Need some Help Here!

C

Chris F.

Guest
Me again with this old Sony projection set (KPR-36XBR). I see my last post
didn't get any replies, perhaps I was a bit too long-winded. I'll keep this
message short.
I located a service manual for a KP-46XBRxx, and it suggested that the
high voltage block does not act as a bleeder resistor, instead, it contains
a cap and supplies a low-voltage reference signal to the HV shutdown
circuit. So it may not be the problem after all.
All I want to know for now is, how can I modify the set to reduce the high
voltage? As I mentioned before, the B+ is regulating properly, and the
design suggests that the HV is regulated by increasing/decreasing the
amplitude of the horiz. osc signal. Is it possible that I could put a
potentiometer, in series with the base of the HOT or something?
I basically just need it to the point, where it will run without arcing
and blowing the HOT. I've blown at least 10 of them already!
Thanks for any advice you can offer.
 
I cannot tell you how to modify the set, but it would be best to fix the
fault. In a standard set, the HV is regulated not by changing the amplitude
of the drive pulses, but is done by changing the duty cycle slightly. The
amplitude change will change the scan width, if the scans are derived from
the HV drive, as done in most TV sets. There is some type of feedback to
sense the HV current, and this goes back to the scan gen circuit area to be
processed.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Chris F." <zappyman@hotmail.com> wrote in message
news:gTIyb.2283$IF6.99597@ursa-nb00s0.nbnet.nb.ca...
Me again with this old Sony projection set (KPR-36XBR). I see my last post
didn't get any replies, perhaps I was a bit too long-winded. I'll keep this
message short.
I located a service manual for a KP-46XBRxx, and it suggested that the
high voltage block does not act as a bleeder resistor, instead, it contains
a cap and supplies a low-voltage reference signal to the HV shutdown
circuit. So it may not be the problem after all.
All I want to know for now is, how can I modify the set to reduce the high
voltage? As I mentioned before, the B+ is regulating properly, and the
design suggests that the HV is regulated by increasing/decreasing the
amplitude of the horiz. osc signal. Is it possible that I could put a
potentiometer, in series with the base of the HOT or something?
I basically just need it to the point, where it will run without arcing
and blowing the HOT. I've blown at least 10 of them already!
Thanks for any advice you can offer.
 
I guess I will probably need a service manual. A local supplier can get it
for me, but $55 Cdn is more than I'd like to invest in this, unless I'm
reasonably certain it can be fully restored to working condition.
Pardon my ignorance, but when you say varying the duty cycle, do you mean
shortening the width of each pulse? There's a chip which is supposed to
control most of the deflection (NTE 1664), I tried replacing it but it made
no difference. All caps etc have been checked and none found bad.....

Jerry G. <jerryg50@hotmail.com> wrote in message
news:bqftr6$3fi$2@news.eusc.inter.net...
I cannot tell you how to modify the set, but it would be best to fix the
fault. In a standard set, the HV is regulated not by changing the
amplitude
of the drive pulses, but is done by changing the duty cycle slightly. The
amplitude change will change the scan width, if the scans are derived from
the HV drive, as done in most TV sets. There is some type of feedback to
sense the HV current, and this goes back to the scan gen circuit area to
be
processed.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Chris F." <zappyman@hotmail.com> wrote in message
news:gTIyb.2283$IF6.99597@ursa-nb00s0.nbnet.nb.ca...
Me again with this old Sony projection set (KPR-36XBR). I see my last
post
didn't get any replies, perhaps I was a bit too long-winded. I'll keep
this
message short.
I located a service manual for a KP-46XBRxx, and it suggested that the
high voltage block does not act as a bleeder resistor, instead, it
contains
a cap and supplies a low-voltage reference signal to the HV shutdown
circuit. So it may not be the problem after all.
All I want to know for now is, how can I modify the set to reduce the
high
voltage? As I mentioned before, the B+ is regulating properly, and the
design suggests that the HV is regulated by increasing/decreasing the
amplitude of the horiz. osc signal. Is it possible that I could put a
potentiometer, in series with the base of the HOT or something?
I basically just need it to the point, where it will run without arcing
and blowing the HOT. I've blown at least 10 of them already!
Thanks for any advice you can offer.
Click to expand...
 
FYI flybacks were high failure items on that set after about 10 years.
The flyback would not only give high HV but would blow the HOT. I
would do a ring test on the flyback, or run it at reduced B+ voltage
by putting a 60 watt light bulb in series with the B+ as it goes to
the flyback and then monitor the HOT collector with o'scope for proper
waveform.

David

"Chris F." <zappyman@hotmail.com> wrote in message news:<gTIyb.2283$IF6.99597@ursa-nb00s0.nbnet.nb.ca>...
Me again with this old Sony projection set (KPR-36XBR). I see my last post
didn't get any replies, perhaps I was a bit too long-winded. I'll keep this
message short.
I located a service manual for a KP-46XBRxx, and it suggested that the
high voltage block does not act as a bleeder resistor, instead, it contains
a cap and supplies a low-voltage reference signal to the HV shutdown
circuit. So it may not be the problem after all.
All I want to know for now is, how can I modify the set to reduce the high
voltage? As I mentioned before, the B+ is regulating properly, and the
design suggests that the HV is regulated by increasing/decreasing the
amplitude of the horiz. osc signal. Is it possible that I could put a
potentiometer, in series with the base of the HOT or something?
I basically just need it to the point, where it will run without arcing
and blowing the HOT. I've blown at least 10 of them already!
Thanks for any advice you can offer.
Click to expand...
 
Just out of curiosity, what is the normal HV and focus for this set? HV
measures about 28.5kV and focus is about 12. Seems rather high to me......
To be honest I've suspected the flyback all along. I will see what I can
do to modify the set (high-wattage resistor in series with the HOT
collector, etc) and I might be able to patch it up. Wouldn't be fit to sell,
but I could still keep it for my own use. I'm not going to shell out the
money for a new flyback, that's for sure.
BTW, any ideas on how to clean up the solidified coolant on the CRT
surfaces??

David <dkuhajda@locl.net> wrote in message
news:68f82f5b.0312011327.7c67696c@posting.google.com...
FYI flybacks were high failure items on that set after about 10 years.
The flyback would not only give high HV but would blow the HOT. I
would do a ring test on the flyback, or run it at reduced B+ voltage
by putting a 60 watt light bulb in series with the B+ as it goes to
the flyback and then monitor the HOT collector with o'scope for proper
waveform.

David

"Chris F." <zappyman@hotmail.com> wrote in message
news:<gTIyb.2283$IF6.99597@ursa-nb00s0.nbnet.nb.ca>...
Me again with this old Sony projection set (KPR-36XBR). I see my last
post
didn't get any replies, perhaps I was a bit too long-winded. I'll keep
this
message short.
I located a service manual for a KP-46XBRxx, and it suggested that the
high voltage block does not act as a bleeder resistor, instead, it
contains
a cap and supplies a low-voltage reference signal to the HV shutdown
circuit. So it may not be the problem after all.
All I want to know for now is, how can I modify the set to reduce the
high
voltage? As I mentioned before, the B+ is regulating properly, and the
design suggests that the HV is regulated by increasing/decreasing the
amplitude of the horiz. osc signal. Is it possible that I could put a
potentiometer, in series with the base of the HOT or something?
I basically just need it to the point, where it will run without
arcing
and blowing the HOT. I've blown at least 10 of them already!
Thanks for any advice you can offer.
Click to expand...
 
Check the line output tuning capacitor located across c-e of
transistor. If this goes o/c the eht will go through the roof.
 
On 1 Dec 2003 18:02:46 -0800, peg@slingshot.co.nz (GPG) wrote:

Check the line output tuning capacitor located across c-e of
transistor. If this goes o/c the eht will go through the roof.
Click to expand...
Hmm.. and tend to blow the HOT instantly. Found this out hard way
when I forgot to install that larger of two cap. :)

Btw, which one of duo caps are you talking about? There is two across
C-E of HOT. One is typically 10nF, other one is appox 680pF for
example in a philips set.

In other set, like zenith, I see multiple smaller caps like 470pF,
two, three, even four along with a few nF value cap.

Cheers,

Wizard
 
Already checked that possibility, cap checked good.
I should also mention that the HOT is running nice and cool, which seems
really odd considering the HV problem. And, the HOT now only blows when the
HV discharges to the chassis (Bang!).
I noticed that, because of the small CRTs, the anode caps are extremely
close to the metal chassis, and I suspect that even under normal
circumstances arcing could be a problem. My current plan is to completely
seal the anode caps with silicone, and insulate that area of the chassis,
thereby eliminating any alternate path for the HV to take. I have a feeling
that might just solve the problem.
But first I must get some more HOTs. Blew another one last night, that makes
#11 I think..... >:-(
GPG <peg@slingshot.co.nz> wrote in message
news:62069f15.0312011802.ed8910@posting.google.com...
Check the line output tuning capacitor located across c-e of
transistor. If this goes o/c the eht will go through the roof.
Click to expand...
 
Btw, which one of duo caps are you talking about? There is two across
C-E of HOT. One is typically 10nF, other one is appox 680pF for
example in a philips set.

In other set, like zenith, I see multiple smaller caps like 470pF,
two, three, even four along with a few nF value cap.

Cheers,

Wizard
Click to expand...
They are all important. The multiple values all add up. Some sets in
the past had specially made non-standard values, eg philips k9, 11.9
nF
 
do to modify the set (high-wattage resistor in series with the HOT
collector, etc) and I might be able to patch it up.
This will cause changes in picture size due to poor eht regulation
Click to expand...

design suggests that the HV is regulated by increasing/decreasing the
amplitude of the horiz. osc signal. Is it possible that I could put a
potentiometer, in series with the base of the HOT or something?
Do not change the base drive. The eht is not regulated in any way.
Click to expand...
http://members.aol.com/JURB6006/HRATE.htm
 
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