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| Sylvia Else... |
 Posted: Mon Nov 09, 2009 9:14 pm |
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Guest
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I bought this on Ebay for $5.50 on the off chance that I could fix it.
It was described as having lost picture with a "pop", and with the
observation that a TV repairman said it sounded like it could be a power
supply issue.
I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.
It's clear what produced the "pop" noise.
http://members.optusnet.com.au/sylviae/tv1.jpg
http://members.optusnet.com.au/sylviae/tv2.jpg
Presumably this diode shorted out. It's on a board close the EHT circuitry.
But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a fairly
major exercise.
Sylvia. |
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| Sylvia Else... |
| Posted: Mon Nov 09, 2009 10:55 pm |
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Sylvia Else wrote:
[quote]I bought this on Ebay for $5.50 on the off chance that I could fix it.
It was described as having lost picture with a "pop", and with the
observation that a TV repairman said it sounded like it could be a power
supply issue.
I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.
It's clear what produced the "pop" noise.
http://members.optusnet.com.au/sylviae/tv1.jpg
http://members.optusnet.com.au/sylviae/tv2.jpg
Presumably this diode shorted out. It's on a board close the EHT circuitry.
But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a fairly
major exercise.
Sylvia.
[/quote]
Um, strike that. Once I started pulling it apart, it was apparent that
that's actually a diode with an inductive bead on its lead.
Sylvia. |
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| D Yuniskis... |
| Posted: Mon Nov 09, 2009 11:40 pm |
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Sylvia Else wrote:
[quote]I bought this on Ebay for $5.50 on the off chance that I could fix it.
It was described as having lost picture with a "pop", and with the
observation that a TV repairman said it sounded like it could be a power
supply issue.
I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.
It's clear what produced the "pop" noise.
http://members.optusnet.com.au/sylviae/tv1.jpg
http://members.optusnet.com.au/sylviae/tv2.jpg
[/quote]
The diode *looks* OK. Though it seems like there
might be a wire or maybe some "glue fibers" draped
across it?
[quote]Presumably this diode shorted out. It's on a board close the EHT circuitry.
[/quote]
I'd look at the switching transistor (HOT) first.
[quote]But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a fairly
major exercise.
[/quote]
<grin> You should see what a nuisance some of the high end
Sony monitors are (were?) to service! :< |
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| Sylvia Else... |
| Posted: Tue Nov 10, 2009 1:11 am |
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D Yuniskis wrote:
[quote]Sylvia Else wrote:
I bought this on Ebay for $5.50 on the off chance that I could fix it.
It was described as having lost picture with a "pop", and with the
observation that a TV repairman said it sounded like it could be a
power supply issue.
I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.
It's clear what produced the "pop" noise.
http://members.optusnet.com.au/sylviae/tv1.jpg
http://members.optusnet.com.au/sylviae/tv2.jpg
The diode *looks* OK. Though it seems like there
might be a wire or maybe some "glue fibers" draped
across it?
Presumably this diode shorted out. It's on a board close the EHT
circuitry.
I'd look at the switching transistor (HOT) first.
But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a fairly
major exercise.
grin> You should see what a nuisance some of the high end
Sony monitors are (were?) to service! :
[/quote]
As far as I can see, and despite the numerous headers, it's impossible
to remove the circuit board from this TV without desoldering some wires
from it. I rather think it was never intended to be repaired. However,
with some of the unpluggable wires unplugged, there is just enough slack
in the remainder to prop the circuit board up into a vertical position.
Based on the described "pop" symptom, I was looking for something
showing physical trauma, but if there's any visible, I'm missing it, and
I've spent a good while looking.
I've established that the HT (190V) is present at the powersupply.
The switching transistor seems OK :(
Sylvia. |
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| Meat Plow... |
| Posted: Tue Nov 10, 2009 8:10 am |
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On Tue, 10 Nov 2009 17:11:45 +1100, Sylvia Else
<sylvia at (no spam) not.at.this.address>wrote:
[quote]D Yuniskis wrote:
Sylvia Else wrote:
I bought this on Ebay for $5.50 on the off chance that I could fix it.
It was described as having lost picture with a "pop", and with the
observation that a TV repairman said it sounded like it could be a
power supply issue.
I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.
It's clear what produced the "pop" noise.
http://members.optusnet.com.au/sylviae/tv1.jpg
http://members.optusnet.com.au/sylviae/tv2.jpg
The diode *looks* OK. Though it seems like there
might be a wire or maybe some "glue fibers" draped
across it?
Presumably this diode shorted out. It's on a board close the EHT
circuitry.
I'd look at the switching transistor (HOT) first.
But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a fairly
major exercise.
grin> You should see what a nuisance some of the high end
Sony monitors are (were?) to service! :
As far as I can see, and despite the numerous headers, it's impossible
to remove the circuit board from this TV without desoldering some wires
from it. I rather think it was never intended to be repaired. However,
with some of the unpluggable wires unplugged, there is just enough slack
in the remainder to prop the circuit board up into a vertical position.
Based on the described "pop" symptom, I was looking for something
showing physical trauma, but if there's any visible, I'm missing it, and
I've spent a good while looking.
I've established that the HT (190V) is present at the powersupply.
The switching transistor seems OK :(
Sylvia.
[/quote]
The "pop" could have come through the speakers and not made by an
exploding cap.
I've heard a lot of pops, snaps, cracks, etc...over my lifetime in the
industry and as a rule pops are generated by older electrolytic caps
as they now have a safety valves built in and only hiss.
When I repaired my first CRT 51" TV it seemed a daunting task with
all the interconnecting boards and other things in the way of the
convergence amp board. But I was driven by necessity. In your case
the $5.50 you paid should be an incentive as long as you remain
curious. |
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| Sylvia Else... |
| Posted: Tue Nov 10, 2009 8:25 am |
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Meat Plow wrote:
[quote]On Tue, 10 Nov 2009 17:11:45 +1100, Sylvia Else
sylvia at (no spam) not.at.this.address>wrote:
D Yuniskis wrote:
Sylvia Else wrote:
I bought this on Ebay for $5.50 on the off chance that I could fix it.
It was described as having lost picture with a "pop", and with the
observation that a TV repairman said it sounded like it could be a
power supply issue.
I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.
It's clear what produced the "pop" noise.
http://members.optusnet.com.au/sylviae/tv1.jpg
http://members.optusnet.com.au/sylviae/tv2.jpg
The diode *looks* OK. Though it seems like there
might be a wire or maybe some "glue fibers" draped
across it?
Presumably this diode shorted out. It's on a board close the EHT
circuitry.
I'd look at the switching transistor (HOT) first.
But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a fairly
major exercise.
grin> You should see what a nuisance some of the high end
Sony monitors are (were?) to service! :
As far as I can see, and despite the numerous headers, it's impossible
to remove the circuit board from this TV without desoldering some wires
from it. I rather think it was never intended to be repaired. However,
with some of the unpluggable wires unplugged, there is just enough slack
in the remainder to prop the circuit board up into a vertical position.
Based on the described "pop" symptom, I was looking for something
showing physical trauma, but if there's any visible, I'm missing it, and
I've spent a good while looking.
I've established that the HT (190V) is present at the powersupply.
The switching transistor seems OK :(
Sylvia.
The "pop" could have come through the speakers and not made by an
exploding cap.
[/quote]
Yes. I also have to confess to wondering whether I've been suckered in,
with the pop being just to give the impression that it might be easily
fixable. The guy wasn't even very interested in his $5.50, and said that
he really just wanted to get rid of of the TV which turned out to be so
heavy it requires two to lift.
There seems to be a lack of sync signals making me suspect that the
fault lies at a low power section where component failure is unlikely to
make a noise.
Turns out that "Rank Arena" is a brand name that is transferred between
companies. The one using the name at the time no longer exists.
[quote]
I've heard a lot of pops, snaps, cracks, etc...over my lifetime in the
industry and as a rule pops are generated by older electrolytic caps
as they now have a safety valves built in and only hiss.
When I repaired my first CRT 51" TV it seemed a daunting task with
all the interconnecting boards and other things in the way of the
convergence amp board. But I was driven by necessity. In your case
the $5.50 you paid should be an incentive as long as you remain
curious.
[/quote]
I've determined that it will cost me a further $10 to take it to the
tip, if it comes to it. Ho hum.
Perhaps I should try to sell it on Ebay.
Sylvia. |
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| D Yuniskis... |
| Posted: Tue Nov 10, 2009 12:25 pm |
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Sylvia Else wrote:
[quote]D Yuniskis wrote:
Sylvia Else wrote:
I bought this on Ebay for $5.50 on the off chance that I could fix
it. It was described as having lost picture with a "pop", and with
the observation that a TV repairman said it sounded like it could be
a power supply issue.
I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.
[/quote]
This is A Good Sign.
[quote]The diode *looks* OK. Though it seems like there
might be a wire or maybe some "glue fibers" draped
across it?
Presumably this diode shorted out. It's on a board close the EHT
circuitry.
I'd look at the switching transistor (HOT) first.
But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a
fairly major exercise.
grin> You should see what a nuisance some of the high end
Sony monitors are (were?) to service! :
As far as I can see, and despite the numerous headers, it's impossible
to remove the circuit board from this TV without desoldering some wires
from it. I rather think it was never intended to be repaired. However,
[/quote]
....like many *cars*! :-/
[quote]with some of the unpluggable wires unplugged, there is just enough slack
in the remainder to prop the circuit board up into a vertical position.
Based on the described "pop" symptom, I was looking for something
showing physical trauma, but if there's any visible, I'm missing it, and
I've spent a good while looking.
I've established that the HT (190V) is present at the powersupply.
[/quote]
That's *mains* voltage (rectified and filtered?). Are you
sure the flyback is working?
> The switching transistor seems OK  |
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| Sylvia Else... |
| Posted: Tue Nov 10, 2009 6:20 pm |
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D Yuniskis wrote:
[quote]Sylvia Else wrote:
D Yuniskis wrote:
Sylvia Else wrote:
I bought this on Ebay for $5.50 on the off chance that I could fix
it. It was described as having lost picture with a "pop", and with
the observation that a TV repairman said it sounded like it could be
a power supply issue.
I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.
This is A Good Sign.
The diode *looks* OK. Though it seems like there
might be a wire or maybe some "glue fibers" draped
across it?
Presumably this diode shorted out. It's on a board close the EHT
circuitry.
I'd look at the switching transistor (HOT) first.
But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a
fairly major exercise.
grin> You should see what a nuisance some of the high end
Sony monitors are (were?) to service! :
As far as I can see, and despite the numerous headers, it's impossible
to remove the circuit board from this TV without desoldering some
wires from it. I rather think it was never intended to be repaired.
However,
...like many *cars*! :-/
with some of the unpluggable wires unplugged, there is just enough
slack in the remainder to prop the circuit board up into a vertical
position.
Based on the described "pop" symptom, I was looking for something
showing physical trauma, but if there's any visible, I'm missing it,
and I've spent a good while looking.
I've established that the HT (190V) is present at the powersupply.
That's *mains* voltage (rectified and filtered?).
[/quote]
I'm in Australia, mains voltage 240V RMS.
[quote]Are you
sure the flyback is working?
[/quote]
At this stage, I'm reasonably sure that it's not, but due to a lack of
appropriate input signals.
I'm somewhat aghast at the sheer complexity of the board that's creating
the horizontal and vertical scanning outputs, and the anode voltage.
It has two LSI circuits, including one that contains a programmable
processor, and no less than six transformers (I don't think any are
chokes, but don't quote me), not including the EHT transformer.
OK, so it's implementing the functions of a multi-sync monitor (the set
has an XVGA input), but even so....
Whatever happened to circuits that just contained a couple of valves?
Sylvia. |
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| Trevor Wilson... |
| Posted: Tue Nov 10, 2009 7:02 pm |
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Guest
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"Sylvia Else" <sylvia at (no spam) not.at.this.address> wrote in message
news:00f2f033$0$23353$c3e8da3 at (no spam) news.astraweb.com...
[quote]
Whatever happened to circuits that just contained a couple of valves?
[/quote]
**There never were any "circuits that just contained a couple of valves".
When they first arrived, TV sets were mindbogglingly complex devices
compared to anything that preceded them (in domestic appliance-speak). They
were also fabulously unreliable. You could figure that the average TV set
would require several repair jobs every year. Your incredibly complex, LSI
controlled, TV set is likely to be vastly more reliable. You've probably
found the first fault it has ever had.
BTW: If you post your request on aus.electronics, with the appropriate model
and chassis numbers, you may gain more of an insight. Even better, you could
join these guys:
http://www.ceta.org.au/
Someone there has almost certainly serviced the same model and, perhaps, the
same fault.
--
Trevor Wilson
www.rageaudio.com.au |
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| Sylvia Else... |
| Posted: Tue Nov 10, 2009 8:15 pm |
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Guest
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Trevor Wilson wrote:
[quote]"Sylvia Else" <sylvia at (no spam) not.at.this.address> wrote in message
news:00f2f033$0$23353$c3e8da3 at (no spam) news.astraweb.com...
Whatever happened to circuits that just contained a couple of valves?
**There never were any "circuits that just contained a couple of valves".
When they first arrived, TV sets were mindbogglingly complex devices
compared to anything that preceded them (in domestic appliance-speak). They
were also fabulously unreliable. You could figure that the average TV set
would require several repair jobs every year. Your incredibly complex, LSI
controlled, TV set is likely to be vastly more reliable. You've probably
found the first fault it has ever had.
[/quote]
Well, OK, but the use of a programmable LSI chip makes it rather hard to
determine whether the chip outputs are what was intended, particular in
the absence of a schematic, and with the manufacture apparently out of
business.
[quote]
BTW: If you post your request on aus.electronics, with the appropriate model
and chassis numbers, you may gain more of an insight. Even better, you could
join these guys:
[/quote]
Well, the model number is RK-32HDP81. Not sure where I'd look for the
chassis number - it doesn't really have a chassis. The serial number is
RK00000027, making me wonder how many of these were sold, though I
suppose the guy I bought it from could have been an early-adopter.
I've added aus.electronics, as per you suggestion, so to summarise the
situation as I perceive it now:
There is no picture, but sound works. The receiver side of the video
clearly works because it outputs to an AV output socket [*], and
plugging a suitable screen into that gives a picture.
The horizontal and vertical scanning outputs appear to be present. At
least, there are substantial signals there - whether they're the right
shape I couldn't say.
The most evident issue is that the EHT switching transistor, which
itself appears intact, has no base drive, and so far I haven't been able
to find a signal by backtracking.
The one good thing I have to say about the boards in this TV is that
they have component numbers on the soldered side of the board.
[quote]
http://www.ceta.org.au/
Someone there has almost certainly serviced the same model and, perhaps, the
same fault.
[/quote]
I couldn't see any sort of public forum, and I wouldn't qualify for
membership.
Sylvia.
[*] The signal remains even when the TV is in standby mode. You can't
change channels in that mode, but the channel the TV was tuned to is
still available. Maybe this is common - I've never looked at other TV
outputs in standby mode, but it doesn't suggest the minimum possible
power consumption in that mode. |
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| Michael A. Terrell... |
| Posted: Tue Nov 10, 2009 10:46 pm |
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Guest
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Trevor Wilson wrote:
[quote]
"Sylvia Else" <sylvia at (no spam) not.at.this.address> wrote in message
news:00f2f033$0$23353$c3e8da3 at (no spam) news.astraweb.com...
Whatever happened to circuits that just contained a couple of valves?
**There never were any "circuits that just contained a couple of valves".
When they first arrived, TV sets were mindbogglingly complex devices
compared to anything that preceded them (in domestic appliance-speak). They
were also fabulously unreliable. You could figure that the average TV set
would require several repair jobs every year. Your incredibly complex, LSI
controlled, TV set is likely to be vastly more reliable. You've probably
found the first fault it has ever had.
[/quote]
It sounds like they only sold crap in Australia, and that you've
never seen the very low parts count in a Muntz TV.
My parents had three service calls in 15 years. Two of those were
due to lightning taking out the front end in the VHF tuner. The third
was a bad electrolytic in a voltage doubler that took out a fusible
resistor. That isn't a couple times a year.
--
The movie 'Deliverance' isn't a documentary! |
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| b... |
| Posted: Wed Nov 11, 2009 12:54 am |
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On 11 nov, 08:37, Sylvia Else <syl... at (no spam) not.at.this.address> wrote:
[quote]Sylvia Else wrote:
I bought this on Ebay for $5.50 on the off chance that I could fix it.
It was described as having lost picture with a "pop", and with the
observation that a TV repairman said it sounded like it could be a power
supply issue.
I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.
It's clear what produced the "pop" noise.
http://members.optusnet.com.au/sylviae/tv1.jpg
http://members.optusnet.com.au/sylviae/tv2.jpg
Presumably this diode shorted out. It's on a board close the EHT circuitry.
But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a fairly
major exercise.
Sylvia.
I've given up on this anyway. Having run out of other ideas, I pulled
apart the box mounted on the neck of the tube, to see whether the
reported "pop" might have come from there. Nothing of note inside,
except yet more large heat-sinks. Anyway, I decided that putting it back
together again was going to be more trouble than it's worth. So it's off
to the tip tomorrow.
Sylvia.
[/quote]
you shouldn't give up yet.
Any static on screen?
what happens if you raise the g2/screen pot on the line o/p
transformer?
have you got volts on the RGB o/p stage on the CRT neck pcb?
have you checked for open resistros in the frame circuit feed (very
common 'black screen' cause)? have you checked components in the line
driver cct?
these are all fundamental first steps - I think your troubleshooting
has not been very systematic if you haven't done 'em!
-B |
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| b... |
| Posted: Wed Nov 11, 2009 12:56 am |
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Rank Arena were old UK names, the Rank/Bush/Murphy brands were all
used in the 60s and 70s. Likely bought out by some chinese/turkish
firm, as have other former respected names like Dual, wharfefdale, and
Sansui.
-B |
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| Sylvia Else... |
| Posted: Wed Nov 11, 2009 2:37 am |
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Guest
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Sylvia Else wrote:
[quote]I bought this on Ebay for $5.50 on the off chance that I could fix it.
It was described as having lost picture with a "pop", and with the
observation that a TV repairman said it sounded like it could be a power
supply issue.
I've determined that the sound works OK, as does the tuner and video
signal stage - it outputs the composite video on an AV out socket.
It's clear what produced the "pop" noise.
http://members.optusnet.com.au/sylviae/tv1.jpg
http://members.optusnet.com.au/sylviae/tv2.jpg
Presumably this diode shorted out. It's on a board close the EHT circuitry.
But what are the chances that that's all that's wrong with it? Just
getting the board out to gain access to the underside will be a fairly
major exercise.
Sylvia.
[/quote]
I've given up on this anyway. Having run out of other ideas, I pulled
apart the box mounted on the neck of the tube, to see whether the
reported "pop" might have come from there. Nothing of note inside,
except yet more large heat-sinks. Anyway, I decided that putting it back
together again was going to be more trouble than it's worth. So it's off
to the tip tomorrow.
Sylvia. |
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| Sylvia Else... |
| Posted: Wed Nov 11, 2009 3:12 am |
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Michael A. Terrell wrote:
[quote]Trevor Wilson wrote:
"Sylvia Else" <sylvia at (no spam) not.at.this.address> wrote in message
news:00f2f033$0$23353$c3e8da3 at (no spam) news.astraweb.com...
Whatever happened to circuits that just contained a couple of valves?
**There never were any "circuits that just contained a couple of valves".
When they first arrived, TV sets were mindbogglingly complex devices
compared to anything that preceded them (in domestic appliance-speak). They
were also fabulously unreliable. You could figure that the average TV set
would require several repair jobs every year. Your incredibly complex, LSI
controlled, TV set is likely to be vastly more reliable. You've probably
found the first fault it has ever had.
It sounds like they only sold crap in Australia, and that you've
never seen the very low parts count in a Muntz TV.
My parents had three service calls in 15 years. Two of those were
due to lightning taking out the front end in the VHF tuner. The third
was a bad electrolytic in a voltage doubler that took out a fusible
resistor. That isn't a couple times a year.
[/quote]
It must be thirty or thirty five years ago that my family in England got
one of the early fully transistorised Philips colour televisions, with
teletext. This was our upgrade from B/W. We rented it, rather than
bought it, which was just as well, because it frequently broke down.
Indeed, the first occasion was within days of its arrival, with an
intermittent fault that the service company never did track down [*].
Often repairs involved fixing dry joints.
So Trevor's comment does fit my own experience. Televisions have become
more reliable. But I wonder whether that's because of improved
construction and quality control, rather than because of the circuitry
now in use. If individual components are very reliable, and they're
fixed properly to the circuit board, then the result can be reliable.
That doesn't mean that the design doesn't use an excessively large
number of components.
[*] The fault had the dual effect of killing the sound, and making the
picture about twice as wide as it should be. Years later, I obtained the
schematics for the set, and it was quite obvious where the fault had to
lie. I can only assume that the technicians who came to fix it either
didn't understand the circuit, or just couldn't be bothered. After they
fiddled with the set a bit, the fault would go away. Later I found that
a good thump on the cabinet would work just as well as calling the
technician.
Sylvia. |
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