there's a cap hierarchy - upgrading by going up the list. ecap std to audio-grade ecap,
film: polyester/mylar to polypropylene or polystyrene. then Teflon for your test.
choice is dictated by cost, lead spacing (does it fit through the existing hole), height
under other components/shields/cover/etc,
some caps do not require replacement - they don't degrade. BUT replacing ceramics
with c0gs, polyester films with polyprops, polyprops with Teflon is your test.
earlier post says signal path - good advice.
over 15years old? recap power supply. add bypasses, upgrading specs
(ESR, operating temp, and usually what most forget - rated hours).
then if you're going to be really good. read the schematics and change
polar caps to non-polars where there's a possibility of signal polarity,
increase the replacement cap working voltage when it appears the
original caps are close to rail voltages but only where this is true.
changing all caps to 1% is not useful - time and money much better spent
elsewhere (like measuring transistors for noise, Hfe, matching, or
for opamps, compensation, PS bypassing, etc)
research frequency response for caps. a 1% change may result in raising or lowering by 0.01 hz.
certainly won't affect bypassing, zobels, and in certain circuits for compensation
and in many cases feedback. in fact if you change a 5uf with a 15uf cap (300%)
you may not hear it, nor be able to measure it unless you have lab instrumentation.
don't change all the resistors for type (MF for CF or CC) until the end,
but before then pull and measure each and every one. replace with identical
before upgrading. this preserves the sonic signatures. Japanese designs
tend to one type over others and still have a mx - this is part of their voicing
that they strive for - the Marantz sound, etc. for example, changing to MFs
lowered the noise floor on a Hafler DH101, better caps widened the sound stage,
each change may or may not work.
compare both units, at the component level, making sure they are identical
with NO parts substitution (by design or by last guy hacking inside), upgrades
or running changes, or by guys who previously decided to test the sound but
gave up and sold you the incomplete unit.
then reflow everything. this eliminates any connection problems due to power
and heat cycling. also ensures reliability. like re-torqueing head bolts.
learn to use a scope, signal gen, etc. proceed to spectrum/distortion analyzers.
mark the PCB for cap orientation, if in doubt or to be thorough, compare board
layout to parts list to schematics - all must be identical.
replace one component at a time: take before picture, pull part, measure old part,
grab new part from labelled bag, measure part, solder part in, take after picture.
do not do newbie flipper by unsoldering 200-300 parts then try to remember
which goes where, and not understanding where a section might have been bad.
if you get into a problem, have someone else look at the pictures, you will never
see the issue - if you did as you were replacing then you might not have had a
problem - this is not a criticism of your skills, nor impugning your IQ/reputation
but a reflection of why the very best organizations separate out the builders
from the QA. they see things differently and will catch issues faster. as a
former member of the computing/programming community it's a guarantee
the coder does not the problems.
however, you may have very special skills and this might just be the vehicle
that brings it out. do return the gift by completely documenting your journey
by not describing it as "replaced everything and sounds wonderful".
and don't slam folks for their input, however smart you may think you
are. that person may have fixed the very receiver that you will be having
problems with (you test a component live, probes slip, kills unit, spend
100 hours isolating down to section, find out components are NLA) and
that person will place you on an ignore list. he may also be a geezer
and has fixed hundreds of units over the last 5 decades and you are
starting your first. and he knows exactly how to re-engineer that NLA part.
thank everyone, you get better advice when you're nice. (poem)
next up, research the AK giants here, how they tackle a problem, how they
fix them, how they upgrade, how they replace entire sections, and mostly
importantly how they improve the device.
I once spent about a year researching a rare amp that I bought, I exhausted
the English URLs, then went to the German sites, and then the Japanese
sites, and had to use the then primitive translation tools. nowadays it's
easier than chugging a small beer.
lastly, if you do all this, post your journey.
good luck