Fixing old Sun Electric test gear

Too damn sick to go out to shop today, stayed in the basement and worked on some old Sun Electric equipment. Figured it might make an interesting tech article if someone was curious about how to fix some old electronic gear dating back to classical antiquity...


Its an old “Coil Condenser Tester” from Sun Electric built in 1966. The only reason I know the date is because Sun seemed to unambiguously stamp a build date on the back side of the case of everything they built. I picked it up at a swap meet a few years ago for a few bucks not knowing what it was or if it worked but figured it was cool enough to find that out later. Sun made a ton of cool gear like this and I figured with a condenser tester with cathode ray tube (CRT) and analog meter would be cool enough just for parts for other projects if it was a total failure.

 

Like most electronic gear from post WW2 and up until about 1970, this thing uses point-to-point wiring and vacuum tubes for amplification. Although the first viable transistor was invented in 1947, they weren't used much in audio or test equipment like this until the 60s, and then they slowly edged out vacuum tubes by the 1970s. Solid state rectifiers have been around since before WW2, but typically only for small current rectification. The condenser tester I'm working on uses both a few triodes (vacuum tubes) for amplification and some transistors, and all solid state rectification.


Vacuum tubes use high voltage at the plates, typically between 250 and 450 volts. CRTs use even higher voltage around 800 volts (so be careful if you are going to dig into gear with tubes or CRTs). Typically the power for these components is supplied through a vacuum tube or solid state rectifier to a high voltage electrolytic capacitor. Back in this era, high voltage electrolytic capacitor were expensive and were somewhat unstable. Over time, they loose their ability to handle high voltage and short out.

 

Most of the other parts besides the electrolytic capacitors is pretty stable. The carbon comp resistors, the transformers, the inductors, the windings in the meters, the CRTs, the tubes and even the wire in gear from this era is built to last and will have no problem lasting a while. The electrolytic capacitors are the only problem. Fortunately, we can fix them.


Electrolytic capacitors are made by building up a layer of aluminum oxide on the plates as an insulator in the capacitor after they are assembled. The thicker the layer the higher the voltage capacity. Over time of disuse the oxide layer breaks down and the voltage capacity is diminished. We can fix them by just bringing up the voltage up slowly, using a variable transformer. Just plug in the equipment and bring the voltage up from 40 volts or so up to the 115 volts that typically comes out of the wall.

 

Bringing up the supply voltage slowly is a procedure that can save lots of old equipment, especially your old black face fender amp that just blows fuses. There are a few things that can go wrong though.


At 70 volts, the supply transformer was getting warm enough to melt the wax out of it, and it popped the circuit breaker in front. Something more than old capacitors was wrong with this thing. The capacitors in this type of gear are easy to spot. Typically, they are in a brown cardboard tube covered in wax. These two are marked 8 micro farad at 450 volts. I desoldered the capacitors and tried it again with the same results. The capacitors tested ok, if not a little low as expected. I disconnected a few things the high voltage supply fed and got the same results. Only thing left was the diodes, and one was, in fact, junk.

 

I didn't have an 800 volt diode in my stash, but 2 400 volt diodes will do the same thing so I put it all back together with them and some new capacitors. Capacitors are cheap these days, 20 cents will buy something 3 times bigger than what was in there. The 22 micro farad replacements wont affect performance because they are just filters, and if they could have used these when they built it in the first place they would have.


Turns out it is also a coil tester as well as an ohm meter. I'm not sure what the CRT is supposed to display, but it works. I'll play with it more after I fix my distributor machine...

 

I hope you take us along when you fix you distributor machine.

 

10-4 on that.

 

I have an old Sun distributor machine that I would like to rebuild. It spins and strobe lights work but the gauges were customized by some jackass years ago. Any ideas for parts? Thanks, Bill

 

Nice work! I love working on classic electronics so much more than mdern stuff because you actually have to trouble shoot down to component level. Most modern stuff you just repalce an IC or entire board and be done with it.

I have 2 entire sun machines I have been planning on redoing but they are still at my uncles house in MI. Definitely want to see your work on your distributer machine.

 

Um, yeah, dad was a sales man for Sun back in the day and so 2 years ago he's takes me to buy a distributor tester... still haven't fired it up and yesterday we drove 400 miles round trip to buy a Master Motor tester.... again. don't even know if it works... I'm gonna be pickin your brain!
Thanks!

 

Very cool info for us 'lectrically challenged folks.

 

Somehow this thread is appropriate. I just picked up the exact same model on e-bay a few days ago. On mine, the meter needed some work, and one large capacitor is leaking (but that will have to wait until I find a replacement on ebay). All-in-all I got lucky because the accessories came with my unit -- those are real hard to find

http://www.garagejournal.com/forum/showthread.php?t=32791

I hang out on the GJ, and among other things I collect vintage Sun equipment.
I've done a few restos, including a Distributor Tester, Engine Analyzer, some older VAT's and few other larger pieces.

 

Seeing the old condenser tester reminded me of a pretty common old shop prank. You would charge up a condenser on the tester and then toss it to your buddy, who would inevitably catch it, when he did, if he had it by the case and the pigtail, he got zapped.

 

Anyone interested in purchasing a working Sun distributor tester? My father has one that is for sale....make an offer.

 

Nice work Dave.

 

I saw that thing on ebay, and was somewhat vindicated by the selling price, as though, "yes, i guess this old thing was worth my time to fix"... I do need to come up with the instructions and maybe make some of the connectors.

I'm less interested in restorations, as cool as it is to have all the proper factory stuff intact, but more interested in restoring the functionality to these obsolete devices. I can't afford to be much of a collector, more of an accumulator, with a keen eye for spotting busted cool crap at swap meets.

Let me know if you come up with a set of instructions or anything regarding the condenser tester. I really have no idea how to use this thing.

 

Way too cool. Thanks for sharing --

 

One of the kids dropped these off last summer. They were in pretty rough shape. They came out pretty good Ive got everything working except the dwell meter on the dist. machine.

 

Those look GREAT!!! nice job -- They'll make a great addition to your garage.
Did you have to repaint these machines? If so, how'd you manage to do the dial faces and the numbers/letters?


I really love these old Sun testers and have refurbished a few over the past three years.


Here are some recent projects.

 

Nice Stuff guys!
I persoanlly have a nice EET 1601 but I could use some leads and I really need a manual (rats turned mine into a nest). My machine is in great working order otherwise. anyone have any manuals or know where they might be found?

FWayne

 

One of the coolest threads in a long time. I have an SS400 scope (The Big one) and an 404 Dist Machine. Got a SS110 scope a while back that I'm working on now. The Sun stuff is very well built. Looking to buy an Engine Simulator that the Sun Repair techs used to test scopes. Really enjoyed this thread ! Great stuff from everyone. It's hard to find car guys and electronic guys at the same time. I have found some Sun Electric Patents to have The circuit and operation explained that really helps in trouble shooting. Google Patent Search is free. Thanks again guys great job!

 

Send Bob Master's an e-mail. He's one of a few that still repair these things commercially. He has quite an extensive library.

[email protected]

Good luck!!

 

So i was digging through some stuff and found this, here's the first four pages. The other to follow in the next post.

k.

 

Here's the last four.

k.

 

Thank you so much!! That's some very good info --
Much appreciated!!!

Here is one I recently refurbished -- before and after.

http://www.garagehangout.com/forum/index.php?topic=2209.0

 

Wow an old armature "Growler" haven't seen one of those in years. You ever have occasion to use it?

 

Sure did -- just to test the thing I took apart an old generator and tested the armature with a hacksaw blade. It worked well, but the sound is somewhat disturbing.

 

It's funny how a used hacksaw blade is part of the setup. And for sure if you hear that sound once you will always recognize it.

 

What kind of paint did you use? I just bought a 1956 Sun Distributor machine and plan on refurbishing it and using it.

 

I used Rustoleum "Verde Green" Hammered Paint.

Good luck!