|
1000+ Volts at B+
Hello, i am working on a 15 inch color monitor. I have a 150W light
bulb connected and when i turn the monitor on, it starts to pulsate for about 10 seconds at 2hz(+-)So it pulsates like 15 to 20 times and then it stays at normal brightness. During all of this the monitor is NOT connected to a PC, but when i do it statrs to pusate again but this time indefenetly. I=B4ve tried changing the refresh rate and this causes the pulses to speed up, so if i go from 800x600/50hz to 800x600/60hz, the pulsating goes from about 1hz to 2hz and if I pull the VGA connector the pulsating stops. Should i try a bigger light bulb? I also get over 1000Vdc (DMM goes blank)both at the chopper transistor=B4s and HOT=B4s drain pin. What controls B+ voltage? is it just the HOT or is there a voltage regulator somewhere? I am looking for a bad V regulatro or maybe a bad resistor somewhere, Am I in the right direction here? Thanks. |
"onyxx" writes:
Hello, i am working on a 15 inch color monitor. I have a 150W light bulb connected and when i turn the monitor on, it starts to pulsate for about 10 seconds at 2hz(+-)So it pulsates like 15 to 20 times and then it stays at normal brightness. During all of this the monitor is NOT connected to a PC, but when i do it statrs to pusate again but this time indefenetly. Iīve tried changing the refresh rate and this causes the pulses to speed up, so if i go from 800x600/50hz to 800x600/60hz, the pulsating goes from about 1hz to 2hz and if I pull the VGA connector the pulsating stops. Should i try a bigger light bulb? I also get over 1000Vdc (DMM goes blank)both at the chopper transistorīs and HOTīs drain pin. What controls B+ voltage? is it just the HOT or is there a voltage regulator somewhere? I am looking for a bad V regulatro or maybe a bad resistor somewhere, Am I in the right direction here? What were the original symptoms? 100 W may be a bit low for a 15 inch monitor to come up properly with a signal. P.S. Don't put your poor DMM on those terminals! If it does come up properly, the DMM may not survive. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
check the H-OUT transistor and any
caps in the power supply near hot spots that may dry out the caps, disconnect the h-out transistor before useing youre metre to check the power supply, then use a light bolb and connect it to ground and the collector side of the h-out transistor on the board with no transistor connected it should be 120-150volts. "onyxx" wrote in message oups.com... Hello, i am working on a 15 inch color monitor. I have a 150W light bulb connected and when i turn the monitor on, it starts to pulsate for about 10 seconds at 2hz(+-)So it pulsates like 15 to 20 times and then it stays at normal brightness. During all of this the monitor is NOT connected to a PC, but when i do it statrs to pusate again but this time indefenetly. Iīve tried changing the refresh rate and this causes the pulses to speed up, so if i go from 800x600/50hz to 800x600/60hz, the pulsating goes from about 1hz to 2hz and if I pull the VGA connector the pulsating stops. Should i try a bigger light bulb? I also get over 1000Vdc (DMM goes blank)both at the chopper transistorīs and HOTīs drain pin. What controls B+ voltage? is it just the HOT or is there a voltage regulator somewhere? I am looking for a bad V regulatro or maybe a bad resistor somewhere, Am I in the right direction here? Thanks. |
Hi
are you using a scope, Digital or Analogue Meter?. There can be a difference due to the waveform. I am not sure what to expect at flyback frequencies. I am only happy when I get the same voltages as on the circuit diagram (schematic) Andy "onyxx" wrote in message oups.com... Hello, i am working on a 15 inch color monitor. I have a 150W light bulb connected and when i turn the monitor on, it starts to pulsate for about 10 seconds at 2hz(+-)So it pulsates like 15 to 20 times and then it stays at normal brightness. During all of this the monitor is NOT connected to a PC, but when i do it statrs to pusate again but this time indefenetly. Iīve tried changing the refresh rate and this causes the pulses to speed up, so if i go from 800x600/50hz to 800x600/60hz, the pulsating goes from about 1hz to 2hz and if I pull the VGA connector the pulsating stops. Should i try a bigger light bulb? I also get over 1000Vdc (DMM goes blank)both at the chopper transistorīs and HOTīs drain pin. What controls B+ voltage? is it just the HOT or is there a voltage regulator somewhere? I am looking for a bad V regulatro or maybe a bad resistor somewhere, Am I in the right direction here? Thanks. |
On 3 Oct 2005 12:09:16 -0700, "onyxx" wrote:
Hello, i am working on a 15 inch color monitor. I have a 150W light bulb connected and when i turn the monitor on, it starts to pulsate for about 10 seconds at 2hz(+-)So it pulsates like 15 to 20 times and then it stays at normal brightness. If it is at normal brightness... During all of this the monitor is NOT connected to a PC, but when i do it statrs to pusate again but this time indefenetly. IÂīve tried changing the refresh rate and this causes the pulses to speed up, so if i go from 800x600/50hz to 800x600/60hz, the pulsating goes from about 1hz to 2hz and if I pull the VGA connector the pulsating stops. Should i try a bigger light bulb? I also get over 1000Vdc (DMM goes blank)both at the chopper transistorÂīs and HOTÂīs drain pin. ....it is no wonder that the DMM is complaining...if only I could remember what "drain" means...FET terminal...equivalent to collector or emmiter? Can't remember...if emitter, something weird is going on. Hmmm. Tom What controls B+ voltage? is it just the HOT or is there a voltage regulator somewhere? I am looking for a bad V regulatro or maybe a bad resistor somewhere, Am I in the right direction here? Thanks. |
| All times are GMT +1. The time now is 01:16 AM. |
Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright Đ2004 - 2014 DIYbanter