Some Vintage Test Gear Madness

[mayfly]

Gentlemen,

I seem to have acquired a taste for old (Vintage?) test gear.  On to my next little acquisitions:  A set of Heathkit substitution boxes!

I did a quick measurement, and the condenser box is ok, but the resistor box is wildly inaccurate!  I've got another project it seems...

 

[Cagey]

Cool! Those things are handy! Resistor sub boxes take a lotta abuse, though. Choosing the wrong value can overheat or burn up a resistor pretty easily before you even know it's dying inside. If it was me, I'd use nothing less than 2 watt or better wirewounds.

 

[mayfly]

Way ahead of ya Cagey!  Digikey once more lived up to it's reputation for speedy service:

I've got a full set of 2Watt, 5%, Metal film, flameproof resistors.  Ready, set, go!

 

[mayfly]

Now I'm finding that the problem with buying old heathkits is somewhat similar to buying a used warmoth:  Someone else built it!  The resistor box was loaded with cold solder joints, especially around the buss bar that snakes around the top.

A little bit of effort and we've got the buss bar off!

Just took a gentle bit of prying 

 

[Cagey]

I expected those resistors to look a lot worse. Those don't look bad at all.

 

[mayfly]

Some of them are a little darker than others...

 

[Cagey]

Still, nothing looks like the smoke's been let out.

 

[mayfly]

Yep - none are actually broken in two 

 

[mayfly]

New Resistors going on!

 

[Cagey]

Nice cleanup on the switches.

Those resistors look like they might taste good. Don't let the cat see them.

 

[rgand]

This is totally fascinating. I know it isn't complex but it's out of my level of electronic understanding. Loving each photo as you make progress.

 

[Cagey]

Just so you know and can appreciate what he's got and why he's restoring it, that's a "resistor substitution box". Those two terminals you see can have wires  run to a place in a circuit where a resistor should be, then you can use those big rotary switches to select different values to satisfy design requirements or experiment with behaviors using different values. Very handy device. Lets you do a little "on the fly" engineering without doing a pile of math or a lotta parts replacement.

The other box he has is the same thing, but is full of different value capacitors instead of resistors. Wanna find out which capacitor works best for a tone control with the pickups you have installed? This will let you try several sizes and pick the one that works best.

 

[Cagey]

Incidentally, you gotta know these things are old. For one thing, Heathkit's been out of the DIY electronics kit business for about 100 years. For another, nobody has called capacitors "condensers" since before they invented dirt.

 

[mayfly]

Thank you gentlemen!

We are making some progress:

Check out my nice clean solder joint here!

and now the secret weapon for why that joint looks so good:  FLUX!!

 

[Logrinn]

But it can't be - FLUX CAPACITOR - surely?
This has to be - FLUX RESISTOR! :icon_biggrin:

 

[rgand]

Lookin good, Mayfly.

Fun stuff. Thanks for the information, Kevin. Logrinn.

 

[mayfly]

No sooner than I got the resistor substitution box complete and tested when my next piece of vintage test equipment landed at my door!

 

[Cagey]

Nice! Yet another handy piece of gear. I would have thought you'd have something like that already.

 

[mayfly]

I've got a killer digital unit that goes from DC to Daylight.  But it's a pain to work with as to change frequency or amplitude you have to go into a menu and click a bunch of stuff.  I find that I'd rather just turn a knob. 

I will say though that this guy is, well, HUGE!

 

[mayfly]

More shots on the inside of the unit:

the obligatory old and dried out caps.  Resistors look ok though.

Check out that vernier actuated variable capacitor!  Pure joy

and an interesting surprise waiting inside!  If I were to eBay that, it would pay for the unit and the replacement caps  :headbang: