is it worth it to replace caps in old equalizer??

[Derwin]

Hello, I have an old 70s-era 5-band equalizer made by Realistic (radio shack),
which I like to use in my guitar effects chain, and I opened it up the other
day just to see what it looked like inside, and I noticed that there are two
large electrolytic capacitors. They look fine, and the unit sounds OK, but
given that it is probably at least 30 years old now, and may have sat around
for many years not being used before I got my hands on it, could I expect
improved performance if I were to replace those two big electrolytics with new
ones?

Thanks for any advice!

 

[Arfa Daily]

Hello, I have an old 70s-era 5-band equalizer made by Realistic (radio
shack),
which I like to use in my guitar effects chain, and I opened it up the
other
day just to see what it looked like inside, and I noticed that there are
two
large electrolytic capacitors. They look fine, and the unit sounds OK,
but
given that it is probably at least 30 years old now, and may have sat
around
for many years not being used before I got my hands on it, could I expect
improved performance if I were to replace those two big electrolytics with
new
ones?

Thanks for any advice!

Probably not. If it sounds OK with no signs of hum, then it's likely that
the caps are still working up to spec. If you have access to an ESR meter,
you could check them, or if not a meter, you could look at the ripple across
them with a scope. I'm a great advocate of " if it ain't broke, don't fix it
" - a philosophy that has served me well for 35 years in the business.
Shotgun replacement of components, or replacing just for the " might be "
hell of it, often results in problems that weren't there in the first place,
in my experience. If they are really easy to get at, and you can get
replacements with similar or better specs, and are determined to put your
stamp on it, as it were, then go ahead and replace them. It won't do any
harm.

Arfa

 

[Laurence Payne]

Hello, I have an old 70s-era 5-band equalizer made by Realistic (radio shack),
which I like to use in my guitar effects chain, and I opened it up the other
day just to see what it looked like inside, and I noticed that there are two
large electrolytic capacitors. They look fine, and the unit sounds OK, but
given that it is probably at least 30 years old now, and may have sat around
for many years not being used before I got my hands on it, could I expect
improved performance if I were to replace those two big electrolytics with new
ones?

No.

 

[William Sommerwerck]

It's not uncommon for electrolytic caps to last 40 years or longer. I have
KLH table radios that are 45 years old, and still work with their original
electrolytics.

Electrolytic caps are odd -- they aren't anywhere nearly as unreliable as
you'd expect them to be.

 

[[email protected]]

Hello, I have an old 70s-era 5-band equalizer made by Realistic (radio shack),
which I like to use in my guitar effects chain, and I opened it up the other
day just to see what it looked like inside, and I noticed that there are two
large electrolytic capacitors. They look fine, and the unit sounds OK, but
given that it is probably at least 30 years old now, and may have sat around
for many years not being used before I got my hands on it, could I expect
improved performance if I were to replace those two big electrolytics with new
ones?

Thanks for any advice!

No. If youre considering doing jobs that dont need doing it may be
time to reevaluate ones life.


NT

 

[Jack]

No. If youre considering doing jobs that dont need doing it may be
time to reevaluate ones life.


NT

Don't replace them till they need it. The old high voltage ones can
last a long time, but if you've got a few spare minutes, some spare
dollars, do it by all means.
Dont worry about re evaluating your life. Life is full of cynics. You
do right, its wrong you do wrong its still right etc . Its how you
feel its your life......
PS Fixing things that dont need fixing is not good, only if youre
there. Priority says fix things that you need that need fixing, or as
a preventative.
Most likely you'll drop the equipment of a truck first...or similar.
Lifes like that....

 

[PeterD]

Hello, I have an old 70s-era 5-band equalizer made by Realistic (radio shack),
which I like to use in my guitar effects chain, and I opened it up the other
day just to see what it looked like inside, and I noticed that there are two
large electrolytic capacitors. They look fine, and the unit sounds OK, but
given that it is probably at least 30 years old now, and may have sat around
for many years not being used before I got my hands on it, could I expect
improved performance if I were to replace those two big electrolytics with new
ones?

Thanks for any advice!

If it ain't broke, don't fix it...

Especially if it is Realistic!

 

[Scott Dorsey]

Hello, I have an old 70s-era 5-band equalizer made by Realistic (radio shack),
which I like to use in my guitar effects chain, and I opened it up the other
day just to see what it looked like inside, and I noticed that there are two
large electrolytic capacitors. They look fine, and the unit sounds OK, but
given that it is probably at least 30 years old now, and may have sat around
for many years not being used before I got my hands on it, could I expect
improved performance if I were to replace those two big electrolytics with new
ones?

Probably not, since all the electrolytic coupling caps in there are bad too.
And even if you do, you're stuck with 1970s Radio-Shack grade op-amp design.
--scott

 

[[email protected]]

I am an expert on audio, certain areas, and this is one of them.

I totally agree with those who say if it ain't broke don't fix it,
but, some things are built broke.

To get the best quality integrated audio, which is the type of signal
for which this EQ was designed, they chose the wrong frequncies.

Now replacing the power supply filters is probably useless because of
the low current drain of the unit, there is simply almost no ripple
current to "wear out" the capacitor. However there are other things
one can do.

I have modified a couple of these, but then that was for integrated
program material, if you use it on a guitar you might want to go a
different direction. I don't remember the component values, but once
you understand how it works you can do things, many things.

A buddy of mine had his speakers in the corners, which made them very
boomy. They have bass, but it is shitty.

At the wiper of the 60Hz control there is a cap, a coil and a
resistor. What I did was to take and change that control to about 35Hz
and made it shelving, that is to extend the control's range all the
way down, instead of that peaked response it originally had. I did
this by taking the resistor value down to less than ½ the original and
installing a capacitor about ten times the capacity of the original.

The 250Hz control was lowered to about 100Hz by cutting the resistor's
value in about ½ and installing a capacitor about three times the
original value.

The 1 Khz control was left alone. The 3.5 Khz control had it's range
extended slightly downward by increasing the value of it's capacitor.

Finally the 10 Khz control was modified to be shelving, and it's range
shifted upward. This brings out the timbre, rather than the tinny
treble. This was accomplished by actually lowering the capacitor value
as well as the resistor value, and shunting the coil with a low value
resistor, about ¼ the resistance of the new resistance value in the
tuned circuit for that band.

Actually if you know how to futz with it, you could have a nice setup.
run the channels in tandem but change some of the frequencies. Lower
the low ones on the left and raise the high ones on the right. And if
you tandem the channels you also can use a Y adapter to pick off the
signal for another amp, between stages.

Tell you what, if you get a chance to play a guitar on two amps at
once, enjoy. Set one clean and one fuzzed out. With a little adjusting
and practice you can make it sound like you are playing two guitars.

JURB

 

[Eeyore]

Hello, I have an old 70s-era 5-band equalizer made by Realistic (radio shack),
which I like to use in my guitar effects chain, and I opened it up the other
day just to see what it looked like inside, and I noticed that there are two
large electrolytic capacitors. They look fine, and the unit sounds OK, but
given that it is probably at least 30 years old now, and may have sat around
for many years not being used before I got my hands on it, could I expect
improved performance if I were to replace those two big electrolytics with new
ones?

As suggested elsewhere, the PSU caps seem to be ok. You might want to consider
replalcing any electrolytics in the signal path though.

Graham

 

[Eeyore]

Most likely you'll drop the equipment of a truck first...or similar.

*After* replacing the caps !

Lifes like that....

Yes.

Graham

 

[[email protected]]

I am an expert on audio, certain areas, and this is one of them.

I totally agree with those who say if it ain't broke don't fix it,
but, some things are built broke.

To get the best quality integrated audio, which is the type of signal
for which this EQ was designed, they chose the wrong frequncies.

Now replacing the power supply filters is probably useless because of
the low current drain of the unit, there is simply almost no ripple
current to "wear out" the capacitor. However there are other things
one can do.

I have modified a couple of these, but then that was for integrated
program material, if you use it on a guitar you might want to go a
different direction. I don't remember the component values, but once
you understand how it works you can do things, many things.

A buddy of mine had his speakers in the corners, which made them very
boomy. They have bass, but it is shitty.

At the wiper of the 60Hz control there is a cap, a coil and a
resistor. What I did was to take and change that control to about 35Hz
and made it shelving, that is to extend the control's range all the
way down, instead of that peaked response it originally had. I did
this by taking the resistor value down to less than ½ the original and
installing a capacitor about ten times the capacity of the original.

The 250Hz control was lowered to about 100Hz by cutting the resistor's
value in about ½ and installing a capacitor about three times the
original value.

The 1 Khz control was left alone. The 3.5 Khz control had it's range
extended slightly downward by increasing the value of it's capacitor.

Finally the 10 Khz control was modified to be shelving, and it's range
shifted upward. This brings out the timbre, rather than the tinny
treble. This was accomplished by actually lowering the capacitor value
as well as the resistor value, and shunting the coil with a low value
resistor, about ¼ the resistance of the new resistance value in the
tuned circuit for that band.

Actually if you know how to futz with it, you could have a nice setup.
run the channels in tandem but change some of the frequencies. Lower
the low ones on the left and raise the high ones on the right. And if
you tandem the channels you also can use a Y adapter to pick off the
signal for another amp, between stages.

Tell you what, if you get a chance to play a guitar on two amps at
once, enjoy. Set one clean and one fuzzed out. With a little adjusting
and practice you can make it sound like you are playing two guitars.

JURB

If youre going to muck with it then start with a 10 band or more,
pointless to play with something as very limited as a 5 band.

If you wanted to adapt it for guitar use only, I'd make each side
different freqs and you can feed the signal thru both sides to get a
10 bander. And refrequency the 1kHz slider, which is the least useful
of them all.

But... its not worth bothering, might have been 25 yrs ago.


NT

 

[James Sweet]

Hello, I have an old 70s-era 5-band equalizer made by Realistic (radio shack),
which I like to use in my guitar effects chain, and I opened it up the other
day just to see what it looked like inside, and I noticed that there are two
large electrolytic capacitors. They look fine, and the unit sounds OK, but
given that it is probably at least 30 years old now, and may have sat around
for many years not being used before I got my hands on it, could I expect
improved performance if I were to replace those two big electrolytics with new
ones?

Thanks for any advice!

If it sounds fine I wouldn't worry about it. On the other hand caps are
cheap and replacement is easy.

 

[Mogens V.]

If youre going to muck with it then start with a 10 band or more,
pointless to play with something as very limited as a 5 band.

If you wanted to adapt it for guitar use only, I'd make each side
different freqs and you can feed the signal thru both sides to get a
10 bander. And refrequency the 1kHz slider, which is the least useful
of them all.

But... its not worth bothering, might have been 25 yrs ago.

Plus many/most inexpensive EQ's arent phase liniar anyways...
Mostly useless for high quality audio. Besides, problems with a hifi
setup is better addressed actually fixing those problems at the source,
not trying to EQ them out.

 

[Mogens V.]

Derwin wrote:




As suggested elsewhere, the PSU caps seem to be ok. You might want to consider
replalcing any electrolytics in the signal path though.

And as Scott mentioned, it's based on quite old opamps.
Not worth the efforts, not even if tone is under par. Then better go get
a better one. Unless the OP prefers that killer vintage tone.

 

[Derwin]

Probably not, since all the electrolytic coupling caps in there are bad too.
And even if you do, you're stuck with 1970s Radio-Shack grade op-amp design.

Actually I opened it hoping I could replace an op amp but there are no ICs in
it at all. But I did eventually realize that the two big electrolytics are
probably part of the power supply.

 

[William Sommerwerck]

Plus many/most inexpensive EQ's arent phase liniar anyways...

Mostly useless for high-quality audio.

Linear, not liniar.

This has been discussed ad-nauseum. If you are correcting for errors (as
opposed to introducing them), you don't want constant group delay. You want
the phase shift the equalizer introduces, because it offsets the phase shift
of the error.

 

[Derwin]

Great ideas, thanks for the response, Zzactly!

 

[Derwin]

No. If youre considering doing jobs that dont need doing it may be
time to reevaluate ones life.

I appreciate your response as well, but the cirumstances are that I have some
free time while I wait for some parts to arrive before I can get back to
recording, and for the past few weeks I've been doing a lot of soldering.
Since I've got all the tools laid out from the previous work, and can't get
back to recording, I figured I'd open up anything I have around that is
essentially worthless but still potentially useful (in my opinion) and see if I
could do any worthwhile modifications (I was hoping I'd be able to replace an
op amp in the equalizer, but there aren't any in it). However it does seem
like my rudimentary self-learned knowledge of electronics has already caused me
to do some useless things, such as replacing the op amps in an Alesis
Microlimiter with ones with lower noise specs, hoping to get a lower noise
floor, which did not happen because I didn't understand the circuit well enough
to realize that swapping op amps wouldn't result in a quieter unit.

 

[Derwin]

Great ideas, thanks for the response, Zzactly!

But unfortunately it appears I won't be able to try them. The plastic ends on
the sliders don't come off the sliders, they're either glued on or were
manufactured that way, so it is impossible to take off the front panel to get
behind it where the circuit board is. Oh well.