Re: First rebuild - Eico HF-87 - where to find parts?
- From: Peter Wieck <pfjw@xxxxxxx>
- Date: Sat, 1 Nov 2008 20:18:13 -0700 (PDT)
On Nov 1, 9:12 pm, !dpli...@xxxxxxx (David Light) wrote:
This is my first attempt at rebuilding a vintage tube amp..
I'm looking for any advice I can find on where to go and where to not
go for parts. I have a quote from Vacuum Tube Valley for a parts
package that seems reasonable. Are they reliable?
Mpffffff..........
Caps is caps - type/capacitance/voltage taken into account.
Diodes is diodes - type/amperage/PIV/voltage taken into account.
Resistors have come a VERY long way in the last 40 years. Keep this in
mind.
www.mouser.com
www.newark.com
And several others will sell you good stuff at far less than boutique
prices.
Cutting to the chase.
It isn't rocket science. Replace all the original small-value caps
with good-quality equal-capacitance, equal-or-greater voltage caps. If
a ceramic cap came out, put a ceramic back in. If a paper cap came
out, put a quality film cap back in. For all electrolytics >2uF or
greater, replace with quality electrolytics as above (capacitance and
voltage). Those of 2uF or less, replace with a film cap of equal-or-
greater voltage.
Test all caps prior to installation. If you have an ESR meter, use it.
Otherwise, test at working voltage if you can.
Take your time, mind polarity on electrolytics. And diodes.
Leave no selenium diodes in place. Replace 100% of them with an equal-
or-better silicon diode. You *may* have to add resistance in some
diode circuits to replace the natural voltage drop of a selenium
diode. But NOT ALL such circuits.
Test all existing resistors. They drift. This is a PITA as you cannot
test them in-circuit. In general, I would replace the entire lot were
it my amp. Exceptions might include precision-cut resistors in the
bias circuit if they are still intact and on-spec.
Phenolic circuit boards are a PITA as the traces often break and the
connections at the tube-sockets often fail. Pay acute attention to
these. Check *ALL* connections.
I will often replace somewhere between 40% and 100% of the point-to-
point wiring if I find any fatigued joints, corrosion or other
indications of potential failure.
Take your time. Repeat: It isn't rocket science. Patience. One thing
at a time.
Take pictures of the BEFORE state of the amp. If you miss something,
it will help you find an error. USE A SCHEMATIC. Understand what you
are doing (and why) before you start to do it. ONE THING (one step) AT
A TIME.
Check your work. Test *EVERY* connection, whether you did it or not.
AND, check B+ when you are done. If you need an explanation of what
that is and means you are not quite ready for a rebuild just yet - but
all the additional information you need is a matter of a few minutes
of explanation with the schematic in-hand.*THEN* you will be ready -
mechanical skills being assumed as adequate.
Hope this helps.
Peter Wieck
Melrose Park, PA
.
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- First rebuild - Eico HF-87 - where to find parts?
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- First rebuild - Eico HF-87 - where to find parts?
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