Tuesday, January 26, 2021

SB-401 Transmitter Rebuild Progress - Part 4 -

 Got the new BNC connector all squared away, and replaced the mismatched hardware on the SO-239 RF Output connector. Still waiting on parts because I can't locate a couple I thought I had.

So I went on to my favorite pastime lately, cleaning wafer switches.

This is the Function Switch, all cleaned and lubed.

Before I got started cleaning the switches, I went through the whole chassis tightening hardware. Seems like every time I put a screwdriver or 1/4" nut driver on a piece of hardware, it was loose. Sometimes maybe an 1/8th of a turn, usually about 1/4 turn loose, and a couple that were over a full turn loose, which is definitely in the "Finger Tight" category. Since most of these either grounded the periphery of a printed circuit board, or were securing a ground lug/terminal strip, it was critical to get them all nice and snug again.

And while doing that, the occasional example of Poor Workmanship popped up, like this wire crudely stuck through the terminal and "soldered" in place.

Judging from how "well" the solder flowed onto the bare wire, I'd say this is either a bad solder joint, or about to be one. This is on the Bandswitch, and poor soldering here can cause all kinds of grief down the road. 

What I've been doing to help prevent that is cleaning/flushing/treating each wafer separately, and then wicking off all the solder, cleaning the wire and terminal, applying a very small amount of new "Flux, Rosin, Type RMA", and resoldering each connection on that wafer.

And you can see how dirty the rotary and stationary contacts are compared to the above picture.

We got about 2" of snow last night, and tonight as of 2330, it's down to 15*. Makes me glad the new track has remote start in case we have to go somewhere. One thing I've noticed is how fast this engine warms up. I'll get in the car in 15~20* weather, start it up, and by the time I'm buckled in and a block away, the temp gauge is up off the peg, and the heater is beginning to blow warm air. One of the things all the manufacturers do these days is to get the engine up to operating temp ASAP, as it greatly aids emissions reduction, and this is a side benefit.


  1. Interesting how you are rebuilding all your old stuff. Cleaning, tightening, working on replacing bad components, making better solder joints.

    Almost like... you're avoiding buying a snowblower... :) (Had to get that in there....)

    Nice that you are bringing old equipment back to life.

  2. HAH!

    We really haven't had much snow this year. Once we got hit hard, and a neighborhood kid came by and offered to do the sidewalks and drive for $10. He did it so well I gave him $20.

    And now one of the neighbors has a new snowblower, a medium size Toro, and he's been doing all the sidewalks on the cul-de-sac.

    So yes, I've been ducking spending $1100 on something we really don't "need" right now.

    I'm glad I did the receiver first. The transmitter has twice as many capacitors, 4 times as many rectifiers, and even more switch wafers to clean.

    It'll probably take another three weeks to finish.

  3. And these radios will survive an EMP. Nice to have around. I have a couple of HW-101s and an SB-100 but they are in storage 250 miles to the north. We are going to build a shop (24'x30' or a maybe a bit bigger) and will be bringing stuff down south to sort through. Most of it is my "junk" but there is other stuff.

    1. As long as you have the manuals, those Heathkits can be put back on the air in short order. Capacitor kits are available from Hayseed Hamfest, and if the manuals are all in tatters, several places sell nicely bound reprints.

      And tubes glowing softly inside the radio have a nice spiritual warmth to them. It's kinda like being gathered around a campfire with your Ham buddies!

  4. Replies
    1. Slowly, but surely.

      Should have another post tonight....


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