15 Jun
2014
15 Jun
'14
3:40 a.m.
During preparation of the machine for VCFE i had a failure in the CRT's high voltage
part.
Yep, flyback burnt..
The high voltage winding was potted as a separate unit, enabled my to rewind the
flyback's primary (was burnt).
Then after replacing 2 transistors, 2 resistors and 1 diode I got a brief few seconds
of live out of the display again.
The hisses accompanying this would indicate the maybe the flyback HV isolation is not good
anymore, however i did not see sparks flying...
Current working assumption is that the secondary potted winding is also compromised.
I will also replace the HV voltage diode, is the HV capacitor something that fails
regularly ?
It is a 17 inch white monochrome Ball HD17-type monitor.
What are my options : repair again, looking for a generic flyback ( is there such a thing
?) , or dumping it into lake Zurich, which is my current mood....
I am not averse to putting some modern solution in place ( to generate the HV that is )
Jos
15 Jun
15 Jun
1:55 p.m.
During preparation of the machine for VCFE i had a failure in the CRT's high voltage
part.
Yep, flyback burnt..
The high voltage winding was potted as a separate unit, enabled my to
rewind the flyback's primary (was burnt).
Are there only 2 windigns? What about any taps on them? A single shorted
turn anywhere will cause problems.
Then after replacing 2 transistors, 2 resistors and
1 diode I got a
brief few seconds of live out of the display again.
When it worked, was the display clear, correct size, etc. Was it stable?
Often EHT problems have otehr effects. Too high an EHT will casue the
iamges to be smaller and brighter than normal, for example.
The hisses accompanying this would indicate the maybe the flyback HV
isolation is not good anymore, however i did not see sparks flying...
Hissing often means corona/brush discharge, nnot sparking. Did you
reoslder anything on the EHT side (connections to the diode, capacitor,
etc). If so, an 'icicle' fo solder cna be annough to cause this, you want
well-roudned sodler blobs
It could also be internal breakdown in the winding (in fact it sounds
like it is).
Current working assumption is that the secondary
potted winding is
also compromised.
I will also replace the HV voltage diode, is the HV capacitor
something that fails regularly ?
Is there a spearate capacitor? Often it's just the coatingso n the CRT.
Yes, the rectifier diodes do fail, often. But if it was shorted you would
get no display at all.
What fialed after the few seconds? The output transistors?
Is the service manual/scheamtic on-=line anywhere? Does the flyback
transofrmer/output stage do anyhting other htan supply the HET (is i nteh
orizontal defleciton stage too)?
It is a 17 inch white monochrome Ball HD17-type monitor.
What are my options : repair ag ain, looking for a generic flyback ( is
there such a thing ?) , or dumping it into lake Zurich, which is my >
current
mood....
Don't do the last, I am not particularly 'green' but don't approove of
polution. Quaiate apart from the fact that the machine is worth
restoroing.
I am not averse to putting some modern solution in
place ( to generate
the HV that is ) >
If this stage also generaes the horizontal defleeciton, you might be able
ot get it working to do that (leave off the EHT winding) and use a
eparate supply (any old flyback transoformer suitable driven, for
example) toi supply the EHT. Of course if it's a separate stage anywahy
(like i nthe Moniterm units I've worked on), you might be able to come up
with somethign that will work.
I wonder about makign a new EHT winding. I've never done it, but soem fo
the model IC engine enthusiasts make ignition coils and vauum impregnate
them with potting compound. I suspect makign this windign is similar.
Might be soemting to look into.
-tony
16 Jun
16 Jun
5:15 a.m.
Tony Duell wrote:
To find the Source of that hiss, you can put some isolation tubing in one
of your ears and use the other end to search the source..
Regards,
Holm
--
Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe,
Freiberger Stra?e 42, 09600 Obersch?na, USt-Id: DE253710583
www.tsht.de, info at tsht.de, Fax +49 3731 74200, Mobil: 0172 8790 741
During preparation of the machine for VCFE i had a failure in the CRT's high voltage
part.
Yep, flyback burnt..
The high voltage winding was potted as a separate unit, enabled my to
rewind the flyback's primary (was burnt).
Are there only 2 windigns? What about any taps on them? A single shorted
turn anywhere will cause problems.
Then after replacing 2 transistors, 2 resistors
and 1 diode I got a
brief few seconds of live out of the display again.
When it worked, was the display clear, correct size, etc. Was it stable?
Often EHT problems have otehr effects. Too high an EHT will casue the
iamges to be smaller and brighter than normal, for example.
The hisses accompanying this would indicate the maybe the flyback HV
isolation is not good anymore, however i did not see sparks flying...
Hissing often means corona/brush discharge, nnot sparking. Did you
reoslder anything on the EHT side (connections to the diode, capacitor,
etc). If so, an 'icicle' fo solder cna be annough to cause this, you want
well-roudned sodler blobs
It could also be internal breakdown in the winding (in fact it sounds
like it is).
Current working assumption is that the secondary
potted winding is
also compromised.
I will also replace the HV voltage diode, is the HV capacitor
something that fails regularly ?
Is there a spearate capacitor? Often it's just the coatingso n the CRT.
Yes, the rectifier diodes do fail, often. But if it was shorted you would
get no display at all.
What fialed after the few seconds? The output transistors?
Is the service manual/scheamtic on-=line anywhere? Does the flyback
transofrmer/output stage do anyhting other htan supply the HET (is i nteh
orizontal defleciton stage too)?
It is a 17 inch white monochrome Ball HD17-type monitor.
What are my options : repair ag ain, looking for a generic flyback ( is
there such a thing ?) , or dumping it into lake Zurich, which is my >
current
mood....
Don't do the last, I am not particularly 'green' but don't approove of
polution. Quaiate apart from the fact that the machine is worth
restoroing.
I am not averse to putting some modern solution
in place ( to generate
the HV that is ) >
If this stage also generaes the horizontal defleeciton, you might be able
ot get it working to do that (leave off the EHT winding) and use a
eparate supply (any old flyback transoformer suitable driven, for
example) toi supply the EHT. Of course if it's a separate stage anywahy
(like i nthe Moniterm units I've worked on), you might be able to come up
with somethign that will work.
I wonder about makign a new EHT winding. I've never done it, but soem fo
the model IC engine enthusiasts make ignition coils and vauum impregnate
them with potting compound. I suspect makign this windign is similar.
Might be soemting to look into.
-tony
10:08 a.m.
On 06/15/2014 10:55 PM, Tony Duell wrote:
No taps, but extra windings for CRT filament.
During preparation of the machine for VCFE i had a failure in the CRT's high voltage
part.
Yep, flyback burnt..
The high voltage winding was potted as a separate unit, enabled my to
rewind the flyback's primary (was burnt).
Are there only 2 windigns? What
about any taps on them? A single shorted
turn anywhere will cause problems. Hissing often means corona/brush discharge, nnot
sparking. Did you
reoslder anything on the EHT side (connections to the diode, capacitor,
etc). If so, an 'icicle' fo solder cna be annough to cause this, you want
well-roudned sodler blobs
It could also be internal breakdown in the winding (in fact it sounds
like it is).
Is there a spearate capacitor? Often it's just the coatingso n the CRT.
It has
a separate 1.5nF Hv capacior.
Yes, the rectifier diodes do fail, often. But if it was shorted you would
get no display at all.
What fialed after the few seconds? The output transistors?
The HV diode
connection.... Primary side is still OK.
Come to think of it, that might have caused the hissing.
When I get the replacement diodes I will try again.
If it fails again, I will rewind the primary again, and increase the windings by 10%, in
order to reduce HV output.
Is the service manual/scheamtic on-=line anywher
Several Ball monitors on Bitsavers, but not this model, not even close. I will trace the
schematic if required.
Does the flyback
transofrmer/output stage do anyhting other htan supply the HET (is i nteh
orizontal defleciton stage too)?
It also supplies the CRT filament, and some secondary gate voltages.
And yes, also the horizontal deflection.
I did have some instabilities in the horizontal deflection for some time, come to think of
it.
> It is a 17 inch white monochrome Ball HD17-type
monitor.
> What are my options : repair ag ain,
looking for a generic flyback ( is
> there such a thing ?) , or dumping it into lake Zurich, which is my > current mood....
> Don't do the last, I am not
particularly 'green' but don't approove of
> polution. Quaiate apart from the fact that the machine is worth
As you probably guessed, that was not a serious suggestion.
Here in .CH you can just bring your waste electronics in for free.
Last time i did that i was rewarded with a P2000C, with manuals and original floppies.
In 2014 that is...
Took it home, booted first time...
1:39 p.m.
On 06/15/2014 10:55 PM, Tony Duell wrote:
No taps, but extra windings for CRT filament.
OK... Does the filimanet look to be the nroaml brightness? You will ahv
eproblems measuring the CRT heater votlage, ist's a very 'peaky' waveform
which confuses most meters, even many true-RMS ones (it is, of cours,e
the RMS vlaue of the heater votlage that is important).
During preparation of the machine for VCFE i had a failure in the CRT's high voltage
part.
Yep, flyback burnt..
The high voltage winding was potted as a separate unit, enabled my to
rewind the flyback's primary (was burnt).
Are there only 2 windigns? What
about any taps on them? A single shorted
turn anywhere will cause problems. What fialed
after the few seconds? The output transistors?
The HV diode connection.... Primary
side is still OK.
Come to think of it, that might have caused the hissing. 
2:41 p.m.
On 06/16/2014 01:39 PM, Tony Duell wrote:
FWIW, if the output transisotrs are not fialing then
generally there's
not a lot wrong with the circuit.
I'm wondering if someone's tried repairing a flyback transformer
exhibiting internal arcing by boiling the core in beeswax. This used to
be the practice in the old days...
--Chuck
4:22 p.m.
On 06/16/2014 2:41 PM, Chuck Guzis wrote:
On 06/16/2014 01:39 PM, Tony Duell wrote:
I have a large chunk of beeswax that I use for resealing 1970s flybacks.
If anyone needs a bit let me know...I bought a 20lb chunk and I only
need about 1lb for the forseeable future.
John :-#)#
--
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
www.flippers.com
"Old pinballers never die, they just flip out"
FWIW, if the output transisotrs are not fialing
then generally there's
not a lot wrong with the circuit.
I'm wondering if someone's tried repairing a flyback transformer
exhibiting internal arcing by boiling the core in beeswax. This used
to be the practice in the old days...
--Chuck
17 Jun
17 Jun
8:11 a.m.
In article <539F7C51.1040609 at telus.net>,
John Robertson <pinball at telus.net> writes:
On 06/16/2014 2:41 PM, Chuck Guzis wrote:
So if I understand this correctly, the point is to encase the entire
transformer in bees wax to keep moisture from infiltrating again?
This thread seems relevant:
<http://www.antiqueradios.com/forums/viewtopic.php?t=94015&view=next>
--
"The Direct3D Graphics Pipeline" free book
<http://tinyurl.com/d3d-pipeline>
The Computer Graphics Museum <http://ComputerGraphicsMuseum.org>
The Terminals Wiki <http://terminals.classiccmp.org>
Legalize Adulthood! (my blog) <http://LegalizeAdulthood.wordpress.com>
On 06/16/2014 01:39 PM, Tony Duell wrote:
I have a large chunk of beeswax that I use for resealing 1970s flybacks.
If anyone needs a bit let me know...I bought a 20lb chunk and I only
need about 1lb for the forseeable future. FWIW, if the output transisotrs are not fialing
then generally there's
not a lot wrong with the circuit.
I'm wondering if someone's tried repairing a flyback transformer
exhibiting internal arcing by boiling the core in beeswax. This used
to be the practice in the old days...
3:10 p.m.
On 06/16/2014 01:39 PM, Tony Duell wrote:
I think there are better potting compounds (or potting composts as a mad
friend of mine insists on clalign them :-)) now. Ones wit ha higher
dielectric strenth. So beeswax may not help that much with the reduced
clearances in a transdormer designed for soemthign that will not break
down so easily.
And break doown it may well do. A lot of insulators are not as good as
you might think. I had a problem with an EHT sense resisotr unit flashing
over the chassis (it was part of the EHT regulator in my Barco monitor,
the plastic casing of the resistor unit was cracked it was othrwise OK).
Anyway, I tried mounting it on a cut down blanking plate fora UK
electricl switch/socket box. It flashed tstraight through that. In the
end I managed ot get some PTFE sheet. About 6mm of PTFE was OK... But I
discovered this _after_ the thing has also flasked over to my figners.
30kV is not pleasant...
-tony
FWIW, if the output transisotrs are not fialing
then generally there's
not a lot wrong with the circuit.
I'm wondering if someone's tried repairing a flyback transformer
exhibiting internal arcing by boiling the core in beeswax. This used to
be the practice in the old days...
3841
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