I have been getting back into radio after a 16 year ‘sabatical’, and I could really use your help, as last night’s events have kept me awake all night……….
I bought a Hallicrafters Super Skyrider SX-28AU (the U is the model with the optional 230V power supply) 2 weeks ago. I paid Top Dollar for it, along with its PM-23 speaker. When I got it, I hooked the ground connector to the 3rd prong in the outlet (it helped minimize the hiss/hum), and I hooked my TV cable to the A1 connector using a Matching Transformer 75ohm to 300ohm. It has been working super great fo weeks, copying code (morse), listening to DXers, and a few audio stations. But I needed a better (ahem, a REAL) antenna….
So I acquired and installed a Jetstream JTD2 discone antenna on my balcony. Eveything went great until I removed the top portion with the disc & Load Coil. When I came to pull it off, it broke. Who knew it was threaded….. I have just spent the last 2 days restoring and polishing it up, had it all apart, and it didnt need any unscrewing the first time….
Anyways, I hooked it up to A1 on my SX-28A for about a minute… is it really bad to hook an antenna without a load coil? did this do initial damage? After 1 minute of scanning the bands, it was just as good as cable tv if not worse.
So I brought the cable tv with matching transformer to the A1 connector, and BARELY touched it, just to see if the signal of BOTH the antenna and the tv cable was better……… What happened is the radio became silent…. no reception.
I turned the radio off for a minute and turned it back on. While I tried to attach the tv cable to A1 again (on it’s own), I could smell something burning. I dropped the tv cable to the floor and opened the top lid of the radio, only to see white/grey smoke comming up from underneath… like from inside the RF box but was not. The smoke came thru the holes near the output & rectifer tubes.
I opened the bottom of the radio while off….. no smoke damage to show what happened. I turned off RF gain, back to AVC off, set to SEND, Bass OUT (off), and fired up the radio again. It stays ON, even on RECEIVE. No smoking, all glass tubes are lit. RF gain to 7 and brought up volume but still NO RADIO SIGNALS. I flicked the BASS switch to IN (on), and I heard the thump of the speaker… so I know the output transformer (T8) is good. Actually, it was replaced by the previous owner in 1990, it is one of those black ones.. perhaps by Peter Dahl.
Please oh please, someone puhleeeze tell me this is an easy fix…. I just spent almost $1000 getting this rig. I do not know how to use an oscilloscope, but I work on tube guitar amps & stuff, and I’m no stranger to a soldering gun. I have the original manual and a list of the components that were already replaced. I scan scan and upload to this forum anything. The previous owner even wrote EVERY component value in this book, along with many pencilled notes, calibration logs, etc etc.
Oh… and maybe someone can explain to me the do’s and don’ts of antenna usage as it related to tube amateur radios….. How does something made to Military Grade Specs start to smoke in my house by a simple antenna contact..?
Thank you all in advance, and yes I feel stupid enough already… *embarrassed*.
1 thought on “HALLICRAFTERS SX-28A – Smoldering . . . _ _ _ . . .”
Did you ever get your SX-28 fixed?