atari sc1435 monitor packed up

[pop]

hi,was playing a game this evening when my monitor suddenly went off when i switch it on now it makes a high pitch sound which gradually decreases when i switch it off. it decreases in discernible fast steps
any ideas
thanks

[teh3pwner]

Is there any picture on it at all????? Maybe its the screen, maybe a loose wire, who know, if you know electronics have a look at it your self, if you don't take it to a guy that knows how to repear TVs, monitors, VCRs an stuff.

[techie_alison]

Hit it.

Sounds like the one I sold a while back. Didn't work on arrival. Yet after sitting for a few days suddenly started worked.

[PaulB]

Same things starting to happen with my colour Atari monitor. I just give it a bit of a tap to the side and it's ok again. I know it'll have to be looked at properly sooner or later but it works for now.

[SiR.BenSon]

Hit it.

Sounds like the one I sold a while back. Didn't work on arrival. Yet after sitting for a few days suddenly started worked.

It's True, It was me
my sm124 just didnt want to work, it just made a noise at me, i left it in the shed (something i dont reccomend doing really) for about two days, took it back in to see if it had changed at all, and hey presto it lived fully =), my advice would be to just leave it a day or two then come back to it,
Hope that helps

[simbo]

the line output transistor has gone short & or the trippler in its lopt is fried

take it to a tv shop for repair

[simbo]

Hit it.

Sounds like the one I sold a while back. Didn't work on arrival. Yet after sitting for a few days suddenly started worked.

the reason this happens isnt voodoo
its actualy quite easy to explain

when the capacitors espcialy the big mains resoviour one
get past there usable ranges

it takes far more cold current {instant current}
to get them to 'boot' and when the cap is cold even more....

replacing the mains resoviour electrolytic capacitor
will perminatly cure it

the rule here is if it screams the psu is aok and its output has a short
usualy the line output stage
this concists of a transistor a few chokes a couple of caps
and a lopt ,line output transformer,sometimes called a flyback transformer

in the lopt is a trippler stage
that provides usualy 25-35KV
to the tube anode cap {thick red wire goes to the top of the tubes envilope }
anyway this stage is made of diodes to multiply the voltage the tranformer makes {this lopt is driven by the line driver {line output transistor}


usualy the trippler goes short and takes out the transistor

it goes short from collector to emiter
so replacing it wont help till the lopt is also replaced

and to find this out i use a variac
its a device that allows you to power tv's monitors very slowly up
to test if the lopt is gone etc without further damage


ALWAYS ALWAYS ALWAYS

allow all equipment to safely
arrive at room tempreture before using it at all
some hardware is more sensative to this like hard disks

[pop]

hi,thanks for the replies.simbo.could i just replace the possible faulty parts you have mentioned,if so where are they sited and where could i get replacements.I have some electronic knowledge and understood what you were describing.is it feasible?
thanks

[simbo]

youll need to look over the schematic http://atari4ever.free.fr/hardware/doc/sc1224.zip
and use a meter to test the various bits for shorts

youll see two places i circled to check

the 2sd1453 is the line output transistor
there is a tag marked wp 11 at the collector
directly below is the emiter
and behind is the base

check for a short between the collector and emiter
using the resistance range of a digital multimeter {2 k range}
it should show open totaly


remember if a psu squeels there is a short something

this is the most likely

now if you had said the picture shrank down to half its height then squeeled
this is the vertical frame driver psu rail ... from the lopt

you see this lopt supplies power to other circuits
that must power after the tube to get a steady picture

very often this transistor goes short becouse of other problems
as i say the other part i circled on the right is the l.op.t
you can see the voltage trippler diodes on the far right

on the side of the transformer is a ticket
{dont wipe it with cloths or sprays etc as they just fragment sometimes}
anyway
this has a number on it

please post the numbers on it
youll find many sets use the same type
but not every monitor uses the same one {chassis}
so you need this to match it up
an original transformer {usualy has the same makers flaws as the set had}
can cost 100 euros or more

a pattern part {fixed makers flaws and uprated}
costs maybe 30 euros
and its lasts much longer



my advice is
if you have a short transistor
replace it and power the monitor
if you get no picture and a high pitched whistle this time turn it off quick

then the lopt has a fried trippler stage.. and needs replaced also

this 2sd line driver thing has an integral damper diode {you can use a bu508DF in europe to replace this crap jap thing }

did you have a normal picture before hand?

not stretched in any way horiz or vert??

you can find C716 C715 or C7something
also circled has issues
desolder them and examine them
for scortched pins under them if they are the rectangle type
some disk types go brown and baked then just go short ...

some disk types {high voltage round usualy blue or yellow}
crack down the middle after a whack of eht from a mains supply spike etc,,,, and then go short accross there plates causing the psu to squeel {or trip it goes ping ping ping and fails to power}

remember to check for a short AFTER removing the transistor also !!!
as this show this fault up easier {set the meter to 200K or bigger to lok for a short you should just get a pulse of low resistance then it traverses to a very much higher one {MEG ohms}

if you replace the transistor and it all works

then dont take this lightly
there will still be a problem somewhere else or the once stable transistor
wouldnt have paked in

best again look at the caps above
and also any other electrolytic caps that are connected to the feeds from the lopt to the sub circuits it powers on start init ....run time
c721 c741 c724
picture noise c703
poor colour dull look c308 c318 c328
{1uf 50v non polerised electro {dry out very fast}}

psu c961 c963 c965
{poor startup sometimes c950 {c952 {this one mostly}} }

in any ac system you have voltage and current nodes and antinodes

if capacitors drop or increase in value or a coils turns go intershorted
youll find these nodes that are usualy balanced
move to different parts of a circuit
causing vast voltage or spot current to appear

and this causes devices not really connected fully to the fault to fail
so sometimes a few bucks spend on caps cures it
or it will come back till you have found it

[simbo]

above is a breakdown guide for another monitor

but this is the general idea

http://www.eserviceinfo.com/download.php?fileid=5865

a similar circuit take here more to replace...

i ALWAYS replace all parts associated with XRAY protection

or youll get a red face
and when you peal off your wallpaper ,,, lol:)

[pop]

thank you very much simbo,will post as soon as i get chance to have a look
The only thing i dont understand is "in any ac system you have voltage and current nodes and antinodes"
whats this?
there was no problem with screen,i had a normal display

the only other thing to mention is that this monitor was stored for some years and packed up within 2 days of being used. what do you think?
much appreciated

[simbo]

could be moisture
or very often the electrolytic caps dried up or a mix of events replace a few anyway
mostly I've found its more the smaller values that cause strange problems
there maybe is a dry one in the line driver stage and this caused some bad timing
the two on the far left in the circuit above that couple the driver isolation coil
this led to the transistor failing maybe

again because a circuit is tuned if the waveform changes this can also cause the nodes/anti nodes to move around and dry caps can cause them to fail in there timing's

or more likely is this

when i repair an old valve radio
before using a new value i have to slowly wind up the anode voltage a bit at a time for this first 24hrs to burn the valve in and it will start to draw less current till it gets back to its spec and it can then be safely fitted

old valve amps & radios you leave lying around tend to do the same
its called valve hardening
BUT in the radio etc. as a whole is a dropper resistor and this acts like a current buffer

anyway

the monitor has a valve the tube

and this will after left alone and packed away
draw on re-use more cold current for many days of intermittent use

the problem is that if you turn on and off all the time during this re windup stage you'll draw more the next
a bit like having to melt a wall or the wall gets thicker next time

so adding stress maybe to parts and causing the line driver or a well used trippler to fail {30kv is heaps diodes just cut it and no more here stress is easy this part is the light bulb of the monitor}

my guess is that there is a couple of problem parts and a few dry caps
and that's it
as i said above probably the lopt trippler has failed and or the transistor lopt driver

so the advice with gear like CRT monitors & anything is simple
when taken out of storage and used
leave it running for 48hr to grind it back in

after this first reuse it will stabilise i think better.??
maybe some views from others about this would be good gather some data

i think by far the worst thing you can do is put them in a very dry place!!!{arid} better to place them in the cellar in a good wraps than the loft

computers& peripherals TTL ECL level chips = loft
monitors & printers = dry cellar



i made it large for others to see


http://en.wikipedia.org/wiki/Node_(circuits)

basically ac is a sine wave tv/monitors have waveform generators

and a node is a point in the cycle
as you go in time you draw more or less current
and this in turn affecter other parts of the circuit

when a thing is designed
this is carefully setup so as to not stress parts etc

but when a part like a cap or a coil in the line stages looses value turns etc this node arrays becomes mistuned

and parts can then have stressful peeks inside them

if you look at the simple model in the wiki above you'll get the idea

today this is done in simulation using spice also

....

[simbo]

a general tip with small value caps is this
you can use a small microphone to determine if there fluid level is low

any electrolytic cap <= 220uf will resonate below 1khz
if they are gubbed
and devoid of fluid


so you need a cap clamp
one side is a piezo one side a mic


so someone can make a pic 16 a-d something that does it

i cant be bothered i just replace them all with 105deg types

...

however ill pass this on to the probe guy
i posted the design links etc in a sticky topic

a usefull device perhaps this simple stage can be added easily to it

would be really handy for sure....

[pop]

hi simbo, had a look today.the transistor marked 7512 on the schematic [which you have circled] appears to be fine.though in circuit it read short,once i took it out it was fine.i also put diode test across the 2 junctions and they both read 0.5v and open with the probes switched.that seems fine to me.the number on the transistor is d1577

the sticker on the side of lopt has numbers-e39144
at2079
37593 TY

and a stamped no 92091

thanks

[simbo]

hi simbo, had a look today.the transistor marked 7512 on the schematic [which you have circled] appears to be fine.though in circuit it read short,once i took it out it was fine.i also put diode test across the 2 junctions and they both read 0.5v and open with the probes switched.that seems fine to me.the number on the transistor is d1577

the sticker on the side of lopt has numbers-e39144
at2079
37593 TY

and a stamped no 92091

thanks

the original lopt is avalible from

http://www.wagner.net.au
australia

http://www.atari-workshop.co.uk/products/ics_spares.htm
uk


konic is germany do one also as a pattern part
ill source the part number later today and a place to get them
as its handy info
....



well re-reading what youve written i think it will most probably be one of the decoupling capacitors on the collector of the transistor to ground
i put a red splodge beside them

...

one is an electrlytic type and most often is aok
its usualy the ceramic one next to the transistor that cooks
goes brown or and cracks

its worth adding that there will be a short from the base to the emiter
even when the transistor is removed

but if it reads ok then cool thing !!!

[pop]

its worth adding that there will be a short from the base to the emiter
even when the transistor is removed

hi,not quite understanding that is it because it contains a diode?

right,had a look at the 2 capacitors and they are both ok. also tested all circled components in circuit and out where needed and no problems.
the only thing i can say is with the transistor removed, measuring across emitter /collector [just the solder pads on pcb with no transistor there] it measures 1.3ohms

i"m stumped

thanks

[simbo]

i would suspect the transformer is short circuit in its internal coils

this is the most likely cause
you will find a plug it comes from the yoke
{at the back of the tube on its neck is some coils {deflection coils}
it usualy has a red a green a blue and most often a yellow wire to it
usualy 4 wires
now if you unplug it does the short disappear???

if it does there is a problem with the psu section HT output rail
if the short collector to emiter stays with this 4 way plug unplugged
then its the transformer that is gubbed

ill bet you $10 its the lopt transformer thats gone

youll need to look carefully at the other components around that transistor collector supply

a component is dead short there
as the collector to emiter should read total open

the transistor with the wrighting towards you the pins
pointing down will be

Base Collector Emiter

the collector to emiter should read open circuit almost totaly

what i usualy do is as i say unplug that 4 way plug
{defelection coils supply}
as the psu passes thru this on the way to the transformer
and transistor

you can also isolate the lopt pin on the underside that supplies the collector and this will let you know that this transistor section is ok or not

and trace it back this way

another method is to use the negative black probe
of the meter to the metal chassis
use a low resistance range and look along the collectors rail
looking for the lowest resistance {can be differances of less than 1 ohm}

this will also show the exact part with the least resistance to ground

and this will most often be the problem part


i hope this help
and ps NEVER give in ever
and simply dont take no for an answer... for sure.its something simple


....

[pop]

i hope this help
and ps NEVER give in ever
and simply dont take no for an answer... for sure.its something simple

hi, really appreciate this im actually quite enjoying it, i was actually getting a little concerned that you might be getting fed up of my posts

will continue with above steps

thank you

[simbo]

not atall

never NEVER

it must be fixed or it ends up for our seeds to get poisoned by

this is my policy .... throw nothing away
if i find something no use
i take it to bits andmake art or other usefull bits
forinstance i found an old microwave oven

and added its front panel to the UV pcb exposure unit i bought on ebay
now i can program the exact time i want it to run up to 2 hrs
and also has a burst timer output to allow for other tyes of purpose
{usualy pulses the microwave over time}

i reused the transformer for a linear 20meter 2kw amp project{planned}
using 4cx2500cx valves as i have a ral

and also i used the rectifier diodes and fuses and magnitron to fix mine
my magnitron had a falulty heater connection althought it worked i replaced it anyway as this one is a higher rating

the stainless panels ill use for shielding panels
and spare metal to rework

and the rest of the plastic and wheels are art ... and ill give them to a girlfriend to rework to her exhibits


.......

[pop]

hi,ok, this is what we have. Removed yoke plug and short still present. I then isolated collecter supply at transformer pin 5 on schematic and guess what.........short disappears and reads open instead! Can i conclude that lopt only needs replacing or are there other things to consider before i get too excited?did you say there was a german site to get pattern part from?

I have a few other questions if you dont mind

I have an sc1224 colour monitor and atari mono monitor also which have been stored in the loft.are there any maintenance tasks that i should undertake.again my st and ste was stored there too and the same question.i am in the process of getting it all active again

i know litle about programming eproms other than i have willem eprom programmer the one from http://www.sivava.com, i have successfully flashed motherboard bios with it and was considering tos upgrade.what method is used to program/erase st eproms,where can i get eproms and tos files or whatever they are called.as i said i dont know what type of programming /erasing is used for st eproms and wondered if my willem could be used

have you had any success with removing yellowing which seems to be prevalent on st cases?

have you had any success removing smd devices i tried to remove a bios chip that was soldered to the board and buggered it up

many thanks

[simbo]

what i usualy do for chips soldered to boards
is cut them off with sidecutters
then take the pins out and sook out the solder in the holes
with a desolder pump
this avoids damage but costs the chip
fine if it was dead you can use desolder braid to remove it if you need it
done carefully this stuff is tricky to use but does work well

however for the bios you need any eprom 1mb ones are good 32 pin
to erase them you need a UV A source

a cheep way is to use a halogen lamp 100watt or less and sit the chip infront of it for an hour or less {20 -30 mins would work } then blank check it {not to close to it or the chip will heat}

or you can get an eprom eraser {try ebay for one}
once its blank checked fine you flash the image file on two chips
they are 8 bit so need two to allow the full bus width

as for the monitor
look for a new LOPT it will be the only damaged part i feel
as i say they go quite easily
after a few years there insulation breaks down
and it goes short or the trippler goes short or leeky
the occasional crackle from it is a sign of a problem emerging

sometime there is a coil that develops shorted turns
5562 {under the coil on the right of the lopt in the diagram } its uses for horizontal width and linearity adjust
under the one marked 'part of AT1201'

you may need to match a wire guage unwind and count the turns then rewind it with new enamled wire {you can get a 100g reel quite cheep}
always wind them in the same direction and place on the bobin etc
avoid damaging the ferrite bobin

most often nodes move around becouse of this coil
the symptom would have been a slimmer or fatter picture and a little brighter

anyway its worth rewinding it as a precausion

when you come to fit the new lopt there is two adjustments need made
first the A1 control called screen
there is usualy two turnable controls
use the right hand only to work with it on
once its fitted and all the bits back in there places and double checked
dont forget to connect the big red or black cap to the back of the tube and the red wires to the tube base panel

turn it on if you see no picture but you get a raster... eeeeeeeee and it sounds normal

adjust the sets brightness control for mid point
then adjust the screen pot on the lopt for a normal brightness level
or you can use a meter and set it exactly from where the red wire connects to the tube base {usualy around 200v see the circuit}

youll find a usefull monitor test prg here http://www.atariactive.com/viewtopic.php?t=10664
this will allow you to adjust the focus control the other pot on the lopt
once these two are done your sorted
make sure there is always someone else around

ps did you checkout c2520 it should also read short
till the pin 3 is isolated also

an electrolytic cap should on a beep test range when you connect the probes to its pins one way then the other beep for a short time



incase of any issues
never work on HT and EHT equipment alone
and never with the left hand

[Stefan jL]

pop did you ever change flyback?

I have the same problem with my Philips CM8833-II (inside says CM11342)

I am more concerned what parts i should not touch on the monitor to avoid discharge... could anybody mark the dangerous parts on this photo?
How do i safetly discharge a monitor?



here is a bigger pic:
http://www.ym2149.com/cm8833ii/cm11342_monitor_1_big.jpg

model:


Flyback type:


A saw at an amiga forum that this flyback can be replaced by "HR7533".
http://www.amibay.com/showthread.php?t=12332&page=7

[Hippy Dave]

I googled this:
http://www.crtsolutions.com/CRTSafety.pdf
Monitors and power supplies can kill you hours
(or even many days) after being unplugged.

The picture tube can violently implode and kill you too.

Note that you can get electrocuted while attempting
the safety procedures (a gotcha).

[Stefan jL]

Thanks for the PDF.

I do actually ahve two broken CM8833 monitors.. i am gonna try on the one that broke first, it has not been used in five years... so maybe that one has less chance to kill me?

[nativ]

Lets hope so!!