Toshiba TV29C90 problem; Image fades to black...

[Dave Plowman (News)]

In article <1118743605.352461.261670@o13g2000cwo.googlegroups.com>,
Wayneos <wayne_m_evans@hotmail.com> wrote:

I need to replace my smoothing capacitors in my guitar amp - they're
5000uf 50v. I tried some 4700uf 63v ones but they blew up!! I couldn't
tell the polarity of the original ones - they just had a pink dot on
one of the terminals, which I assumed was negative, so wired the new
ones accordingly. Did they blow because of the incorrect polarity or
are they the wrong rating? If they are the wrong rating, can anyone
point in the direction of the correct replacements (maplin order code
or something??)

Pink would have originally been red, so positive. Black would be negative.
On all the electronics I've come across.

Why did you think red was negative?

5000uF 50v is an old standard value. 4700 63V should work just fine.

--
*(on a baby-size shirt) "Party -- my crib -- two a.m

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Dr. Polemic]

On Tue, 14 Jun 2005 01:14:42 -0800, floyd@barrow.com (Floyd L. Davidson) wrote:

Dr. Polemic <nospam@aol.com> wrote:
Danged, several weeks of work shot because it just hadn't
occurred to him that ni-cad would boil at room temperature.

I doubt that it *boils* at room temperature; evaporates slowly, maybe. At least, not at
the temperature of any rooms I've been in.

Oh, it boiled off!

So, tell me, what is the vapor pressure of Cadmium at 20 degrees C?

Damned fast too! And no, you wouldn't fit
into the 18" vacuum jar this was in.

The way to get ni-cad to boil at room temperature is simply
reduce the pressure to something significantly below its vapor
pressure. We did it knowingly with gold too once, and that was
nothing short of beautiful as far as the results went. The
entire inside of the bell jar was very faintly plated with gold.
That particular experiment was testing the voltage breakdown of
ceramic wafers, so in addition to the gold plating there was the
bluish white glow from a high voltage arc too. Really great
visual effects!

That was 40 years ago...

 

[Tim Mitchell]

In article <1118723229.619344.265500@g43g2000cwa.googlegroups.com>,
TDWesty <vwdiesels@gmail.com> writes

I have an NAD 3125 integrated amp (1986 vintage) with a strange left
channel problem. With a lower level input, such as my 4125 tuner, or a
VCR, the left amp channel drops out to almost nothing. Switching the
amp to mono equalizes both channels. I have swapped speakers, wires,
patch cables, and tried all of the line level inputs on the amp, with
the same results. I have swapped left&right, etc, but the problem is
always the left channel of the amp. The tuner works fine on both
channels with another amp.

With a higher level input such as CD or DVD, both channels work and
sound fine. The left channel behaviour was inconsistent for a while,
but is now consistent, and has been for months.

I have done some reading about replacing caps on older amps, along with
checking for bad solder joints, but have found no visible problems in
either case. I have had the amp for 20 years, and it has never been
abused.

I would consider replacing the caps myself, if I had some idea where to
start (ie: which ones are the mostly likely culprits, or which ones
should be replaced due to age), but I would prefer to have a schematic
to work with. I have found the schematic for the NAD 3120, which has
test voltage values, etc., but so far no luck on the 3125.

I'm not familiar with the particular amp, but your testing so far shows

that the problem is in the input stages of the amp not the power stages
(as if you turn it to mono, you get the same volume). So you are looking
for a problem on the left channel somewhere between the input terminals
and the mono switch. This narrows it down quite a lot.

It sounds like a bad connection which has gradually oxidised or
something. Jacks with switch terminals can do what you describe, if you
put in a small signal it doesn't get through but if you put in a larger
signal then it does get through. I would visually trace through the
signal path from the input connector and see if you can see anything
amiss.
--
Tim Mitchell

 

[John Fields]

On Mon, 13 Jun 2005 23:15:06 -0800, floyd@barrow.com (Floyd L.
Davidson) wrote:

I knew a fellow one time who put together a nice little
experiment where he bolted everything together with nice shiny
nickel-cadmium plated screws.

---
Nickel-cadmium usually refers to the metals used in fabricating a
family of secondary cells used in redchargeable batteries, while
cadmium, by itself, was once used to plate mechanical fasteners. It
has dropped out of favor and its use may now be prohibited for that
purpose due to its toxicity and effect on the environment.

--
John Fields
Professional Circuit Designer

 

[Bob Shuman]

At that age, I'd also suspect oxidized/dirty contacts on the controls. Have
you tried playing with all the knobs, buttons and switches (speakers A/B,
tone defeat, loudness, bass, treble, balance, etc) on the front panel? Many
times this will help to isolate the bad contact since the behavior will
change as you move the control between different positions. Once you
determine the cause, a good cleaning with a good contact cleaner should help
a lot.

Also, as a thought, is there a speaker relay near the final output? If so,
it is possible that the left channel contacts are pitted or worn and need
some attention. Many times you can remove the plastic cover on the relay
and assert some pressure to see if the behavior changes. If it does, then
you can use a small file or some emery cloth and contact cleaner to try to
clean up the contacts.

Good luck!

Bob

"Tim Mitchell" <timng@sabretechnology.co.uk> wrote in message
news:vhGSBguGRtrCFAt0@tega.co.uk...

In article <1118723229.619344.265500@g43g2000cwa.googlegroups.com>,
TDWesty <vwdiesels@gmail.com> writes
I have an NAD 3125 integrated amp (1986 vintage) with a strange left
channel problem. With a lower level input, such as my 4125 tuner, or a
VCR, the left amp channel drops out to almost nothing. Switching the
amp to mono equalizes both channels. I have swapped speakers, wires,
patch cables, and tried all of the line level inputs on the amp, with
the same results. I have swapped left&right, etc, but the problem is
always the left channel of the amp. The tuner works fine on both
channels with another amp.

With a higher level input such as CD or DVD, both channels work and
sound fine. The left channel behaviour was inconsistent for a while,
but is now consistent, and has been for months.

I have done some reading about replacing caps on older amps, along with
checking for bad solder joints, but have found no visible problems in
either case. I have had the amp for 20 years, and it has never been
abused.

 

[John Larkin]

On Mon, 13 Jun 2005 22:01:12 -0700, The Phantom <phantom@aol.com>
wrote:

Total and utter horseshit.

"DC" is simply the first (or "offset" term in the Fourier expression of
any repetitive waveform.

DC, of course, cannot exist at all ever. Because it would have to be
unvarying through infinite time.

So, the first Fourier term is always zero. Got it.




Damn, this thread will hit 200 posts soon. The less the content, the
bigger the thread.


John

 

[none]

On Mon, 13 Jun 2005 12:23:46 -0400 "rainbow" <rain.bowwwwt.net> wrote in
Message id: <B5SdnQlIPYGWLjDfRVn-rA@rogers.com>:

God is an almighty spirit, who cannot be seen, but knows all things
about us.

Proof please, or shut the fuck up.

 

[Dave Plowman (News)]

In article <1118751361.430462.314770@g14g2000cwa.googlegroups.com>,
Wayneos <wayne_m_evans@hotmail.com> wrote:

I wasn't thinking along those lines, I was taking the view that on most
capacitors it's the negative that's marked.

Ahh - true. But with a - sign, not a colour?

But if it had a marked tag, surely it was wired rather than PCB mounting?
If so, what colour were the wires?

Anyway thanks for the advice.

No problem.

--
*I don't suffer from insanity; I enjoy every minute of it.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Rich Grise]

On Tue, 14 Jun 2005 02:49:32 +0000, NSM wrote:

"Mac" <foo@bar.net> wrote in message
On Mon, 13 Jun 2005 10:14:41 -0500, Mike Berger wrote:

The freezing point and boiling point of water are both have
a clearly defined intrinsic meaning to a chemist.

[snip]

Well, "intrinsic" may be a bit to strong of a word. Boiling and freezing
points very considerably with pressure.

And purity and other factors.

No, the "intrinsic" _meaning_ (in case you'd care to check the original

post) of "boiling" or "freezing" doesn't change, no matter what the
temperature and pressure you're applying.

You're confusing _meaning_ with _parameters_. I have seen water
freeze and boil simultaneously in a single container. Anybody can
do this - just get a decent bell jar and a good vacuum pump. The
"boiling point" certainly changes with ambient pressure, but that
does not change the intrinsic nature of _what boiling is_. I think
this might have been Mike Berger's point here.

Thanks,
Rich

 

[John Larkin]

On Tue, 14 Jun 2005 00:41:47 -0700, Don Bowey <dbowey@comcast.net>
wrote:

On 6/13/05 10:01 PM, in article sfosa1dics75vdhajk3079g0scasm6rqp2@4ax.com,
"The Phantom" <phantom@aol.com> wrote:

DC, of course, cannot exist at all ever. Because it would have to be
unvarying through infinite time.

Horse pucky. I think I can afford to miss the tutorials on your website.

He has tutorials? You've got to be kidding.

John

 

[Floyd L. Davidson]

Dr. Polemic <nospam@aol.com> wrote:

On Tue, 14 Jun 2005 01:14:42 -0800, floyd@barrow.com (Floyd L. Davidson) wrote:

Dr. Polemic <nospam@aol.com> wrote:
Danged, several weeks of work shot because it just hadn't
occurred to him that ni-cad would boil at room temperature.

I doubt that it *boils* at room temperature; evaporates slowly, maybe. At least, not at
the temperature of any rooms I've been in.

Oh, it boiled off!

So, tell me, what is the vapor pressure of Cadmium at 20 degrees C?

I don't know. Look it up.

Takes a nice little vaccuum pump to do it though.

--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@barrow.com

 

[nst1]

Randy Thompson Wrote:

On Fri, 10 Jun 2005 20:53:38 -0500, Don Hickey wrote:

I believe a more likely candidate than the PC would be the monitor.
High
voltage for the screen requires some large electrolytic capacacitors.
Have
you taken any steps to isolate the failing unit.... PC, monitor,
scanner,
external drives, etc?

I had a Philips VCR that had a bad power supply, when i got it back
from the repair shop and let it warm up, it would give out a bleach
type smell, turned out to be excess solder flux (the orange stuff)
around the joins - when the transformer in the PSU would warm up it
would give off the stink. I left it plugged in and the smell 'burned'
itself away in about a week.
Also, my LG CRT monitor gives off a less noticable smell, caused by the
deflection yoke, if you leave the room and come back in a few minutes
later you can smell the nice warm fuzzy monitor, Ahhhhh!


--
nst1

 

[John Fields]

On Tue, 14 Jun 2005 08:32:09 -0800, floyd@barrow.com (Floyd L.
Davidson) wrote:

Dr. Polemic <nospam@aol.com> wrote:
On Tue, 14 Jun 2005 01:14:42 -0800, floyd@barrow.com (Floyd L. Davidson) wrote:

Dr. Polemic <nospam@aol.com> wrote:
Danged, several weeks of work shot because it just hadn't
occurred to him that ni-cad would boil at room temperature.

I doubt that it *boils* at room temperature; evaporates slowly, maybe. At least, not at
the temperature of any rooms I've been in.

Oh, it boiled off!

So, tell me, what is the vapor pressure of Cadmium at 20 degrees C?

I don't know. Look it up.

Takes a nice little vaccuum pump to do it though.

---
Yer fulla shit.

--
John Fields
Professional Circuit Designer

 

[John Larkin]

On Tue, 14 Jun 2005 11:42:15 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Tue, 14 Jun 2005 08:32:09 -0800, floyd@barrow.com (Floyd L.
Davidson) wrote:

Dr. Polemic <nospam@aol.com> wrote:
On Tue, 14 Jun 2005 01:14:42 -0800, floyd@barrow.com (Floyd L. Davidson) wrote:

Dr. Polemic <nospam@aol.com> wrote:
Danged, several weeks of work shot because it just hadn't
occurred to him that ni-cad would boil at room temperature.

I doubt that it *boils* at room temperature; evaporates slowly, maybe. At least, not at
the temperature of any rooms I've been in.

Oh, it boiled off!

So, tell me, what is the vapor pressure of Cadmium at 20 degrees C?

I don't know. Look it up.

Takes a nice little vaccuum pump to do it though.

---
Yer fulla shit.

--
John Fields
Circuit Designer

 

[John Popelish]

John Fields wrote:

On Tue, 14 Jun 2005 08:32:09 -0800, floyd@barrow.com (Floyd L.
Davidson) wrote:


Dr. Polemic <nospam@aol.com> wrote:

On Tue, 14 Jun 2005 01:14:42 -0800, floyd@barrow.com (Floyd L. Davidson) wrote:


Dr. Polemic <nospam@aol.com> wrote:

Danged, several weeks of work shot because it just hadn't
occurred to him that ni-cad would boil at room temperature.

I doubt that it *boils* at room temperature; evaporates slowly, maybe. At least, not at
the temperature of any rooms I've been in.

Oh, it boiled off!

So, tell me, what is the vapor pressure of Cadmium at 20 degrees C?

I don't know. Look it up.

Takes a nice little vaccuum pump to do it though.

Yer fulla shit.

I think he is confusing boiling with sputtering.

 

[John Fields]

On Tue, 14 Jun 2005 09:45:52 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

--
John Fields
Circuit Designer

---
LOL

Slow day and nothin' better to do than to edit folks' dotsigs, huh?^)

--
John Fields
Professional Circuit Designer

 

[John Fields]

On Tue, 14 Jun 2005 13:07:05 -0400, John Popelish <jpopelish@rica.net>
wrote:

John Fields wrote:
On Tue, 14 Jun 2005 08:32:09 -0800, floyd@barrow.com (Floyd L.
Davidson) wrote:


Dr. Polemic <nospam@aol.com> wrote:

On Tue, 14 Jun 2005 01:14:42 -0800, floyd@barrow.com (Floyd L. Davidson) wrote:


Dr. Polemic <nospam@aol.com> wrote:

Danged, several weeks of work shot because it just hadn't
occurred to him that ni-cad would boil at room temperature.

I doubt that it *boils* at room temperature; evaporates slowly, maybe. At least, not at
the temperature of any rooms I've been in.

Oh, it boiled off!

So, tell me, what is the vapor pressure of Cadmium at 20 degrees C?

I don't know. Look it up.

Takes a nice little vaccuum pump to do it though.

Yer fulla shit.


I think he is confusing boiling with sputtering.

---
Ahhhh! I think you're right!-)

--
John Fields
Professional Circuit Designer

 

[Don Bowey]

On 6/14/05 2:28 AM, in article 87oea9p9s6.fld@barrow.com, "Floyd L.
Davidson" <floyd@barrow.com> wrote:

Don Bowey <dbowey@comcast.net> wrote:
On 6/13/05 10:01 PM, in article sfosa1dics75vdhajk3079g0scasm6rqp2@4ax.com,
"The Phantom" <phantom@aol.com> wrote:

DC, of course, cannot exist at all ever. Because it would have to be
unvarying through infinite time.

Horse pucky. I think I can afford to miss the tutorials on your website.

Pure DC, or something close to it, is actually pretty rare
stuff.

Even on battery power plants, which are extremely good filters,
there is some AC on the leads of just about anything powered
from the battery unless either the battery or the load is all
but embedded in the other.

For example, the 48 volt battery plants that telephone companies
have, use some rather large cables to supply voltage to
equipment. Yet a filter is required at every fuse bay to
decouple the AC noise on the supply cable from the equipment in
the bay. Even then, the supply lines have an astounding amount
of AC noise on them.

That was particularly true back in the days of mechanical
switches, when a telco switch was filled with "DC" switched
lines that had mechanical contacts, and most of the loads being
switched were inductive.

There is even more of the same going on in modern digital
switching systems, minus the inductive kick, but those are
filtered much more effectively because unlike the old mechanical
monster, these new ones will malfunction themselves if the noise
isn't filtered out.

I agree with your examples of DC power supplies and AC noise. Been there,
done that.

Defining how may angels can dance on a DC power cable without having to
redefine it is pointless, however. Everyone I knew in the telco industry
had good, workable terms for the cause of the need for filters, not only at
the FB, but at the equipment rack too; it was noise, trash, crap.
spikes....., but the 48V and 130V "power" were always DC and we knew the
noise had to be dealt with as AC riding the DC. No other esoteric, mindless
definitions are needed even though the terms AC and DC may be misnomers.
They are historic and work very well.

Don

 

[Dr. Polemic]

On Tue, 14 Jun 2005 13:07:05 -0400, John Popelish <jpopelish@rica.net> wrote:

John Fields wrote:
On Tue, 14 Jun 2005 08:32:09 -0800, floyd@barrow.com (Floyd L.
Davidson) wrote:


Dr. Polemic <nospam@aol.com> wrote:

On Tue, 14 Jun 2005 01:14:42 -0800, floyd@barrow.com (Floyd L. Davidson) wrote:


Dr. Polemic <nospam@aol.com> wrote:

Danged, several weeks of work shot because it just hadn't
occurred to him that ni-cad would boil at room temperature.

I doubt that it *boils* at room temperature; evaporates slowly, maybe. At least, not at
the temperature of any rooms I've been in.

Oh, it boiled off!

So, tell me, what is the vapor pressure of Cadmium at 20 degrees C?

I don't know. Look it up.

I had a feeling that something like this would be his response.

The CRC handbook indicates that the vapor pressure of cadmium is about 10^-12 torr at
room temperature (20 degrees). This is better than the vacuum at the moon. The best
vacuum pumps available today can't hit that in a bell jar, much less 40 years ago.

No way did he "...get ni-cad to boil at room temperature (by) simply
reduc(ing) the pressure to something *significantly* below its vapor
pressure. We did it knowingly with gold too once..."

Gold has a vapor pressure of 10^-11 torr at about 800 degrees. I don't think gold will
boil even in interstellar space (10^-17 torr) at 20 degrees. It *will* evaporate, though;
so will tungsten! Slowly!

Takes a nice little vaccuum pump to do it though.

Yer fulla shit.


I think he is confusing boiling with sputtering.

But he says it *boiled*; he couldn't be mistaken, could he?

 

[Don Lancaster]

Don Bowey wrote:
No other esoteric, mindless

definitions are needed even though the terms AC and DC may be misnomers.
They are historic and work very well.

Don

The only tiny problem is that the definitions are wrong.


--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com