Toshiba TV29C90 problem; Image fades to black...

[N_Cook]

Engineer <junk2007@rogers.com> wrote in message
news:7f07a866-d94b-4244-b883-c72b1c5e8059@2g2000hsn.googlegroups.com...
On Jul 2, 9:28 am, "N_Cook" <dive...@tcp.co.uk> wrote:

I find desolder braid or vacuum suckers only work well enough on flat pcb
pads not bulbous solder and wire/s around tags of older stuff.

Anyone have improvements or alternatives to the technique I use.
Firstly assuming that the component lead length is not enough to cut and
re-use further along the wire. So definitely a matter of desoldering and
re-using what is there, maybe more than one wire , all quite properly,
looped through the tag before the original soldering.

The first thing I do is fix some small (ratchet clamping) medical artery
forceps / angler's hook remover tool/s on the exposed bit of the metal of
the wire/s up close to the tag to act as heatsinks to avoid melting the
sleeving , due to prolonged solder-iron heating of the tag. Then with what
I
call a needle-probe, a large sewing needle, set into wooden dowel handle,
I
explore while melting the solder blob and unhook the "free" end of the
wire/s and then pull through using the forceps.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list
onhttp://home.graffiti.net/diverse:graffiti.net/

On vintage gear I use a spring loaded solder sucker plus a sharp
aluminum (aluminium) probe (like the OP's needle probe - solder won't
stick to it.) Usefully, one end has a 1 mm slot about 3 mm deep with
sharp points on each side. This allows a controlled rotational
leverage to unhook those "mechanically anchored" wires that are such a
pain to get off.
As other posters have said, the addition of a little new solder can
give a better heat transfer from the "iron" and assist flow in the old
joint.
Cheers,
Roger

Aluminium ? I can't beleive that is strong enough.
Sewing needles are stainless steel which is fine with lead/tin solder but
interestingly, for diagnosis purposes, lead-free solder will adhere to
stainless steel, requiring more than just a fingernail to scrape it off,
more likely requiring pliers of some sort.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[GregS]

In article <7ca64b55-2a2b-4e32-a63e-0689408fbb1c@z66g2000hsc.googlegroups.com>, dke3591 <dke3591@yahoo.com> wrote:

Thanks everyone,

I tried the olive oil so far seems to help somewhat, but I'll probably
try one if the other options also.

Oils dry out. By using a wax that melts the surface like car wax, it pretty
much stays the same for a long time. They also have Plexaglass counpound which is much the same.

greg

 

[N_Cook]

Jeff Liebermann <jeffl@cruzio.com> wrote in message
newsjbn64t4ll098ll4hg3hp7ur95r93rou2d@4ax.com...

On Wed, 02 Jul 2008 08:04:01 -0700, Jeffrey D Angus
jangus@socal.rr.com> wrote:

Peter Wieck wrote:
I use a solder-sucker.

One of these things:
http://www.eclipsetools.com/ProductPics/Latest%20.jpegs/900-001N.JPG

Those really suck.

The little rubber bulb squeezy things are inadequate to the amount
of solder to be removed from the terminals.

The rubber also seems to crack and crumble after a few years. I had
several in my tool/junk box, all of which are now useless.

There are also fancy vacuum-aided devices for which I have never (yet)
had the need, but I hear-tell they are super at what they do.

They work quite well. I have a Pace desoldering station and a much
cheaper Chinese clone at home. I still use the solder pump, but for
unsoldering a board full of components, nothing beats the desoldering
machine. Highly recommended, but not cheap. Plan on buying some
spare tips and a tip cleaner as they do clog if used often.

For the most part, the vacuum pump desoldering irons are great for
printed circuit board work, but are also inadequate for vintage
equipment desoldering. The primary problem being the small size of
reservoir requires emptying about every 5-6 "normal vintage radio
joint"

It's not the reservoir that fills. It's the cotton plug inside the
glass cylinder that fills. However, it's not important as the tip
will clog long before the reservoir fills with dross.

My solution for large parts is a bit more disgusting. I don't care
about saving the solder or where it lands. So, I use an air
compressor to *BLOW* the solder off the terminals instead of sucking.
A piece of box cardboard serves as a sacrificial target. Safety
glasses, gloves, and a long sleeve shirt are quite useful. Get the
joint hot, and hit it with 120 psi of compressed air and it's
instantly clean. The dross comes off easily from everything except
plastic and rubber insulated wire, which the dross will melt.

Incidentally, the air compressor technique is also effective for
deslobbering large circuit boards full of useful components. In the
past, I would insert the board into a bench vice, heat up the solder
side with a propane torch, pull back on the board, and let spring
tension launch the components in the opposite direction. Kinda messy,
but very easy and effective. However, some boards simply will not
bend enough to make this method effective. In addition, the
components near the bench vice usually fail to desolder themselves.
So, I now use a propane torch and air compressor to do the
desoldering. That works much better, creates a more concentrated
mess, can be performed in any position, but does take somewhat longer.

In addition to the probe technique, I will heat up the terminal,
then wiggle the one lead in particular as it cools off. This gives
me a nice "cold solder joint" and makes it obvious as to which lead
is the one that needs to be gone. I'll use a sharp pair of cutters
to clip the specific loop around the terminal. When reheated again,
the lead usually pulls straight out and the wrapped part falls off.

Yeah, that also works. I get the same effect with short blast of cold
air from the air compressor. Instant dross.

Jeff

The other Jeff.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

I like this idea , I'll set my mind to how to get a short burst of
compressed air and give it a go. At the moment thinking of a pumped-up
innertube and a solenoid valve, I doubt full compressed air pressure would
be required for molten solder.
No workshop compressed airline unfortunately.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

Timelord wrote:

Third In order to do any good Sam would have to send the
original email to me.

What part of

"He clearly stated 'The letter came via the ebay internal mail
system as well as to my email address.' Unless he is just a
total liar (and if he is you would be stupid to trust any copy
of any email he sent you; he could simply edit a legit email
from ebay if he is a liar) that proves that your 'it was a
fake email that fooled you' theory is wrong."

are you having trouble understanding?

 

[GMAN]

In article <20d1lm.3ss.19.3@news.alt.net>, Meat Plow <meat@petitmorte.net> wrote:

On Wed, 02 Jul 2008 09:11:07 +0100, Arfa Daily wrote:


"Ron" <BigELilE05@msn.com> wrote in message
news:93b8e32f-997a-48b9-91fa-858c504de3b8@a70g2000hsh.googlegroups.com...
I have two Panasonic VCR's, model numbers PV-V4540 and PV-9450.

They are almost idenical on the outside and very simular on the inside.

The "newer" model - PV-V4540 - seems to have a head going bad from
everything I've read.

The PV-9450 works fine, but doesn't have the features that the PV- V4540
has.

I would like to install the head unit from the PV-9450 (the older one)
in the PV-V4540 (the newer one).

They look the same, but are they the same? And if I swap the headunits,
will the alignment be the same?

Here are pics of the head units. The one thing that I wondering about is
the "arm" on the center post of the (newer) PV-V4540...what is that?



The arm in the centre is for static discharge. Without it, on a machine
originally fitted with one - which most are - you tend to get little white
dots on the playback picture. Provided the heads *are* exactly the same,
then there are no alignment issues with head swaps on modern VCRs. It is
only two screws, so give it a go. Normally, the screw holes are offset
slightly to make sure that you don't get it on 180 degrees out. At worst,
it just won't work. As a matter of interest, what are the symptoms for
your diagnosis of failing heads on the first one ?


The OP should be advised that in certain cases (unless things have changed
in the past decade)you need a head puller. I've replaced many voice coils
from inexperienced techs who destroyed them while removing a head.


He's not wanting to remove just the heads, he wants to remove and replace the

whole cylinder with heads attached to the other unit. Its only 2 or 4 screws
on the thing and you move it over and place it down in the other VCR.I have
done this sucessfully from an old Mitsubishi U-760 to a U-770 if i remember
right(Its been years).

But with his situation, the parts are completely different between the units.
I would advise against it with these two units.

 

[Jim Yanik]

"N_Cook" <diverse@tcp.co.uk> wrote in
news:g4gs4i$vuc$1@registered.motzarella.org:

Jeff Liebermann <jeffl@cruzio.com> wrote in message
newsjbn64t4ll098ll4hg3hp7ur95r93rou2d@4ax.com...
On Wed, 02 Jul 2008 08:04:01 -0700, Jeffrey D Angus
jangus@socal.rr.com> wrote:

Peter Wieck wrote:
I use a solder-sucker.

One of these things:
http://www.eclipsetools.com/ProductPics/Latest%20.jpegs/900-001N.JPG

Those really suck.

The little rubber bulb squeezy things are inadequate to the amount
of solder to be removed from the terminals.

The rubber also seems to crack and crumble after a few years. I had
several in my tool/junk box, all of which are now useless.

There are also fancy vacuum-aided devices for which I have never
(yet) had the need, but I hear-tell they are super at what they
do.

They work quite well. I have a Pace desoldering station and a much
cheaper Chinese clone at home. I still use the solder pump, but for
unsoldering a board full of components, nothing beats the desoldering
machine. Highly recommended, but not cheap. Plan on buying some
spare tips and a tip cleaner as they do clog if used often.

For the most part, the vacuum pump desoldering irons are great for
printed circuit board work, but are also inadequate for vintage
equipment desoldering. The primary problem being the small size of
reservoir requires emptying about every 5-6 "normal vintage radio
joint"

It's not the reservoir that fills. It's the cotton plug inside the
glass cylinder that fills. However, it's not important as the tip
will clog long before the reservoir fills with dross.

My solution for large parts is a bit more disgusting. I don't care
about saving the solder or where it lands. So, I use an air
compressor to *BLOW* the solder off the terminals instead of sucking.
A piece of box cardboard serves as a sacrificial target. Safety
glasses, gloves, and a long sleeve shirt are quite useful. Get the
joint hot, and hit it with 120 psi of compressed air and it's
instantly clean. The dross comes off easily from everything except
plastic and rubber insulated wire, which the dross will melt.

Incidentally, the air compressor technique is also effective for
deslobbering large circuit boards full of useful components. In the
past, I would insert the board into a bench vice, heat up the solder
side with a propane torch, pull back on the board, and let spring
tension launch the components in the opposite direction. Kinda
messy, but very easy and effective. However, some boards simply will
not bend enough to make this method effective. In addition, the
components near the bench vice usually fail to desolder themselves.
So, I now use a propane torch and air compressor to do the
desoldering. That works much better, creates a more concentrated
mess, can be performed in any position, but does take somewhat
longer.

In addition to the probe technique, I will heat up the terminal,
then wiggle the one lead in particular as it cools off. This gives
me a nice "cold solder joint" and makes it obvious as to which lead
is the one that needs to be gone. I'll use a sharp pair of cutters
to clip the specific loop around the terminal. When reheated again,
the lead usually pulls straight out and the wrapped part falls off.

Yeah, that also works. I get the same effect with short blast of
cold air from the air compressor. Instant dross.

Jeff

The other Jeff.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


I like this idea , I'll set my mind to how to get a short burst of
compressed air and give it a go. At the moment thinking of a pumped-up
innertube and a solenoid valve, I doubt full compressed air pressure
would be required for molten solder.
No workshop compressed airline unfortunately.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

I suppose you could look into one of those "portable air" systems out
now,that use paintball gun tanks and a regulator to supply air/nitrogen/CO2
to air-powered tools,they hang off your belt.Tanks of varying sizes are
available,too.Refill them wherever paintball refills are offered.

there are inexpensive air accessory kits available that include a coiled
hose,nozzle,quik-connects,tire inflators.

--
Jim Yanik
jyanik
at
kua.net

 

[Steve]

sam@ece.drexel.edu wrote in news:16ea6110-be19-4a21-aecc-
10780259cc1d@e39g2000hsf.googlegroups.com:

On Jul 2, 3:35 pm, alphamnemonic <shmotm...@gmail.com> wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply I am
working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is putting
out a sawtooth wave. I am testing it in 'standby mode', in which Q4 is
off and R33 is in control of the duty cycle. Replacing the IC1 has no
effect. Does anyone have any ideas?

Where are you seeing sawtooths? Pin 13?

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header
above is
ignored unless my full name AND either lasers or electronics is
included in the
subject line. Or, you can contact me via the Feedback Form in the
FAQs.

That is my question. Why do you have output A and output B (pin 11 and 14)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you have this
connected as an output?

 

[William Sommerwerck]

"hr(bob) hofmann@att.net" <hrhofmann@att.net> wrote in message
news:b644c0a7-4710-4d53-8b97-acf8dc18f932@e53g2000hsa.googlegroups.com...
On Jul 2, 2:43 pm, Adrian C <em...@here.invalid> wrote:

William Sommerwerck wrote:

I don't think those who replied got the point I was making. You'll have
no
trouble finding a remote labelled as being right for your TV. The
"catch" is
that the advanced functions MIGHT NOT BE SUPPORTED.

Some closer that others. The manufacturer's original right on!!! This
isn't the toughest chore on the planet. Do you run a TV shop?

I contacted MCM and they said tht a remote with the PIP functions is
not available (thru them at least).

Thanks. I was rather busy today.

Is that true for any and all brands? Or just some?

 

[Paul P]

Keep some sacrificial tube around and put them in the socket before
desoldering. I have cracked too many empty sockets. Especially the Philco
40-*** grey locktail socket on the second tube in the line up.

I try to splice (hooks) in the new componants unless the under chassis is
supposed to be replicate/restored.

Paul P.

 

[Arfa Daily]

"nipperchipper" <nipperchipper@hotmail.com> wrote in message
news:J-SdnUraL6u1MPbVnZ2dnUVZ_hOdnZ2d@posted.sasktel...

"Ron" <BigELilE05@msn.com> wrote in message
news:93b8e32f-997a-48b9-91fa-858c504de3b8@a70g2000hsh.googlegroups.com...
I have two Panasonic VCR's, model numbers PV-V4540 and PV-9450.

They are almost idenical on the outside and very simular on the
inside.

The "newer" model - PV-V4540 - seems to have a head going bad from
everything I've read.

The PV-9450 works fine, but doesn't have the features that the PV-
V4540 has.

I would like to install the head unit from the PV-9450 (the older one)
in the PV-V4540 (the newer one).

They look the same, but are they the same? And if I swap the
headunits, will the alignment be the same?

Here are pics of the head units. The one thing that I wondering about
is the "arm" on the center post of the (newer) PV-V4540...what is
that?



PV-V4540 head unit
http://i126.photobucket.com/albums/p96/bigelile/IM002417-1.jpg

PV-9450 head unit
http://i126.photobucket.com/albums/p96/bigelile/IM002411-1.jpg

PV-V4540 face
http://i126.photobucket.com/albums/p96/bigelile/IM002414-1.jpg

PV-9450 face
http://i126.photobucket.com/albums/p96/bigelile/IM002413-1.jpg


from the parts list pvv4540 uses the beliow listed upper cylinder head
VEGS0427 ( A )
VEGS0428 ( B,C,D )
VEGS0429 ( E,F )

pv9450 uses
VEHS0571 ( A )
VEHS0570 ( B,C )
VEHS0567 ( D,E )
not much help but swapping may not hurt



Given that info, it's probably not going to work right. Hifi sound is

critical of correct head performance, so if there are any specification
differences between the head drums, there will likely be a problem. As far
as swapping the entire head drum assembly goes, you will often find that
even identical-looking assemblies won't fit because a screw hole or chassis
locating boss has been deliberately offset to prevent it. As for having to
use a puller to remove the upper head drum (which I have always thought is a
far more straightforward job than swapping the whole assembly) on some
machines, that used to be a given, but I always found that Pans came off ok.

Not that for some years it's been a viable proposition to replace heads,
even on 'good' machines. The cost of the head drum alone, without any
labour, exceeded tha cost of a bargain warehouse all singing and dancing
machine with a shiny new 2 year warranty ...

Arfa

 

[Arfa Daily]

"Dave" <daveem@webtv.net> wrote in message
news:6d42acf1-5646-4ab9-b353-3fd96ab12abd@a32g2000prf.googlegroups.com...
On Jul 1, 1:50 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

- Show quoted text -
I hate to sound stupid, but How do I find the switched line from the
control micro to see if it toggles? Didn't I do this when I checked
all of the power supply pins going to my video board?
I do have a glowing LED on the front of the set which turns on the
minute I plug the set in, but it is continually on, and does not
blink. I also tested every pin on my power supply board and found them
to be dead, except for the 5 volt stand by voltage. I did notice when
measuring the five volt line on the power switch it dropped to 0 volts
when I pushed the switch. Am I misunderstanding anything your
saying?

OK. The fact that you are getting a standby light shows that the 5v you
are
seeing at the power supply, is definitely an output from it, not an
input
from elsewhere, that is not moving. Seeing the 5v at the set's standby
pushbutton, again verifies that the 5v is reaching the main board, and
is
also getting to the system control micro (to which the standby button
will
almost certainly be connected). In response to that line being dropped
from
5v to zero, by pushing the standby button, the system control micro
should
issue a "power on" signal to the power supply. This is the usual
arrangement. It is highly unlikely that the standby pushbutton, is
connected
directly to the power supply.

So, assuming that the standby switching line's pin is not marked at the
power supply, and that you do not have a set of schematics (or even a
board
interconnect diagram will do) then the only way that you can proceed, is
to
go looking for the standby switching line at the power supply, by
looking
at
every external connector pin that doesn't have any legend to tell you
what
it does, with a 'scope set to DC coupling. As you move to each pin, you
need
to push the standby button, and wait a couple of seconds to see if the
DC
level on the pin you are checking, moves, or even if a pulse is
produced.
Wait ten seconds before moving on to the next pin to test, to allow any
'problem' that the system control micro may have detected, to reset to
the
'try again' condition.

If you find a pin that's toggling, then the chances are that it is not
your
mainboard that's primarily at fault (as such) and that the problem lies
either with the power supply, or one of the loads that it's feeding. If
there is no pin that's toggling, then the system control is not issuing
a
"power on" signal, and trouble shooting the power supply, is not the
right
path.

Unfortunately, these things are not straightforward like in the 'good
ol'
days', and can be very difficult to fault-find on, without a lot of
experience, and spare boards to try in them. Let us know if you manage
to
find the standby switching line, and we might be able to proceed a bit
further, from there. Do you know what chassis is fitted by any chance ?
It's
not a Vestel is it ? Are there any numbers / letters at the corner of
the
PSU ?

Arfa- Hide quoted text -

- Show quoted text -

Thanks Arfa,
There are a bunch of numbers on the power supply board, starting with
a VLT70039.50 LOGAH REV5 UA-4141-1-LF
I just recieved the service manual from Andrews on this set and its a
joke. The only page that shows a schematic is so blury its useless.

I did find what I believe to be the return line from the micro going
to my power supply board, It says "PWR ON" so I'm going to assume this
is the right one, but I get no voltage what so ever when I press my
power on button. Thanks again.
Any further suggestions would be appreciated.
Dave

OK Dave. That line is definitely the power switching line. If it has no
voltage on it at all (check this with a 'scope set to DC, in case it just
pulses too quickly to see on a meter) then there's a good chance that the
micro is not telling the power supply to turn on. If at all possible from
the manual, you want to trace this signal back at least to where it comes
off the mainboard, and preferably all the way back to a pin on the micro,
just to prove that there are no simple connector isues. Also, now that you
have the manual, try to see if you can verify that standby supplies are 5v
only on that set i.e. that you don't have say a 3v3 standby rail that's
missing. Also, try to verify that there is not a 3v3 regulator on the
mainboard that derives its input from the 5v standby rail, and that's not
working. After that, is where it starts to get hairy ...

If the "power on" line is low, never changes - even immediately after a
fully-unplugged-from-the wall-outlet repower - and the power supply is in
standby, then the chances are that the line should shift from low (0v) to
high (5v) in order to wake the power supply up. You can thus now verify
the
power supply by disconnecting the line (usually you can easily pop the pin
from the connector shell to isolate any wire) and then connecting a low
value resistor - start with 100 ohms - between the 5v standby supply, and
the actual power supply pin where you have disconnected the wire from. If
this brings the power supply to life, then the chances are that you have a
bad mainboard, and you are unlikely to be able to fix that. You might try
looking on e-Bay for replacement boards. These often pop up this side of
the
pond, at very reasonable prices, as sets often get broken up for spares as
a
result of insurance write offs from LCD panel damage.

One word of caution, I am assuming that you have enough knowledge of
switch
mode power supplies to realise that they are potentially *very* dangerous
at
their front ends. The main filter cap on one that's not running, can
remain
charged to a very high voltage, long after you disconnect it from line
power. Also, most of these LCD PSUs have a resonant PFC stage at the front
end, which will run, producing full front end rectified DC across the main
filter cap, with as little as 40v ac input applied to the supply.

Good luck. Let us know if you make any progress.

Arfa- Hide quoted text -

- Show quoted text -

Even if I can't fix it I appreciate all your help in expanding my
understanding of LCD power supplies. I will let you know if I have any
luck.
Dave

No problem. There's something 'new' to challenge us every day ... d;~}

Arfa

 

[John]

"Bill" <bbaka@comcast.net> wrote in message
newsyyak.16018$Ri.15434@flpi146.ffdc.sbc.com...

Meat Plow wrote:
Anyone ever successfully acquired one? I doubt they exist but I thought
I'd put it out here just in case. I have a 915GAC that lost its 12 volt
CPU core power distribution and another for parts that has another
unrelated fault.

Hi Meat,
Why bother unless it is an expensive board, like over $200 to replace?
The boards for the last ten years or so have been using Point of Load
switching regulators right at the CPU. I don't think Intel would ever give
a schematic to anyone but a certified repair house, so good lick with
that.
Bill Baka (XP/Ubuntu)

I'd love to see some MOBO schematics, not because I would actually need to
use them; however I love reading schematics, and have always been interested
in how they squeeze all that stuff into such a small amount of real estate.
Something similar to 'Hacking The X-Box' would really be cool.
John

 

Timelord wrote:

"me" <me@privacy.net> wrote...

Timelord wrote:

Third In order to do any good Sam would have to send the
original email to me.

What part of

"He clearly stated 'The letter came via the ebay internal mail
system as well as to my email address.' Unless he is just a
total liar (and if he is you would be stupid to trust any copy
of any email he sent you; he could simply edit a legit email
from ebay if he is a liar) this proves that your 'it was a
fake email that fooled you' theory is wrong."

are you having trouble understanding?

Hi Sam,

Who is sam?

As I said before The only thing that would any good was to forward
the entire email with all headdress.

What part of

"He clearly stated 'The letter came via the ebay internal mail
system as well as to my email address.' Unless he is just a
total liar (and if he is you would be stupid to trust any copy
of any email he sent you; he could simply edit a legit email
from ebay if he is a liar) this proves that your 'it was a
fake email that fooled you' theory is wrong."

are you having trouble understanding?

For tracing Your original email suggest strongly an invasion
type phashing email And that is all I can say without seeing
the original email

What part of

"He clearly stated 'The letter came via the ebay internal mail
system as well as to my email address.' Unless he is just a
total liar (and if he is you would be stupid to trust any copy
of any email he sent you; he could simply edit a legit email
from ebay if he is a liar) this proves that your 'it was a
fake email that fooled you' theory is wrong."

are you having trouble understanding?

Moron.

 

[Arfa Daily]

"Ron" <BigELilE05@msn.com> wrote in message
news:e8c1e0ec-6f17-47f5-a292-02716c2a47b4@m73g2000hsh.googlegroups.com...
On Jul 2, 4:11 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

"Ron" <BigELil...@msn.com> wrote in message

news:93b8e32f-997a-48b9-91fa-858c504de3b8@a70g2000hsh.googlegroups.com...



I have two Panasonic VCR's, model numbers PV-V4540 and PV-9450.

They are almost idenical on the outside and very simular on the
inside.

The "newer" model - PV-V4540 - seems to have a head going bad from
everything I've read.

The PV-9450 works fine, but doesn't have the features that the PV-
V4540 has.

I would like to install the head unit from the PV-9450 (the older one)
in the PV-V4540 (the newer one).

They look the same, but are they the same? And if I swap the
headunits, will the alignment be the same?

Here are pics of the head units. The one thing that I wondering about
is the "arm" on the center post of the (newer) PV-V4540...what is
that?

The arm in the centre is for static discharge. Without it, on a machine
originally fitted with one - which most are - you tend to get little white
dots on the playback picture. Provided the heads *are* exactly the same,
then there are no alignment issues with head swaps on modern VCRs. It is
only two screws, so give it a go. Normally, the screw holes are offset
slightly to make sure that you don't get it on 180 degrees out. At worst,
it
just won't work. As a matter of interest, what are the symptoms for your
diagnosis of failing heads on the first one ?

Arfa

When the video starts to get noticeably bad a screen will pop-up that
says the heads need to be cleaned. So for yrs I've been taking the top
off and cleaning the heads when the screen appears. (white piece of
paper with rubbing alcohol holding it against the heads on the upper
drum while turning it counterclockwise - alcohol and Q Tips for the
erase and audio heads) Put the top back on and everything is great
until they get dirty again.

So earlier this week the picture started looking *really* bad, and
sure enough there is the screen telling me the heads are dirty...so I
do my usual procedure, only this time, the picture still looks like
crap. The warning screen isn't coming up, but previously recorded
tapes in EP mode look horrible, any tapes I make in EP mode look
horrible.

Tapes that I've previously made in SP mode look OK and store bought
movies look OK also. Not great, just OK. (Same with making a tape in
SP)

Before any of this happened, while watching a recorded EP mode tape if
I were to hit rewind to back up the tape, about 25% of the upper
screen was nothing but noise lines/snow.

But, this would only happen if it was near the beginning of the tape.
Once you got past a certain point (3/8ths - 1/2 way) this problem
would go away.

After cleaning the heads, this problem is still present. I can fix
that problem by adjusting (big adjustment 1/4 turn) the feed side
roller guide, but the picture still looks horrible.

So, after reading many articles, I can only come to the conclusion
that one of the 4 heads in the drum/cylinder went bad.

I haven't had time to switch the heads yet, when I do I will post the
results.

Meatplow, after removing the 2 small screws, the upper part of the
drum/cylinder, what ever you wanna call it, just lifts right off.



Yes, that is normally the case with Pans. Sounds as though one of the heads
may have become chipped, but it is also possible that one of them has become
badly blocked. Sometimes when that is the case, it's necessary to get a bit
vicious with it. A trick that was shown to me by a manufacturer's service
course lecturer, is to hold a fingernail against a running tape, as it is
around the head drum - so that you can feel the heads going "DRRRRRRRRR"
against your nail, through the tape, if you see what I mean. It is amazing
how quickly and how well this recovers a head that has become badly clogged
from a tape that is moist from condensation, or is shedding oxide. It has
got me out of trouble on many occasions.

Arfa

 

[Arfa Daily]

"Ron" <BigELilE05@msn.com> wrote in message
news:1891bc14-833b-49d3-925e-c49589ea997a@c58g2000hsc.googlegroups.com...
On Jul 3, 4:40 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

"nipperchipper" <nipperchip...@hotmail.com> wrote in message

news:J-SdnUraL6u1MPbVnZ2dnUVZ_hOdnZ2d@posted.sasktel...



"Ron" <BigELil...@msn.com> wrote in message
news:93b8e32f-997a-48b9-91fa-858c504de3b8@a70g2000hsh.googlegroups.com...
I have two Panasonic VCR's, model numbers PV-V4540 and PV-9450.

They are almost idenical on the outside and very simular on the
inside.

The "newer" model - PV-V4540 - seems to have a head going bad from
everything I've read.

The PV-9450 works fine, but doesn't have the features that the PV-
V4540 has.

I would like to install the head unit from the PV-9450 (the older one)
in the PV-V4540 (the newer one).

They look the same, but are they the same? And if I swap the
headunits, will the alignment be the same?

Here are pics of the head units. The one thing that I wondering about
is the "arm" on the center post of the (newer) PV-V4540...what is
that?

PV-V4540 head unit
http://i126.photobucket.com/albums/p96/bigelile/IM002417-1.jpg

PV-9450 head unit
http://i126.photobucket.com/albums/p96/bigelile/IM002411-1.jpg

PV-V4540 face
http://i126.photobucket.com/albums/p96/bigelile/IM002414-1.jpg

PV-9450 face
http://i126.photobucket.com/albums/p96/bigelile/IM002413-1.jpg

from the parts list pvv4540 uses the beliow listed upper cylinder head
VEGS0427 ( A )
VEGS0428 ( B,C,D )
VEGS0429 ( E,F )

pv9450 uses
VEHS0571 ( A )
VEHS0570 ( B,C )
VEHS0567 ( D,E )
not much help but swapping may not hurt

Given that info, it's probably not going to work right. Hifi sound is
critical of correct head performance, so if there are any specification
differences between the head drums, there will likely be a problem.

Well, that is an understatement.

Put the head drum from the older working VCR into the newer one, there
was no signal on the face plate for "HiFi".

So I put it back into the - what was working unit - and NO HiIFi.

Don't know what happened, but the newer VCR fried something in the
older ones head drum.

Now I have 2 Panasonics that don't work.



I feel that to be highly unlikely, as the coupling between the heads and the
amplification electronics is completely isolated by a rotary transformer,
the primary of which is in the upper head drum, and the secondary, in the
lower.

Far more likely is that the screw-holes are not offset, and you have managed
to get the upper drums 180 degrees out on the centre spindle. Unscrew the
formerly good one again, and try turning it through 180 degrees, and see if
the holes still line up. If they do, screw it down again, and retest. If
that gets you back to working, then try your swap again, taking note of the
same potential problem.

Arfa

 

[Steve]

alphamnemonic <shmotmail@gmail.com> wrote in
news:ba29f199-331f-48c1-ab96-28c3a81d42d8@i18g2000prn.googlegroups.com:

On Jul 2, 6:20 pm, Steve <nob...@nobody.com> wrote:
s...@ece.drexel.edu wrote in news:16ea6110-be19-4a21-aecc-
10780259c...@e39g2000hsf.googlegroups.com:





On Jul 2, 3:35 pm, alphamnemonic <shmotm...@gmail.com> wrote:
Hi Everybody

This chip normally puts out square pulses. In the power supply I
am working on (http://www.laserfaq.org/sam/150rcsch.pdf) it is
putting out a sawtooth wave. I am testing it in 'standby mode', in
which Q4 is off and R33 is in control of the duty cycle. Replacing
the IC1 has no effect. Does anyone have any ideas?

Where are you seeing sawtooths?  Pin 13?

--- sam | Sci.Electronics.Repair FAQ:http://www.repairfaq.org/
 Repair | Main Table of Contents:http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ:http://www.repairfaq.org/sam/lasersam.htm
        | Mirror Sites:http://www.repairfaq.org/REPAIR/F_mirror
.html

Important: Anything sent to the email address in the message header
above is
ignored unless my full name AND either lasers or electronics is
included in the
subject line.  Or, you can contact me via the Feedback Form in the
FAQs.

That is my question. Why do you have output A and output B (pin 11
and 14
)
grounded?

Also, pin 13 is VC in for the transistor collectors. Why do you have
this connected as an output?- Hide quoted text -

- Show quoted text -

Yes the sawtooth is on pin 13. Pin 13 is being used as an output and
pins 11 and 14 are grounded because the chip is being used in single-
ended supply mode (see
http://www.datasheetcatalog.org/datasheet/motorola/SG3525AN.pdf p.6
for an example of this configuration). I can see why you find that
strange--I did too!

I'd avoid the funky setup you have. In my opinion I'd connect pin 13 and 15
together and use either output A or B.

I'm not sure what Q4 is doing, I've never seen it used this way, but you
must know more than me since you designed this elaborte circuit.


Keep us posted at what you do to resolve the problem.

 

[Mike Anton]

<sam@ece.drexel.edu> wrote in message
news:4a73866c-bb48-48f3-bd76-9a8bae3dcd9d@e53g2000hsa.googlegroups.com...

OK, a bit off topic but may apply to others at universities as they
upgrade their computer
systems.

So UPenn and Drexel have pulled the plug on their USENET news
servers. I'm looking for recommendations on newsgroup access,
preferably via GNUS, which many consider antiquated, as far as I can
tell, it is 10 times faster to read and post than using the fancy GUI
"modern" alternatives.

Thanks!

I've been using news.astraweb.com as of late, mostly for binaries groups
though, since my ISP dropped binary groups (damn Telus).
What I like about them, is you can buy a 110GB block for $25, that never
expires. I would imagine if you mostly use text news groups that this would
last almost forever.

Mike

 

[GMAN]

In article <1891bc14-833b-49d3-925e-c49589ea997a@c58g2000hsc.googlegroups.com>, Ron <BigELilE05@msn.com> wrote:

On Jul 3, 4:40=A0am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:
"nipperchipper" <nipperchip...@hotmail.com> wrote in message

news:J-SdnUraL6u1MPbVnZ2dnUVZ_hOdnZ2d@posted.sasktel...



"Ron" <BigELil...@msn.com> wrote in message
news:93b8e32f-997a-48b9-91fa-858c504de3b8@a70g2000hsh.googlegroups.com..=
..
I have two Panasonic VCR's, model numbers PV-V4540 and PV-9450.

They are almost idenical on the outside and very simular on the
inside.

The "newer" model - PV-V4540 - seems to have a head going bad from
everything I've read.

The PV-9450 works fine, but doesn't have the features that the PV-
V4540 has.

I would like to install the head unit from the PV-9450 (the older one)
in the PV-V4540 (the newer one).

They look the same, but are they the same? And if I swap the
headunits, will the alignment be the same?

Here are pics of the head units. The one thing that I wondering about
is the "arm" on the center post of the (newer) PV-V4540...what is
that?

PV-V4540 =A0head unit
http://i126.photobucket.com/albums/p96/bigelile/IM002417-1.jpg

PV-9450 head unit
http://i126.photobucket.com/albums/p96/bigelile/IM002411-1.jpg

PV-V4540 face
http://i126.photobucket.com/albums/p96/bigelile/IM002414-1.jpg

PV-9450 face
http://i126.photobucket.com/albums/p96/bigelile/IM002413-1.jpg

from the parts list pvv4540 uses the beliow listed upper cylinder head
VEGS0427 =A0( A )
VEGS0428 =A0( B,C,D )
VEGS0429 =A0( E,F )

pv9450 uses
VEHS0571 =A0( A )
VEHS0570 =A0( B,C )
VEHS0567 =A0( D,E )
not much help but swapping may not hurt

Given that info, it's probably not going to work right. Hifi sound is
critical of correct head performance, so if there are any specification
differences between the head drums, there will likely be a problem.

Well, that is an understatement.

Put the head drum from the older working VCR into the newer one, there
was no signal on the face plate for "HiFi".

So I put it back into the - what was working unit - and NO HiIFi.

Don't know what happened, but the newer VCR fried something in the
older ones head drum.

Now I have 2 Panasonics that don't work.

Didnt the fact that they were two completely different model numbers on the

heads and drums tip you off?

 

[GMAN]

In article <oeSdnZcWvuVwyvDVnZ2dnUVZ_hjinZ2d@earthlink.com>, "Michael A. Terrell" <mike.terrell@earthlink.net> wrote:

Ron wrote:

Orlando huh? Wanna help out a neighbor?


I would, but I'm closer to Gainesville these days. Orlando was 20+
years ago, and I've slowly moved North since then.


So has half of Cuba.

 

[N_Cook]

Engineer <junk2007@rogers.com> wrote in message
news:238c21d8-7c6a-4abb-b56d-84b852bdf05b@l42g2000hsc.googlegroups.com...
On Jul 2, 1:38 pm, "N_Cook" <dive...@tcp.co.uk> wrote:

Engineer <junk2...@rogers.com> wrote in message

news:7f07a866-d94b-4244-b883-c72b1c5e8059@2g2000hsn.googlegroups.com...
On Jul 2, 9:28 am, "N_Cook" <dive...@tcp.co.uk> wrote:



I find desolder braid or vacuum suckers only work well enough on flat
pcb
pads not bulbous solder and wire/s around tags of older stuff.

Anyone have improvements or alternatives to the technique I use.
Firstly assuming that the component lead length is not enough to cut and
re-use further along the wire. So definitely a matter of desoldering and
re-using what is there, maybe more than one wire , all quite properly,
looped through the tag before the original soldering.

The first thing I do is fix some small (ratchet clamping) medical artery
forceps / angler's hook remover tool/s on the exposed bit of the metal
of
the wire/s up close to the tag to act as heatsinks to avoid melting the
sleeving , due to prolonged solder-iron heating of the tag. Then with
what
I
call a needle-probe, a large sewing needle, set into wooden dowel
handle,
I
explore while melting the solder blob and unhook the "free" end of the
wire/s and then pull through using the forceps.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list

onhttp://home.graffiti.net/diverse:graffiti.net/

On vintage gear I use a spring loaded solder sucker plus a sharp
aluminum (aluminium) probe (like the OP's needle probe - solder won't
stick to it.) Usefully, one end has a 1 mm slot about 3 mm deep with
sharp points on each side. This allows a controlled rotational
leverage to unhook those "mechanically anchored" wires that are such a
pain to get off.
As other posters have said, the addition of a little new solder can
give a better heat transfer from the "iron" and assist flow in the old
joint.
Cheers,
Roger

Aluminium ? I can't beleive that is strong enough.
Sewing needles are stainless steel which is fine with lead/tin solder but
interestingly, for diagnosis purposes, lead-free solder will adhere to
stainless steel, requiring more than just a fingernail to scrape it off,
more likely requiring pliers of some sort.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list
onhttp://home.graffiti.net/diverse:graffiti.net/- Hide quoted text -

- Show quoted text -

That was my first thought but it's not broken yet, and it's had a few
tough twists over the years! Perhaps it's an alloy. It came with my
old Weller solder gun over 25 years ago, both still going strong.
I only use tin/lead solder so the stainless sewing needle is a good
idea (but you don't get that "slot twist".) I'll ask my wife for one,
she's from Southsea (not far from you), so pretty resourceful!
Cheers,
Roger
(near Toronto, Canada)


In UK size terms , use a darning needle somewhere between size 5 and 12.
Drill an undersize hole in the dowel, insert with glue and bind the end of
the wood tightly with wire to reinforce against splitting/opening up.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/