Dummy load for SMPS
 

I am troubleshooting a SMPS for a projection tv and am not too sure on
what the load should be. The prints only mention voltages, no loads.
The schematics show that a +130vdc line is connected to a
photocoupler, so im assuming this is the line that is used for
feedback regulation, and therefore the one that needs the load. I have
looked all over google for "dummy load" and cant really find a good
site to help me out on this. Any ideas Sam? The sticker on the outside
of the smps says 120v 150w if that helps.

Dummy load for SMPS
 

A 60 watt light bulb makes a near perfect load for the 130 volt line.
The other section of that power supply doesn't like to be run unloaded, just
desolder the wire(coil) that supplies the STRS5141G while you test the
section with the STRS6301.

Good Luck,
Bill Jr



"Brian" wrote in message
om...
I am troubleshooting a SMPS for a projection tv and am not too sure on
what the load should be. The prints only mention voltages, no loads.
The schematics show that a +130vdc line is connected to a
photocoupler, so im assuming this is the line that is used for
feedback regulation, and therefore the one that needs the load. I have
looked all over google for "dummy load" and cant really find a good
site to help me out on this. Any ideas Sam? The sticker on the outside
of the smps says 120v 150w if that helps.

Dummy load for SMPS
 

Okay, you are good. How did you know it was using a STR6301? And the
other half was a STR5041...you were close. So desolder the supply to the
transformer or the regulator IC?

Bill Jr wrote:
A 60 watt light bulb makes a near perfect load for the 130 volt line.
The other section of that power supply doesn't like to be run unloaded, just
desolder the wire(coil) that supplies the STRS5141G while you test the
section with the STRS6301.

Good Luck,
Bill Jr



"Brian" wrote in message
om...

I am troubleshooting a SMPS for a projection tv and am not too sure on
what the load should be. The prints only mention voltages, no loads.
The schematics show that a +130vdc line is connected to a
photocoupler, so im assuming this is the line that is used for
feedback regulation, and therefore the one that needs the load. I have
looked all over google for "dummy load" and cant really find a good
site to help me out on this. Any ideas Sam? The sticker on the outside
of the smps says 120v 150w if that helps.

Dummy load for SMPS
 

Even with dummy load, output voltages are all messed up. I have already
replaced the caps on primary side. Could it be the regulator IC? or the
Opticoupler?

Brian wrote:

I am troubleshooting a SMPS for a projection tv and am not too sure on
what the load should be. The prints only mention voltages, no loads.
The schematics show that a +130vdc line is connected to a
photocoupler, so im assuming this is the line that is used for
feedback regulation, and therefore the one that needs the load. I have
looked all over google for "dummy load" and cant really find a good
site to help me out on this. Any ideas Sam? The sticker on the outside
of the smps says 120v 150w if that helps.

Dummy load for SMPS
 

If output voltages on STR5041 side are bad (high), replace C920,
10mfd@100v,105c. You'll probably have to replace the vertical IC (LA7838) as
well, since the runaway B+ to the chip fries it (usually). If the STRS6301
voltages are high, change C914,47mfd@50v. Too low, change the SE130.

Dummy load for SMPS
 

If output voltages on STR5041 side are bad (high), replace C920,
10mfd@100v,105c. You'll probably have to replace the vertical IC (LA7838) as
well, since the runaway B+ to the chip fries it (usually). If the STRS6301
voltages are high, change C914,47mfd@50v. Too low, change the SE130.