Tech: Monitor warm up takes ages

[eggwheatis]

[ukvac] Tech: Monitor warm up takes ages
Hi all,
What would cause the monitor in my Mr Do. to take 10 minutes to get a
picture after switching on.The screen stays blank for 5 minutes then
starts to appear at the top of the screen then takes another 5mins to
fill the screen. Seems to take longer every time I switch it on. It's
got a hantarex MTC900 in it.

Chanks Philip

 

[LukeWells]

Re: [ukvac] Tech: Monitor warm up takes ages
(1) you could be talking knackered caps .... taking ages to get charged up
to a capacity where they will work

(2) check your b+ power supply is outputting the right voltage on power up
.... there is a vr to adjust this at the front left of the pcb i think if i
remeber rightly. (rv12) its supposed to be 115volt dead on. Oh and you need
to turn the screen control right down before doing the adjusting.

(3) maybe the heaters on the crt are knackered .... ?

Thats all i can think of ... but then again i dont know what i am talking
about anyway

> Hi all,
> What would cause the monitor in my Mr Do. to take 10 minutes to get a
> picture after switching on.The screen stays blank for 5 minutes then
> starts to appear at the top of the screen then takes another 5mins to
> fill the screen. Seems to take longer every time I switch it on. It's
> got a hantarex MTC900 in it.
>
> Chanks Philip
>
>

 

[guddler]

RE: [ukvac] Tech: Monitor warm up takes ages
> (1) you could be talking knackered caps .... taking ages to
> get charged up to a capacity where they will work

If the caps were knackered, wouldn't the capacity at which they will
work be greatly lowered, and therefore they would charge up way too
quickly?

> (2) check your b+ power supply is outputting the right
> voltage on power up .... there is a vr to adjust this at the
> front left of the pcb I think if I remeber rightly. (rv12)
> its supposed to be 115volt dead on. Oh and you need to turn
> the screen control right down before doing the adjusting.

If the b+ voltage is out at start-up, but settles down after 5 or 10
minutes, then it wouldn't be advisable to adjust it as it will be wrong
when things have warmed up after 5 or 10 minutes...

> (3) maybe the heaters on the crt are knackered .... ?

Sounds more like it, but I have absolutely no knowledge of them
whatsoever :O)

Guddler.



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[JCRS]

Re: [ukvac] Tech: Monitor warm up takes ages
Worn out LOPT (Line Output Transformer) possible.. one of these can make a
monitor take ages in "warming up"

My Mr Do cab, has recently suffered a similar thing, but its down to the
suction cup of the HT loosing its suction on the tube of the monitor.

Any one got any ideas of reviving this cup ? Its not brittle but just fails
to stay firmly to the tube, so I get alot of arching between the gap.

 

[eggwheatis]

[ukvac] Re: Tech: Monitor warm up takes ages
Hi John,
mines suffering the same problem with the ht cap so maybe thats whats
causing it. I'm now wondering wether this ht leakage can damage the
LOPT cos its been getting worse.

Cheers Philip

 

[Guests]

Re: [ukvac] Re: Tech: Monitor warm up takes ages
>> but its down to the suction cup of the HT loosing its suction
>> on the tube of the monitor.
>
>mines suffering the same problem with the ht cap so maybe thats whats
>causing it.

There is no such thing as a suction cap on a monitor. It is not held
on by suction, and if it is on your monitor, then you're inviting an
expensive fireworks display in the back of your cab, that will
probably destroy the monitor and gameboard. I've tried to repair a
gameboard that was damaged by a monitor with EHT arcing, and the
results are that I'm still looking for a boardset for a T2

The EHT cap should always be held on firmly by the EHT connection
itself. If it is not, then discharge the tube, and remove the cap,
and refit it properly. It will either have a sprung 'popper' cap
that will snap firmly inside the EHT connection of the tube, or it
will have two stiff wires, that should be squeezed together and
clipped inside the EHT connection of the tube.

If there has been any arcing around the EHT connection then
thoroughly clean both the CRT and the rubber cap, before refitting.
I prefer to use meths on a cloth, but keep it away from the silver
'aquadag' coating on the back of the tube, as on some older tubes it
can remove the coating as well (and you definately don't want to do
that).

And of course, take every possible safety precaution when working
on monitors. 'Cause if you do something stupid and kill yourself,
then it was the cat who wrote this message and not me.

Dave.



DATA Imported from archives: originally posted by Dave Roberts (daverob@cwcom.net)

 

[JCRS]

Re: [ukvac] Re: Tech: Monitor warm up takes ages
I know its not a suction cap so to speak, that was just my wording for I
know it needs a good seal to stop arcing.

Both the stiff pins on the EHT are fine, but the cap it self seems very hard
(early brittle stages maybe ?)
and is no longer creating a firm seal against the tube.

** YES I KNOW HOW DODGY THE FOLLOWING IS **

If I hold the EHT cap firmly to the tube, the monitor works fine, release it
and a gap appears between the cap & tube.

I use to do monitor repair back when Amstrad was fashion (if it ever was),
and we used to use a compound which would help create a seal
/ aid the EHT cap to the monitor, and for the life of me a cant remember
what ?

Before someone replies there is no such thing, maybe there isnt but we used
something, and it worked no matter how unsafe it may have been.

Jon

 

[John Bennett]

RE: [ukvac] Re: Tech: Monitor warm up takes ages
what you need is some HT grease from your local TV Repair man.. Go to his
shop and ask for a scoop of it.. does the trick nicely i've been told..

Kip



DATA Imported from archives: originally posted by Kip (kip@thedvdproject.com)

 

[LukeWells]

Re: [ukvac] Re: Tech: Monitor warm up takes ages
I fixed an arcing monitor last night, I soaked the rubber cap in alcohol for
a while, and then heated it with a hair dryer for 5mins. After this it was
very soft and flexible and so squashes down over the tube and creates a good
seal.

> I know its not a suction cap so to speak, that was just my wording for
I
> know it needs a good seal to stop arcing.
>
> Both the stiff pins on the EHT are fine, but the cap it self seems very
hard
> (early brittle stages maybe ?)
> and is no longer creating a firm seal against the tube.
>
> ** YES I KNOW HOW DODGY THE FOLLOWING IS **
>
> If I hold the EHT cap firmly to the tube, the monitor works fine, release
it
> and a gap appears between the cap & tube.
>
> I use to do monitor repair back when Amstrad was fashion (if it ever was),
> and we used to use a compound which would help create a seal
> / aid the EHT cap to the monitor, and for the life of me a cant remember
> what ?
>
> Before someone replies there is no such thing, maybe there isnt but we
used
> something, and it worked no matter how unsafe it may have been.
>
>
>
>
> Jon
>
>
>
>
>
>