k-7500 P.s. issue

[paul400]

having trouble with a k7500 wells. I isolated the issue to the power supply changed out u101 and q101, replaced r104. I checked all the diodes in that section and all resistors seem to be in spec. I also changed all caps in that section. With L100 lifted isolating it from the rest of the chassis I have a 60 watt light bulb attached to it and ground. all I get is a slight ticking. if I install a 10 watt led I can get it to light. c119 and 121 replaced they were not shorted but changed anyways. I replaced all the polys in this section. I am getting -32vdc on all the pins of u101 correct? . checked all the stuff in the AC before the four diodes which check out and the four diodes are good,I went through the whole power supply section swapped out a bunch of parts including q101 and u101. swapped out all the ceramic caps, that big 10k resistor was off spec so swapped that. checked all the resistors and all seem to be in spec., no shorted diodes. I cant get this bulb/60watt to light, if I put an lcd light in there which is only 10 watts it will light and all readings on everthing is good and can adjust that with the B+ pot. any suggestions?

[paul400]

Q101 and U101. have more on order. if the fet is bad it should blow the fuse or can it fail without blowing the fuse. either way I ordered more. I have gone through this ps 10 times comparing to a working chassis, I havent seen anything too far off the percentage wise to the working one.  beeped out all circuits and havent found any broken traces.

[FUNWIZ]

Not sure about the one your working on, but found this on the K7000: To disable the shutdown circuit, short pin 5,IC2 to ground.

k7500
TP 202: 117.20 V
TP 103: -3.20 V
TP 200: 4.80 V
TP 204: 14.70 V
TP 104: 17.10 V

Recheck caps, differences in 7400 vs 7500, one uses a BP cap near the HOT with an empty spot next to it. The other uses a polarized cap in the empty spot and is empty where the BP cap is on the other. Putting the wrong values or a cap in the wrong spot can cause shutdown.

[paul400]

right now I am just trying to get the power supply to operate via a lightbulb and L100  I pulled the HOT to test it and its fine.

[HammysHangout ( Hammy )]

maybe the 60watt is too much of an inductive load for startup? try adding a 50watt to it after the 10watt is lit. it may think there is a short and shutting down.

[paul400]

maybe the 60watt is too much of an inductive load for startup? try adding a 50watt to it after the 10watt is lit. it may think there is a short and shutting down.

60 watt is good for this test. I have done this test many times  to test PS. and when working they always light the bulb, I actually have another sitting next to this one that lights the bulb fine.

[atarijim]

once in a while, the B+ pot goes bad due to the glue; it's a cheap and quick try.

aj

[paul400]

once in a while, the B+ pot goes bad due to the glue; it's a cheap and quick try.

aj

replaced the B+ pot and it will brighten and dim the led 10 watt bulb  but will  still will not light the 60 watt.

[paul400]

http://www.youtube.com/watch?v=xcxQTSiD8VA

[Spicules]

Thanks for posting the video - I found out I was doing the test wrong!

[FUNWIZ]

Where's the smoke?  Where's the explosions?  The Big Bang!  There's no fireworks...