 ---------- - Still thinking about working on the SX-28. Really want to get it going, but it is a challenge. But I will. 7 years sure went by fast. Also need to fix the snow thrower. - BC-348-P is one step closer. Completely undid the pre-amp mod. Only disconnected it before. This time removed all wiring and set it back to as it was. Radio still doesn't work. Low B+ voltage (~70V). Checked the caps at 38-* & 39-* and they're leaky. Ordered new modern caps and now waiting they're arrival. 01-03-2010 ---------- - Replaced the 12 oil/paper caps. Then replaced another 11 stupid micamold paper caps. Didn't help... voltage is still around 70V.