Ahhh… the smell of dust burning off 50 year old vacuum tubes is like the smell of your favorite Christmas dish wafting in from the kitchen …. its a special smell, though few appreciate is as much as us old radio guys.
I *finally* got off my butt and put the new AF Gain pot in the Hallicrafters SX-140 I bought on eBay some months back. The pot came from an eBay seller, and not a bad replacement. The mounting shaft is a bit smaller than the original, but no problems otherwise. I had to replace the original because the pot was missing the shaft(!). Huh? Yeah, the control was there but the shaft was gone.
After looking at the factory pots, its clear how that happened. The shafts stick through the pots, which have no closed back to them. The shaft has some “crimps” to keep the shaft from pulling frontward, only its evident if you pull on them hard enough, i.e., trying to pull off a knob, you could pull the shaft entirely out of the control.
I bought it this way, though the seller opted to omit this fact, and used a photo that didn't highlight the front of the radio so well it was clearly obvious. Thankfully the problem wasn't a huge one to fix.
Last night I finished the repair and tried the receiver. It's circa 1962 or so, and it was Hallicrafter's entry-level ham bands receiver, matched to the HT-40 transmitter and aimed at the Novice market.
How's it work? Amazingly well!
I was checking out 40 today, and found (ironically) the Hallicrafters net on 7280 (at least that's where it was on the SX-140). The sliderule dial isn't exactly known for its precision; the 40 meter band is marked off in 25 kHz segments! But the Hallicrafters net was about 5×6, with my damned line noise competing at times due to QSB.
After the rig warmed up, the drifting wasn't so bad, even on SSB. Unlike other cheap receivers, you could tap the case and not send the rig's VFO into spasms. The switches and pots are dirty, and I'm going to invest in some contact cleaner.
After listening to the rcvr a while, I thought I would compare it with the signals on 40 using the Yaesu FT-2000. I was surprised to find the signal levels were essentially the same; nothing on the FT-2000 improved my ability to copy the Hallicrafters net. All the signals across the band were comparable as far as strength and audio quality.
While running the SX-140 I found a guy running some CW in the old Novice segment on 40, and I tuned him in a copied a while. The rig was stable (as much as you could expect from an old tube rig) and audio sounded great.
This is the second SX-140 I own; the first one arrived DOA, and without a workspace to really tear into it, I opted to shop for a working example rather than fumble with the first one. I also own the matching HT-40 txmtr and the HA-5 VFO. My goal was to have the complete station operating, and now I can finally do that. The problem is the SX-140/HT-40 station is on the right radio table, and I have HTs chargers, books and other stuff stacked on the table in front of the station. I'll have to clear out the table top first, something I probably should do anyway.
I've been doing some major cleaning spurts in the shack; my goal is to get a 3-foot folding table in here so I can have a spot to tear open a radio without cluttering up my operating position or other desk space.
I have another “project” rig to tear into sometime — my KnightKit R-100A receiver. It apparently has at least one wiring error, because the antenna trimmer doesn't “tune” the first stage, but it varies the main VFO. The Knight probably has some other issues too, though it may just be the nature of the beast. The rcvr drifts constantly; it's alignment is way off, and it receives images of strong signals in places they should not be. It suffers from the “slap the case and watch the frequency jump” syndrome too.
I have the matching T-150 transmitter; they're both Boat Anchors of the First Order, though each component isn't as heavy as the large case may imply. The T-150 seems fairly stable, though the output isn't what it probably should be. It has a horrible eHam rating of less than 2(!), but from what I can tell the chirp doesn't seem to be bad on mine. My T-150 apparently saw uses on RTTY, believe it or not; the rig had a toggle switch added to the front panel labeld “FSK” with selections for 20 or 40 meters. There's an FSK jack too added to the rig. I suspect they used it on crystal control, but can't confirm that.
Most of my vintage gear CW operating is usually on 80 and 40, and as a rule, these rigs have less chirp on the lower bands. The T-150 uses grid-block keying, and puts considerable voltage on the keying line — a fact I found out for myself!
The rig uses two 6146s in the output, and should put out 100 watts or more. I can't get anywhere near that, but I haven't checked a single tube in it yet so there's probably an issue there.
It would probably be better served to put both the KnightKits on eBay and let someone enjoy them as a retro experience. I could use the space for … one of my many other classic rigs I don't have room for in the shack.
73 es CUL … de KY4Z … dit dit …