Thursday, January 14, 2021

SB-301 Rebuild Progress - Part 5 -

 I spent last night removing the old two-wire AC Input socket, and making way for the new three-wire socket. 

First, remove the old. This an "inside view" after I unsoldered and removed the old socket.

Then using my good friends Caliper, Nibbler, and the two File brothers, I set to work enlarging the opening from .500" x .875" to 1.2" x .875".

This is NOT something for the faint-of-heart or the mechanically inept! Taking tools in hand and removing chunks of metal from a pristine chassis like this, and not screwing it up, takes some patience and skill. As my Dad taught me, "Measure Twice, Cut Once, Or Buy A New Board!", and I've always taken that advice to heart. So, I measured about ten times, marked it out with pencil several times, held the part up to the markings, made some adjustments, took a deep breath, and cut metal.

I roughed it out with my good old Adel Nibber, and then had the File brothers attack the problem, smoothing things out the rest of the way to my pencil marks.

Yeah, I gotta be more careful to use the guidelines in the camera viewfinder to ensure the pix don't look tipped.

But, it fit!

And there was plenty of lead length on the original wires to restore the AC connections.

Drill two holes, and add hardware to finish:

One thing that's always bothered me was Heathkit's wide use of RCA Phono jacks for RF connectors. Looking at the pix of the back panel reveals a forest of them, and for RF use up to 10MHz or so they're "OK", but I always thought using them for the antenna connection was pretty cheep.

It turns out that if you remove the RCA jack, the punched hole is almost a perfect fit for a BNC connector, a "proper" RF connector.

So I swapped it out....

And no, "BNC" does NOT stand for "British Naval Connector" or any other such nonsense. It means "Bayonet Neil-Councilman", for the type of locking mechanism it uses, and the two guys that invented it.

So at this point the cleaning and replacing is done, along with resoldering several dozen connections, and cleaning up some General Workmanship Issues that would have gotten you an "F" grade in my soldering classes.

I've cleaned the workbench again, and shifted from "Repair" to "Alignment" mode, and my test gear's been warming up for about the last hour, so it's time to head back down and began the alignment process.

"Part 6" of this will either be "It's Finished", or "Awww RATS, Look What Else I found".

Stay tuned.....


  1. Replies
    1. Passed the power-on test last night, so I didn't make any undiscovered mistakes in the power supply.

      BUT - The very first test is to calibrate the crystal calibrator, and the crystal calibrator doesn't seem to be working.

      Project for today: Get the 100kHz Crystal Calibrator to do it's thing....

  2. Getting there is half the fun, the other half is powering up and NOT getting any smoke out of the box!

    1. You betcha! While I still have a few bottles of "Lucas Replacement Smoke", I don't have any "Heathkit Replacement Smoke", so I'd be SOL!


Keep it civil, please....