30 Sep
2001
30 Sep
'01
3:09 p.m.
Heller to everyone and Tony. ;-)
What do you do about a squealing CRT? I've got this nice terminal which is
working, but it emits a high-pitched whine which is not only unpleasant and
annoying, but quite scary, too. It feels as thoughit's going to blow in your
face any minute.
The terminal in question is a green-screen TECO VA120.
--
En ligne avec Thor 2.6a.
Ky?suke: Jag heter Kurre, Kurre Carlsson!
Jag: Det heter du inte alls!
1 Oct
1 Oct
10:17 a.m.
Jeffrey S. Sharp skrev:
On 1 Oct 2001, Iggy Drougge wrote:
> What do you do about a squealing CRT? I've
got this nice terminal
> which is working, but it emits a high-pitched whine
Don't all (most?) CRTs emit some form of whine?
Depends on your ears. =)
While it's true that there is an audible squeal in most (all) CRTs, this is a
really annoying one.
--
En ligne avec Thor 2.6a.
A conservative is a worshipper of dead radicals.
30 Sep
30 Sep
10:18 p.m.
At 04:09 AM 01/10/2001 +0100, you wrote:
Heller to everyone and Tony. ;-)
What do you do about a squealing CRT? I've got this nice terminal which is
working, but it emits a high-pitched whine which is not only unpleasant and
annoying, but quite scary, too. It feels as thoughit's going to blow in your
face any minute.
The terminal in question is a green-screen TECO VA120.
--
En ligne avec Thor 2.6a.
Ky?suke: Jag heter Kurre, Kurre Carlsson!
Jag: Det heter du inte alls!
Assuming the CRT doesn't have a crack in it, in which case it wont
squeal long, it sounds like a horizontal output transformer that is
vibrating at an audible frequency.
You might try tightening any screws you find around the core of
the H.O.T. (With the power off and the circuit discharged.)
Regards
Charlie Fox
Chas E. Fox Video Productions
793 Argyle Rd. Windsor ON N8Y 3J8
foxvideo(a)wincom.net
Check out:
Camcorder Kindergarten at http://chasfoxvideo.com
1 Oct
1 Oct
8:45 a.m.
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4 Oct
4 Oct
3:08 a.m.
Tony Duell skrev:
(I'm a bit late in replying since I've been waiting for the terminal to lose
its charge before opening it up)
> Heller to everyone and Tony. ;-)
Yet again I'm a nobody. Well, if I'm not in the
set of 'everyone' I must
be, right :-)
It's comme-il-faut on this list by now, what is one to do?
> What do you do about a squealing CRT? I've got
this nice terminal which i=
I've never heard a CRT squeal. I've heard one
hiss, but that was when the
pinch-off tube got cracked and the vacuum was leaking out. That effect
only lasts for a few seconds, and then the owner starts squealling as he
has to look for a replacement CRT.
The squeal from most monitors/TVs comes from the
flyback transformer
(horizontal output transformer, line output transformer, call it what you
will). THe core vibrates at the horizontal scan frequency.
Is that the neck at the back of the tube? I see a key-like screw protruding at
a 90? angle from the neck, which seems to be coupled to a metal band wrapped
across the neck.
The cure is to make sure the core can't vibrate. If
there are clamps on
the core, tighten them (not hard enough to crack the core of course. If
not, then often a squirt of hot-melt glue around the core and windings
will silence it, but don't blame me if it ruins the transformer.
There is a big squirt of glue around the mountain of wire (what you call a
coil, I think) where the neck begins.
> s
> working, but it emits a high-pitched whine which is not only unpleasant a=
> nd
> annoying, but quite scary, too. It feels as thoughit's going to blow in y=
> our
> face any minute.
Don't worry about that. THis effect has not other
consequences (other
than annoying sound)
That's a relief.
--
En ligne avec Thor 2.6a.
Georgie beundrade stor?gt sin pappa som med v?ldsamma slag gick l?s p? det
stora tr?det. Han badade i svett, och den muskul?sa kroppen bl?nkte i
solskenet. Hon ?lskade honom.
Lady Georgie, TMS 1983
10:45 a.m.
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6 Oct
6 Oct
1:05 p.m.
Tony Duell skrev:
> >The squeal from most monitors/TVs comes from
the flyback transformer
> >(horizontal output transformer, line output transformer, call it what yo=
> u
> >will). THe core vibrates at the horizontal scan frequency.
>
> Is that the neck at the back of the tube? I see a key-like screw protrudi=
> ng at
> a 90=B0 angle from the neck, which seems to be coupled to a metal band wr=
> apped
> across the neck.
No, that's the deflection yoke. The flyback
transformer is on the PCB
normally. The easy way to find it most of the time is to follow the EHT
cable from the flare of the CRT back to a plastic-encased lump on the
PCB. That's normally the flyback transformer (it could be a voltage
multiplier in some older colour monitors, but I don't think that's an
issue here).
All right, I stole some sticks of hot glue from the scale modellers and poured
it onto the thing which looks like this:
,-----------.
| _ |
| | |WARNING|
| | | HIGH |
| | |VOLTAGE|
| | | |
|_| |_______|
It sits on the main board in the monitor section, connected to that dangerous
red wire fit with a suction cup onto the CRT itself.
But it doesn't really look like something which will vibrate or rattle in any
way. I've done some reading up on flybacks, though, and apparently there are
some advanced wirings inside that package.
Then I let it dry and turned it on. Still the same horrible sound. I walked
around the thing for a bit, and it seemed as though the noise emanated from
the black cage containg what is probably the mains transformer.
A recent posting in the ongoing "wobbly PET" thread suggests that some sheet
steel contraption inside the PSU is dissolving and vibrating at mains
frequency. Could this be the case here?
--
En ligne avec Thor 2.6a.
The generation of random numbers is too important to be left to chance.
9:53 p.m.
In a way, yes: if you have a switched power supply, it could be (rather
small)
mains transformer that is vibrating at high frequencies. But with an
analog PSU,
it humms at 50-60 Hz, this is not "squealing", no....
OTOH, flybacks are often sealed in plastic and vibrate **inside** the
sealing.
I never managed to stop a monitor from beeping and squealing (nice word
8-),
except by replacing the flyback transformer or by treating it with a
very small
hammer (really!!), trying to "shake it into shape". Don't do this at
home!
ms
Iggy Drougge wrote:
Tony Duell skrev:
--
Michael Schneider email (home): ms(a)silke.rt.schwaben.de
Schleestr.8 http://www.vaxcluster.de
72766 Reutlingen Phone: +49 7121 492781
Germany FAX: +49 7121 479331
People disagree with me. I just ignore them.
(Linus Torvalds)
> >The squeal from most monitors/TVs comes
from the flyback transformer
> >(horizontal output transformer, line output transformer, call it what yo=
> u
> >will). THe core vibrates at the horizontal scan frequency.
>
> Is that the neck at the back of the tube? I see a key-like screw protrudi=
> ng at
> a 90=B0 angle from the neck, which seems to be coupled to a metal band wr=
> apped
> across the neck.
No, that's the deflection yoke. The flyback
transformer is on the PCB
normally. The easy way to find it most of the time is to follow the EHT
cable from the flare of the CRT back to a plastic-encased lump on the
PCB. That's normally the flyback transformer (it could be a voltage
multiplier in some older colour monitors, but I don't think that's an
issue here).
All right, I stole some sticks of hot glue from the scale modellers and poured
it onto the thing which looks like this:
,-----------.
| _ |
| | |WARNING|
| | | HIGH |
| | |VOLTAGE|
| | | |
|_| |_______|
It sits on the main board in the monitor section, connected to that dangerous
red wire fit with a suction cup onto the CRT itself.
But it doesn't really look like something which will vibrate or rattle in any
way. I've done some reading up on flybacks, though, and apparently there are
some advanced wirings inside that package.
Then I let it dry and turned it on. Still the same horrible sound. I walked
around the thing for a bit, and it seemed as though the noise emanated from
the black cage containg what is probably the mains transformer.
A recent posting in the ongoing "wobbly PET" thread suggests that some sheet
steel contraption inside the PSU is dissolving and vibrating at mains
frequency. Could this be the case here?
--
En ligne avec Thor 2.6a.
The generation of random numbers is too important to be left to chance.
11:20 p.m.
Michael Schneider skrev:
In a way, yes: if you have a switched power supply, it
could be (rather
small)
mains transformer that is vibrating at high frequencies. But with an
analog PSU,
it humms at 50-60 Hz, this is not "squealing", no....
It could almost come from an insect,only it is at a higher frequency.
OTOH, flybacks are often sealed in plastic and vibrate
**inside** the
sealing.
I never managed to stop a monitor from beeping and squealing (nice word
8-),
except by replacing the flyback transformer or by treating it with a
very small
hammer (really!!), trying to "shake it into shape". Don't do this at
home!
A hammer? Perhaps I'll try that today... OTOH, it should still hold a charge
today, considering I had it plugged in as late as this Friday.
--
En ligne avec Thor 2.6a.
Es gibt zweierlei M?dchen: die einen, die Pullover stricken, und die anderen,
die sie ausf?llen.
--- Daliah Lavi
11:24 p.m.
Oh my dear, what have i done!!!!!
Be careful.....
ms
Iggy Drougge wrote:
Michael Schneider skrev:
--
Michael Schneider email (home): ms(a)silke.rt.schwaben.de
Schleestr.8 http://www.vaxcluster.de
72766 Reutlingen Phone: +49 7121 492781
Germany FAX: +49 7121 479331
People disagree with me. I just ignore them.
(Linus Torvalds)
In a way, yes: if you have a switched power
supply, it could be (rather
small)
mains transformer that is vibrating at high frequencies. But with an
analog PSU,
it humms at 50-60 Hz, this is not "squealing", no....
It could almost come from an insect,only it is at a higher frequency.
OTOH, flybacks are often sealed in plastic and
vibrate **inside** the
sealing.
I never managed to stop a monitor from beeping and squealing (nice word
8-),
except by replacing the flyback transformer or by treating it with a
very small
hammer (really!!), trying to "shake it into shape". Don't do this at
home!
A hammer? Perhaps I'll try that today... OTOH, it should still hold a charge
today, considering I had it plugged in as late as this Friday.
--
En ligne avec Thor 2.6a.
Es gibt zweierlei M?dchen: die einen, die Pullover stricken, und die anderen,
die sie ausf?llen.
--- Daliah Lavi
7 Oct
7 Oct
6:25 a.m.
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8 Oct
8 Oct
2:55 p.m.
Tony Duell skrev:
> >No, that's the deflection yoke. The
flyback transformer is on the PCB
> >normally. The easy way to find it most of the time is to follow the EHT
> >cable from the flare of the CRT back to a plastic-encased lump on the
> >PCB. That's normally the flyback transformer (it could be a voltage
> >multiplier in some older colour monitors, but I don't think that's an
> >issue here).
>
> All right, I stole some sticks of hot glue from the scale modellers and
> poured it onto the thing which looks like this:
The place to put it is between the ferrite core and the
block containing
the windings (with all the connecting pins on the bottom)
IOW, between the big block and the little handle? That was hard to reach.
> ,-----------.
> | _ |
> | | |WARNING|
> | | | HIGH |
> | | |VOLTAGE|
> | | | |
> |_| |_______|
>
That looks just like a flyback transformer :-)
It looks like a kettle to me. =)
> Then I let it dry and turned it on. Still the same
horrible sound. I walked
> around the thing for a bit, and it seemed as though the noise emanated from
> the black cage containg what is probably the mains transformer.
Sounds like a switch mode PSU. Any transformer can
vibrate, such as the
one in the SMPSU circuit. Now, it should oscillate at an ultrasonic
frequency so you won't hear it, but dried up capacitors in the SMPSU
circuit can make the thing drop in frequency, sometimes with no other
effects...
The old dried up capacaitors problem...
If you can get an ESR meter (and IMHO if you repair
monitors or SMPSUs
you _need_ some way of measuring the effective series resistance of
capacitors) then you could test all the electrolytics in the power supply
section.
I don't intend to take up high-voltage repairs as another hobby of mine. I'm
too intent on keeping on living with all my bodily functions intact.
--
En ligne avec Thor 2.6a.
G? med i SUGA, Swedish Usergroup of Amiga!
WWW: http://swedish.usergroup.amiga.tm/
BBS: 08-6582572, telnet://sua.ath.cx:42512
9 Oct
9 Oct
2:48 a.m.
Geoff Reed skrev:
At 03:55 AM 10/9/01 +0100, you wrote:
>I don't intend to take up high-voltage repairs as another hobby of mine. I'm
>too intent on keeping on living with all my bodily functions intact.
Aw, you haven't lived until you've been kicked
across the room by a HV
powersupply
I think the taste I got from a SCSI box a few months ago was enough of an
appetiser. I'd rather not try again to see whether that was really HV.
--
En ligne avec Thor 2.6a.
Vi m?ste vara r?dda om varandra
- det ?r det enda reciproka pronomen vi har.
5:26 a.m.
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8245
days inactive
8254
days old
16 comments
6 participants
participants (6)
-
ard＠p850ug1.demon.co.uk -
foxvideo＠wincom.net -
geoffr＠zipcon.net -
jss＠subatomix.com -
ms＠silke.rt.schwaben.de -
optimus＠canit.se