Replacement HW8 VFO tuning caps available

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From: Mike Czuhajewski (wa8mcq@comcast.net)
Date: Fri Apr 04 2003 - 08:33:40 CST


I'd long ago given up hope of finding an exact, drop-in replacement for the
VFO tuning capacitor in the HW-8. Every now and then someone asks how to fix
the plates on theirs, since they sometimes fall off the shaft. (The problem
is caused by the amount of torque that the reduction drive can supply, as
explained below, and continuing to turn the knob after the capacitor hits
the end stops.) Although they can be put back in place it can be a pain and
may not last forever, and it would be better to have a replacement
capacitor.

Suddenly, like a bolt out of the blue, I got e-mail yesterday from Larry
Baker, WB5OFD, telling me that he tracked down the company that made
them--still in business--and found that they can still supply the capacitor.
He said he's looking at a lot of overtime coming up at work so I offered to
post the info for him. He really went beyond the call of duty in tracking
down the company, and HW-8 owners will be grateful for years to come :-)

And you don't have to own an HW-8 to take advantage of this, since the
capacitor can be used in any VFO that you might want to build.

Here's his info--

HW-8 VFO Tuning Capacitor

For anyone with an HW-8 collecting dust because of a broken VFO tuning
capacitor you may take heart, an exact replacement is available.

I recently purchased an HW-8 in which the rotor plates had become detached
from the tuning shaft. BIG PROBLEM. Or at least I thought so. This HW-8
was destined to become a spare parts donor. After removing the capacitor
from the case I noticed the Heathkit part number 26-152 stamped into the
frame, as well as the letters ASP*7703.

After a few days of attempting to remember (talking with some old timers) or
discover (search the web) who or what ASP stood for, I got lucky.

ASP stands for American Steel Packaging or American Star Products depending
on what they manufactured and when. As you can see from above, 26-152
ASP*7703 is a Heathkit part number and a manufacturer code.

ASP is now known as Oren Elliot Products. They are located in Edgerton,
Ohio, and their plant facilities have been producing capacitors since l925.
They are the largest domestic manufacturer of air-dielectric variable
capacitors. Their web site can be found at www.orenelliottproducts.com.

With thanks to Mr. Steven Elliot I was able to obtain the following
information:

The VFO tuning capacitor in the HW-8 is a model NS-51, with direct drive,
and two rotor and two stator blades with a 0.032" air gap. It has CCW
rotation, mounting holes tapped for 6-32 threads, with a trimmer and copper
stator blades. This capacitor has a range of 5.2 pF to 15.1 pF. The
trimmer can add 2-15 pF to both the minimum and maximum.

This capacitor, as well as others, was manufactured for the Heathkit Company
product line over many years.

Mr. Elliot was also able to shed some light on how this capacitor could be
easily damaged. The vernier drive on the HW-8 is a reduction drive
(planetary) with a probable output torque of about 100 inch ounces. The
26-152 can only stand about 20 inch ounces of pressure (at the end of the
stop) before succumbing to damage. You would only have to exert an input
torque force of about three inch ounces on the VFO knob, with the capacitor
at the end of its rotation, before possible failure.

I purchased the last 26-152 that was still in stock. However, the good news
is that Mr. Elliott can provide a newly manufactured replacement capacitor,
identical to the original 26-152. Contact him at: Oren Elliott Products,
telephone (419) 298-2306, fax (419) 298-3545, or e-mail: oep@bright.net. In
case this gets passed on to someone without e-mail, their postal address is
128 W. Vine St., PO Box 638, Edgerton, OH 43517 USA.

Current pricing is:

1 capacitor: $14.00
2 capacitors: $11.50 ea.
5 capacitors: $9.50 ea.

OEP also has a slightly different capacitor that may be suitable for use on
the HW-8. It has the same capacitance value; however the shaft is 0.25
inches longer and it has a built-in 8:1 planetary reduction drive unit.
This acts as sort of a viscous slip clutch, slipping when the capacitor
reaches its minimum or maximum rotation. Use of this capacitor would help
prevent damage as described above but will necessitate a number of changes
to the original Heathkit design. A new mounting bracket would be required as
well as ensuring the VFO dial markings track correctly since this shaft will
rotate 8 times faster than the rotor. I will experiment with this very soon
and determine if it is feasible.

If anyone needs an HW-8 VFO tuning capacitor, contact Mr. Elliot and request
a direct drive, 26-152 replacement. Please be sure to thank him for
supporting QRP ARCI and hams in general.

Larry Baker - WB5OFD wb5ofd@wcc.net


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