Toshiba TV29C90 problem; Image fades to black...

[Chuck Harris]

Norm Dresner wrote:

My point in checking for oscillations was that sometimes an oscillating Op
Amp can give some very strange readings on a simply DMM.

Norm

It is probably just a blown opamp, but I have also seen this behavior
on some manufacturers 741's when any input is forced to be higher than
1.2V from the + rail.

As a simple check, short the inv and non inv inputs of the opamp together,
and then:

a) check their voltage relative to the +supply. and
b) check the output voltage.

-Chuck Harris

 

[Franc Zabkar]

On 25 Oct 2004 13:57:07 -0700, radiotubes@fast.net (Jiri Placek) put
finger to keyboard and composed:

Does anyone please have datasheet for NEC ľPC-1213C or NTE 1615?

I think you mean NTE1516.

I don't have a datasheet, but the pinouts are:

1 input
2 NC
3 filter
4 Vcc
5 feedback
6 output
7 bypass
8 feedback

Tab is ground.

Rating - 1.8W, Vcc = 11V max


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Sparkchaser]

Thank you very much mastertv for that very helpful information. I have a
tektronix storage scope so the info on scoping the waveform will be very
helpful. I have never attempted to ohm out a flyback before so can you
ohm it like a normal xformer or is there something else I should know
about the readings I should see? Once again your info is greatly
appreciated.

 

[Syl's Old Radioz]

"Jiri Placek" a écrit dans le message

Does anyone please have datasheet for NEC ľPC-1213C or NTE 1615?

http://www.nteinc.com/specs/1600to1699/pdf/nte1615.pdf

Syl

 

[JURB6006]

What he said.

Also if it's cool or cold outside it might have weal lytics. Cool them down
enough and they act up, but they're OK when warm. If it's shutting down
immediately there are probably weak lytics in the power supply, and it's
possible the seller wasn't even aware of it. IT's actually possible that there
was no damage, and really no culpability anywhere here, except maybe the
manufacturer.

An ESR meter would be handy about now.

JURB

 

[Norm Dresner]

"mike" <spamme0@juno.com> wrote in message news:417D71B6.7030009@juno.com...

Norm Dresner wrote:


Just to be clear, I recommended you use the lm317 to power the new 741.
The sine distortion is gonna be critically dependent on the stability
of this reference voltage. I never used a 317 anywhere I cared about
voltage stability and have no direct experience. May be just fine.
Also, if you use it to replace the supply, you also need to worry about
voltage differential when you short the 20V supply. Don't remember what
the max differential for a lm317 might be.

While you're at it, put some resistance in
pin 3 of U410 so C406 won't blast the input on power down.

mike

My point in checking for oscillations was that sometimes an oscillating
Op
Amp can give some very strange readings on a simply DMM.

Norm

Aha! I understand -- use the IC regulator to drop the voltage to the Op Amp
to a level where I could use a commercial grade safely. Good point.
Regarding max voltage inputs, I think I can safely use an LM7824 to drop
whatever the input is down to 24 volts to drive a jellybean 741 and I've got
one or two in some drawer somewhere around here.

As for C406, my circuit diagram shows a diode CR410 whose anode is connected
to the + side of the capacitor and the cathode to the V+ input to the Op Amp
to keep its input voltage no more than a diode drop above the supply
voltage. I couldn't find the diode on the circuit board anywhere or in the
parts location diagram but it's clearly on the schematic. If I can't find
it, I'll put a 1N4148 in as a "jumper"

Thanks
Norm

 

[Norm Dresner]

"Chuck Harris" <cf-NO-SPAM-harris@erols.com> wrote in message
news:JoidnT_G6PCr8-DcRVn-oA@rcn.net...

Norm Dresner wrote:


This 741 is the error amplifier with an MJE340 pass transistor which is
supposed to output a regulated +20V based on the zener input. This is
an
ancient Tektronix FG501 plug-in function generator which I bought used
knowing that the pilot light came on and that it was otherwise untested.

Norm


Ok, I have the schematic for a SG505 in front of me, which ought to be
similar to your FG501 supply, and what I see is a simple application for
any 741 opamp. The 741 is rated for use to a maximum of 44V in a single
supply circuit, and your circuit has only 30V.

Am I missing something here? Why aren't you simply replacing the opamp?

The circuit's input comes from the 25V AC on the backplane. Through the
diode bridge and the filter capacitors, we'd expect ~34 volts peak on the
input. Allowing for some high line voltage puts this at 37 or so. A
commercial grade 741 is only "guaranteed" to +-18V or 36V single supply.
The Tektronix schematics and parts lists indicate that U410 should be
"selected for +-20V supply" which more or less agrees with my calculation
and says that I'll need something better than a commercial grade Op Amp.

I don't have any MIL-grade 741's in 8-pin DIPs at the moment. I'm pretty
sure that some of the 14-pin ceramic DIPs I have are full range and could be
used if I make the space by replacing the 8-pin package by 8 pins of a
wire-wrap socket to raise the 14-pin body above the other components. I may
also have one or two 741's in 8-pin TO-5 cans that are better than
commercial but I'm not certain.

The original question was:

SO ... I'm stuck it seems with several alternatives:
1. Finding a supplier of the higher grade 741 Op Amp.
2. Trying to select from my own stock one or two ICs that meet the
criterion
3. Finding an acceptable substitute.

And I commented that option 1 was expensive and time-consuming, that option
2 was likely to involve destructive testing and that I had no real knowledge
of any "acceptable" substitutes where the substitute was a commercial grade
Op Amp that I was likely to have easy access to.
Also, neither of my two main suppliers, DigiKey and Mouser, had any
MIL-grade 741's in stock according to their websites.

It's been suggested that I use a 3-terminal IC regulator as a pre-regulator
for the Op Amp to drop it's supply voltage down to where I could use a
commercial part and I think that also makes a lot of sense.

Thanks
Norm

 

[Christian Treldal]

Den Mon, 25 Oct 2004 09:55:25 -0700. skrev I. Frank:

I have a Hitachi 50EX12B (50" Projection TV purchased in 1996) that
stopped working a few weeks ago. My investigation leads me to believe
that there is a short in the flyback transformer (part# 2436493).
However, I called every Hitachi authorized distributor in America and
they are all out of stock and the part was discontinued last year.
Does anyone know where I could get one of these?

Sorry to say 0 in stock in nothern europe and no replacement from
http://www.hrdiemen.es ; but try to write to them.

--
Med venlig hilsen

Christian Treldal

 

[Robert Mozeleski]

I typed in the NTE number but is says SIP-9 pin.
http://www.findchips.com/


"Jiri Placek" <radiotubes@fast.net> wrote in message news:20d99877.0410251257.16519b2e@posting.google.com...

Does anyone please have datasheet for NEC ľPC-1213C or NTE 1615? Ir
is a DIP-8, 2.4 W audio amplifier IC used without any cooling fin in
SONY ICF-6500W shortwave portable receiver. The chip is apparently
overloaded since it frequently fails in this radio. My options are
either to buy a replacement at Mouser or to install another IC with
more power. To find an acceptable more powerful IC I need a data
sheet for the original one. The web search failed to locate any data.

Any lead is greatly appreciated.

Jiri Placek
Boyertown, PA

 

[Jim Yanik]

Chuck Harris <cf-NO-SPAM-harris@erols.com> wrote in
news:JoidnT_G6PCr8-DcRVn-oA@rcn.net:

Ok, I have the schematic for a SG505 in front of me, which ought to be
similar to your FG501 supply,

SG505 PS is not going to be close to the FG501's PS circuitry.

--
Jim Yanik
jyanik-at-kua.net

 

[Syl's Old Radioz]

"Robert Mozeleski" a écrit dans le message

Opps, are you sure it's not NTE1516? That one is coming up as a dip 8
audio amp.

I think you're right. I double checked using an ECG catalog from1998
and it is indeed an 8 pins dip rated at 1.8W, no cooling tab?

It is also discontinued in the 1998 catalog...Oh..Oh...

Syl

 

[Chuck Harris]

Jim Yanik wrote:

Ok, I have the schematic for a SG505 in front of me, which ought to be
similar to your FG501 supply,


SG505 PS is not going to be close to the FG501's PS circuitry.

Really? It is drawn just as the OP describes. The only
real difference from his description is they use a 1458 in
the SG505, and a 741 in the FG501.

-Chuck Harris

 

[Leonard Caillouet]

Actually, there are other failure methods. Some caps will test fine for
capacitance and ESR but have high dielectric absorption and/or dc leakage.
These are hard to test for without the proper equipment. Like I (and
others) have said, when in doubt, replace electrolytic caps. They are cheap
and plentiful. You should be able to find the right caps from one of a
number of suppliers, most likely DigiKey or Mouser.

Leonard

"larrymoencurly" <larrymoencurly@my-deja.com> wrote in message
news:755e968a.0410251431.31ab4a44@posting.google.com...

"Leonard Caillouet" <no@no.com> wrote in message
news:<PH4fd.74459$hj.51928@fed1read07>...

I find leaky caps that test fine for ESR all the time. If
they are mounted so that you can't see the legs, which most
larger caps are, you have to perform the "smell" test or
remove them to inspect them. The smell test consists of heating
the legs and noting whether you smell bad tuna or not.

When in doubt replace. A few caps is not worth the time to have
to go back into the unit a second time.

Thanks for the information. I wrongly thought that if a capacitor had
low ESR and wasn't shorted that it was OK. That's interesting about
the smell test.

I was going to replace all the caps, but the only ones available
locally are either too fat, mystery brands, or old enough to have been
made at the same time as all those defective Taiwan caps.

 

[Bob]

Usually the case snaps together. Sometimes there is a screw under the
little plastic where you'd slip in the telephone number. Also look under
labels, which may be pasted on over a screw.

 

[James Sweet]

"Grant" <grogers@lineone.net> wrote in message
news:1098712984.902953.21220@c13g2000cwb.googlegroups.com...

Hi all,

I have done some soldering on my gameboy advance and have created a dry
joint, I would like to know if is possible to test a solder joint using
a multimeter if so how and what make is recommended (I don't need
anything fancy).

Thanks
Grant

Just look at it, if it's dry it'll look dull. Don't use lead-free solder if
you can help it, that stuff is crap, even after years of soldering I still
can't make a nice joint with it.

 

[Franc Zabkar]

On Mon, 25 Oct 2004 23:34:16 GMT, "Mike Kennedy"
<mikek400@R3MOVE.earthlink.net> put finger to keyboard and composed:

example how it could get out of alignment.. Say the bearings started to
loosen up or say the read head that is glued on to the metal arm loosens up
and moves very slightly.. A hdd is a very precision instrument, it doens't
take much to mess one up.

I would think that if a head came adrift then the drive would suffer a
head crash, in which case both the head and the data surface would be
catastrophically damaged.

"Franc Zabkar" <fzabkar@optussnet.com.au> wrote in message
news:vnhln0p90qfleaar6ukchjjas62t0mtiqv@4ax.com...
On Sat, 23 Oct 2004 16:50:56 GMT, "Mike Kennedy"
mikek400@R3MOVE.earthlink.net> put finger to keyboard and composed:

It could be a mechanical problem. Have you ever taken apart a hdd? The
read
head is very small and very sensitive. The drive has to compensate for
heating and cooling off in normal operation. If it didnt, it wouldnt work
once the drive started to heat up. I think it may have gotten a out of
alginment from getting too hot and freezing it was just enough to get it
back inside specs.

Modern HDDs use an embedded servo, so I can't understand how alignment
could be an issue.

- Mike

"Ken" <user@domain.invalid> wrote in message
news:QOsed.750782$Gx4.671534@bgtnsc04-news.ops.worldnet.att.net...
LASERandDVDfan wrote:
1. Semiconductor junctions have a leakage current that is temperature
dependent.
2. Solder joints that are intermittent can be thermally sensitive.
3. A hairline crack in a circuit board can be thermally sensitive.

Others will no doubt add more.



I don't think there is anything more to add.
As you said in a fantastically detailed fashion, it is likely a
problem
in the
drive electronics which has made one or more critical components
thermal
sensitive.

What is important now is determining how the drive sustained such
damage
to
allow this condition in the first place.

For instance, if it was the result of an overheating problem in the
computer
itself, this would be an issue that requires effective ventilation to
prevent
it from occuring again. - Reinhart

Thanks to all who replied. One thing I did NOT mention in my original
post was that I had acquired an identical HD with the same firmware so
that if the logic board was the cause of failure, I could get the data
off the disk. Swapping out the logic board did not improve the
situation. My reason for suspecting the logic board was that the HD
appeared not to get up to speed fast enough. Upon powering up the HD,
the computer bios would NOT initially detect it. If I did a warm
reboot
while still powered up, it would detect the drive as being present on
the second attempt. This logic board swap DID NOT improve the ability
to read the drive, but I thought the motor drive might not be getting
the disk up to the proper RPM's fast enough. When this did not solve
my
problem, I went into desperation mode and froze the drive.

Myself, I tend to agree that some connection or the IC inside the disk
was being effected by the cold enough to allow an otherwise weak signal
to be read. It is hard to understand how a mechanical function could
be
effected by the cold that would give the same results. However, I am
always willing to learn new things.


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- Franc Zabkar
--
Please remove one 's' from my address when replying by email.


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- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Chuck Harris]

Norm Dresner wrote:

Browsing through some papers, I just discovered that the "Signetics"
NE5534N Op Amp has an absolute maximum voltage spec of +-22V. I've got a
bunch of them and it sounds like this should solve my problem. Well, I
might have to add some additional compensation to slow it down to 741-speed,
but I think that's the way to go.

Norm

The ST part is a grand total of $0.88 each. If you buy nothing else, then

that will be coupled with a $5 shipping charge... still not too bad for the
real thing.

-Chuck

 

[Ken]

Franc Zabkar wrote:

On Mon, 25 Oct 2004 23:34:16 GMT, "Mike Kennedy"
mikek400@R3MOVE.earthlink.net> put finger to keyboard and composed:


example how it could get out of alignment.. Say the bearings started to
loosen up or say the read head that is glued on to the metal arm loosens up
and moves very slightly.. A hdd is a very precision instrument, it doens't
take much to mess one up.


I would think that if a head came adrift then the drive would suffer a
head crash, in which case both the head and the data surface would be
catastrophically damaged.

Although I have no way of ascertaining exactly what the problem was, it
might be noteworthy to say that NOT ALL the data on the drive was
recoverable with the freezing technique. Some areas of the disk were
able to be read when the drive was cold, but others were not. One would
think that if the heads were out of alignment or there was some other
mechanical problem, that ALL the locations would be equally effected.

During the recovery attempt it appeared that some locations were more
easily read than others, and that once the temperature rose, even they
were more difficult to read. That being said, it appeared that those
areas were marginal and that the colder temperature pushed them slightly
over a threshold.

Please do not construe my comments as having arrived at an explanation
to my question. I have no proof one way or the other, and all comments
or theories are welcome. This might remain one of life's great mysteries???

"Franc Zabkar" <fzabkar@optussnet.com.au> wrote in message
news:vnhln0p90qfleaar6ukchjjas62t0mtiqv@4ax.com...

On Sat, 23 Oct 2004 16:50:56 GMT, "Mike Kennedy"
mikek400@R3MOVE.earthlink.net> put finger to keyboard and composed:


It could be a mechanical problem. Have you ever taken apart a hdd? The

read

head is very small and very sensitive. The drive has to compensate for
heating and cooling off in normal operation. If it didnt, it wouldnt work
once the drive started to heat up. I think it may have gotten a out of
alginment from getting too hot and freezing it was just enough to get it
back inside specs.

Modern HDDs use an embedded servo, so I can't understand how alignment
could be an issue.


- Mike

"Ken" <user@domain.invalid> wrote in message
news:QOsed.750782$Gx4.671534@bgtnsc04-news.ops.worldnet.att.net...

LASERandDVDfan wrote:

1. Semiconductor junctions have a leakage current that is temperature
dependent.
2. Solder joints that are intermittent can be thermally sensitive.
3. A hairline crack in a circuit board can be thermally sensitive.

Others will no doubt add more.



I don't think there is anything more to add.
As you said in a fantastically detailed fashion, it is likely a

problem

in the

drive electronics which has made one or more critical components

thermal

sensitive.

What is important now is determining how the drive sustained such

damage

to

allow this condition in the first place.

For instance, if it was the result of an overheating problem in the

computer

itself, this would be an issue that requires effective ventilation to

prevent

it from occuring again. - Reinhart

Thanks to all who replied. One thing I did NOT mention in my original
post was that I had acquired an identical HD with the same firmware so
that if the logic board was the cause of failure, I could get the data
off the disk. Swapping out the logic board did not improve the
situation. My reason for suspecting the logic board was that the HD
appeared not to get up to speed fast enough. Upon powering up the HD,
the computer bios would NOT initially detect it. If I did a warm

reboot

while still powered up, it would detect the drive as being present on
the second attempt. This logic board swap DID NOT improve the ability
to read the drive, but I thought the motor drive might not be getting
the disk up to the proper RPM's fast enough. When this did not solve

my

problem, I went into desperation mode and froze the drive.

Myself, I tend to agree that some connection or the IC inside the disk
was being effected by the cold enough to allow an otherwise weak signal
to be read. It is hard to understand how a mechanical function could

be

effected by the cold that would give the same results. However, I am
always willing to learn new things.


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.782 / Virus Database: 528 - Release Date: 10/22/04



- Franc Zabkar
--
Please remove one 's' from my address when replying by email.


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.782 / Virus Database: 528 - Release Date: 10/22/04




- Franc Zabkar

 

[Sam Goldwasser]

netspider4@lycos.com (Karl-Hugo Weesberg) writes:

Luke Skywalker has badly damaged it, but I think it CAN be repaired.

What do I need?

Give up. From what I recall, there wasn't much remaining.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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Important: Anything sent to the email address in the message header is ignored.
To contact me, please use the feedback form on the S.E.R FAQ Web sites.

 

[jtaylor]

Jiri Placek <radiotubes@fast.net> wrote in message
news:20d99877.0410251257.16519b2e@posting.google.com...

Does anyone please have datasheet for NEC ľPC-1213C or NTE 1615? Ir
is a DIP-8, 2.4 W audio amplifier IC used without any cooling fin in
SONY ICF-6500W shortwave portable receiver. The chip is apparently
overloaded since it frequently fails in this radio. My options are
either to buy a replacement at Mouser or to install another IC with
more power.

Or glue some fins on it.