Toshiba TV29C90 problem; Image fades to black...

[N_Cook]

Bill M <radioexray@geemail.com> wrote in message
news:gk8osu02h35@news2.newsguy.com...

N_Cook wrote:

The broken one, a bit of the paint with the
green spot , broken away.
Body and end blob , both orange, presumably 33pF
http://home.graffiti.net/diverse:graffiti.net/puffy_cap.jpg
ruler 0.1 inch markings, solid black core material

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



This thread must have taken a turn that I missed. The device in the
photo sure looks like a resistor !?!

-Bill

My first thought on seeing that solid black core, expecting tubes if caps.
But all of that size and format measured over 30M ohm, if resistors, and
that broken one >500 Meg on an insulation tester. Also very small physical
size , for the time, if they were resistors. Anyone interested in a
microscope view of that core?, i could take such a pic, or any suggestions
for chemistry test ?

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

 

[Bill M]

N_Cook wrote:

My first thought on seeing that solid black core, expecting tubes if caps.
But all of that size and format measured over 30M ohm, if resistors, and
that broken one >500 Meg on an insulation tester. Also very small physical
size , for the time, if they were resistors. Anyone interested in a
microscope view of that core?, i could take such a pic, or any suggestions
for chemistry test ?

Thats a new on for me. So what forms the two sides of the capacitor?
Is there any sort of plating on the black core underneath the paint?

-Bill

 

[N_Cook]

Bill M <radioexray@geemail.com> wrote in message
news:gka5nq01mqc@news4.newsguy.com...

N_Cook wrote:

My first thought on seeing that solid black core, expecting tubes if
caps.
But all of that size and format measured over 30M ohm, if resistors, and
that broken one >500 Meg on an insulation tester. Also very small
physical
size , for the time, if they were resistors. Anyone interested in a
microscope view of that core?, i could take such a pic, or any
suggestions
for chemistry test ?

Thats a new on for me. So what forms the two sides of the capacitor?
Is there any sort of plating on the black core underneath the paint?

-Bill

The paint is laid directly on the black stuff. In a x30 microscope it has a
slightly porous structure like scaled down clinker but not regular fine
structure like ferrite slugs.
Some ceramic type materials used in 1954 reference for capacitor
construction were Clineonstatite, Magnesium Titanate, Rutile, Strontium
Titanate, Barium Titanate, Barium-strontium titanate. But what any of them
look like I've no idea.


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

 

[jakdedert]

Roy wrote:

Hi, I wonder if anyone can help me with this. Two of the keys do not produce
any sound and one of the keys (approximately in the middle) seems to be
sticking up about 8 mm proud of the other keys. Although I am from an
electronics background (TVand Video servicing) I have never had any dealings
with one of these before. If anyone can point me in the right direction for
a workshop service manual or has any tips I would really appreciate it! I
have spent a couple of hours googling but all I can find is that it was
manufactured in 1988 or thereabouts. I found how to do the factory reset but
this didnt do anything, and also got the user manual. Thanks in advance for
any help.
Roy


I expect you're going to have to open it up. Since you already have one

strictly mechanical issue with the keyboard--the misplaced key--I think
it's reasonable to at least suspect mechanical issues with the other
two. In any case, it's going to have to come open to fix the one key;
so repost if you can't figure out the problem with the other two *after*
you've looked inside.

jak

 

[Andrew Erickson]

In article <%Arcl.252712$XB5.12137@newsfe29.ams2>,
"Roy" <rladdressinvalid@blueyonder.co.uk> wrote:

Hi, I wonder if anyone can help me with this. Two of the keys do not produce
any sound and one of the keys (approximately in the middle) seems to be
sticking up about 8 mm proud of the other keys. Although I am from an
electronics background (TVand Video servicing) I have never had any dealings
with one of these before. If anyone can point me in the right direction for
a workshop service manual or has any tips I would really appreciate it!

I'm not familiar at all with this specific model, but from your
description it certainly sounds like some mechanical damage to or
maladjustment of the keyboard assembly. Disassembly and inspection
should eventually reveal what the problem is, and likely also if it is
feasible to make/invent a repair or not.

The electronics almost certainly uses some form of matrixed scanning of
the keys to then digitally activate the sounds, perhaps in octave or
half octave increments, so the actual electronic core would seem to be
perfectly OK and the problems lie only in the keyboard mechanism itself
or its interconnection to the "brain."

Good luck.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he cannot
lose." -- Jim Elliot

 

[Gareth Magennis]

"jakdedert" <jakdedert@bellsouth.net> wrote in message
news:nZscl.5366$e13.4379@bignews5.bellsouth.net...

Roy wrote:
Hi, I wonder if anyone can help me with this. Two of the keys do not
produce any sound and one of the keys (approximately in the middle) seems
to be sticking up about 8 mm proud of the other keys. Although I am from
an electronics background (TVand Video servicing) I have never had any
dealings with one of these before. If anyone can point me in the right
direction for a workshop service manual or has any tips I would really
appreciate it! I have spent a couple of hours googling but all I can find
is that it was manufactured in 1988 or thereabouts. I found how to do the
factory reset but this didnt do anything, and also got the user manual.
Thanks in advance for any help.
Roy

The key that is sticking up is almost certainly broken. The keys that don't
sound are almost certainly because the key contacts are dirty or worn.

You don't need a service manual. Just take off the lower casing and work
out what is required to remove the keyframe assembly - usually unscrewing
lots of screws and perhaps removing some circuit boards.
The key contact strips are under the keys. On some keyboards you need to
remove the keys to access them, on others you unscrew the circuit boards
from under the keys to access them leaving the keys in place.

You may be able to clean the dirtry strips and the PCB they act on, or it
may be better to buy a new set of strips with the new key you will need to
buy from Roland, neither are particularly expensive. Clean the PCB contacts
carefully with alcohol and cotton buds before fitting the new or cleaned
strips.



Gareth.

 

[William Sommerwerck]

My gut reaction is that you're correct -- it has no memory. I don't see
anything in it that could be used as a memory.

You're right -- the "correct" way to implement a bingo counter would require
a microprocessor and some memory.

 

[Roy]

"Gareth Magennis" <gareth.magennis@ntlworld.com> wrote in message
news:FsEcl.72125$626.30409@newsfe09.ams2...

"jakdedert" <jakdedert@bellsouth.net> wrote in message
news:nZscl.5366$e13.4379@bignews5.bellsouth.net...
Roy wrote:
Hi, I wonder if anyone can help me with this. Two of the keys do not
produce any sound and one of the keys (approximately in the middle)
seems to be sticking up about 8 mm proud of the other keys. Although I
am from an electronics background (TVand Video servicing) I have never
had any dealings with one of these before. If anyone can point me in the
right direction for a workshop service manual or has any tips I would
really appreciate it! I have spent a couple of hours googling but all I
can find is that it was manufactured in 1988 or thereabouts. I found how
to do the factory reset but this didnt do anything, and also got the
user manual. Thanks in advance for any help.
Roy



The key that is sticking up is almost certainly broken. The keys that
don't sound are almost certainly because the key contacts are dirty or
worn.

You don't need a service manual. Just take off the lower casing and work
out what is required to remove the keyframe assembly - usually unscrewing
lots of screws and perhaps removing some circuit boards.
The key contact strips are under the keys. On some keyboards you need to
remove the keys to access them, on others you unscrew the circuit boards
from under the keys to access them leaving the keys in place.

You may be able to clean the dirtry strips and the PCB they act on, or it
may be better to buy a new set of strips with the new key you will need to
buy from Roland, neither are particularly expensive. Clean the PCB
contacts carefully with alcohol and cotton buds before fitting the new or
cleaned strips.



Gareth.
Thanks for the responses guys. I will probably be ok once I manage to get

into the beast (one of the reasons I was after a service manual). So far
have removed all of the arrowed screws on the underside together with a
couple that were not arrowed. (7 x 20mm round head, 2 x 12mm roundhead and 2
x 20mm countersunk).The only ones I have not removed are four marked "Do Not
Remove" (natch!). Judging by the spacing I think they are probably securing
the power supply/transformer. The top does still not want to part company
with the bottom and I do not want to start jemmying. It seems to seperate by
about 20mm all the way round except at the back.

Roy

 

[N_Cook]

Arfa Daily <arfa.daily@ntlworld.com> wrote in message
news:8Y%cl.254245$XB5.36409@newsfe29.ams2...

Booked in by shop as a 'Bingo calling unit'. It has a large 5 digit 7 seg
display made from discrete LEDs. Has two 5 digit BCD encoded switch units
to
set start and end number. Has jack input to which is connected a hand-held
push button unit. Chip date codes indicate that this thing is from 1981.
It
looks 'professionally' hand built, if you see what I mean. It has stickers
on with a company name, but that could be largely meaningless. Two
problems
reported. First that it had a problem with the LEDs, and secondly that it
had "lost its memory".

LED problem was straightforward enough. One segment of one digit was not
lighting due to one LED in the series chain of five which made up the
segment, being open circuit. A replacement LED restored that.

Now, the second problem. For playing bingo, the start number would be set
to
"1", and the end number to "90". All ok so far, and if this is done, it
does
indeed generate random numbers in the range 1 to 90, one per button push.

The next requirement is that the unit is going to need to know for any
game
in progress, which of the numbers between 1 and 90 that it has already
produced so that they are not duplicated, and this is where it all goes
tits
up.

After a while, numbers *do* start to duplicate. If you set the start and
end
numbers to say "1" and "10", it might take 15 button pushes to get all ten
numbers out, the other five being one or more times dups.

So I have a good look at what's in it. 2 x 4027 dual J-K, 3 x 4011 quad
NAND, 2 x 4081 quad AND,
1 x 4040 12 stage counter, 1 x 4020 14 stage counter, 1 x 555 timer
and
last but not least, 1 x MK50395 decoder / driver. Now I don't know if I'm
just being dumb-arsed here, or having a senior moment, but I'm buggered if
I
can see any chips in that line up that could form a memory and comparator
for potentially 99999 numbers. Or even for 90 numbers come to that ... If
this is what it was meant to do, even back in '81, I would have expected
to
see a couple of CMOS memory chips, and a Z80 or 8080 processor, maybe.

What am I missing here ? Could it be that they are mistaken in thinking
that
it can be used to properly call a game of bingo ? Is it in fact a raffle
ticket drawing machine, where you would set the serial numbers of the
first
and last tickets sold out of a batch of perhaps 1000 and then draw maybe
10
prize ticket numbers with the chances of it duplicating any when it's only
generating ten random numbers out of a pool of 1000, being at worst, slim
?

Haven't managed to get hold of the owners again yet to check if they feel
that it has ever worked as a bingo calling machine, but at the moment, my
feeling is that it is a 'new acquisition' to some little club, and that it
has been given to them after sitting long forgotten in an attic somewhere
for 20 years.

Any thoughts anyone ?

Arfa

I repaired something similar about 15 years ago, it had upper and lower
bounds set on thumbwheel sw on the top
I think you could set it for auction rostrum incrementing or a random number
generator but no repeat delete facility.


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

 

[jakdedert]

Roy wrote:

"Gareth Magennis" <gareth.magennis@ntlworld.com> wrote in message
news:FsEcl.72125$626.30409@newsfe09.ams2...
"jakdedert" <jakdedert@bellsouth.net> wrote in message
news:nZscl.5366$e13.4379@bignews5.bellsouth.net...
Roy wrote:
Hi, I wonder if anyone can help me with this. Two of the keys do not
produce any sound and one of the keys (approximately in the middle)
seems to be sticking up about 8 mm proud of the other keys. Although I
am from an electronics background (TVand Video servicing) I have never
had any dealings with one of these before. If anyone can point me in the
right direction for a workshop service manual or has any tips I would
really appreciate it! I have spent a couple of hours googling but all I
can find is that it was manufactured in 1988 or thereabouts. I found how
to do the factory reset but this didnt do anything, and also got the
user manual. Thanks in advance for any help.
Roy


The key that is sticking up is almost certainly broken. The keys that
don't sound are almost certainly because the key contacts are dirty or
worn.

You don't need a service manual. Just take off the lower casing and work
out what is required to remove the keyframe assembly - usually unscrewing
lots of screws and perhaps removing some circuit boards.
The key contact strips are under the keys. On some keyboards you need to
remove the keys to access them, on others you unscrew the circuit boards
from under the keys to access them leaving the keys in place.

You may be able to clean the dirtry strips and the PCB they act on, or it
may be better to buy a new set of strips with the new key you will need to
buy from Roland, neither are particularly expensive. Clean the PCB
contacts carefully with alcohol and cotton buds before fitting the new or
cleaned strips.



Gareth.
Thanks for the responses guys. I will probably be ok once I manage to get
into the beast (one of the reasons I was after a service manual). So far
have removed all of the arrowed screws on the underside together with a
couple that were not arrowed. (7 x 20mm round head, 2 x 12mm roundhead and 2
x 20mm countersunk).The only ones I have not removed are four marked "Do Not
Remove" (natch!). Judging by the spacing I think they are probably securing
the power supply/transformer. The top does still not want to part company
with the bottom and I do not want to start jemmying. It seems to seperate by
about 20mm all the way round except at the back.

Roy


Use something like a heavy guitar pick to work around the seam. Likely

either top needs to flex in, or vice versa, to release a tab.

(Almost as likely: you've already figured this out....)

jak

 

[Roy]

"jakdedert" <jakdedert@bellsouth.net> wrote in message
news:384dl.6050$G24.5163@bignews6.bellsouth.net...

Roy wrote:
Thanks for the responses guys. I will probably be ok once I manage to get
into the beast (one of the reasons I was after a service manual). So far
have removed all of the arrowed screws on the underside together with a
couple that were not arrowed. (7 x 20mm round head, 2 x 12mm roundhead
and 2 x 20mm countersunk).The only ones I have not removed are four
marked "Do Not Remove" (natch!). Judging by the spacing I think they are
probably securing the power supply/transformer. The top does still not
want to part company with the bottom and I do not want to start jemmying.
It seems to seperate by about 20mm all the way round except at the back.

Roy
Use something like a heavy guitar pick to work around the seam. Likely
either top needs to flex in, or vice versa, to release a tab.

(Almost as likely: you've already figured this out....)

jak

Yes thanks jak, tried all the usual stuff, but all encoragement/ideas
greatly appreciated. Just discovered a screw at the middle of the bottom -
in a deep hole. Guess what? the screw wont turn...bugger! Assuming its the
same cross head as the other screws found a driver bit with a perfect fit -
still no good. Also noted two holes at the rear of the top which look like
they may have been plugged with something, whatever it is, its not rubber
and not soft. Wonder if there are screws hiding under there?

Roy

 

[Gareth Magennis]

"Roy" <rladdressinvalid@blueyonder.co.uk> wrote in message
news:B05dl.59533$t64.45946@newsfe17.ams2...

"jakdedert" <jakdedert@bellsouth.net> wrote in message
news:384dl.6050$G24.5163@bignews6.bellsouth.net...
Roy wrote:
Thanks for the responses guys. I will probably be ok once I manage to
get into the beast (one of the reasons I was after a service manual). So
far have removed all of the arrowed screws on the underside together
with a couple that were not arrowed. (7 x 20mm round head, 2 x 12mm
roundhead and 2 x 20mm countersunk).The only ones I have not removed are
four marked "Do Not Remove" (natch!). Judging by the spacing I think
they are probably securing the power supply/transformer. The top does
still not want to part company with the bottom and I do not want to
start jemmying. It seems to seperate by about 20mm all the way round
except at the back.

Roy
Use something like a heavy guitar pick to work around the seam. Likely
either top needs to flex in, or vice versa, to release a tab.

(Almost as likely: you've already figured this out....)

jak

Yes thanks jak, tried all the usual stuff, but all encoragement/ideas
greatly appreciated. Just discovered a screw at the middle of the bottom -
in a deep hole. Guess what? the screw wont turn...bugger! Assuming its the
same cross head as the other screws found a driver bit with a perfect
fit - still no good. Also noted two holes at the rear of the top which
look like they may have been plugged with something, whatever it is, its
not rubber and not soft. Wonder if there are screws hiding under there?

Roy

I've never found any screws in Roland keyboards covered by any sort of cap,
and I've opened hundreds. This might be for a music stand?

You will have to get the screw on the bottom out first anyhow. With the
keyboard upside down on the bench and protected, put in your perfectest
fitting screwdriver and hold it tight and bang it hard with a hammer a few
times, that should loosen whatever is holding it tight. This may sound
drastic, but a confident bang or two is gonna shift it, pussyfooting around
is going to round the head and you will be in real trouble.



Gareth.


Gareth.

 

[Andrew Erickson]

In article <384dl.6050$G24.5163@bignews6.bellsouth.net>,
jakdedert <jakdedert@bellsouth.net> wrote:

Roy wrote:
Thanks for the responses guys. I will probably be ok once I manage to get
into the beast (one of the reasons I was after a service manual). So far
have removed all of the arrowed screws on the underside together with a
couple that were not arrowed. (7 x 20mm round head, 2 x 12mm roundhead and
2
x 20mm countersunk).The only ones I have not removed are four marked "Do
Not
Remove" (natch!). Judging by the spacing I think they are probably securing
the power supply/transformer. The top does still not want to part company
with the bottom and I do not want to start jemmying. It seems to seperate
by
about 20mm all the way round except at the back.

Roy


Use something like a heavy guitar pick to work around the seam. Likely
either top needs to flex in, or vice versa, to release a tab.

(Almost as likely: you've already figured this out....)

This probably goes without saying, but it might be necessary to remove
any grub nuts, binding screws, etc. from the various connectors on the
back panel and/or knobs etc. from the switchgear on top.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he cannot
lose." -- Jim Elliot

 

[Roy]

"Andrew Erickson" <gmavt@drewe.reverse2mail.net> wrote in message
news:gmavt-408D89.18451819012009@sn-ip.vsrv-sjc.supernews.net...

In article <384dl.6050$G24.5163@bignews6.bellsouth.net>,
jakdedert <jakdedert@bellsouth.net> wrote:

Roy wrote:
Thanks for the responses guys. I will probably be ok once I manage to
get
into the beast (one of the reasons I was after a service manual). So
far
have removed all of the arrowed screws on the underside together with a
couple that were not arrowed. (7 x 20mm round head, 2 x 12mm roundhead
and
2
x 20mm countersunk).The only ones I have not removed are four marked
"Do
Not
Remove" (natch!). Judging by the spacing I think they are probably
securing
the power supply/transformer. The top does still not want to part
company
with the bottom and I do not want to start jemmying. It seems to
seperate
by
about 20mm all the way round except at the back.

Roy


Use something like a heavy guitar pick to work around the seam. Likely
either top needs to flex in, or vice versa, to release a tab.

(Almost as likely: you've already figured this out....)

This probably goes without saying, but it might be necessary to remove
any grub nuts, binding screws, etc. from the various connectors on the
back panel and/or knobs etc. from the switchgear on top.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he cannot
lose." -- Jim Elliot

Hi again guys, finally managed to get into the beast. The screw in the
middle was an absolute pig to remove. Turning the unit rightside up, I was
able to flip the lid over to the rear. This revealed a pleasant surprise,
not a surface mount component in sight! Oh Joy!. The keyboard itself was a
complete unit retained by 4 screws into the cabinet base, electrically
connected via a pcb connector on a short ribbon cable to one of the main
boards so I was able to remove it in its entirety. The contacts, if you can
call them that, look like short lengths of springy heavy gauge silvered
guitar string, soldered at pcb ends and passing between two wire contacts to
the end of the key. The wires to the ends of the dead keys had popped out of
the ends of the keys. Fixed in a jiffy! The other fault with the key
standing proud of the others seems to be the loss of a plastic or rubber
stop which fits on a metal tab beneath the key. It doesnt seem to be
floating around in the cabinet anywhere so I will probably improvise
something ie bit of coax sleeving or somesuch. I an going to have to remove
the key to get at it though - and its not immediately apparent what holds
the keys on.
Thanks for all the help and advice so far.

Roy

 

[N_Cook]

Roy <rladdressinvalid@blueyonder.co.uk> wrote in message
news:Fcodl.11052$Ig4.8980@newsfe19.ams2...

"Andrew Erickson" <gmavt@drewe.reverse2mail.net> wrote in message
news:gmavt-408D89.18451819012009@sn-ip.vsrv-sjc.supernews.net...
In article <384dl.6050$G24.5163@bignews6.bellsouth.net>,
jakdedert <jakdedert@bellsouth.net> wrote:

Roy wrote:
Thanks for the responses guys. I will probably be ok once I manage to
get
into the beast (one of the reasons I was after a service manual). So
far
have removed all of the arrowed screws on the underside together with
a
couple that were not arrowed. (7 x 20mm round head, 2 x 12mm
roundhead
and
2
x 20mm countersunk).The only ones I have not removed are four marked
"Do
Not
Remove" (natch!). Judging by the spacing I think they are probably
securing
the power supply/transformer. The top does still not want to part
company
with the bottom and I do not want to start jemmying. It seems to
seperate
by
about 20mm all the way round except at the back.

Roy


Use something like a heavy guitar pick to work around the seam. Likely
either top needs to flex in, or vice versa, to release a tab.

(Almost as likely: you've already figured this out....)

This probably goes without saying, but it might be necessary to remove
any grub nuts, binding screws, etc. from the various connectors on the
back panel and/or knobs etc. from the switchgear on top.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he
cannot
lose." -- Jim Elliot

Hi again guys, finally managed to get into the beast. The screw in the
middle was an absolute pig to remove. Turning the unit rightside up, I was
able to flip the lid over to the rear. This revealed a pleasant surprise,
not a surface mount component in sight! Oh Joy!. The keyboard itself was a
complete unit retained by 4 screws into the cabinet base, electrically
connected via a pcb connector on a short ribbon cable to one of the main
boards so I was able to remove it in its entirety. The contacts, if you
can
call them that, look like short lengths of springy heavy gauge silvered
guitar string, soldered at pcb ends and passing between two wire contacts
to
the end of the key. The wires to the ends of the dead keys had popped out
of
the ends of the keys. Fixed in a jiffy! The other fault with the key
standing proud of the others seems to be the loss of a plastic or rubber
stop which fits on a metal tab beneath the key. It doesnt seem to be
floating around in the cabinet anywhere so I will probably improvise
something ie bit of coax sleeving or somesuch. I an going to have to
remove
the key to get at it though - and its not immediately apparent what holds
the keys on.
Thanks for all the help and advice so far.

Roy

I usually use a bit of silicone sleeving for those rubbery things. If it is
the wrong sort of material it grabs at the key, it should be only slightly
resistive to motion , ie a damper of sorts AFAIK. You may want to swap
it/them with those under keys at the, less used, high or low end of the
keyboard as they are quite critical to the action of the keys.


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

 

[N Cook]

Dr. Barry L. Ornitz <BLOrnitz84@charter.net> wrote in message
news:WHshl.23847$wB5.16069@newsfe08.iad...

"N Cook" <diverse8@gazeta.pl> wrote in message
news:gm1g0v$223$1@inews.gazeta.pl...
I'm aware of the term "doll's disease" relating to the breakdown , to
vinegar, of the soft plastics used on antique dolls. But in my area of
electronics eg "rubber" grommets will "melt" hard plastic storage
drawers, a
mains cable wrapped around a hard plastic topped record deck, over a few
years such storage, will create "melted" ruts in the hard plastic.
Anyone
aware of a precise term for this plasticiser leeching process to
research
it
further, eg temp or humidity effect on the process, surface treatment to
avoid it etc.

What you refer to as "Doll's Disease" is an entirely different phenomena
that the leaching of plasticizer. Doll's Disease is actually a result of
cellulose acetate reacting with the moisture in air to produce degraded
cellulose and acetic acid (the vinegar smell). Originally it was seen in
celluloid movie film, collar stays, etc. Celluloid is cellulose nitrate
with a little plasticizer but the plasticizer has nothing to do with the
reaction. With cellulose nitrate, nitric acid is produced. Once the
reaction occurs, the acid catalyzes further degradation of the cellulosic
plastic. Museum storage in sealed glass cases actually promotes the
process. About all that can be done is to neutralize the acid by washing
in a dilute sodium carbonate or bicarbonate solution, drying carefully,
and
placing the item back in storage with flowing dry air.

The problem you are seeing is the leaching out of plasticizer from
polyvinyl chloride or polyvinyl acetate items. If you are old enough to
remember vinyl automobile seats, you probably also remember the greasy
film
formed on the inside of windows when the car was parked in the hot sun.
Over time, the vinyl would get brittle, shrink, and crack. The film was
plasticizer that evaporated from the vinyl. As it left the PVC, the
shrinkage. brittleness and cracking occurred.
One of the more common plasticizers was bis(2-ethylhexyl) phthalate, more
commonly known as dioctyl phthalate or DOP. It is still in wide use
today,
but many newer plasticizers are also available today such as
trioctyltrimellitate (TOTM), dioctyladipate (DOA), diisononyl phthalate
(DINP), di(2-ethyl hexyl) adipate (DEHA), acetyl triethyl citrate (ATEC),
and even tricresyl phosphate (TCP).

Plasticizers are incorporated with PVC in the manufacturing process.
Contrary to what Armor-AllŽ and similar products might claim, you cannot
put plasticizer back into the vinyl with a surface applied product. Many
products may contain significant amounts of plasticizers. Very soft and
rubbery PVC compounds may contain as much as 40 to 50% plasticizer.
Preventing the leaching out or evaporation of plasticizers from vinyl
products is prevented more by the choice of plasticizer than anything
else,
although low temperatures slow the rate significantly. The Wiki page on
plasticizers lists a large number of plasticizers and tells where they are
most used.
http://en.wikipedia.org/wiki/Plasticizer#Plasticizers_for_plastics

About the only way to prevent plasticizer damage to other plastics is to
keep vinyl products away from them. Most coaxial cables for radio
frequency use have a center conductor insulated with polyethylene, a wire
braid shield, and a plasticized PVC jacket. When the plasticizer leaches
from the jacket into the polyethylene, its electrical losses increase
greatly. One modern innovation uses either aluminum foil or metalized
polyester to wrap around the braid preventing the ingress of the
plasticizer. But it also provides better shielding allowing the braid
coverage to be lessened from 90 to 95% coverage to less than 75% coverage
leading to a much lower weight.

Powodzenia.

--
Dr. Barry L. Ornitz, Amateur Radio WA4VZQ
BLOrnitz84@charter.net
[transpose digits to reply]

Many thanks for the full reply.
I was totally unaware of the last point, so have added s.e.r as probably a
lot there are unaware also.
Recently reminded me of this effect because a "rubbery" presumably soft PVC
suspension inside a phono cartridge was leaching plasticizer and softening
the surrounding hard plastic etc. I don't know if it is also related but
often if one "rubber" drive band in a VCR or audio tape deck perishes, then
all the others are likely to fail in a sort of contagion -plasticizer gas
wafting around inside ?

 

[Dr. Barry L. Ornitz]

"N Cook" <diverse8@gazeta.pl> wrote in message
news:gm6bim$cs8$1@inews.gazeta.pl...

Many thanks for the full reply.
I was totally unaware of the last point, so have added s.e.r as probably
a
lot there are unaware also.
Recently reminded me of this effect because a "rubbery" presumably soft
PVC
suspension inside a phono cartridge was leaching plasticizer and
softening
the surrounding hard plastic etc. I don't know if it is also related but
often if one "rubber" drive band in a VCR or audio tape deck perishes,
then
all the others are likely to fail in a sort of contagion -plasticizer gas
wafting around inside ?

You are quite welcome. Eastman Chemical Company, a former employer, made
both cellulosic plastics and a large number of plasticizers. I even worked
on a project to replace plasticized PVC in medical intravenous solution
bags with an elastomeric polyester because of the fears of plasticizers
leaching into the solutions (which they do!). While being more expensive
than PVC, our material was much stronger allowing thinner bags which offset
this higher raw material cost. But the perimeter radio frequency sealing
process required new equipment and the bag manufacturers were unwilling to
modify their manufacturing lines.

As far as VCR decks, I cannot think of any mechanism whereby the failure of
one drive belt via plasticizer migration would cause the others to fail
unless the plasticizer leaching from one belt actually dripped on another
belt. Remember that all belts were likely made at approximately the same
time, and had been in the VCR exposed to similar high temperatures for the
same time too.

--
73, Dr. Barry L. Ornitz WA4VZQ
BLOrnitz84@charter.net
[transpose digits to reply]

 

[Dr. Barry L. Ornitz]

"Ron Jones" <ron@ronjones.org.uk> wrote in message
news:gm7hik$s9m$1@energise.enta.net...

Dr. Barry L. Ornitz wrote:
"N Cook" <diverse8@gazeta.pl> wrote in message
news:gm1g0v$223$1@inews.gazeta.pl...
snip
About the only way to prevent plasticizer damage to other plastics is
to keep vinyl products away from them. Most coaxial cables for radio
frequency use have a center conductor insulated with polyethylene, a
wire braid shield, and a plasticized PVC jacket. When the
plasticizer leaches from the jacket into the polyethylene, its
electrical losses increase greatly. One modern innovation uses
either aluminum foil or metalized polyester to wrap around the braid
preventing the ingress of the plasticizer. But it also provides
better shielding allowing the braid coverage to be lessened from 90
to 95% coverage to less than 75% coverage leading to a much lower
weight.

The problem occurs in all sorts of areas - leisure boats on UK canals are
generally steel, and so have thick polystyrene insulation against the
hull, then covered with wood panels. All cables running in this space
have to be run in a conduit, as it was found that the polystyrene would
suck all the plasticizer out of the cable making it brittle and liable to
break without warning.

Thanks for the follow-up, Ron.

I know that polyvinyl chloride has been banned from many applications in
Europe. I believe that this is because most garbage is incinerated in
Europe. I guess that PVC wire insulation is still permitted.

Here in the USA, electrical conduit is often made of PVC. I do not know if
quenching agents are used here to reduce the limited flammability even
more. PVC is also used extensively for plumbing. In both cases, little or
no plasticizer is used. But PVC is also used in most wire insulations, and
plasticizer is used here. Rigid polyurethane foams are usually used for
home construction and I do not believe that plasticizer leaching will cause
major problems to these foams. But polystyrene foams are used occasionally
and your warning is an excellent one.

While I am familiar with many IEC standards, my knowledge of electrical
wiring for Europe is limited. Here in the USA, we have what is known as
THHN (Thermoplastic High Heat-resistant Nylon-coated) wire. This utilizes
a thin, colored PVC insulation clad in a Nylon jacket. It is frequently
used in conduits because of the ease with which it can be pulled without
abrading the insulation. I suspect that the Nylon will provide a good
barrier to plasticizer migration too.
[UL (Underwriters Laboratories) lists THHN as oil resistant to 60° C.]

--
73, Dr. Barry L. Ornitz WA4VZQ
BLOrnitz84@charter.net
[transpose digits to reply]

 

[Ron Jones]

Dr. Barry L. Ornitz wrote:

"Ron Jones" <ron@ronjones.org.uk> wrote in message
news:gm7hik$s9m$1@energise.enta.net...
Dr. Barry L. Ornitz wrote:
"N Cook" <diverse8@gazeta.pl> wrote in message
news:gm1g0v$223$1@inews.gazeta.pl...
snip


Thanks for the follow-up, Ron.

I know that polyvinyl chloride has been banned from many applications
in Europe. I believe that this is because most garbage is
incinerated in Europe. I guess that PVC wire insulation is still
permitted.
Here in the USA, electrical conduit is often made of PVC. I do not
know if quenching agents are used here to reduce the limited
flammability even more. PVC is also used extensively for plumbing. In
both cases, little or no plasticizer is used. But PVC is also
used in most wire insulations, and plasticizer is used here. Rigid
polyurethane foams are usually used for home construction and I do
not believe that plasticizer leaching will cause major problems to
these foams. But polystyrene foams are used occasionally and your
warning is an excellent one.
While I am familiar with many IEC standards, my knowledge of
electrical wiring for Europe is limited. Here in the USA, we have
what is known as THHN (Thermoplastic High Heat-resistant
Nylon-coated) wire. This utilizes a thin, colored PVC insulation
clad in a Nylon jacket. It is frequently used in conduits because of
the ease with which it can be pulled without abrading the insulation.
I suspect that the Nylon will provide a good barrier to plasticizer
migration too. [UL (Underwriters Laboratories) lists THHN as oil
resistant to 60° C.]

As I said - this is for boats (that of course vibrate - and cables getting
brittle - even 12V ones are not a good idea). Not sure what "standard"
mains wiring is made of - web sites tend to say things like "BASEC approved
6242Y Twin and Earth cable. Grey sheathed with harmonised core colours. BS
6004". Which is not a lot of help. They are probably reluctant to give too
much info, as the rules (here) are now that mains wiring be only carried out
by a electrican.... Nanny state....

--
Ron Jones
Process Safety & Development Specialist
Don't repeat history, unreported chemical lab/plant near misses at
http://www.crhf.org.uk Only two things are certain: The universe and
human stupidity; and I'm not certain about the universe. ~ Albert
Einstein

 

Yesterday I reported the following information quoted below.

However, as details roll in, it's MUCH WORSE than was originally
thought.

TODAY (February 17, 2009), IS THE END OF THE WORLD !!!

This is no joke........

Our last report stated that all plugged in DTV converters would
explode and burst into flames on this date. However, we have now
determined that no converter is needed to cause complete anhilation of
our planet.

Unless we can stop these tv stations from switching to digital
television today, EVERYONE on earth will DIE.
As these tv stations go to full power, the powerful radiation will
turn the entire planet into a gigantic microwave oven.

Every living creature on Earth will begin to heat. In minutes, bodies
will die, dehydrate, and burst into flames. This includes all human
beings, animals, insects, plants, trees, everything. Flammable
structures will erupt in flames. Metals will shoot huge bolts of
lightning just like putting metal in a microwave oven. NO ONE AND
NOTHING WILL SURVIVE. The entire planet will become scorched earth.

We MUST STOP these tv stations from switching their digital
transmitters to full power, if we want to continue life on Earth. We
only have hours left. If you want to continue living, CALL YOUR LOCAL
TV STATIONS IMMEDIATELY, and plead with them to NOT POWER UP THEIR
DIGITAL TRANSMITTERS.

EVERYONE must contact them NOW, or we will be dead and turned to ashes
before the end of February 17th. WE HAVE NO OTHER OPTIONS.

If they refuse, we have no other choice but to shut down their
electric suppliers. Begin by contacting the TV stations, if they
refuse, contact your local electric companies and explain to them that
they MUST cut power to these tv stations. If they also refuse, we
only have one last chance of survival. "We the people" MUST shut down
the entire electrical grid by stopping the generators. The government
is NOT going to help us. They are the ones who want to destroy our
lives. We must do this ourselves. "We the people" MUST stop the
government from allowing television stations to destroy all life on
Earth.

WE ONLY HAVE A FEW HOURS LEFT...... ACT NOW !!!!

This will be my final report, unless we survive.
If we don't survive, I wish you all well in the afterlife !

*** GOD HELP US ***


The Newscaster


---------------------------------------------------------



On Mon, 16 Feb 2009 02:31:49 -0600,
newscaster@gazette.news.invalid.com wrote:

--- OFFICIAL WARNING ---

Your life is in Danger

Tuesday February 17, 2009 is less only about 24 hours away. This is
the original date when all analog tvs will go blank. The government
recently extended this date until June, but most tv stations are
changing on the original Feb. 17th date.

So you got your DTV converter box and feel safe knowing that you will
still be able to watch the Tv Soaps, Jerry Springer, and lots of
commercials. What you dont know is that these DTV converters are
under the control of terrorists. On February 17, these terrorists are
going to take control of these boxes and all of them will ignite and
violently explode, destroying everything within a one mile radius.

Nearly half the homes in the United States now own one of these bombs.
The entire USA will burst into flames around noon on Feb.17th.
Millions will die. In fact it's estimated that from 75 to 98% of the
US population will be killed.

If you own one of these DTV converters, unplug it immediately. Better
yet, dispose of it as far from your home as soon as possible, and tell
your neighbors to do the same. Just because you got rid of your box,
does not insure your safety. If you have a neighbor within one mile
of your home, their converter can and will kill you.

In the next 24 hours, everyone in the United States of America MUST
dispose of their DTV converters. Don't let these terrorists destroy
our country and likely your life.

DO NOT take this lightly. The future of life on earth depends on
ridding the USA of these most dangerous "converters" within the next
24 hours. They are appropriately named "converters", because they
will convert our country to rubble and destroy most if not all human
life.

(If you know of any homes in your neighborhood, that may possibly
contain a plugged in DTV converter, and if can not locate the
homeowner, or they refuse to unplug or destroy it, disconnect their
electrical power. You can do this by cutting the wires that service
their home. DO NOT take NO for an answer, either they disable their
converter, or they lose their electricity).

Please destroy your DTV converters immediately......

The Newscaster