HP-23 recap

[Glen Zook]

Frankly, over the years, I have had more "computer
grade" capacitors fail than the "normal" type.  In
fact, I had the same computer grade electrolytic (in
the same place in the circuit) capacitor fail in two
Motorola service monitors within one week of each
other a few months back!

The main differences between the "normal" and the
"computer" grades are the fact that the "computer"
grade capacitors are +/- 10 percent and the "normal"
are +/- 20 percent.  Also, the leakage through the
"computer" grade is "guaranteed" to be less than the
"normal" type.  Neither of these really applies to
power supplies like the HP-23 that were designed for
the -50 / +80 percent capacitors.  Also, I would be
willing to bet that in 99 out of 100 times (probably
even higher percentage) that the "normal" capacitors
(of new manufacture) will last just as long as the
"computer" grade, possibly longer.

I have no fault with someone who wants to spend their
money on whatever they want to.  I, for one, am a
strict believer in the principles of the conservation
of my finances and energy (I admit to being "cheap and
lazy"!).  When I am actually restoring a piece of
equipment (and not repairing) I actually try to get as
close to the original parts as humanly possible.
However, this often results in a degrading of
performance since the original parts are often no
where as good as modern components.  But, the
definition of restore is to return the equipment to
its original configuration.  This does include things
like orange drop capacitors in place of paper
capacitors, etc.  When you restore, you don't use
orange drops, you put back in the old paper, often wax
type, capacitors.

So, no one is criticizing you for spending up to three
times the funds necessary to repair your HP-23.  As
for myself, and I believe the vast majority of
amateurs, I go for the least expensive fix that does
the job!  Doing the job includes reliability!

Yes, the modern components are better and I definitely
use them in any repairs that I make.  However,
repairing is NOT restoring.  The same thing goes for
modifications.  They often make the equipment perform
better.  But, this is modifying and not restoring even
if the case is repainted, the front panel
re-silkscreened, etc.

I do have a collection of about 100 antique and
vintage radio sets from the 1920s until the 1950s
(mostly 20s and 30s) that are restored.  You can't
tell them from the way that they came from the
factory.  Also, they behave like they came from the
factory.  This collection was recognized by the
Smithsonian a while back.  Also, I supplied two of the
four "antique" radios that are on display at the LBJ
Presidential Library in Austin, Texas.

Unless you use exactly the same type components you
are only repairing, not restoring.

By the way, the deep space probes of the late 1960s /
early 1970s each has 7 of my signatures on board.  I
did the finally inspection on the thick-film
assemblies that were used in the television cameras.
Each substrate was personally signed by me before the
final clear encapsulation.  This was when I was the
head of the applications engineering department for
the thick film manufacturer.

I think I can "match" you credential for credential.
But, you are turning what was a legitimate request for
information about replacing the electrolytic
capacitors in a Heath power supply into a flame war.
As I said before, no one is criticizing you for
putting in the "computer" grade capacitors.  You seem
to be taking the fact that there are definitely less
expensive ways of doing exactly the same job
(including reliability) for less money as an attack on
your abilities.  This is not the fact.

Frankly, I think that the moderator of this forum is
probably getting very tired of the whole subject.
Therefore, I, for one, will say no more about the
differences in opinion.  If someone asks again about
the capacitors I will again give them the information
about the 450 volt 120 mfd capacitors.  It is up to
them to decide if they want to have the same
performance from the cheaper capacitors or if they
want to pay almost three times as much!

Glen, K9STH

--- "Charles W. Morehouse" <w4gbw at BREVARD.NET> wrote:
I fear you are from that school.  As an RF design
engineer at the Cape, I designed a lot of the
communications checkout equipment used on the orbiter.
I always used the best components that I could find.
That equipment is still in use today. Now retired I
have a lot of fun restoring the lovely old ladies and
my goals are the same. Use the best parts you can
find, and try to keep the look of the unit the same.
Might cost a bit more but I want my restorations
working for future generations. A little money up
front is well worth it.

__________________________________________________
Do You Yahoo!?
Find a job, post your resume.
http://careers.yahoo.com

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://interactive.tempe.gov/archives/HEATH.html