Kenwood L-1000T , 1990

[N_Cook]

Expensive looking fm tuner not keeping stations etc in memory. Not fully
dismantled as quite a workup to get to the stage of getting to the C11
supercap with only 1/4V on it. Anyone aware of anything else that needs
changing as a lot of normal electros on the Vdd line through different
parts of the kit. I will change the fractional farad (if I can find such a
squat one) but how to test these to confirm it is failed? charge to 5V and
time discharge through an R but what sort of value , high enough not to
phase it , and low enough for reasonable time to 2.5V? ESR I imagine is
irrelevant. Schematic is on e-service

 

[William Sommerwerck]

If there's only 1/4 volt across the supercap, what's the cause? Is the
charging voltage low, or is the cap leaky/shorted?

For testing, I'd try charging the cap through 100 ohms or so. That should
give a time constant in a range suitable for following along on your DVM.

Unless you have zero vertical clearance, a replacement cap can be mounted
just about anywhere. The lead length doesn't matter.

 

[David]

"William Sommerwerck" wrote in message
news:[email protected]...

If there's only 1/4 volt across the supercap, what's the cause?
Is the
charging voltage low, or is the cap leaky/shorted?

For testing, I'd try charging the cap through 100 ohms or so.
That should
give a time constant in a range suitable for following along on
your DVM.

Unless you have zero vertical clearance, a replacement cap can
be mounted
just about anywhere. The lead length doesn't matter.

You should know that these types of capacitors have an extremely
high internal series resistance so the internal resistance would
swamp out 100 ohms and make the measurement useless. Low ESR is
not needed since they only need to supply micro-amps when called
to duty.

David

 

[William Sommerwerck]

For testing, I'd try charging the cap through 100 ohms

You should know that these types of capacitors have an
extremely high internal series resistance so the internal
resistance would swamp out 100 ohms and make the
measurement useless.

I once replaced a nicad battery in a tuner with a supercap, fed through
about 5K. The capacitor charges up quickly, which does not suggest an
extremely high series internal resistance. (I can check this, if you like.
The tuner is in my bedroom.)

The Wikipedia article says that EDLCs have a very high /power/ density --
that is, they can deliver their stored energy very quickly. This is
inconsistent with an extremely high series internal resistance. In fact, the
article lists the following advantage...

"Extremely low internal resistance (ESR) and consequent high cycle
efficiency (95% or more) and extremely low heating levels."

 

[N_Cook]

If there's only 1/4 volt across the supercap, what's the cause? Is the
charging voltage low, or is the cap leaky/shorted?

For testing, I'd try charging the cap through 100 ohms or so. That should
give a time constant in a range suitable for following along on your DVM.

Unless you have zero vertical clearance, a replacement cap can be mounted
just about anywhere. The lead length doesn't matter.

Wiring across from the cavernous central space makes sense. The very squat
form factor of the original may well have precipitated its failure. I was
forgetting about all the diodes along the power rail route so only one
nearby standard electro (assuming the diodes are ok)

 

[Art Todesco]

I once replaced a nicad battery in a tuner with a supercap, fed through
about 5K. The capacitor charges up quickly, which does not suggest an
extremely high series internal resistance. (I can check this, if you like.
The tuner is in my bedroom.)

The Wikipedia article says that EDLCs have a very high /power/ density --
that is, they can deliver their stored energy very quickly. This is
inconsistent with an extremely high series internal resistance. In fact, the
article lists the following advantage...

"Extremely low internal resistance (ESR) and consequent high cycle
efficiency (95% or more) and extremely low heating levels."

I may be wrong, but I think that we're confusing 'high internal
resistance' and 'leakage resistance'. Internal resistance would be in
series with the capacitor. Leakage resistance would be across the
capacitor, causing it to discharge.

 

[David]

"William Sommerwerck" wrote in message

You should know that these types of capacitors have an
extremely high internal series resistance so the internal
resistance would swamp out 100 ohms and make the
measurement useless.

The Wikipedia article says that EDLCs have a very high /power/
density --
that is, they can deliver their stored energy very quickly. This
is
inconsistent with an extremely high series internal resistance.
In fact, the
article lists the following advantage...

"Extremely low internal resistance (ESR) and consequent high
cycle
efficiency (95% or more) and extremely low heating levels."

Note that we are not talking about super-caps here but memory
backup capacitors that are very small considering their
capacitance and CV^2 value. Super capacitors are a very
different chemistry and for a different purpose entirely.

David

 

[N_Cook]

I once replaced a nicad battery in a tuner with a supercap, fed through
about 5K. The capacitor charges up quickly, which does not suggest an
extremely high series internal resistance. (I can check this, if you like.
The tuner is in my bedroom.)

The Wikipedia article says that EDLCs have a very high /power/ density --
that is, they can deliver their stored energy very quickly. This is
inconsistent with an extremely high series internal resistance. In fact, the
article lists the following advantage...

"Extremely low internal resistance (ESR) and consequent high cycle
efficiency (95% or more) and extremely low heating levels."

I was not aware of the promising automotive use of supercaps, safe
ultra-fast charge etc

 

[William Sommerwerck]

We are not talking about super-caps here but memory

backup capacitors that are very small considering their
capacitance and CV^2 value. Super capacitors are a very
different chemistry and for a different purpose entirely.

Are you certain? A "conventional" cap would not be able to retain the memory
very long. You need something 0.1F or larger -- and conventional caps rarely
come in that size.

I installed a supercap in my Lux tuner, and it holds the memory two or three
days.

 

[Baron]

William Sommerwerck Inscribed thus:

Are you certain? A "conventional" cap would not be able to retain the
memory very long. You need something 0.1F or larger -- and
conventional caps rarely come in that size.

I installed a supercap in my Lux tuner, and it holds the memory two or
three days.

I would concur with William. I have a 0.22F @ 5v on my desk at the
moment, it holds its charge for many days.

 

[David]

"Baron" wrote in message

William Sommerwerck Inscribed thus:

Are you certain? A "conventional" cap would not be able to
retain the
memory very long. You need something 0.1F or larger -- and
conventional caps rarely come in that size.

I installed a supercap in my Lux tuner, and it holds the memory
two or
three days.

I would concur with William. I have a 0.22F @ 5v on my desk at
the
moment, it holds its charge for many days.

--
Best Regards:
Baron.

Lets get things correct here. Memory backup capacitors can have
very high capacitance values and extremely low leakage. That is
not in dispute. The term supercap does not refer to the typical
memory capacitor installed on consumer electronics equipment.
That is a different type that has high series resistance. If you
have a ESR meter, measure one for yourself but discharge it first
for a long time.

David

 

[Baron]

David Inscribed thus:

"Baron"  wrote in message

William Sommerwerck Inscribed thus:


I would concur with William. I have a 0.22F @ 5v on my desk at
the
moment, it holds its charge for many days.

Best Regards:
Baron.

Lets get things correct here. Memory backup capacitors can have
very high capacitance values and extremely low leakage. That is
not in dispute. The term supercap does not refer to the typical
memory capacitor installed on consumer electronics equipment.
That is a different type that has high series resistance. If you
have a ESR meter, measure one for yourself but discharge it first
for a long time.

David

Thanks for your note.
Yes the cap I have is intended for memory retention service. I do have
an ESR meter but it hadn't occurred to me to actually measure it,
though I do take your point about discharging it first. I did
discharge it some time ago and was surprised by how much the voltage
had recovered the following day.

 

[William Sommerwerck]

Lets get things correct here. Memory backup capacitors can have

very high capacitance values and extremely low leakage. That is
not in dispute. The term supercap does not refer to the typical
memory capacitor installed on consumer electronics equipment.
That is a different type that has high series resistance. If you
have a ESR meter, measure one for yourself but discharge it first
for a long time.

I'm not sure what the "typical" memory capacitor is. With respect to my Lux
5T50, the cap was one I selected and installed.

 

[Baron]

William Sommerwerck Inscribed thus:

I'm not sure what the "typical" memory capacitor is. With respect to
my Lux 5T50, the cap was one I selected and installed.

Hi William,
I found references to "Super Cap" on EPCOS website.
http://www.epcos.com/inf/20/25/ds/b32330_b32332_450.pdf
Not quite what I expected.

 

[William Sommerwerck]

I found references to "Super Cap" on EPCOS website.

http://www.epcos.com/inf/20/25/ds/b32330_b32332_450.pdf
Not quite what I expected.

This is an AC starter cap -- dubbed a Super Motor Cap. Not the same thing.

 

[N_Cook]

Old 0.047F , 5.5V dropped from about 5V to 1V in about 1 sec with DVM load.
Replacement .2F one , connected to 5V ps via 220R took 35 sec to rise from
3V to 4V

 

[Baron]

Baron Inscribed thus:

David Inscribed thus:

Thanks for your note.
Yes the cap I have is intended for memory retention service. I do
have an ESR meter but it hadn't occurred to me to actually measure it,
though I do take your point about discharging it first. I did
discharge it some time ago and was surprised by how much the voltage
had recovered the following day.

Just and update: I got the marked value wrong, its 2.2F @ 5v. There is
no indication of the manufacturer. I've currently got a 4.5v 60ma
torch bulb connected across it to discharge it. It took a few seconds
for the bulb to stop glowing. Anyway I'm going to leave it overnight
and check its ESR tomorrow. It should be well and truly discharged by
then.

 

[Cydrome Leader]

I'm not sure what the "typical" memory capacitor is. With respect to my Lux
5T50, the cap was one I selected and installed.

for something like that from 1990, it would most likely be a cap made by
Elna (quite likely dark blue) NEC (possibly green) or Panasonic (all sorts
of colors). Standard Oil was even making them at the time.

Also, they didn't have 'low' ESR supercaps like they do now, so ignore any
crap off wikipedia or comparisons to modern datasheets for products that
look the same.

 

[William Sommerwerck]

I'm not sure what the "typical" memory capacitor is. With respect

For something like that from 1990, it would most likely be a cap
made by Elna (quite likely dark blue) NEC (possibly green) or
Panasonic (all sorts of colors). Standard Oil was even making
them at the time.

Try 1980. I don't remember the brand, but I don't think it was any of these.

Regardless of what you do or don't think, IT WORKS. The storage time -- when
the tuner is turned off and left off -- is about 40% of the original tiny
nicad battery the supercap replaced (3 days versus a week). This seems
reasonable, and is consistent with the information given in the Wikipedia
article.

Also, they didn't have "low" ESR supercaps like they do now,
so ignore any crap off Wikipedia or comparisons to modern
datasheets for products that look the same.

I don't think anyone here knows what they're talking about. I'm certainly
aware of my own ignorance.

 

[N_Cook]

for something like that from 1990, it would most likely be a cap made by
Elna (quite likely dark blue) NEC (possibly green) or Panasonic (all sorts
of colors). Standard Oil was even making them at the time.

Also, they didn't have 'low' ESR supercaps like they do now, so ignore any
crap off wikipedia or comparisons to modern datasheets for products that
look the same.

I discharged overnight an NEC U6 265 green, 0.2F, 5.5V and got an ESR of
5.6R