Fuse location SX-62A/B

[Edward Cain]

   I'm recapping my SX-62 and thought that while I was at it I'd install a fuse and thermistor inrush limiter. As far as I can tell the SX-62 didn't come with a fuse whereas the A and B models did. What I can't figure out from looking at the manuals is where the fuse was located and what type of holder it was in. I would like to duplicate the original, if possible.
   Anyone on the board have an A or B model or otherwise know the fuse location?

Thanks,
Ed

[Todd, KA1KAQ]

I've got a B model Ed, and the fuse is located to the far right on the chassis, right in front of the power transformer. If your chassis is labeled with the tube numbers, the fuse would be located between the transformer and the 5U4GB label.

[Edward Cain]

Thanks very much Todd. With your information I was able to look closely at some online photos and see what looks like a panel mount fuse holder mounted through the chassis at that location. Should be an easy mod.

Ed

[WQ9E]

My B is set up just like Todd's.  Your other option is to install an inline fuse holder below chassis if you do not want to drill any additional holes for a mounting point.  With an inrush limiter you shouldn't have any nuisance blowing so if a fuse goes you would likely need to take it out of the cabinet anyway to address the cause of the blown fuse.

The SX-62 series runs pretty hot and the transformer is none too big for the load.  I would seriously consider going to an SS rectifier with proper dropping resistor which will dump the rectifier filament load from the transformer and allow it to run a bit cooler.  If your line voltage is on the high side you could connect the now unused 5 volt winding properly phased in series with the primary winding to reduce the secondary output voltages somewhat and further reduce transformer heating.

I have 3 SX-62 series receivers and an SX-42 and all of them had bad mica caps in the FM discriminator transformer.  With a leaky cap the discriminator will neither tune nor function properly.  In a properly performing SX-62 FM will be cleanly demodulated when tuned "on the nose" and it will also demodulate FM via slope detection if mis-tuned slightly to either side of center.  If the discriminator is not working properly, the center tune point will either be non-existent or worse than the slope detection results on either side.

I used an SX-62A for the first week as a novice.  While I don't recommend it as a ham receiver (even with steady 14 year old hands tuning was very critical) it does make a good sounding nice looking band cruiser.

[KM1H]

The fuse became standard on the SX-62A MK 2 chassis.

Carl
KM1H

[Edward Cain]

Carl, thanks for the additional info.

Rodger,
   Too late. While you were writing I was punching a hole in the chassis. This was not original when I got it. The previous owner had done some mods; one of which I don't quite understand. Perhaps you can shed some light. He ran a short length of coax from pins 2 and 3 of the 7F8 tube, up along the side plate of the chassis and into what looks like a phono socket mounted to the side plate facing toward the interior. So to access this socket you need to open the cabinet.

   I'm going to use the 62 for general SWL and, hopefully, some nice sounding FM broadcast.

   I am also working on an SX-42 which is going slower than the 62. Got the 42 working on the lower bands but nothing on the upper band in FM.

Ed

[WQ9E]

Ed,

Pin 2 is the grounded filament connection in the SX-62 and Pin 3 is the plate of the mixer section so it sounds like it was intended for use with a Q multiplier.

The SX-62 already has a decent crystal filter albeit of limited usefulness given the lack of band spread.  A Q multiplier could be a problem with this receiver since the mixer output is either 455 Khz. or 10.7 Mhz. depending upon the range selected.  The coax is going to cause some definite de-tuning of the 10.7 Mhz. IF transformer and it would have been realigned to compensate.

If I were you I would remove the added coax connection from the 7F8 and avoid any issues which may have been created by this mod.   

[ke7trp]

Mine has the Fuse holder. Must be a later model.

I love my SX62. It has the best sound out of any tube rig I have owned. I use it with nice studio monitor type speaker.

If you want a display. The AADE DFD1 works great with NO mods, You can clip lead it in and run the wires out the back and have a Nice display. They have a model that will read all the bands even when the IF changes to 10.7.  It really is sharp.

You can also add an S meter. I was lucky enough to find an original Hallicrafters External S meter. The guys here helped me hook that up.  While NOT a good ham reciever, Its one of the best SWL or FM tube radios I have come across.

C

[WQ9E]

If I ever come across a somewhat ugly SX-62 I would be tempted to remove the h emblem on the right of the front escutcheon and mount a magic eye tube "S meter" in its place. 

The SX-62 is a nice looking receiver and it has great fidelity.  The SX-42 has almost identical circuitry but is much better suited for amateur use with its bandspread system and front panel BFO and crystal phasing controls.  Near the end of the SX-42 production life Halli was advertising the SX-62 for $294 and the SX-42 for $299.  For the extra $5 you got bandspread and gave up a 500 kc calibrator which is a pretty good tradeoff.

[ke7trp]

Yeah.. The SX62 has one purpose in life really.  SWL and music. Its really big and heavy, almost no ham features.  It also overloads easy with BIG AM ham radio signals.

I got mine after seeing that this was the presidential reciever for JFK.  I ran across an incredible example and purchased it from a friend.  Its in the game room near the kitchen. I turn it on when cooking or cleaning. It really sounds nice.

C

[Todd, KA1KAQ]

The 62 has my favorite dial on it: all of the SW stations listed by country on the different bands, and that wonderful 'Band in Use' lighting scheme really completes it. Mine sat in the parlor of the old house with a big speaker above it on the wall. Used it to listen to 620 WCRN when they were playing Big Band and American Standards. When they went to moldie oldie 60s-70s stuff, the use diminished.

Haven't been inside mine for a few years now, but the late A models (MKII or III?) and Bs were the last models produced, so I'd guess the issues of bad caps and the likes shouldn't be such an issue due to new/better components? Just a guess. IIRC, my B has a bunch of red caps in it.

Sounds good on FM, but I seem to remember drift being more noticeable?

The issue with mine is a problem with the tuning needle snapping back when I stop tuning. It would appear that the tuning string has actually shrunk a bit over time. Easily accessed for repair, but still a PITA.

[ke7trp]

Mine has wonderfull FM. I can find the sweat spot easy.  The only issue I have is the dial indicator is off a bit. Even with the front panel adjustment, its off.  Close enough. I would like to kick it over one day so the the pointer is dead on with the adjustment in the middle.

[KM1H]

I use mine on FM a lot also and for a 1947 or so design it sure is hot.

The overload is due to the 6AG5 RF amp, not exactly a linear tube and not very good with AGC. At least only 1 RF stage is selected on the lowest bands. Ive often wished that I had made a few mods for different tubes when mine were under the knife.

Carl
KM1H