realized that I would have to
completely disassemble it and
unsolder every component in order to
bring it up to my standards.
I wasn’t planning on restoring it
to an all-original museum piece, but I
did want it to look nice and work. The
finished restoration is shown in Figure
3. I was pleased with the result. The
old metal cabinet had some light rust
on it and I had planned on trying to
match the original Heathkit gray
wrinkle paint. After unsuccessfully
trying a few automotive sprays, I went
for the ultimate: a gray hammertone
powder coat. The finish looks great
(as you can see in Figure 4) and it’s
tough as nails.
The front panel was missing a red
binding post, and the rest of the posts
were dirty and tarnished inside. I tried
finding a matching post, but in the
end I bought six dozen brand new
ones. Their bright color gives the front
panel a real pop.
Taking the unit apart was easy. It
was putting it back together and pre-testing each circuit
that took the time. I took lots of “before” digital pictures
and made sketches of the critical wiring so I wouldn’t lose
track of things. A few days later when I was surfing the
Internet, I was amazed to come across scans of both the
original Heathkit EC-1 assembly and operational manuals.
They were available as two 40+ page pdf files and
contained complete schematics for the amplifiers, power
supplies, and front panel controls. To download the
manuals, please see the web address in the Resources
If you are ever thinking
about buying and restoring a
piece of electronic equipment, I
have several bits of advice for
you to consider:
1. Be sure the front panel
and its silk screening are as clean
as possible. It can be difficult to
restore the delicate silk screening
or big scratches. Plus, any
calibration or inventory stickers
can leave discolored areas.
2. If you are buying a unit on
eBay, be sure you see at least
one photo of the interior. Sometimes
bad things can be found within, like
overheated transformers, water
damage, missing parts, etc.
3. A little grime is okay, but
extensive corrosion or a broken one-of-a-kind component can be hard to
replace or restore.
Getting to Work
One of the big no-no’s with
vintage equipment is to plug it in the
wall to “see if it works.” Even using a
variac is not the best way. Some
components — like electrolytics — tend
to degrade with time, and if you apply
full voltage they can actually explode.
So, the trick is to either “re-form,”
rebuild, or replace them. The Internet
contains a plethora of excellent advice
on how to re-form electrolytics.
Sometimes it’s successful, sometimes
not. For this restoration, I chose to
rebuild the electrolytics and replace
the smaller caps with modern ones.
Figure 5 illustrates the four steps I took to dissect the old
electrolytics and slide the new ones inside the paper
sleeves. I thought that using the original sleeves would
give the restoration a more vintage look.
After all the other components had been unsoldered,
I measured a number of the carbon resistors and
potentiometers (pots), and was surprised to find that many
were out of spec. So, I decided to replace them all. The
wire-wound power resistors were fine.
The only major deviation from using all original parts
was the replacement of the nine “amplifier balance” pots
located along the very bottom of
the front panel, as seen in Figure
4. During the past 50+ years, the
original pots had degraded in
value, from 3,000 ohms to as low
as 2,150 ohms, and several of
them didn’t even have enough
range to balance the amplifiers.
The original pots had screwdriver
adjustment slots, but I chose to
buy pots with shafts and add a
small knob because this way,
they were much easier to adjust.
They made the front panel look
different from the original, but
what the heck.
The rectifiers were a strange
mix of silicon and series-wired
By David Goodsell
May 2016 41
FIGURE 4. The new binding posts
enhanced the look of the front panel.
The nine “amplifier balance” pots along
the bottom had degraded during the past
50 years and were replaced.
FIGURE 5. Rebuilding the large electrolytic
capacitors involved slipping new capacitors into
the old paper sleeves to retain the vintage look.
Post comments on this article and find any associated files and/or downloads at